Combining ability of summer-squash lines with different degrees of parthenocarpy and PRSV-W resistance

Abstract

The aim was to assess heterosis in a set of 16 summer-squash hybrids, and evaluate the combining capacity of the respective parental lines, which differed as to the degree of parthenocarpy and resistance to PRSV-W (Papaya Ringspot Virus-Watermelon strain). The hybrids were obtained using a partial diallel cross design (4 × 4). The lines of parental group I were 1 = ABX-037G-77-03-05-01-01-bulk, 2 = ABX-037G-77-03-05-03-10-bulk, 3 = ABX-037G-77-03-05-01-04-bulk and 4 = ABX-037G-77-03-05-05-01-bulk, and of group II, 1′ = ABX-037G-77-03-05-04-08-bulk, 2′ = ABX-037G-77-03-05-02-11-bulk, 3′ = Clarice and 4′ = Caserta. The 16 hybrids and eight parental lines were evaluated for PRSV-W resistance, parthenocarpic expression and yield in randomized complete-block designs, with three replications. Parthenocarpy and the resistance to PRSV-W were rated by means of a scale from 1 to 5, where 1 = non-parthenocarpic or high resistance to PRSV-W, and 5 = parthenocarpic or high susceptibility to PRSV-W. Both additive and non-additive gene effects were important in the expression of parthenocarpy and resistance to PRSV-W. Whereas estimates of heterosis in parthenocarpy usually tended towards a higher degree, resistance to PRSV-W was towards higher susceptibility. At least one F1 hybrid was identified with a satisfactory degree of parthenocarpy, resistance to PRSV-W and high fruit-yield.

Zucchini lineages with levels of resistance to ZYMV and SqMV viruses

“…The development of resistant cultivars to the cucurbits virus is usually a long and complex process. In the initial phase, it is necessary to select an appropriate source of resistance to certain species of viruses or to more than one species (Silveira et al, 2009;Nogueira et al, 2011).…”

“…cucurbitae), black rot (Didymella bryoniae), fusarium wilt (Fusarium oxysporum), bacterial blackleg (Pectobacterium carotovorum subsp. carotovorum) and virus (Papaya ringspot virus, Zucchini yellow mosaic virus, Squash mosaic virus and Watermelon ringspot virus) (Nogueira et al, 2011;Agrofit, 2017).…”

“…The phytoviroses have no curative control, and, thus, preventive measures are needed for crop management (Rodríguez et al, 2016;Cutler et al, 2018). Existing strategies to decrease dissemination include the development of cultivars or hybrids with genetic resistance to viral infections (Nogueira et al, 2011).…”

Selection of melon genotypes with resistance to <i>Didymella bryoniae</i> using a diallel approach

“…Diallel crosses in the selection of parents and, in particular, partial diallel crosses are useful when the objective is to combine favourable phenotypes that are found in different groups of parents, as in the case of productive and susceptible lines and wild and resistant accessions, where the combinations within each group are not of interest. The partial diallels have been used for this purpose in other vegetable crops, such as zucchini (Nogueira et al, 2011) and tomato (Pádua et al, 2010;Andrade et al, 2014).…”

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

“…Even though PRSV-W resistance in C. pepo 'Whitaker' has been reported (Nogueira et al 2011), its mode of inheritance has not been established yet. This study reports on the mode of inheritance of PRSV-W resistance in Whitaker C. pepo line.…”