Abstract
Two watermelon genotypes were used as parental in crosses designed to study the inheritance of resistance to PRSV-W: the cultivar Crimson Sweet (susceptible) and the accession 'PI 595201'(resistant). Plants of the generations P1, P2, F1, F2, BC11 e BC12 were inoculated with a Brazilian isolate of PRSV-W and were evaluated by recording symptoms. Genetic and phenotypic parameters of PRSV-W resistance were estimated and tests based on hypothesis of monogenic inheritance and maximum likelihood methods were performed. The additive component [a] of resistance was higher than the non-additive [d]. The estimates of the broad-sense heritability (0.80) and of narrow-sense heritability (0.67) indicated that the genetic variance was greater than the environmental, allowing higher genetic gains in selecting more resistant plants in segregating populations. The inheritance is more complex than a typical monogenic inheritance. The importance of the additive genetic effects in the expression of resistance to PRSV-W was evidenced.
Highlights
Papaya ringspot virus-watermelon strain (PRSVW, formerly Watermelon Mosaic Virus-1=WMV-1) is a potyvirus that affects all of the cultivated species of Cucurbitaceae, achieving great economic importance because of its destructiveness
The virus is transmitted in a non-persistent manner by numerous species of aphids, including Myzus persicae and Aphis spp. (Bateson et al 2002)
It has become one of the most limiting pathogens to cucurbit crops in warm climate countries as Brazil, where aphids can survive throughout the year
Summary
Papaya ringspot virus-watermelon strain (PRSVW, formerly Watermelon Mosaic Virus-1=WMV-1) is a potyvirus that affects all of the cultivated species of Cucurbitaceae, achieving great economic importance because of its destructiveness. Araújo and Souza (1988) identified the watermelon accession ‘Ouricuri’ as a source of PRSV-W resistance. Hojo et al (1991) identified an African bitter-fruited watermelon accession BT-8501 that was supposed to be resistant to PRSV-W, based on absence of leaf symptoms after mechanical viral inoculation. Made at the Universidade Federal de Lavras- UFLA, Lavras-MG, Brazil, a number of watermelon accessions were released as being resistant to the related potyvirus Watermelon Mosaic Virus (WMV). One of these lines - PI 595201- was resistant to PRSV-W. The mode of inheritance of this resistance was not previously known, and is reported in this paper
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