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.
Highlights
Commercial deployment of summer-squash (Cucurbita pepo L.) hybrids is increasing, due to the reported heterosis for yield-related traits (Firpo et al, 1998; López-Anido et al, 1998; Ahmed et al, 2003) and the possibility of combining parental resistance to various pathogens.Papaya ringspot virus-watermelon strain (PRSV-W) is responsible for significant losses in summer squash, whose cultivars are usually highly susceptible to this virus
The heterosis effects were only significant for average heterosis, thereby indicating that hybrids deviated from the parental means for this trait
Estimates of heterosis related to parental means (Table 3) varied from -8,3% (05-01 x Caserta) to 87,3% (01-01 x Clarice) - a wide variation, in which positive values predominated, a reflection of the reported dominance of the allele controlling parthenocarpic fruit-set (Menezes et al, 2005; Silva et al, 2009)
Summary
Commercial deployment of summer-squash (Cucurbita pepo L.) hybrids is increasing, due to the reported heterosis for yield-related traits (Firpo et al, 1998; López-Anido et al, 1998; Ahmed et al, 2003) and the possibility of combining parental resistance to various pathogens.Papaya ringspot virus-watermelon strain (PRSV-W) is responsible for significant losses in summer squash, whose cultivars are usually highly susceptible to this virus. The aims were to (a) develop summer-squash hybrids among lines with a high degree of parthenocarpy and PRSV-W resistance, derived from the Caserta x ‘Whitaker’ cross; (b) select competitive hybrids for the local market; (c) estimate heterosis in these hybrids and (4) assess the combining capacity of hybrid parental lines.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
