Genotypic variability of sugarcane resistance to the aphid Melanaphis sacchari, vector of the Sugarcane yellow leaf virus.

The objective of this study was to analyse the genotypic variability of sugarcane resistance to the main aphid vector of the Sugarcane yellow leaf virus ( Sc YLV) ( Polerovirus, Luteoviridae), Melanaphis sacchari. We assessed the incidence of aphids in a field trial comparing 181 sugarcane cultivars. Based on the percentage of infested leaves, aphid incidence was scored every two weeks during three cropping seasons. Analysis of variance revealed highly significant genotype, and genotype × year variance, and high broad sense heritability. Using semivariograms, we showed that the alpha lattice design used in the field trial was able to cope with spatial correlation issues caused by the patchy nature of aphid infestations. Twenty-two aphid resistant cultivars were identified. A laboratory study of the development of M. sacchari on four of these 22 resistant cultivars confirmed the resistant status of three of them. We observed modest positive phenotypic and genetic correlations between the aphid incidence and the incidence of Sc YLV. The 22 cultivars resistant to M. sacchari showed twofold lower mean virus incidence than the remaining 159 cultivars. [ABSTRACT FROM AUTHOR]