Melhoramento do cafeeiro. X - Seleção visando eliminar o defeito "lojas vazias do fruto" no café Mundo Novo

Abstract

As progênies de café Mundo Novo em estudo na Seção de Genética, desde 1943, se têm revelado altamente produtivas e vigorosas, porém apresentam numerosas plantas com rendimento desfavorável devido à alta incidência de lojas do fruto desprovidas de sementes. Estudos detalhados sôbre a constituição dessas progênies, com relação a êsse defeito, foram iniciados em 1950 verificando-se, nessa ocasião, que algumas eram constituídas apenas de plantas normais, enquanto outras se apresentavam formadas de cafeeiros normais e plantas com o defeito de alta quantidade de lojas sem sementes. A seleção foi dirigida a fim de eliminar, da população Mundo Novo, êsse grave defeito. Resolveu-se multiplicar apenas os cafeeiros mais produtivos das melhores progênies e que não apresentassem o defeito de alta quantidade de lojas vazias, pois seria de esperar que suas progênies fossem constituídas de plantas normais, a julgar pelos dados então obtidos nos descendentes do cafeeiro bourbon n.° 44, que também apresentava o mesmo defeito. Os resultados da amostragem realizada na primeira plantação de café Mundo Novo formada com essas sementes selecionadas, e discutidos no presente trabalho, dão indicações de que a seleção foi bastante eficiente, reduzindo a incidência de plantas com o defeito, de 50% na população original para cêrca de 2 a 7% nesta nova plantação. Em vista dêstes resultados as sementes aí colhidas em 1953 foram aproveitadas para sdstribuição aos lavradores de São Paulo, pela Divisão de Fomento Agrícola, a fim de ie formarem 148 plantações modelo dessa nova variedade comercial. - As comparações feitas, entre as produções de café beneficiado, calculadas a partir do rendimento para os cafeeiros de mais alta produção de cereja, indicam que se deve primeiramente concentrar a seleção em plantas produtivas e sem elevada quantidade de lojas sem sementes, tal como já vem sendo feito desde 1950.

A high proportion of plants of the Mundo Novo coffee (a strain of Coffea arabica L. var. bourbon (B. Rodr.) Choussy) produce an abnormally large number of fruits with empty locules. Since this character reduces the rate of coffee beans per weight of fruit, selection was started aiming at reducing or eliminating plants having this defect, and thereby increasing the yeild of coffee beans. Preliminary investigations carried out in 1950 on the occurrence of empty locules in selfed progenies and hybrids of the bourbon plant No. 44, which presents a high percentage of this defect, indicated that this characteristic was heritable. It was also determined that only normal plants were found in progenies of normal individuals, even when these belonged to progenies in which some of the sibs produced large number of fruits with empty locules. Based on this information, seeds from normal, high yielding plants of Mundo Novo coffee were released to coffee growers in 1950. In one of the first farms to use selected seeds of Mundo Novo coffee, approximately 7,000 trees (one tree is really a group of four plants in the same hill) were planted with seeds produced by the best plants of five of the most outstanding progenies of this variety. A small crop was available in 1953. Due to the increasing demand for selected seeds of Mundo Novo coffee, it was then suggested that the State Extension Service buy the seeds produced in this farm and distribute them to coffee growers that were willing to plant them for seed production. Before this suggestion was put into effect, the whole planting was surveyed for the presence of plants producing large numbers of fruits with empty locules. By means of a sampling technique, it was determined that only from 2 to 7 per cent of abnormal plants were found in the plantation. When these numbers were contrasted with the 50 per cent index of undesirable trees normally found in the original Mundo Novo plantings, it became evident that selection to eliminate plants producing large number of fruit with empty locules had been quite successful. If must be noted that such a low percentage of undesirable plants having the same defective character is normally found in plantings of the current commercial varieties such as bourbon and others. Details of the sampling results and the influence of a high rate of empty locuels on the yield of coffee beans are discussed. The possibility of selecting exceptionally high-vielding individuals, although having this defect, is considered. The elimination of trees which gave unusually large quantity of fruit with empty locules allowed the establishment of pilot plantings. It mg/y be said that an increase in productivity was attained by this method of selection.