Jairo Palta - Academia.edu (original) (raw)

Papers by Jairo Palta

• Background on soybean. -US soybean production. -Soybean breeding programs. -Soybean genomic res... more • Background on soybean. -US soybean production. -Soybean breeding programs. -Soybean genomic resources. -Soybean germplasm collections. • Putting the germplasm and genomic resources together. -Soybean aphid resistance. • New genetic technologies. • Soybean grown on 29 million hectares in the US in 2008, primarily in the Midwestern US. • Total US production in 2008 is projected to be 81 million metric tons. • Farm value of 18 billion US dollars. Public Sector Research Public Sector Research • Public sectors is moving out of general use cultivar development. • Focus of effort on: -Cultivars for specialty markets. -Germplasm development. -Identification of new genes from the germplasm collection. -Basic research. -Student educations. • Research largely funded by farmer check off programs. -21,064 accessions. -18,893 Glycine max (soybean). -1,169 Glycine soja (wild annual soybean). • Success in using germplasm for defensive traits. • The maturities of Dowling (MG VIII), Jackson (MG VII) and PI 200538 (MG VIII) make them incompatible for production in the Midwest. • The resistance gene(s) need to be bred into northern soybean backgrounds. • These genes were mapped quickly with SSR markers using bulked segregant analysis.

Frontiers in Microbiology, Nov 10, 2022

It is critical to identify and evaluate efficient phosphate-solubilizing bacteria (PSB) that enab... more It is critical to identify and evaluate efficient phosphate-solubilizing bacteria (PSB) that enable P uptake from unavailable forms, and therefore improve the phosphorus (P) uptake efficiency of crops. The Enterobacter cloacae strain NG-33, belonging to PSB, was isolated and identified from calcareous rhizosphere soils in Nonggang National Reserve, Guangxi, China. The stain NG-33 could reduce the pH of the medium to below 5.6, and had the ability to release soluble phosphorus (P; 180.7 μg ml -1 ) during the culture in the National Botanical Research Institute's Phosphate medium (NBRIP), and produced such organic acids as gluconic acid (4,881 mg L -1 ), acetic acid (346 mg L -1 ), and indole-3-acetic acid (20.4 μg ml -1 ). It could also convert inorganic P in AlPO 4 (Al-P) and FePO 4 (Fe-P) into soluble P, with conversion efficiencies of 19.2 μg ml -1 and 16.3 μg ml -1 , respectively. Under pot experiments and when compared controls without inoculating NG-33, the shoot and root biomass of maize seedlings showed increases by 140% for shoot biomass and by 97% for root biomass in loamy soil (P sufficient) inoculated with NG-33. In sandy soil (P deficit) supplemented with tricalcium phosphate and inoculated with NG-33, the soluble P content was significantly higher, 58.6% in soil and 33.6% in roots, meanwhile, the biomass of shoots and roots increased by 14.9 and 24.9%, respectively. The growth-promoting effects coupled to the significant increase in leaf net photosynthetic rate and stomatal conductance of plants grown in NG-33-inoculated soil. Inoculating NG-33 could significantly improve the diversity and richness of bacterial population and altered the dominant bacterial population in soil.

Frontiers in Plant Science, Aug 19, 2020

In the Mediterranean-type environment of Australia and other parts of the world, end-ofseason or ... more In the Mediterranean-type environment of Australia and other parts of the world, end-ofseason or terminal drought is the most significant abiotic stress affecting wheat grain yields. This study examined the response of two wheat cultivars with contrasting root system size to terminal drought and the effect of terminal drought on grain yield and yield components. The cultivars were grown in 1.0 m deep PVC columns filled with soil in a glasshouse under well-watered conditions until the onset of ear emergence (Z51) when well-watered and terminal drought treatments were imposed. Terminal drought reduced stomatal conductance, leaf photosynthesis, and transpiration rates faster in Bahatans-87 (larger root system size) than Tincurrin (smaller root system size). Terminal drought reduced grain yield in both cultivars, more so in Bahatans-87 (80%) with the large root system than Tincurrin (67%) with the small root system, which was mainly due to a reduction in grain number and grain size in Bahatans-87 and grain size in Tincurrin. In the terminal drought treatment, Bahatans-87 had 59% lower water use efficiency than Tincurrin, as Bahatans-87 used 39% more water and reduced grain yield more than Tincurrin. The lesser reduction in grain yield in Tincurrin was associated with slower water extraction by the small root system and slower decline in stomatal conductance, leaf photosynthesis, and transpiration rates, but more importantly to faster phenological development, which enabled grain filling to be completed before the severe effects of water stress.

Agronomy, Jul 18, 2019

Abscisic acid (ABA) plays a central role in the plant response to water deficit by inducing stoma... more Abscisic acid (ABA) plays a central role in the plant response to water deficit by inducing stomatal closure to conserve water when the soil dries. Exogenous ABA was applied at 45 days after sowing (DAS) as a soil drench, the physiological and seed yield response of soybean to exogenous ABA were examined as the soil was drying. Three experiments were conducted using the drought-tolerant soybean cultivar Jindou 19, grown in pots at the Yuzhong Experimental Station of Lanzhou University, China. In experiment 1, plants were exposed to progressive soil drying and leaf ABA concentration, leaf photosynthesis rate, leaf relative water content (RWC) and osmotic adjustment (OA) were measured. In experiment 2, plants were under progressive soil drying and lethal leaf water potential was measured. In experiment 3, flower production and abortion, and grain yield were measured in plants under well-watered (WW), moderate (MWD) and severe water deficits (SWD). Exogenous ABA application increased ABA accumulation in leaves and reduced the rate of soil drying. It also increased leaf photosynthetic rate, stomatal conductance and transpiration rate at 7-10 days after withholding water. The intrinsic and instantaneous water use efficiency (WUE) was consistently higher with exogenous ABA than without ABA as the soil dried. Exogenous ABA increased OA when the leaf relative water content (RWC) decreased at eight days after withholding water, lowering the lethal leaf water potential by 0.4 MPa. Exogenous ABA reduced water use, increased WUE for grain yield under WW and MWD, and had no effect on flower number, flower abortion or grain yield in any water treatment. We concluded that (1) exogenous ABA induced OA, improved leaf photosynthetic rate, leaf water relations and desiccant tolerance, but did not benefit grain yield in soybean under water deficits; (2) exogenous ABA improved the WUE at the leaf level as soil drying and WUE for grain yield under moderate water deficit.

Frontiers in Plant Science, Feb 13, 2018

Journal of Agronomy and Crop Science, Sep 17, 2020

Maize (Zea mays L.) is susceptible to salinity but shows genotypic variation for salt tolerance. ... more Maize (Zea mays L.) is susceptible to salinity but shows genotypic variation for salt tolerance. How maize genotypes with contrasting root morphological traits respond to salt stress remains unclear. This study assessed genotypic variation in salinity tolerance of 20 maize genotypes with contrasting root systems exposed to NaCl for 10 days (0, 50 mM or 100 mM NaCl, added in four increments every other day from 14 days after transplanting, DAT) in a semi-hydroponic phenotyping system in a temperature-controlled greenhouse. Considerable variation was observed for each of the 12 measured shoot and root traits among the 20 genotypes under NaCl treatments. Salt stress significantly decreased biomass production by up to 54% in shoots and 37% in roots compared with the non-saline control. The 20 genotypes were classified as salt-tolerant (8 genotypes), moderately tolerant (5), and salt-sensitive (7) genotypes based on the mean shoot dry weight ratio (the ratio of shoot dry weight at 100 mM NaCl and non-saline control) ± one standard error. The more salt-tolerant genotypes (such as Jindan52) had less reductions in growth, and lower shoot Na + contents and higher shoot K + /Na + ratios under salt stress. The declared salt tolerance was positively correlated with shoot height, shoot dry weight and primary root depth, and negatively correlated with shoot Na + content at 100 mM NaCl. Primary root depth is critical for identifying salt responsiveness in maize plants and could be suggested as a selection criterion for screening salt tolerance of maize during early growth. The selected salt-tolerant genotypes have potentials for cultivation in saline soils and for developing high-yielding salt-tolerant maize hybrids in future breeding programs. KEYWORDS phenotyping, salt tolerance, root traits, biomass, K + /Na + ratio * Significant at P≤0.05, ** Significant at P≤0.01 Salt tolerance was evaluated by the ratio of shoot dry weight at 50 mM NaCl to root dry weight in the non-saline controls

Agronomy, Nov 22, 2019

In dry environments, potato (Solanum tuberosum L.) is grown under mulching for water conservation... more In dry environments, potato (Solanum tuberosum L.) is grown under mulching for water conservation and improving tuber yield and nitrogen use efficiency (NUE). A meta-analysis was conducted to determine how mulching improved tuber yield and NUE in potato and how yield and NUE is influenced by fertilization, tillage practices, and growing environment in China. A search of peer-reviewed publications was performed to collect data on the effects of mulching on yield and NUE in potato grown in China. The data included were from field studies with a mulching and a no mulching treatment and data on tuber yield and NUE. A total of 169 publications (17 in English and 152 in Chinese) containing 1802 observations from 105 sites were compiled into the dataset. Mulching significantly increased both tuber yield and NUE by an average of 24% compared to no mulching, respectively. Plastic film mulching was more effective in improving yield and NUE than straw mulching. The yield and NUE increase were highest under plastic film mulching on ridge-furrow plots and straw mulching on flat plots. Mulching was more effective at improving yield and NUE in the Northwest dryland region at a plant density between 55,000 and 70,000 plants ha -1 and with application of synthetic N and P 2 O 5 at rates of 100-200 kg ha -1 , K fertilization at 0-100 kg K 2 O ha -1 , and without organic fertilization. Integrated use of organic fertilizer and mulching was found to reduce synthetic N and P fertilizer input by 50% and K fertilizer input by 100% for production without affecting yield and NUE. These results demonstrate that mulching increases yield and NUE in potato in China, but the benefits occur when the growing region, tillage, and fertilization practices are appropriately considered.

Frontiers in Plant Science, Jul 18, 2017

End-of-season drought or "terminal drought," which occurs after flowering, is considered the most... more End-of-season drought or "terminal drought," which occurs after flowering, is considered the most significant abiotic stress affecting crop yields. Wheat crop production in Mediterranean-type environments is often exposed to terminal drought due to decreasing rainfall and rapid increases in temperature and evapotranspiration during spring when wheat crops enter the reproductive stage. Under such conditions, every millimeter of extra soil water extracted by the roots benefits grain filling and yield and improves water use efficiency (WUE). When terminal drought develops, soil dries from the top, exposing the top part of the root system to dry soil while the bottom part is in contact with available soil water. Plant roots sense the drying soil and produce signals, which on transmission to shoots trigger stomatal closure to regulate crop water use through transpiration. However, transpiration is linked to crop growth and productivity and limiting transpiration may reduce potential yield. While an early and high degree of stomatal closure affects photosynthesis and hence biomass production, a late and low degree of stomatal closure exhausts available soil water rapidly which results in yield losses through a reduction in post-anthesis water use. The plant hormone abscisic acid (ABA) is considered the major chemical signal involved in stomatal regulation. Wheat genotypes differ in their ability to produce ABA under drought and also in their stomatal sensitivity to ABA. In this viewpoint article we discuss the possibilities of exploiting genotypic differences in ABA response to soil drying in regulating the use of water under terminal drought. Root density distribution in the upper drying layers of the soil profile is identified as a candidate trait that can affect ABA accumulation and subsequent stomatal closure. We also examine whether leaf ABA can be designated as a surrogate characteristic for improved WUE in wheat to sustain grain yield under terminal drought. Ease of collecting leaf samples to quantify ABA compared to extracting xylem sap will facilitate rapid screening of a large number of germplasm for drought tolerance.

Frontiers in Plant Science, Feb 7, 2022

Plants, Aug 21, 2022

High temperature and water deficit are the most critical yield-limiting environmental factors for... more High temperature and water deficit are the most critical yield-limiting environmental factors for wheat in rainfed environments. It is important to understand the heat avoidance mechanisms and their associations with leaf morpho-physiological traits that allow crops to stay cool and retain high biomass under warm and dry conditions. We examined 20 morpho-physiologically diverse wheat genotypes under ambient and elevated temperatures (T air ) to investigate whether increased water use leads to high biomass retention due to increased leaf cooling. An experiment was conducted under well-watered conditions in two partially controlled glasshouses. We measured plant transpiration (T r ), leaf temperature (T leaf ), vapor pressure deficit (VPD), and associated leaf morpho-physiological characteristics. High water use and leaf cooling increased biomass retention under high temperatures, but increased use did not always increase biomass retention. Some genotypes maintained biomass, irrespective of water use, possibly through mechanisms other than leaf cooling, indicating their adaptation under water shortage. Genotypic differences in leaf cooling capacity did not always correlate with T r (VPD) response. In summary, the contribution of high water use or the leaf cooling effect on biomass retention under high temperature is genotype-dependent and possibly due to variations in leaf morpho-physiological traits. These findings are useful for breeding programs to develop climate resilient wheat cultivars.

Annual ryegrass (Lolium rigidum) reduces the uptake and utilisation of fertiliser-nitrogen by wheat

Australian Journal of Agricultural Research, 2001

The effect of timing of annual ryegrass (Lolium rigidum) emergence on the uptake and utilisation ... more The effect of timing of annual ryegrass (Lolium rigidum) emergence on the uptake and utilisation of N by wheat was investigated in a field trial on a duplex soil at Katanning, Western Australia, and in a glasshouse study in which 15N-fertiliser was applied. Three treatments were used to investigate the effect of timing of annual ryegrass emergence on the uptake and utilisation of N by wheat: simultaneous sowing of wheat and annual ryegrass, sowing of annual ryegrass 1 week before wheat, and sowing of the annual ryegrass 1 week after wheat. A control treatment, consisting of wheat sown alone, was also included. Plant densities during the field trial were 105 and 140 plants/m2 for wheat and annual ryegrass, respectively, whereas in the glasshouse they were 105 plants/m2 for wheat and 155 plants/m2 for annual ryegrass. Fertiliser-N was applied at seeding of wheat at 50 kg N/ha in the field trial and 60 kg N/ha in the glasshouse. The introduction of annual ryegrass into the wheat system...

Adaptation of Plants to Water-Limited Mediterranean Environments

ABSTRACT

Water relations, gas exchange, nodulation, nitrogen fixation and growth of faba bean (Vicia faba L.) in relation to the drying of surface roots

Adapting wheat germplasm for elevated CO2 and higher temperatures–environment characterisation, trait screening and crop modelling

Functional Plant Biology, 2012

An assay system that provides rapid and reproducible germination under low soil water content (&l... more An assay system that provides rapid and reproducible germination under low soil water content (<10% water holding capacity (WHC)) was developed and used to compare how chickpea (Cicer arietinum L.) genotypes complete germination, without the technical difficulties of accurately controlling water levels. The system consisted of small plastic containers (50 mm × 50 mm × 60 mm) filled with river sand and tightly closed (but not sealed) to minimise water loss and maintain constant soil water content during germination. Seed size influenced germination performance at low WHC. Small seeds within a single genotype germinated successfully and entered into the early stages of seedling growth, but germination of large seeds was inhibited, failing to germinate at 5% WHC. Small seeds were more efficient in remobilising seed reserves to seedling tissues than larger seeds. Under optimal WHC, the germination rate and subsequent radicle growth was similar among genotypes but at low WHC, there wa...

Elevated CO2 will affect water use efficiency of wheat cultivars differently

ABSTRACT

European Journal of Agronomy, Mar 1, 2021

Large distribution of roots in topsoil layers allow more uptake of soil water and nutrients durin... more Large distribution of roots in topsoil layers allow more uptake of soil water and nutrients during the vegetative growth, but it may be disadvantageous if soil water deficits develops during the reproductive stage. The relationship between the distribution of roots in the topsoil (0-0.4 m) and soil water use, dry matter and N accumulations, and grain yield was examined in winter wheat (Triticum aestivum L.) with contrasting root size in the topsoil. Two old landraces (CW134 and JM47, larger root length and biomass in the topsoil) and two modern wheat cultivars (CH58 and LH7, smaller root system size in the topsoil), were grown in the field during two seasons (2016-2017 and 2017-2018) under rainfed and irrigation conditions in the semi-arid Loess Plateau of China. Root biomass and root length density (RLD) in topsoil (0-0.4 m) was significantly higher in old landraces than in modern cultivars (P < 0.05) under rainfed and irrigation and in both seasons (no such difference in subsoil, 0.4-1.0 m). The modern cultivars had significantly higher grain yield, grain N concentration, WUE, and 1000grain weight (P< 0.05). Seasonal water use was similar among all cultivars, but post-anthesis water use was higher in the modern cultivars, particularly under rainfed conditions in both seasons. Root biomass and RLD in the topsoil was positively correlated with pre-anthesis water use, but negatively correlated with soil water use after anthesis. Post-anthesis water use was closely related to post-anthesis dry matter and N accumulation, post-anthesis dry matter had a strong positive effect on yield and WUE, and post-anthesis N accumulation had a positive effect on grain N concentration under rainfed conditions. To conclude, large distribution of roots in the topsoil had non-advantage for wheat grown under rainfed conditions. The small distribution of roots in the topsoil (characteristics of modern wheat cultivars) enhanced post-anthesis water use, increased post-anthesis dry matter and N accumulation and hence attained higher grain yield and grain N when grown in the semi-arid environment.

Agronomy, Oct 5, 2019

Understanding the changes in phenotype resulting from the selection pressure and agronomic adapta... more Understanding the changes in phenotype resulting from the selection pressure and agronomic adaptation of grain yield provide an indication of the pathways for future increases in grain yield. Six dry land representative winter wheat cultivars (Triticum aestivum L.) released from 1942 to 2004 in the Loess Plateau of China were investigated to determine how the yield components of winter wheat were associated with grain yield at the Changwu Agricultural Research Station during the 2011-2012 and 2012-2013 seasons, using a completely randomized block design with three replicates. Plant height, aboveground biomass, grain yield, and yield components were measured, together with the traits of superior and inferior grains and the pre-anthesis stored dry matter remobilized to the grain was determined. In the relatively wet 2011-2012 season, there was a significant increase in grain yield and aboveground biomass with the year of release, but not in the dry 2012-2013 season. The harvest index (HI) and average grain weight (AGW) increased significantly with the year of release in both cropping seasons. HI and AGW are likely potential traits for improving grain yield of winter wheat in the Loess Plateau. The increase in HI mainly resulted from the decrease in plant height, and the increase in the use of pre-anthesis stored assimilates for grain filling. The increase in AGW mainly resulted from the increase in the proportion of superior grain (SG) and the decrease in the proportion of inferior grain (IG) in the whole spike in both cropping seasons. Depending on the climatic conditions, the different winter wheat cultivars showed different ability to use pre-anthesis stored assimilates. Modern wheat cultivars had higher yield under different rainfall conditions, and high ability to use pre-anthesis stored assimilates to fill the grain than earlier released cultivars. Both, the increase in sink capacity and source availability, should be considered as a strategy for increasing future grain yield in Loess Plateau of China.

How How molecular molecular nutraceutics nutraceutics does does help in help in understanding und... more How How molecular molecular nutraceutics nutraceutics does does help in help in understanding understanding lupin lupin seed seed protein protein role role Case Case-studies studies of of selected selected white white lupin lupin seed seed proteins proteins Concluding Concluding remarks remarks Summary of Summary of Lupinus Lupinus albus albus conglutins conglutins ' ' main main features features Congl. Protein family % of total globulin Native protein Monomer composition Protein function in the seed M r , kDa pI Quaternary structure Subunit name M r , kDa pI Glycosylat ion α 11S legumin 35-37 330-430

• Background on soybean. -US soybean production. -Soybean breeding programs. -Soybean genomic res... more • Background on soybean. -US soybean production. -Soybean breeding programs. -Soybean genomic resources. -Soybean germplasm collections. • Putting the germplasm and genomic resources together. -Soybean aphid resistance. • New genetic technologies. • Soybean grown on 29 million hectares in the US in 2008, primarily in the Midwestern US. • Total US production in 2008 is projected to be 81 million metric tons. • Farm value of 18 billion US dollars. Public Sector Research Public Sector Research • Public sectors is moving out of general use cultivar development. • Focus of effort on: -Cultivars for specialty markets. -Germplasm development. -Identification of new genes from the germplasm collection. -Basic research. -Student educations. • Research largely funded by farmer check off programs. -21,064 accessions. -18,893 Glycine max (soybean). -1,169 Glycine soja (wild annual soybean). • Success in using germplasm for defensive traits. • The maturities of Dowling (MG VIII), Jackson (MG VII) and PI 200538 (MG VIII) make them incompatible for production in the Midwest. • The resistance gene(s) need to be bred into northern soybean backgrounds. • These genes were mapped quickly with SSR markers using bulked segregant analysis.

Frontiers in Microbiology, Nov 10, 2022

It is critical to identify and evaluate efficient phosphate-solubilizing bacteria (PSB) that enab... more It is critical to identify and evaluate efficient phosphate-solubilizing bacteria (PSB) that enable P uptake from unavailable forms, and therefore improve the phosphorus (P) uptake efficiency of crops. The Enterobacter cloacae strain NG-33, belonging to PSB, was isolated and identified from calcareous rhizosphere soils in Nonggang National Reserve, Guangxi, China. The stain NG-33 could reduce the pH of the medium to below 5.6, and had the ability to release soluble phosphorus (P; 180.7 μg ml -1 ) during the culture in the National Botanical Research Institute's Phosphate medium (NBRIP), and produced such organic acids as gluconic acid (4,881 mg L -1 ), acetic acid (346 mg L -1 ), and indole-3-acetic acid (20.4 μg ml -1 ). It could also convert inorganic P in AlPO 4 (Al-P) and FePO 4 (Fe-P) into soluble P, with conversion efficiencies of 19.2 μg ml -1 and 16.3 μg ml -1 , respectively. Under pot experiments and when compared controls without inoculating NG-33, the shoot and root biomass of maize seedlings showed increases by 140% for shoot biomass and by 97% for root biomass in loamy soil (P sufficient) inoculated with NG-33. In sandy soil (P deficit) supplemented with tricalcium phosphate and inoculated with NG-33, the soluble P content was significantly higher, 58.6% in soil and 33.6% in roots, meanwhile, the biomass of shoots and roots increased by 14.9 and 24.9%, respectively. The growth-promoting effects coupled to the significant increase in leaf net photosynthetic rate and stomatal conductance of plants grown in NG-33-inoculated soil. Inoculating NG-33 could significantly improve the diversity and richness of bacterial population and altered the dominant bacterial population in soil.

Frontiers in Plant Science, Aug 19, 2020

In the Mediterranean-type environment of Australia and other parts of the world, end-ofseason or ... more In the Mediterranean-type environment of Australia and other parts of the world, end-ofseason or terminal drought is the most significant abiotic stress affecting wheat grain yields. This study examined the response of two wheat cultivars with contrasting root system size to terminal drought and the effect of terminal drought on grain yield and yield components. The cultivars were grown in 1.0 m deep PVC columns filled with soil in a glasshouse under well-watered conditions until the onset of ear emergence (Z51) when well-watered and terminal drought treatments were imposed. Terminal drought reduced stomatal conductance, leaf photosynthesis, and transpiration rates faster in Bahatans-87 (larger root system size) than Tincurrin (smaller root system size). Terminal drought reduced grain yield in both cultivars, more so in Bahatans-87 (80%) with the large root system than Tincurrin (67%) with the small root system, which was mainly due to a reduction in grain number and grain size in Bahatans-87 and grain size in Tincurrin. In the terminal drought treatment, Bahatans-87 had 59% lower water use efficiency than Tincurrin, as Bahatans-87 used 39% more water and reduced grain yield more than Tincurrin. The lesser reduction in grain yield in Tincurrin was associated with slower water extraction by the small root system and slower decline in stomatal conductance, leaf photosynthesis, and transpiration rates, but more importantly to faster phenological development, which enabled grain filling to be completed before the severe effects of water stress.

Agronomy, Jul 18, 2019

Abscisic acid (ABA) plays a central role in the plant response to water deficit by inducing stoma... more Abscisic acid (ABA) plays a central role in the plant response to water deficit by inducing stomatal closure to conserve water when the soil dries. Exogenous ABA was applied at 45 days after sowing (DAS) as a soil drench, the physiological and seed yield response of soybean to exogenous ABA were examined as the soil was drying. Three experiments were conducted using the drought-tolerant soybean cultivar Jindou 19, grown in pots at the Yuzhong Experimental Station of Lanzhou University, China. In experiment 1, plants were exposed to progressive soil drying and leaf ABA concentration, leaf photosynthesis rate, leaf relative water content (RWC) and osmotic adjustment (OA) were measured. In experiment 2, plants were under progressive soil drying and lethal leaf water potential was measured. In experiment 3, flower production and abortion, and grain yield were measured in plants under well-watered (WW), moderate (MWD) and severe water deficits (SWD). Exogenous ABA application increased ABA accumulation in leaves and reduced the rate of soil drying. It also increased leaf photosynthetic rate, stomatal conductance and transpiration rate at 7-10 days after withholding water. The intrinsic and instantaneous water use efficiency (WUE) was consistently higher with exogenous ABA than without ABA as the soil dried. Exogenous ABA increased OA when the leaf relative water content (RWC) decreased at eight days after withholding water, lowering the lethal leaf water potential by 0.4 MPa. Exogenous ABA reduced water use, increased WUE for grain yield under WW and MWD, and had no effect on flower number, flower abortion or grain yield in any water treatment. We concluded that (1) exogenous ABA induced OA, improved leaf photosynthetic rate, leaf water relations and desiccant tolerance, but did not benefit grain yield in soybean under water deficits; (2) exogenous ABA improved the WUE at the leaf level as soil drying and WUE for grain yield under moderate water deficit.

Frontiers in Plant Science, Feb 13, 2018

Journal of Agronomy and Crop Science, Sep 17, 2020

Maize (Zea mays L.) is susceptible to salinity but shows genotypic variation for salt tolerance. ... more Maize (Zea mays L.) is susceptible to salinity but shows genotypic variation for salt tolerance. How maize genotypes with contrasting root morphological traits respond to salt stress remains unclear. This study assessed genotypic variation in salinity tolerance of 20 maize genotypes with contrasting root systems exposed to NaCl for 10 days (0, 50 mM or 100 mM NaCl, added in four increments every other day from 14 days after transplanting, DAT) in a semi-hydroponic phenotyping system in a temperature-controlled greenhouse. Considerable variation was observed for each of the 12 measured shoot and root traits among the 20 genotypes under NaCl treatments. Salt stress significantly decreased biomass production by up to 54% in shoots and 37% in roots compared with the non-saline control. The 20 genotypes were classified as salt-tolerant (8 genotypes), moderately tolerant (5), and salt-sensitive (7) genotypes based on the mean shoot dry weight ratio (the ratio of shoot dry weight at 100 mM NaCl and non-saline control) ± one standard error. The more salt-tolerant genotypes (such as Jindan52) had less reductions in growth, and lower shoot Na + contents and higher shoot K + /Na + ratios under salt stress. The declared salt tolerance was positively correlated with shoot height, shoot dry weight and primary root depth, and negatively correlated with shoot Na + content at 100 mM NaCl. Primary root depth is critical for identifying salt responsiveness in maize plants and could be suggested as a selection criterion for screening salt tolerance of maize during early growth. The selected salt-tolerant genotypes have potentials for cultivation in saline soils and for developing high-yielding salt-tolerant maize hybrids in future breeding programs. KEYWORDS phenotyping, salt tolerance, root traits, biomass, K + /Na + ratio * Significant at P≤0.05, ** Significant at P≤0.01 Salt tolerance was evaluated by the ratio of shoot dry weight at 50 mM NaCl to root dry weight in the non-saline controls

Agronomy, Nov 22, 2019

In dry environments, potato (Solanum tuberosum L.) is grown under mulching for water conservation... more In dry environments, potato (Solanum tuberosum L.) is grown under mulching for water conservation and improving tuber yield and nitrogen use efficiency (NUE). A meta-analysis was conducted to determine how mulching improved tuber yield and NUE in potato and how yield and NUE is influenced by fertilization, tillage practices, and growing environment in China. A search of peer-reviewed publications was performed to collect data on the effects of mulching on yield and NUE in potato grown in China. The data included were from field studies with a mulching and a no mulching treatment and data on tuber yield and NUE. A total of 169 publications (17 in English and 152 in Chinese) containing 1802 observations from 105 sites were compiled into the dataset. Mulching significantly increased both tuber yield and NUE by an average of 24% compared to no mulching, respectively. Plastic film mulching was more effective in improving yield and NUE than straw mulching. The yield and NUE increase were highest under plastic film mulching on ridge-furrow plots and straw mulching on flat plots. Mulching was more effective at improving yield and NUE in the Northwest dryland region at a plant density between 55,000 and 70,000 plants ha -1 and with application of synthetic N and P 2 O 5 at rates of 100-200 kg ha -1 , K fertilization at 0-100 kg K 2 O ha -1 , and without organic fertilization. Integrated use of organic fertilizer and mulching was found to reduce synthetic N and P fertilizer input by 50% and K fertilizer input by 100% for production without affecting yield and NUE. These results demonstrate that mulching increases yield and NUE in potato in China, but the benefits occur when the growing region, tillage, and fertilization practices are appropriately considered.

Frontiers in Plant Science, Jul 18, 2017

End-of-season drought or "terminal drought," which occurs after flowering, is considered the most... more End-of-season drought or "terminal drought," which occurs after flowering, is considered the most significant abiotic stress affecting crop yields. Wheat crop production in Mediterranean-type environments is often exposed to terminal drought due to decreasing rainfall and rapid increases in temperature and evapotranspiration during spring when wheat crops enter the reproductive stage. Under such conditions, every millimeter of extra soil water extracted by the roots benefits grain filling and yield and improves water use efficiency (WUE). When terminal drought develops, soil dries from the top, exposing the top part of the root system to dry soil while the bottom part is in contact with available soil water. Plant roots sense the drying soil and produce signals, which on transmission to shoots trigger stomatal closure to regulate crop water use through transpiration. However, transpiration is linked to crop growth and productivity and limiting transpiration may reduce potential yield. While an early and high degree of stomatal closure affects photosynthesis and hence biomass production, a late and low degree of stomatal closure exhausts available soil water rapidly which results in yield losses through a reduction in post-anthesis water use. The plant hormone abscisic acid (ABA) is considered the major chemical signal involved in stomatal regulation. Wheat genotypes differ in their ability to produce ABA under drought and also in their stomatal sensitivity to ABA. In this viewpoint article we discuss the possibilities of exploiting genotypic differences in ABA response to soil drying in regulating the use of water under terminal drought. Root density distribution in the upper drying layers of the soil profile is identified as a candidate trait that can affect ABA accumulation and subsequent stomatal closure. We also examine whether leaf ABA can be designated as a surrogate characteristic for improved WUE in wheat to sustain grain yield under terminal drought. Ease of collecting leaf samples to quantify ABA compared to extracting xylem sap will facilitate rapid screening of a large number of germplasm for drought tolerance.

Frontiers in Plant Science, Feb 7, 2022

Plants, Aug 21, 2022

High temperature and water deficit are the most critical yield-limiting environmental factors for... more High temperature and water deficit are the most critical yield-limiting environmental factors for wheat in rainfed environments. It is important to understand the heat avoidance mechanisms and their associations with leaf morpho-physiological traits that allow crops to stay cool and retain high biomass under warm and dry conditions. We examined 20 morpho-physiologically diverse wheat genotypes under ambient and elevated temperatures (T air ) to investigate whether increased water use leads to high biomass retention due to increased leaf cooling. An experiment was conducted under well-watered conditions in two partially controlled glasshouses. We measured plant transpiration (T r ), leaf temperature (T leaf ), vapor pressure deficit (VPD), and associated leaf morpho-physiological characteristics. High water use and leaf cooling increased biomass retention under high temperatures, but increased use did not always increase biomass retention. Some genotypes maintained biomass, irrespective of water use, possibly through mechanisms other than leaf cooling, indicating their adaptation under water shortage. Genotypic differences in leaf cooling capacity did not always correlate with T r (VPD) response. In summary, the contribution of high water use or the leaf cooling effect on biomass retention under high temperature is genotype-dependent and possibly due to variations in leaf morpho-physiological traits. These findings are useful for breeding programs to develop climate resilient wheat cultivars.

Annual ryegrass (Lolium rigidum) reduces the uptake and utilisation of fertiliser-nitrogen by wheat

Australian Journal of Agricultural Research, 2001

The effect of timing of annual ryegrass (Lolium rigidum) emergence on the uptake and utilisation ... more The effect of timing of annual ryegrass (Lolium rigidum) emergence on the uptake and utilisation of N by wheat was investigated in a field trial on a duplex soil at Katanning, Western Australia, and in a glasshouse study in which 15N-fertiliser was applied. Three treatments were used to investigate the effect of timing of annual ryegrass emergence on the uptake and utilisation of N by wheat: simultaneous sowing of wheat and annual ryegrass, sowing of annual ryegrass 1 week before wheat, and sowing of the annual ryegrass 1 week after wheat. A control treatment, consisting of wheat sown alone, was also included. Plant densities during the field trial were 105 and 140 plants/m2 for wheat and annual ryegrass, respectively, whereas in the glasshouse they were 105 plants/m2 for wheat and 155 plants/m2 for annual ryegrass. Fertiliser-N was applied at seeding of wheat at 50 kg N/ha in the field trial and 60 kg N/ha in the glasshouse. The introduction of annual ryegrass into the wheat system...

Adaptation of Plants to Water-Limited Mediterranean Environments

ABSTRACT

Water relations, gas exchange, nodulation, nitrogen fixation and growth of faba bean (Vicia faba L.) in relation to the drying of surface roots

Adapting wheat germplasm for elevated CO2 and higher temperatures–environment characterisation, trait screening and crop modelling

Functional Plant Biology, 2012

An assay system that provides rapid and reproducible germination under low soil water content (&l... more An assay system that provides rapid and reproducible germination under low soil water content (<10% water holding capacity (WHC)) was developed and used to compare how chickpea (Cicer arietinum L.) genotypes complete germination, without the technical difficulties of accurately controlling water levels. The system consisted of small plastic containers (50 mm × 50 mm × 60 mm) filled with river sand and tightly closed (but not sealed) to minimise water loss and maintain constant soil water content during germination. Seed size influenced germination performance at low WHC. Small seeds within a single genotype germinated successfully and entered into the early stages of seedling growth, but germination of large seeds was inhibited, failing to germinate at 5% WHC. Small seeds were more efficient in remobilising seed reserves to seedling tissues than larger seeds. Under optimal WHC, the germination rate and subsequent radicle growth was similar among genotypes but at low WHC, there wa...

Elevated CO2 will affect water use efficiency of wheat cultivars differently

ABSTRACT

European Journal of Agronomy, Mar 1, 2021

Large distribution of roots in topsoil layers allow more uptake of soil water and nutrients durin... more Large distribution of roots in topsoil layers allow more uptake of soil water and nutrients during the vegetative growth, but it may be disadvantageous if soil water deficits develops during the reproductive stage. The relationship between the distribution of roots in the topsoil (0-0.4 m) and soil water use, dry matter and N accumulations, and grain yield was examined in winter wheat (Triticum aestivum L.) with contrasting root size in the topsoil. Two old landraces (CW134 and JM47, larger root length and biomass in the topsoil) and two modern wheat cultivars (CH58 and LH7, smaller root system size in the topsoil), were grown in the field during two seasons (2016-2017 and 2017-2018) under rainfed and irrigation conditions in the semi-arid Loess Plateau of China. Root biomass and root length density (RLD) in topsoil (0-0.4 m) was significantly higher in old landraces than in modern cultivars (P < 0.05) under rainfed and irrigation and in both seasons (no such difference in subsoil, 0.4-1.0 m). The modern cultivars had significantly higher grain yield, grain N concentration, WUE, and 1000grain weight (P< 0.05). Seasonal water use was similar among all cultivars, but post-anthesis water use was higher in the modern cultivars, particularly under rainfed conditions in both seasons. Root biomass and RLD in the topsoil was positively correlated with pre-anthesis water use, but negatively correlated with soil water use after anthesis. Post-anthesis water use was closely related to post-anthesis dry matter and N accumulation, post-anthesis dry matter had a strong positive effect on yield and WUE, and post-anthesis N accumulation had a positive effect on grain N concentration under rainfed conditions. To conclude, large distribution of roots in the topsoil had non-advantage for wheat grown under rainfed conditions. The small distribution of roots in the topsoil (characteristics of modern wheat cultivars) enhanced post-anthesis water use, increased post-anthesis dry matter and N accumulation and hence attained higher grain yield and grain N when grown in the semi-arid environment.

Agronomy, Oct 5, 2019

Understanding the changes in phenotype resulting from the selection pressure and agronomic adapta... more Understanding the changes in phenotype resulting from the selection pressure and agronomic adaptation of grain yield provide an indication of the pathways for future increases in grain yield. Six dry land representative winter wheat cultivars (Triticum aestivum L.) released from 1942 to 2004 in the Loess Plateau of China were investigated to determine how the yield components of winter wheat were associated with grain yield at the Changwu Agricultural Research Station during the 2011-2012 and 2012-2013 seasons, using a completely randomized block design with three replicates. Plant height, aboveground biomass, grain yield, and yield components were measured, together with the traits of superior and inferior grains and the pre-anthesis stored dry matter remobilized to the grain was determined. In the relatively wet 2011-2012 season, there was a significant increase in grain yield and aboveground biomass with the year of release, but not in the dry 2012-2013 season. The harvest index (HI) and average grain weight (AGW) increased significantly with the year of release in both cropping seasons. HI and AGW are likely potential traits for improving grain yield of winter wheat in the Loess Plateau. The increase in HI mainly resulted from the decrease in plant height, and the increase in the use of pre-anthesis stored assimilates for grain filling. The increase in AGW mainly resulted from the increase in the proportion of superior grain (SG) and the decrease in the proportion of inferior grain (IG) in the whole spike in both cropping seasons. Depending on the climatic conditions, the different winter wheat cultivars showed different ability to use pre-anthesis stored assimilates. Modern wheat cultivars had higher yield under different rainfall conditions, and high ability to use pre-anthesis stored assimilates to fill the grain than earlier released cultivars. Both, the increase in sink capacity and source availability, should be considered as a strategy for increasing future grain yield in Loess Plateau of China.

How How molecular molecular nutraceutics nutraceutics does does help in help in understanding und... more How How molecular molecular nutraceutics nutraceutics does does help in help in understanding understanding lupin lupin seed seed protein protein role role Case Case-studies studies of of selected selected white white lupin lupin seed seed proteins proteins Concluding Concluding remarks remarks Summary of Summary of Lupinus Lupinus albus albus conglutins conglutins ' ' main main features features Congl. Protein family % of total globulin Native protein Monomer composition Protein function in the seed M r , kDa pI Quaternary structure Subunit name M r , kDa pI Glycosylat ion α 11S legumin 35-37 330-430