Observações sobre cafeeiros com diferentes fatores de resistência a Hemilea vastatrix plantados na mesma cova.

Abstract

Coffea arábica progenies homozygous for the independent genes SH 5 SH„ SHsSK,, SHsSHj, SH 5 SH 4 were evaluated in a randomized block experiment. Two seedlings of dif- ferent genotypes were planted together in the same hill in 10 different combinations. The effects of these combined genotypes were studied in relation to plant development, yield and incidence of the leaf rust disease. Progenies of Mundo Novo and Catuaí Ver- melho cultivars homozygous for the gene SH 5 were used as controls. Comparison of the total yield from 1974 to 1977 indicated that 'Catuaí Vermelho' was more productive than any other combination, in spite of being susceptible to the disease. The genptype combinations SHgSIL. with SH 5 SH 3 and SH 3 SH 2 with SH 5 SH 4 yielded more than the combinations SHjSH! with SH 5 SH 4 and SH 3 SH 3 with SH5SH1. However the differences were not significant. Differences were noticed in the degree of leaf rust incidence for the genotype com- oination SHjSHi with SH 5 SH> in relation to the combination of SHsSH! with SHsSH 4 . A small negative effect on the general aspect of plant and the plant height was observed for all plants when associated with those having the genotype SH,SH 2 , probably due to the fact that these latter plants were previously selected for yield and plant vigour.