ESTIMATION OF GENETIC VARIANCES OF SUGAR CANE RESISTANCE TO RUST THROUGH A FACTORIAL DESIGN OF CROSSES: INFECTED LEAF AREA

Abstract

Progenies from a factorial cross design on sugar cane (Saccharum spp.), were studied for rust (Puccinia melanocephala) resistance to natural infection on field conditions in seedling and clonal stages over a period from 45-250 days after planting. Genetic variances and heritabilities from resistance variables were compared. Degrees of genetic determination and heritability estimates increased considerably on a family basis indicating that selection of clones from these populations as potential parents can be successful if the material is repli-cated. Additive genetic variance is more important than non-additive genetic variance. For selection purposes the resistance variables expressed as percent of attacked leaf area over the period from 5-6 months after planting, are the most convenient. All resistance variables presented low correlation with yield components. The validity of assumptions made for these analyses using one factorial design is discussed.