Genética de coffea. XXV— Ligação genética dos fatôres anormalis e anomala

Abstract

The anormalis factor (Am Am) of Coffea arábica controls the size of the plant, its branching habit and its leaves, flowers, fruits and seeds. The internodes of the branches are shorter than those in the typica variety, taken as a standard. The leaves are extremely abnormal, often almost palmate and of various sizes. The corolla has a variable number of lobes, the stamens are almost normal, but the style and stigma are very reduced and misshaped. The number of flowers and fruits is normal. The seeds have a slightly corrugated surface, A rather high percentage of locules contain more than one ovule. The anormalis shows incomplete dominance in F1. The anômala mutant also controls the plant growth, its type of branching, the shape and size of the leaves, and the morphology of flowers, fruits and seeds. The number of flowers and fruits is very low and the occurrence of locules with more than one seed is, however, very high in some years. The anômala is recessive (an an), the Ft being almost normal, with the exception that, occasionally, a pair of leaves develops with slightly misshaped apex. The F1 hybrids of anormalis and anomala are like anormalis heterorygotes; sometimes they have smaller and more irregular leaves, indicating a certain interaction of both factors. Backcrosses with typica or bourbon plants with the genotype am am An An, gave an indication (Table 1) of linkage of the two factors involved, with a recombination value of about 15%. Due to difficulties in the separation of the classes Am An/am An from Am an/am An this recombination value is not precise and can be anywhere between 10 and to 20%. Backcrosses with lhe double recessive type are difficult to obtain, due to the small number of flowers that it produces. It is to be noted that the anormalis and anômala genes, producing rather similar phenotypes and having a very intensive pleiotropic effect, are, up to now, the only factors to give indication of linkage in Coffea arabica.