Inheritance of resistance to papaya ringspot virus-watermelon strain (PRSV-W) in 'Whitaker' summer squash line

Abstract The objective of this work was to study the genetic control of the PRSV-W (Papaya Ringspot Virus - Watermelon Strain) resistance in Cucurbita pepo 'Whitaker' line. Plants of parental lines Whitaker (resistant) and Caserta (susceptible), and of the generations F1, F2, BC11 and BC12 were evaluated for their reactions to PRSV-W. Caserta plants showed severe mosaic symptoms, while Whitaker grew vigorously and remained almost totally symptom-free. Most of the F1, F2 and backcross plants also presented severe mosaic symptoms. Data were used to test a hypothesis of monogenic inheritance under different presumed degrees of dominance, and genetic models were tested using maximum likelihood tests of genetic control. Broad-sense heritability was of 0.57 for the first evaluation. Resistance to PRSV-W in C. pepo 'Whitaker' is due to a major gene effect summed to polygenic effects.