Karen Harris-Shultz - Academia.edu (original) (raw)

Papers by Karen Harris-Shultz

Golfers and golf course superintendents expect a lot from their putting greens. They want fine, l... more Golfers and golf course superintendents expect a lot from their putting greens. They want fine, lush, carpetlike surfaces that a ball will roll smoothly across. They also want a grass that tolerates frequent low mowing, has uniform color and texture, tolerates pests and cold temperatures, and offers a dense canopy that shades out weeds to minimize the need for herbicides. Southern putting greens are made up of single cultivars of bermudagrass, but golf course superintendents have complained for years about the appearance of nonuniform plants, or “off-types,” that can throw off the green’s appearance and “playability.” The bermudagrass cultivar Tifgreen, released in 1956, launched the era of high-quality, vegetatively propagated turfgrasses, but has also led to problems with the appearance of off-types on putting greens. Off-types can be caused by bermudagrass weeds or mutation of the cultivar. Mowing as well as birds and other natural phenomena increase the risk of weeds appearing o...

Crop Protection, 2021

Abstract In the U.S. since 2013, the sugarcane aphid is a perennial pest to all types of sorghum.... more Abstract In the U.S. since 2013, the sugarcane aphid is a perennial pest to all types of sorghum. Rating sugarcane aphid population density, plant damage, and other traits in sorghum requires a large amount of labor and ratings, especially damage ratings, may vary by evaluator. Thus Unmanned Aerial Systems (UAS)–based imagery may be exceedingly useful to more accurately quantify the effects on sorghum caused by sugarcane aphids. This study quantified the dynamic nature of sugarcane aphid infestations on silage sorghum varieties using UAS-based imagery data, and demonstrated the UAS-based measurements correlated to ground measurements. Two UAS platforms equipped with RGB (red, green, and blue) and multispectral cameras respectively were used to evaluate the silage sorghum variety trials during the growing seasons of 2019 and 2020. For the purpose of high throughput phenotyping in sorghum breeding, a new workflow scheme was developed including UAS image processing, raster calculation, DTM (digital terrain model) and CHM (canopy height model) generation, image extraction of sorghum plants, and tabular dataset generation from zonal statistics for further statistical analyses. Ground-based measurements included aphid sampling, aphid damage ratings, plant height, and biomass yields. The normalized difference red edge index (NDRE) and canopy cover collected by the UAS showed negative linear relationship with aphid damage ratings in both trials (R2 = 0.55 – 0.64). In addition to assessing spatial differences among the varieties in 2019, temporal change in both NDRE and canopy cover from the baseline sampling date in 2020 better estimated aphid damage, R2 of 0.68 and 0.79 respectively, than using the spatial difference of NDRE (R2 = 0.55) and canopy cover (R2 = 0.57) before harvest. Plant height (R2 = 0.84, Root-Mean-Square Error (RMSE) = 0.16 m) can be estimated with efficiency and precision using UAS-derived measurements during high throughput phenotyping of sorghum. Fresh yield estimates for the primary harvests were consistent in both years, but green yield estimates differed among harvests and need to be improved. Future development of UAS-based high throughput phenotyping would benefit from increased temporal resolutions of growth parameters and vegetation indices throughout a growing season.

Insects

Melanaphis sorghi (Hemiptera: Aphididae), are an economically important pest to sorghum in the Am... more Melanaphis sorghi (Hemiptera: Aphididae), are an economically important pest to sorghum in the Americas. Previous studies have found that a super-clone that belongs to multilocus lineage (MLL)-F predominated in the U.S. from 2013 to 2018 and uses multiple hosts besides sorghum. In contrast, previous studies found that aphids in South America belong to MLL-C, but these studies only examined aphids collected from sugarcane. In this study we sought to determine if the superclone persisted in the U.S. in 2019–2020 and to determine the MLL of aphids found on sorghum in the largest country in South America, Brazil. Melanaphis spp. samples (121) were collected from the U.S. in 2019–2020 and Brazil in 2020 and were genotyped with 8–9 Melanaphis spp. microsatellite markers. Genotyping results showed that all samples from the U.S. in 2019 and Brazil in 2020 had alleles identical to the predominant superclone. Of the 52 samples collected in the U.S. in 2020, 50 samples were identical to the pr...

Journal of Plant Registrations

International Turfgrass Society Research Journal, 2021

Many efforts in the USA have focused on turfgrass tolerances to drought imposition as means to re... more Many efforts in the USA have focused on turfgrass tolerances to drought imposition as means to reduce their need for irrigation. As part of this effort, our research groups have subjected multiple species and varieties to drought and collected transcript expression profiles of genes that were differentially expressed under stress and control conditions. We generated lists of transcripts and gene families differentially expressed in Kentucky bluegrass, perennial ryegrass, and creeping bentgrass; and we compared each species' differentially expressed transcript set across all three species. The gene families with differentially expressed transcript isoforms in each species and across all three species were annotated and characterized. By examining these datasets, we found key genetic mechanisms by which these species respond to drought stress. Specific genes, such as ABA responsive LEA homologs, show their crucial nature upon drought stress in all three species. Other gene families, such as E3 ubiquitin ligases, exhibited different gene family members in each species and highlight the species-specific responses to drought.

structure of peanut cultivars and breeding lines

Australian Cynodon germplasm has not been comprehensively exploited for bermudagrass improvement.... more Australian Cynodon germplasm has not been comprehensively exploited for bermudagrass improvement. In this paper we will describe ‘EcoTurf’ a four year (2007-2011) project to develop water and nutrient use efficient bermudagrasses from Australian biodiversity. We describe the sampling strategies of Australian biodiversity, the physiological and molecular tools used to characterise the collected germplasm of over 1000 ecotypes and detail some of the important outcomes.

The sugarcane aphid (Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae)) has become a serious p... more The sugarcane aphid (Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae)) has become a serious pest of sorghum (Sorghum bicolor (L.) Moench) in the United States since it was detected in 2013. The sugarcane aphid was considered only a pest of sugarcane in Florida and Louisiana for over three decades before the 2013 outbreak. Recent studies suggest that the 2013 outbreak in sorghum was due to the introduction of a new genotype. Our scope for this study was to quantify phenotypic behaviors (host suitability as measured through life table statistics) and genetic diversity among sugarcane aphid clones collected from different hosts. We collected sugarcane aphid clones from sorghum (SoSCA), sugarcane (SuSCA), and Columbus grass (CoSCA) and determined biodemographic data and host suitability when offered five different hosts plants including, sugarcane, Columbus grass, Johnsongrass, and a resistant and susceptible grain sorghum. Sugarcane aphid clones collected from different hosts varie...

Trends in Entomology, 2019

Introductions of greenbug [Schizaphis graminum (Rondani)], Russian wheat aphid [Diuraphis noxia, ... more Introductions of greenbug [Schizaphis graminum (Rondani)], Russian wheat aphid [Diuraphis noxia, (Mordvilko)], and sugarcane aphid [Melanaphis sacchari (Zehntner)] into the U.S. has disrupted the production of barley (Hordeum vulgare L.), sorghum [Sorghum bicolor (L.) Moench], wheat (Triticum spp. L.) and other small grain crops and has caused great economic losses. In this review article, information is given about each cereal aphid, its biotypic variation, genetic variability, as well as its management. Although multiple biotypes have been identified for the greenbug, Russian wheat aphid, and sugarcane aphid, a limited number of biotypes are of agronomic importance. For the greenbug and Russian wheat aphid, the aphid biotypes of agronomic importance are highly genetically similar. The sugarcane aphid biotype that has spread on sorghum and Johnsongrass [S. halepense (L.) Pers.] in all sorghum-growing regions is largely one 'super-clone'. Lessons learned from the past invasions of the greenbug and Russian wheat aphid directly apply to the current sugarcane aphid outbreak. The use of insecticides with multiple modes of action and the use of sorghum hybrids with multiple resistance genes may delay or prevent new sugarcane aphid biotypes from developing. Lastly since the use of classical biological control for management of the greenbug and Russian wheat aphid outbreaks had limited success, classical biological control is not recommended for the management of sugarcane aphids.

Journal of Entomological Science

We surveyed the occurrence of bees and wasps (Hymenoptera) in nine centipedegrass lawns in centra... more We surveyed the occurrence of bees and wasps (Hymenoptera) in nine centipedegrass lawns in central and south Georgia in 2019 that had no prior exposure to insecticides. In each lawn, an area of 9.3 m2 was marked and not mowed while the remainder of the lawn area was mowed regularly. When each centipedegrass lawn reached anthesis, pan traps filled with soapy water were placed in nonmowed and mowed areas of each lawn. After 3 d, trap contents were collected and transported to the laboratory for insect sorting and identification. Each lawn site was sampled 3–5 times. Of 173 total bees collected from the centipedegrass lawns, 79.2% were Lasioglossum spp. followed by 6.9% Halictus and 4% Melissodes. Only four Bombus spp. were collected, while other bees collected were Augochlorella spp., Agapostemon spp., Megachile, Apis, Peponapis, Ceratina, Ptilothrix, Svastra, and Nomia spp. Most of the Lasioglossum spp. were collected in August (48.6%) and September (26.6%). Lasioglossum spp. were sa...

Environmental and Experimental Botany

Abstract For the cool-season turfgrass Kentucky bluegrass, improving germplasm for drought tolera... more Abstract For the cool-season turfgrass Kentucky bluegrass, improving germplasm for drought tolerance is an increasingly important priority. Although genetic mechanisms behind drought tolerance have been characterized for model and agronomic plant species, the critical genes, gene families, and transcript isoforms important in Kentucky bluegrass are unclear. Using an RNAseq approach across three germplasm sources that differ in their regrowth, relative water content, and turf quality under drought stress, we have identified transcript isoforms exhibiting a shared response of all three germplasm sources to drought stress and transcript isoforms exhibiting a tolerance response where the more drought-tolerant germplasm sources exhibited higher transcript differences compared to the drought-susceptible cultivar Midnight. Annotation and transcript profile groupings both identified abundant chaperone gene families with protein folding and protective functions, such as heat shock proteins, DNAj, and late embryogenesis abundant genes. Transcript isoforms within these gene families were tolerance related and known to respond to abscisic acid. Two dehydrin genes, RAB15 and HVA1, were induced in several more drought-tolerant germplasm sources and show promise as candidate genes for selection.

Since 2013, the sugarcane aphid (SCA), Melanaphis sacchari (Zehntner), has been a serious pest th... more Since 2013, the sugarcane aphid (SCA), Melanaphis sacchari (Zehntner), has been a serious pest that hampers all types of sorghum production in the U.S. Our understanding of sugarcane aphid resistance in sorghum is limited to knowledge about a few genetic regions on chromosome SBI-06. In this study, a subset of the Sorghum Association Panel (SAP) was used along with some additional lines to identify genetic and genomic regions that confer sugarcane aphid resistance. SAP lines were grown in the field and visually evaluated for SCA resistance during the growing seasons of 2019 and 2020 in Tifton, GA. In 2020, the SAP accessions were also evaluated for SCA resistance in the field using drone-based high throughput phenotyping (HTP) and visual scoring under greenhouse conditions. Plant height and flowering time were also recorded in the field to confirm that our methods were sufficient for identifying known quantitative trait loci (QTL). This study combined phenotypic data from field-base...

Journal of the American Society for Horticultural Science

Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses affecting w... more Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses affecting watermelon [Citrullus lanatus (Thunb.) Matsun & Nakai var. lanatus] in the United States. The ZYMV-Florida strain (ZYMV-FL) is considered a major limitation to commercial watermelon production in the United States. Inheritance of resistance to ZYMV-FL is conferred by a recessive gene. This report describes the identification of single-reaction, polymerase chain reaction-based markers linked to the ZYMV-FL resistance gene in watermelon. In this study, we identified a marker ZYMV-resistant polymorphism (ZYRP) linked to the ZYMV-FL resistance gene locus (genetic distance of 8 cM) in an F2 population, and in a backcross one to the resistant parent population (BC1R) (genetic distance of 13 cM). The identification of a single nucleotide polymorphism within the ZYRP marker for the parental genotypes allowed the development of a sequence-characterized amplification region marker linked to the ZYM...

Journal of the American Society for Horticultural Science

In this study, we report a simple procedure for developing and using new types of polymerase chai... more In this study, we report a simple procedure for developing and using new types of polymerase chain reaction (PCR) primers, named “high-frequency oligonucleotides–targeting active genes” (HFO-TAG). The HFO-TAG primers were constructed by first using a “practical extraction and report language” script to identify oligonucleotides (8, 9, and 10 bases) that exist in high frequency in 4700 expressed sequence tag (EST)-unigenes of watermelon (Citrullus lanatus) fruit. This computer-based screening yielded 3162 oligonucleotides that exist 32 to 335 times in the 4700 EST-unigenes. Of these, 192 HFO-TAG primers (found 51 to 269 times in the 4700 EST-unigenes) were used to amplify genomic DNA of four closely related watermelon cultivars (Allsweet, Crimson Sweet, Charleston Gray, and Dixielee). The average number of DNA fragments produced by a single HFO-TAG primer among these four watermelon cultivars was considerably higher (an average of 5.74 bands per primer) than the number of fragments p...

Journal of the American Society for Horticultural Science

Genetic linkage maps of bermudagrass (Cynodon spp.) species using 118 triploid individuals derive... more Genetic linkage maps of bermudagrass (Cynodon spp.) species using 118 triploid individuals derived from a cross of T89 [C. dactylon (2n = 4x = 36)] and T574 [C. transvaalensis (2n = 2x = 18)] were enriched with expressed sequence tags-derived simple sequence repeat (EST-SSR) markers. Primers were developed from 53 ESTs containing SSRs producing 75 segregating markers from which 28 could be mapped to the T89 and T574 genetic maps. With the addition of previously generated marker data, 26 T89 linkage groups and eight T574 linkage groups were formed using a log-of-odds (LOD) value of 4.0. The T89 and T574 linkage maps spanned 1055 cM and 311.1 cM and include 125 and 36 single-dose amplified fragments (SDAFs), respectively. Many of the SDAFs displayed disomic segregation and thus T89 may be a segmental allotetraploid or an allotetraploid. The additional EST-SSR markers add value to the maps by increasing marker density and provide markers that can be easily transferred to other bermudag...

Golfers and golf course superintendents expect a lot from their putting greens. They want fine, l... more Golfers and golf course superintendents expect a lot from their putting greens. They want fine, lush, carpetlike surfaces that a ball will roll smoothly across. They also want a grass that tolerates frequent low mowing, has uniform color and texture, tolerates pests and cold temperatures, and offers a dense canopy that shades out weeds to minimize the need for herbicides. Southern putting greens are made up of single cultivars of bermudagrass, but golf course superintendents have complained for years about the appearance of nonuniform plants, or “off-types,” that can throw off the green’s appearance and “playability.” The bermudagrass cultivar Tifgreen, released in 1956, launched the era of high-quality, vegetatively propagated turfgrasses, but has also led to problems with the appearance of off-types on putting greens. Off-types can be caused by bermudagrass weeds or mutation of the cultivar. Mowing as well as birds and other natural phenomena increase the risk of weeds appearing o...

Crop Protection, 2021

Abstract In the U.S. since 2013, the sugarcane aphid is a perennial pest to all types of sorghum.... more Abstract In the U.S. since 2013, the sugarcane aphid is a perennial pest to all types of sorghum. Rating sugarcane aphid population density, plant damage, and other traits in sorghum requires a large amount of labor and ratings, especially damage ratings, may vary by evaluator. Thus Unmanned Aerial Systems (UAS)–based imagery may be exceedingly useful to more accurately quantify the effects on sorghum caused by sugarcane aphids. This study quantified the dynamic nature of sugarcane aphid infestations on silage sorghum varieties using UAS-based imagery data, and demonstrated the UAS-based measurements correlated to ground measurements. Two UAS platforms equipped with RGB (red, green, and blue) and multispectral cameras respectively were used to evaluate the silage sorghum variety trials during the growing seasons of 2019 and 2020. For the purpose of high throughput phenotyping in sorghum breeding, a new workflow scheme was developed including UAS image processing, raster calculation, DTM (digital terrain model) and CHM (canopy height model) generation, image extraction of sorghum plants, and tabular dataset generation from zonal statistics for further statistical analyses. Ground-based measurements included aphid sampling, aphid damage ratings, plant height, and biomass yields. The normalized difference red edge index (NDRE) and canopy cover collected by the UAS showed negative linear relationship with aphid damage ratings in both trials (R2 = 0.55 – 0.64). In addition to assessing spatial differences among the varieties in 2019, temporal change in both NDRE and canopy cover from the baseline sampling date in 2020 better estimated aphid damage, R2 of 0.68 and 0.79 respectively, than using the spatial difference of NDRE (R2 = 0.55) and canopy cover (R2 = 0.57) before harvest. Plant height (R2 = 0.84, Root-Mean-Square Error (RMSE) = 0.16 m) can be estimated with efficiency and precision using UAS-derived measurements during high throughput phenotyping of sorghum. Fresh yield estimates for the primary harvests were consistent in both years, but green yield estimates differed among harvests and need to be improved. Future development of UAS-based high throughput phenotyping would benefit from increased temporal resolutions of growth parameters and vegetation indices throughout a growing season.

Insects

Melanaphis sorghi (Hemiptera: Aphididae), are an economically important pest to sorghum in the Am... more Melanaphis sorghi (Hemiptera: Aphididae), are an economically important pest to sorghum in the Americas. Previous studies have found that a super-clone that belongs to multilocus lineage (MLL)-F predominated in the U.S. from 2013 to 2018 and uses multiple hosts besides sorghum. In contrast, previous studies found that aphids in South America belong to MLL-C, but these studies only examined aphids collected from sugarcane. In this study we sought to determine if the superclone persisted in the U.S. in 2019–2020 and to determine the MLL of aphids found on sorghum in the largest country in South America, Brazil. Melanaphis spp. samples (121) were collected from the U.S. in 2019–2020 and Brazil in 2020 and were genotyped with 8–9 Melanaphis spp. microsatellite markers. Genotyping results showed that all samples from the U.S. in 2019 and Brazil in 2020 had alleles identical to the predominant superclone. Of the 52 samples collected in the U.S. in 2020, 50 samples were identical to the pr...

Journal of Plant Registrations

International Turfgrass Society Research Journal, 2021

Many efforts in the USA have focused on turfgrass tolerances to drought imposition as means to re... more Many efforts in the USA have focused on turfgrass tolerances to drought imposition as means to reduce their need for irrigation. As part of this effort, our research groups have subjected multiple species and varieties to drought and collected transcript expression profiles of genes that were differentially expressed under stress and control conditions. We generated lists of transcripts and gene families differentially expressed in Kentucky bluegrass, perennial ryegrass, and creeping bentgrass; and we compared each species' differentially expressed transcript set across all three species. The gene families with differentially expressed transcript isoforms in each species and across all three species were annotated and characterized. By examining these datasets, we found key genetic mechanisms by which these species respond to drought stress. Specific genes, such as ABA responsive LEA homologs, show their crucial nature upon drought stress in all three species. Other gene families, such as E3 ubiquitin ligases, exhibited different gene family members in each species and highlight the species-specific responses to drought.

structure of peanut cultivars and breeding lines

Australian Cynodon germplasm has not been comprehensively exploited for bermudagrass improvement.... more Australian Cynodon germplasm has not been comprehensively exploited for bermudagrass improvement. In this paper we will describe ‘EcoTurf’ a four year (2007-2011) project to develop water and nutrient use efficient bermudagrasses from Australian biodiversity. We describe the sampling strategies of Australian biodiversity, the physiological and molecular tools used to characterise the collected germplasm of over 1000 ecotypes and detail some of the important outcomes.

The sugarcane aphid (Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae)) has become a serious p... more The sugarcane aphid (Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae)) has become a serious pest of sorghum (Sorghum bicolor (L.) Moench) in the United States since it was detected in 2013. The sugarcane aphid was considered only a pest of sugarcane in Florida and Louisiana for over three decades before the 2013 outbreak. Recent studies suggest that the 2013 outbreak in sorghum was due to the introduction of a new genotype. Our scope for this study was to quantify phenotypic behaviors (host suitability as measured through life table statistics) and genetic diversity among sugarcane aphid clones collected from different hosts. We collected sugarcane aphid clones from sorghum (SoSCA), sugarcane (SuSCA), and Columbus grass (CoSCA) and determined biodemographic data and host suitability when offered five different hosts plants including, sugarcane, Columbus grass, Johnsongrass, and a resistant and susceptible grain sorghum. Sugarcane aphid clones collected from different hosts varie...

Trends in Entomology, 2019

Introductions of greenbug [Schizaphis graminum (Rondani)], Russian wheat aphid [Diuraphis noxia, ... more Introductions of greenbug [Schizaphis graminum (Rondani)], Russian wheat aphid [Diuraphis noxia, (Mordvilko)], and sugarcane aphid [Melanaphis sacchari (Zehntner)] into the U.S. has disrupted the production of barley (Hordeum vulgare L.), sorghum [Sorghum bicolor (L.) Moench], wheat (Triticum spp. L.) and other small grain crops and has caused great economic losses. In this review article, information is given about each cereal aphid, its biotypic variation, genetic variability, as well as its management. Although multiple biotypes have been identified for the greenbug, Russian wheat aphid, and sugarcane aphid, a limited number of biotypes are of agronomic importance. For the greenbug and Russian wheat aphid, the aphid biotypes of agronomic importance are highly genetically similar. The sugarcane aphid biotype that has spread on sorghum and Johnsongrass [S. halepense (L.) Pers.] in all sorghum-growing regions is largely one 'super-clone'. Lessons learned from the past invasions of the greenbug and Russian wheat aphid directly apply to the current sugarcane aphid outbreak. The use of insecticides with multiple modes of action and the use of sorghum hybrids with multiple resistance genes may delay or prevent new sugarcane aphid biotypes from developing. Lastly since the use of classical biological control for management of the greenbug and Russian wheat aphid outbreaks had limited success, classical biological control is not recommended for the management of sugarcane aphids.

Journal of Entomological Science

We surveyed the occurrence of bees and wasps (Hymenoptera) in nine centipedegrass lawns in centra... more We surveyed the occurrence of bees and wasps (Hymenoptera) in nine centipedegrass lawns in central and south Georgia in 2019 that had no prior exposure to insecticides. In each lawn, an area of 9.3 m2 was marked and not mowed while the remainder of the lawn area was mowed regularly. When each centipedegrass lawn reached anthesis, pan traps filled with soapy water were placed in nonmowed and mowed areas of each lawn. After 3 d, trap contents were collected and transported to the laboratory for insect sorting and identification. Each lawn site was sampled 3–5 times. Of 173 total bees collected from the centipedegrass lawns, 79.2% were Lasioglossum spp. followed by 6.9% Halictus and 4% Melissodes. Only four Bombus spp. were collected, while other bees collected were Augochlorella spp., Agapostemon spp., Megachile, Apis, Peponapis, Ceratina, Ptilothrix, Svastra, and Nomia spp. Most of the Lasioglossum spp. were collected in August (48.6%) and September (26.6%). Lasioglossum spp. were sa...

Environmental and Experimental Botany

Abstract For the cool-season turfgrass Kentucky bluegrass, improving germplasm for drought tolera... more Abstract For the cool-season turfgrass Kentucky bluegrass, improving germplasm for drought tolerance is an increasingly important priority. Although genetic mechanisms behind drought tolerance have been characterized for model and agronomic plant species, the critical genes, gene families, and transcript isoforms important in Kentucky bluegrass are unclear. Using an RNAseq approach across three germplasm sources that differ in their regrowth, relative water content, and turf quality under drought stress, we have identified transcript isoforms exhibiting a shared response of all three germplasm sources to drought stress and transcript isoforms exhibiting a tolerance response where the more drought-tolerant germplasm sources exhibited higher transcript differences compared to the drought-susceptible cultivar Midnight. Annotation and transcript profile groupings both identified abundant chaperone gene families with protein folding and protective functions, such as heat shock proteins, DNAj, and late embryogenesis abundant genes. Transcript isoforms within these gene families were tolerance related and known to respond to abscisic acid. Two dehydrin genes, RAB15 and HVA1, were induced in several more drought-tolerant germplasm sources and show promise as candidate genes for selection.

Since 2013, the sugarcane aphid (SCA), Melanaphis sacchari (Zehntner), has been a serious pest th... more Since 2013, the sugarcane aphid (SCA), Melanaphis sacchari (Zehntner), has been a serious pest that hampers all types of sorghum production in the U.S. Our understanding of sugarcane aphid resistance in sorghum is limited to knowledge about a few genetic regions on chromosome SBI-06. In this study, a subset of the Sorghum Association Panel (SAP) was used along with some additional lines to identify genetic and genomic regions that confer sugarcane aphid resistance. SAP lines were grown in the field and visually evaluated for SCA resistance during the growing seasons of 2019 and 2020 in Tifton, GA. In 2020, the SAP accessions were also evaluated for SCA resistance in the field using drone-based high throughput phenotyping (HTP) and visual scoring under greenhouse conditions. Plant height and flowering time were also recorded in the field to confirm that our methods were sufficient for identifying known quantitative trait loci (QTL). This study combined phenotypic data from field-base...

Journal of the American Society for Horticultural Science

Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses affecting w... more Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses affecting watermelon [Citrullus lanatus (Thunb.) Matsun & Nakai var. lanatus] in the United States. The ZYMV-Florida strain (ZYMV-FL) is considered a major limitation to commercial watermelon production in the United States. Inheritance of resistance to ZYMV-FL is conferred by a recessive gene. This report describes the identification of single-reaction, polymerase chain reaction-based markers linked to the ZYMV-FL resistance gene in watermelon. In this study, we identified a marker ZYMV-resistant polymorphism (ZYRP) linked to the ZYMV-FL resistance gene locus (genetic distance of 8 cM) in an F2 population, and in a backcross one to the resistant parent population (BC1R) (genetic distance of 13 cM). The identification of a single nucleotide polymorphism within the ZYRP marker for the parental genotypes allowed the development of a sequence-characterized amplification region marker linked to the ZYM...

Journal of the American Society for Horticultural Science

In this study, we report a simple procedure for developing and using new types of polymerase chai... more In this study, we report a simple procedure for developing and using new types of polymerase chain reaction (PCR) primers, named “high-frequency oligonucleotides–targeting active genes” (HFO-TAG). The HFO-TAG primers were constructed by first using a “practical extraction and report language” script to identify oligonucleotides (8, 9, and 10 bases) that exist in high frequency in 4700 expressed sequence tag (EST)-unigenes of watermelon (Citrullus lanatus) fruit. This computer-based screening yielded 3162 oligonucleotides that exist 32 to 335 times in the 4700 EST-unigenes. Of these, 192 HFO-TAG primers (found 51 to 269 times in the 4700 EST-unigenes) were used to amplify genomic DNA of four closely related watermelon cultivars (Allsweet, Crimson Sweet, Charleston Gray, and Dixielee). The average number of DNA fragments produced by a single HFO-TAG primer among these four watermelon cultivars was considerably higher (an average of 5.74 bands per primer) than the number of fragments p...

Journal of the American Society for Horticultural Science

Genetic linkage maps of bermudagrass (Cynodon spp.) species using 118 triploid individuals derive... more Genetic linkage maps of bermudagrass (Cynodon spp.) species using 118 triploid individuals derived from a cross of T89 [C. dactylon (2n = 4x = 36)] and T574 [C. transvaalensis (2n = 2x = 18)] were enriched with expressed sequence tags-derived simple sequence repeat (EST-SSR) markers. Primers were developed from 53 ESTs containing SSRs producing 75 segregating markers from which 28 could be mapped to the T89 and T574 genetic maps. With the addition of previously generated marker data, 26 T89 linkage groups and eight T574 linkage groups were formed using a log-of-odds (LOD) value of 4.0. The T89 and T574 linkage maps spanned 1055 cM and 311.1 cM and include 125 and 36 single-dose amplified fragments (SDAFs), respectively. Many of the SDAFs displayed disomic segregation and thus T89 may be a segmental allotetraploid or an allotetraploid. The additional EST-SSR markers add value to the maps by increasing marker density and provide markers that can be easily transferred to other bermudag...