Biology and Sources of Inoculum of Geotrichum candidum Causing Sour Rot of Peach and Nectarine Fruit in California (original) (raw)
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Plant Disease, 2012
Yaghmour, M. A., Bostock, R. M., Adaskaveg, J. E., and Michailides, T. J. 2012. Propiconazole sensitivity in populations of Geotrichum candidum, the cause of sour rot of peach and nectarine, in California. Plant Dis. 96:752-758. * The e-Xtra logo stands for "electronic extra" and indicates that a supplemental figure is included in the online edition and that Figure 1 appears in color online.
The aim of this study was to estimate yield losses induced by the agent associated with Huanglongbing, Candidatus Liberibacter asiaticus (CLas) in Persian lime (Citrus latifolia Tanaka) in Mexico, by evaluating morphological and organoleptic fruit variables. A four-year old Persian lime orchard in the state of Yucatán, Mexico, was selected; the trees were under same disease management and infection; this feature was verified by qPCR. The study was conducted under four severity levels (0=healthy, 1=25, 2=50, 3=75, 4=100, percentage of canopy with HLB symptoms). Eight morphological and organoleptic variables were evaluated in a restricted random block design with healthy and CLas infected trees. The values of weight, size, skin thickness, juice volume (JV) and pH were statistically higher in fruits from healthy trees as well as in asymptomatic branches of positive trees, in comparison with symptomatic branches (Tukey, P=0.05). CLas induced reduction on weight (17.3 %) and JV (18.6 %), with more damage in trees showing 100 % of canopy with HLB symptoms; the regression models were: Y weight = 217.2-4.2x+0.03x 2 , R 2 = 0.86; Y volume = 645.4-11.7x+0.09x 2 , R 2 = 0.82.
European Journal of Plant Pathology, 2008
Five field experiments were performed in commercial orchards located in Lleida (Spain) over three growing seasons, 2000–2002, in order to estimate the relationship between the incidence of latent infection caused by Monilinia spp. in peaches and the incidence of post-harvest brown rot. No latent infection was recorded at popcorn and the maximum incidence occurred pre-harvest; in some orchards a second peak was detected during the pit hardening period. Monilinia laxa is the most prevalent species isolated from peaches with brown rot. There was a positive correlation between the incidence of latent infection and that of post-harvest brown rot. The average incidence of latent infection during the crop season explained 55% of the total variation in the incidence of post-harvest brown rot. The effect of temperature (T) and duration of wetness (W) on the incidence of latent infection in peach and nectarine orchards was analysed using multiple regression. The regression analysis indicated that T and W jointly explained 83% of the total variation in the incidence of latent infection. The model predicts no latent infections when T 22 h wetness are required when T = 8°C but only 5 h at 25°C are necessary for latent infection to occur. The incidence of brown rot and latent infection of peaches caused by M. laxa under controlled experimental conditions were also affected by T and W, as well as by fruit maturity and inoculum concentration. Latent infections were produced in fruit when T was not suitable for the development of brown rot symptoms. In these experiments more than 4–5 h of daily wetness were required after embryo growth in fruit sprayed to run-off with an inoculum concentration higher than 104 conidia ml−1 of M. laxa for brown rot and latent infections to develop. The fitted model obtained from the field data was able to predict the observed data obtained under controlled environmental conditions.
Australasian Plant Pathology, 2017
This study assessed and optimized an in vivo method to evaluate the levels of susceptibility/resistance in fruit from the EEAD-CSIC peach germplasm to an isolate of Monilinia laxa (Aderhold & Ruhland) Honey from peach. A total of four commercial cultivars and six genotypes, descendants of three families, of peach [Prunus persica (L.) Batsch] were superficially inoculated in fruits as "uninjured inoculation fruit test". Inoculum was obtained from artificially infected peach fruit after five days of incubation under a photoperiod of 12 h supplied by fluorescent lighting system. Spores were harvested from the fruit, incubated at 20-26 o C, of 40-60 % RH, being careful to avoid contamination. Production of inoculum (conidia) was rapid and adequate using these inoculation and incubation conditions (five days at 23 o C) indicating that the M. laxa used was highly pathogenic and inoculation protocol suitable to screen the peach material and commercial cultivars. Lesion diameter and colonization extent were measured on inoculated fruits to estimate disease severity (colonization severity and lesion severity) to establish levels of
Plant Disease, 2010
Immediately following the identification of Monilinia fructicola in a Spanish peach orchard in the Ebro Valley in 2006, this orchard and two other orchards in the same valley were intensively sampled for potential tree and ground sources of primary Monilinia inoculum before and during three growing seasons between 2006 and 2008. Overwintered Monilinia spp. produced inoculum from only mycelium, and no apothecia were found in any of the three orchards over the three growing seasons. Mummies on trees were the main source of primary inoculum. More than 90% of Monilinia isolates on all fruit mummies were M. laxa. Positive relationships were found between (i) the number of mummified fruit and the incidence of postharvest brown rot (P = 0.05, r = 0.75, n = 8), and (ii) the number of mummified fruit and nonabscised aborted fruit in the trees and the number of conidia on the fruit surface (P = 0.04, r = 0.71; P = 0.01, r = 0.94, respectively, n = 8) and the incidence of latent infection (P =...
Identifying and Characterizing Summer Diseases on 'Babygold' Peach in South Carolina
Plant Health Progress, 2006
Summer diseases can cause significant yield losses in processing peach varieties, such as the ‘Babygold’ lines. In this study we identified and characterized the pathogens responsible for disease outbreaks in two orchards (PH and JC) located in the northern ‘Piedmont’ area of South Carolina. Three pathogens, Geotrichum candidum, Colletotrichum acutatum, and Botryosphaeria dothidea, the causal agents of sour rot, anthracnose, and Botryosphaeria fruit rot disease respectively, were identified on fruit from orchard PH using symptomology, culture and spore morphology, and ribosomal DNA analysis. G. candidum and C. acutatum were also isolated from symptomatic fruit from orchard JC. The QoI fungicide azoxystrobin and a mixture of pyraclostrobin and boscalid were evaluated for their in vitro efficacy against five isolates of each of the three pathogens to investigate their possible usefulness in designing management strategies. Azoxystrobin inhibited mycelial growth of C. acutatum isolates...
Microbiological Research, 2016
Sour rot is a major postharvest disease of citrus fruit and is caused by the fungal pathogen Geotrichum citri-aurantii. A lack of chemicals certified for the control of this disease has led to the consideration of alternative methods and strategies, such as the use of yeasts as biocontrol agents. The purpose of the present study was to test the ability of yeasts isolated from leaves, flowers, fruit, and soil, and six Saccharomyces cerevisiae isolates to control citrus sour rot, to assess the mechanisms of action of the yeast isolates that were demonstrated to be effective for biocontrol, and to identify the most effective yeast isolates for the biocontrol of G. citri-aurantii. In in vivo assays, three yeast isolates (ACBL-23, ACBL-44, and ACBL-77) showed a potential for controlling sour rot in citrus fruits, both preventatively and curatively. Most of the eight yeast isolates that were assessed for a mechanism of action did not produce antifungal compounds in an amount sufficient to inhibit the growth of the pathogen. Additionally, nutrient competition among the yeast strains was not found to be a biocontrol strategy. Instead, killer activity and hydrolytic enzyme production were identified as the major mechanisms involved in the biocontrol activity of the yeasts. Isolates ACBL-23, ACBL-44, and ACBL-77, which controlled sour rot most effectively, were identified as Rhodotorula minuta, Candida azyma, and Aureobasidium pullulans, respectively. To our knowledge, this is the first report of the potential of C. azyma as a biological control agent against a postharvest pathogen and its ability to produce a killer toxin.
Plant Disease, 2020
Fungi in the genus Colletotrichum cause apple, blueberry, and strawberry fruit rots, which can result in significant losses. Accurate identification is important because species differ in aggressiveness, fungicide sensitivity, and other factors affecting management. Multiple Colletotrichum species can cause similar symptoms on the same host, and more than one fruit type can be infected by a single Colletotrichum species. Mixed-fruit orchards may facilitate cross-infection, with significant management implications. Colletotrichum isolates from small fruits in Kentucky orchards were characterized and compared with apple isolates via a combination of morphotyping, sequencing of voucher loci and whole genomes, and cross-inoculation assays. Seven morphotypes representing two species complexes (C. acutatum and C. gloeosporioides) were identified. Morphotypes corresponded with phylogenetic species C. fioriniae, C. fructicola, C. nymphaeae, and C. siamense, identified by TUB2 or GAPDH barco...