Collecting isolates of Early Blight on tomato and determining ones with high virulent and evaluation of tomato germplasms
2006
Zarbakhsh, Abdoljamil | Hajiyan Far, Ramin
In order to study the agent of Early blight disease of tomato and determine isolates causing severe disease for using in evaluation of tomato germplasms, infected samples from tomato in central and southern regions of country collected and agent of disease isolated and purified in laboratory during first year.Macroscopic characters of isolates like shape,color and growth rate of colony as well as microscopic characters of them such as type of mycellium,conidiofore and conidium were studied carefully. According to the characteristics of Alternaria species mentioned in the Ellis keys the isolates belonged to two species. most of ones caused early blight disease on tomato were detected as A .alternata which produce conidia with obclavate in shape and short narrow beak.Few isolate that caused early blight disease on tomato were detected as A .tenuissima which produced conidia with ellipsoid body tapering gradually to fairly long beak. pathogenicity of first type of isolates were tested on Imperial cultivar in greenhouse and percent of blight and defoliation were determined .the result showed that isolates B-8 from Booshehr DKA-5 , DKA-10 from Desfol with means of %98.3 , %89.56 ,%87.76 disease severity respectively were the most virulent isolates on tomato.In this study the disease caused by virulent fungi responsible for Alternaria blight (DKA-5) Was evaluated in the field and greenhouse on 21 varieties and genotypes of tomato simultaneously. Progress of disease infection and disease index in the field and also percent of infected leaves , leaf blight area and disease index in the greenhouse was determined.Infection was based on artificial inoculation by SB-3 and DSF-2 isolates. Further evaluation showed that varieties and genotypes of super 2270 ,Kingstone ,Early orbano and 8402 had the least disease progress and index in the field.Syria variety showed a considerable disease spot but could produce the highest means of yield of 91.64 ton/ha. compared to other varieties and genotypes ,hence considered to be tolerant variety. Super 2270 ,Kingstone Kalgi and genotype 8403 had the least infection in the greenhouse ,where as variety Peto early CH and genotypes 8406 ,8405 ,8407 in the field and variety Imperial with the genotype 8406 in the greenhouse had the maximum infection.In both field and greenhouse experiment varieties Super 2270 ,King stone with very low infection to the disease considered as resistant , where as genotypes 8406 with maximum disease infection were considered as susceptible genotype.
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