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Tomato (Lycopersicon esculentum Mill.) genotypes evaluated for early blight [Alternaria solani (Ellis & Martin) Jones and Grout] resistance included five tolerant breeding lines, a susceptible cultivar, and seven hybrids among them. Three of the genotypes (`Castlejay', NC EBR-2, and 87B187) were crossed in a diallel mating design to estimate general combining ability and specific combining ability for the resistance trait. Parental, F1, F2, and backcross generations of the family Cl943 x `Castlejay' were evaluated for resistance and included in generation mean analysis. Hybrid means for area under the disease progress curve were not significantly different from respective midparent values, indicating additive genetic control. Diallel and generation mean analyses also detected significant additive genetic effects. Epistasis was present in the Cl943 × `Castlejay' family.

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Heritability of resistance to early blight disease in potatoes (Solarium tuberosum L.) incited by Alternaria solani (En. & Martin) Ser. was estimated in tetraploid × diploid crosses. Susceptible tetraploid cultivars and breeding lines were the female parents. Diploids that produced a high proportion of first-division restitution (FDR) gametes and possessed different levels of early blight resistance were the male parents. Tubers from seedlings that resulted from the tetraploid × diploid crosses were planted in a field and artificially inoculated with spores of Alternaria solani. Resistance was measured as the slope (r) of the regression of the logit of the percent defoliation of each plant vs. time. Higher r values indicated lower resistance. Mean r values ranged from 0.123 to 0.157 for the tetraploid parents, and from 0.054 to 0.116 for the diploid parents. Mean r values for the tetraploid × diploid crosses were intermediate, ranging from 0.077 to 0.143. Narrow-sense heritability (h2) was 0.815. The partial correlation coefficient between r and mean maturity values was – 0.2086.

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The use of mulches in vegetable production is undergoing a radical change away from high-input, nonrenewable resources, such as plastic, to the use of high-residue organic mulches from cover crops. The purpose of this study was to compare the marketable yield of various fresh-market tomato genotypes when grown under plastic and hairy vetch mulches. In 1996 and 1997, 12 fresh-market tomato genotypes were evaluated for yield on the North Farm of the Beltsville Agricultural Research Center (BARC), MD in a randomized split-plot design. Tomatoes were grown in conventional tillage plastic mulch (PM) and no-till hairy vetch mulch (HVM). Early blight, caused by Alternaria solani Sor., developed naturally in the plots both years and was recorded over time. All 12 genotypes were susceptible to early blight. Area under the disease progress curve (AUDPC) was calculated for each plot. AUDPC was similar both years. However, the year × mulch and year × mulch × genotype interactions were significant for AUDPC. Adjusting yields for AUDPC had a minimal effect on the data. Overall, yields were similar in PM and HVM both before and after adjusting for AUDPC. However, the mulch × genotype interaction was significant. The yield of eight of the genotypes was significantly higher in the HVM than in the PM system both years, ranging from 12% to 57% higher in 1996 and 10% to 48% higher in 1997. There was no yield difference for one genotype in HVM as compared to PM. The yield in the remaining three genotypes was either higher under HVM than PM or there was no difference. As yields from the HVM system are greater than or equal to yields in the PM system, soil compaction is reduced and nitrogen inputs are lower. The no-till HVM system is at least as good, and often better, than the conventional tillage PM system.

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worms ( Helicoverpa armigera Hubner), mites ( Tetranychus evansi Baker & Pritchard), and thrips ( Frankliniella occidentalis Pergande), and diseases, such as bacterial wilt ( Ralstonia solanacearum Smith), early blight ( Alternaria solani Sorauer

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Heirloom tomato cultivars Proc. Florida State Hort. Soc. 110 391 392 Vloutoglou, I. Kalogerakis, S.N. 2000 Effects of inoculum concentration, wetness duration and plant age on development of early blight ( Alternaria solani ) and on shedding of leaves in

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. infestans ) and EB caused by ( Alternaria solani ); a susceptible control cultivar susceptible to LB, EB, and SLS caused by ( Septoria lycopersici ); and segregating breeding populations derived from crosses of parent germplasm with desirable traits. We

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