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Verticillium dahliae infects over 300 cultivated plants, including strawberry. The fungus destroys vascular tissues causing drought stress resembling foliar symptoms. The outer leaves wilt and turn brown and the inner wilt but remain bluish green

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Abstract

The effects of soil fumigation with Telone C-17 on yield, petiole NO3-N levels and verticillium wilt (incited by Verticillium albo-atrum Reinke & Berth and V. dahliae Kleb.) of potatoes (Solanum tuberosum L.) grown continuously and in a 2-year rotation with corn since 1972 at 8 rates of nitrogen were studied in 1978 and 1979. Soil fumigation resulted in significant yield increases where potatoes were grown continuously. Potatoes grown in rotation responded to fumigation only in 1979. Continuous culture of potatoes resulted in reduced yields in both years. Nitrate-N levels were substantially lower in petioles from fumigated plots than in non-fumigated plots. Yield responses from fumigation and rotation were the result of reduced severity of verticillium wilt infestation. Soil fumigation and rotation had equal effects on yield and verticillium wilt, particularly in 1979.

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Abbreviations: Fol 1 and 2, Fusarium oxysporum f. sp. lycopersici races 1 and 2; Forl, Fusarium oxysporum f. sp. radicis-lycopersici; Mel, Meloidogyne incognita; TMV, tobacco mosaic virus; Verd, Verticillium dahliae. 1 Assistant Professor

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Strawberry genotypes were retained from biparental progenies previously identified as either relatively susceptible or resistant to wilt caused by Verticillium dahliae based on a phenotypic resistance score. Runner plants from these selected genotypes were inoculated with a conidial suspension containing a mixture of five isolates obtained from symptomatic strawberry plants at 106 conidia/mL, then scored for disease symptoms. Genotypes from resistant progenies had significantly higher phenotypic resistance scores (1 = severe symptoms, 5 = no detectable symptoms) than those from susceptible progenies (4.15 vs. 2.23), and there also was a correlated selection response for the percent plants severely stunted or dead (26.4 and 69.1 for resistant and susceptible selections, respectively). Comparisons of the resistance scores for selected groups with those for the original parents (2.76) indicated that selection had changed relative resistance significantly in both directions and that realized response had been 24% to 43% larger than predicted for selection in both directions. Although several of the selections from resistant progenies were highly susceptible, five of the 21 resistant selections had resistance scores outside the range of the original parents, representing possible transgressive segregants. This comparison is limited by the precision with which individual resistance scores are estimated and by the scope of the disease symptoms in this trial. Detecting genotypes with sufficient resistance ultimately will depend on development of screening methods with greater sensitivity than those used here.

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Resistance to wilt caused by Verticillium dahliae Kreb. was evaluated for 41 strawberry genotypes from the Univ. of California breeding program and 1000 offspring from crosses among 23 of these genotypes. Runner plants from these genotypes and seedlings were inoculated with a conidial suspension containing a mixture of five isolates of V. dahliae from strawberry. Symptoms were scored as the number of dead or seriously stunted plants per plot, or based on a subjective phenotypic resistance score assigned to each plot on five dates during the spring after planting. Most of the California germplasm is highly susceptible to V. dahliae, with an average resistance score of 2.1 (±0.10) and 84.1% (±2.1) plants stunted or dead compared with a score of 3.2 (±0.24) and 57.4% (±4.9) of plants stunted or dead for a control set of six non-California genotypes identified previously as resistant. However, a broad range of intermediate resistance was detected, and 4 of the 41 California genotypes evaluated had resistance scores superior to the mean score for the non-California resistant checks. Plot-mean heritabilities for resistance and stunting scores estimated using genotypic, full-sib family, and offspring-parent analyses ranged from 0.44 to 0.88. Comparison of different estimates of variance components suggests that half or more of the genotypic variance for resistance traits detected is due to the additive effects of genes. There appears to be sufficient variation within the California population to proceed with an effective selection program, despite the absence of directional selection for resistance during the past 3 decades. However, developing cultivars with adequate resistance will ultimately depend on the recovery of transgressive segregants from superior parents, as even the most resistant genotypes from all sources showed some disease symptoms.

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a few accessions that are important sources of genes for disease resistance, such as the verticillium wilt (caused by Verticillium dahliae )-resistant cultivar La Brillante, Batavia, and Latin-type cultivars resistant to bacterial leaf spot (caused

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analyses in crops. GWAS has previously been used to examine verticillium wilt ( Verticillium dahliae ) resistance in cotton ( Gossypium hirsutum ) based on 158 cotton germplasm accessions ( Zhao et al., 2014 ). Jun et al. (2008) reported that Satt571

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Fusarium wilt of strawberry is caused by Fof and is a major soil-borne disease of strawberry worldwide. This disease quickly kills infected plants by impeding water and nutrient movement in the vascular tissues of the plant. Since the introduction

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Abstract

Parental, F1, F2, and backcross generations of tomato (Lycopersicon esculentum Mill.) lines Morden MEL2668170G (MEL) and ‘Walter’ (WA) were screened as seedlings for resistance to verticillium wilt (Verticillium dahliae Kleb.) race 2. Disease reaction means, based on the number of leaves and cotyledons with symptoms 5.5 weeks after inoculation, were 2.7 for MEL and 4.6 for WA. Resistance in MEL appeared to be recessive with narrow sense heritability estimated at 0.25 or less. Disease severity was sometimes inadequate to avoid the selection of escapes in advanced generations. Analysis of F3 progenies, however, indicated 3 genes or less might be involved. Results suggest race-2 resistance can be maintained in advanced generations by the elimination of highly susceptible plants and by progeny testing to insure recovery of the most resistant individuals rather than escapes.

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biochemical indexes for evaluating the resistance of eggplant ( Solanum melongena ) to verticillium wilt ( Verticillium dahliae ), Zhou (2012) investigated the activities of defense-related enzymes, including PAL, peroxidase (POD), and CAT. They found that

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