Résumé
Sugarcane yellow leaf virus (SCYLV) can infect many modern sugarcane varieties and cause insidious yield losses in susceptible cultivars. Information about the heritability of resistance to SCYLV is useful in designing appropriate breeding strategies likely to generate genetic gains and develop resistant varieties. This study aimed at computing quantitative estimates of narrow-sense heritability (h(2)) of resistance to SCYLV using the parent-offspring regression method. A set of 37 genitors and a total of 41 derived bi-parental progenies were tested in field trials in natural conditions of infection prevailing in Guadeloupe. Parents and progenies were assessed for leaf SCYLV incidence in separate randomized complete-block designs through tissue-blot immunoassay. Trial designs and diagnostic protocols gave access to a high accuracy of phenotypic values of both parents and progenies. Narrow-sense heritability of virus resistance was estimated to be h(2)=0.29 or 0.44 in two parent-offspring regressions based on the study of a set of 10 and 31 progenies, respectively. Assessments of parents and their progenies made in separate trials have avoided any risk of inflation in h(2) estimates due to possible environmental covariance between relatives across generations. On the contrary, these estimates are probably lower than the genuine heritability existing in the studied material. The lower level of infection of the progenies compared to their parents has influenced downward the mathematical ratio that determines the computation of heritability. Our study provides the first report on heritability of sugarcane resistance to SCYLV. Estimates obtained indicate that the trait is at least moderately heritable. Part of the genetic variance of additive nature could be advantageously exploited. Breeding strategies taking into account values of parents for their resistance to yellow leaf disease should be effective.