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Phenotypic expression of quantitative and qualitative components of partial resistance to powdery mildew ( Sphaerotheca fuliginea race 1) in melon ( Cucumis melo ) germplasm
Author(s) -
Boiteux L. S.,
Reifschneider F. J. B.,
Pessoa H. B. S. V.
Publication year - 1995
Publication title -
plant breeding
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.583
H-Index - 71
eISSN - 1439-0523
pISSN - 0179-9541
DOI - 10.1111/j.1439-0523.1995.tb00789.x
Subject(s) - sphaerotheca , powdery mildew , cucumis , biology , germplasm , melon , inoculation , horticulture , cucurbitaceae , plant disease resistance , botany , spore , hybrid , gene , genetics
A study was conducted to investigate the expression of four components of partial resistance to Sphaerotheca fuliginea race 1 in selected melon ( Cucumis melo L.) lines viz. infection frequency, latent period, spore production, and disease‐severity score. Those components were evaluated at two developmental stages of the host: the cotyledon stage and the stage of the first two true leaves. Detached plant parts (disks of cotyledons and true leaves) were inoculated using a vacuum‐operated settling tower. All four components showed significant variation among genotypes, and correlations between components at both developmental stages were large and significant. The line ‘CNPH 83–095’ (without any major resistance gene to powdery mildew) presented the highest level of partial resistance in both vegetative stages for almost all components evaluated. The lines ‘W‐6’ ( Pm1Pm1, Pm2Pm2 ), ‘Cinco’ ( Pm1Pm1, Pm2Pm2 ), and CNPH ‘84–147’ ( Pm1Pm1 ), even though carrying the major gene Pm1 for complete resistance to race 1 of the fungus, showed slight but significant differences for quantitative components of partial resistance at the cotyledonal stage. Different levels of partial resistance may be expressed, even in lines with a major race‐specific resistance gene to powdery mildew, in specific developmental stages of the melon plants.