Produção de mudas de cará São Tomé (Dioscorea alata L.) a partir de segmentos de túberas

Abstract

The different species of Dioscorea spp. (Dioscoreaceae) grown in Brazil are known by several common names, among which yam and cará. Yam is sometimes associated with species from other botanical families that also have an edible starchy underground structure. The São Tomé yam (Dioscorea alata L.) is a plant of African origin that produces edible tubers of high nutritional and economic value, widely cultivated in Brazil for domestic consumption and export. Its tubers are rich in carbohydrates, fiber, protein, B vitamins and have a low glycemic index. Propagation of yams and yams is usually done using seed tubers or pieces of tubers. Although the use of seed tubers is the most suitable way of propagation, it is still little used due to its high cost and low availability. Among the main factors that limit the productivity of yams and carás, there is the occurrence of diseases, with emphasis on the black bark, which represents the main phytosanitary problem of these crops in Brazil, having as etiological agents the migratory endoparasitic nematodes Pratylenchus spp. and Scutellonema bradys. The increase in this disease is mainly due to the constant dissemination of nematodes through successive plantings using contaminated seed tubers. With the reduced production of pathogen-free seed tubers, the values of this material are high, which leads producers to seek other alternatives to make the planting of the crop feasible. Therefore, studies are needed to make it possible to obtain low-cost propagules that have phytosanitary quality to carry out safe and disease-free plantings. In this perspective, this work aimed to establish an alternative to produce seedlings of São Tomé yam (Dioscorea alata L.) from different positions and weights of tuber segments capable of, in the future, supplying tuber- seeds or high-quality commercial tuber with phytosanitary and physiological quality that meets the commercial needs of producers. The study had two experiments carried out separately and a randomized block design was adopted. The first experiment consisted of 3 treatments and 12 repetitions. The treatments consisted of different positions of tuber segments (apical segment; medial segment and basal segment) and a single weight of 200g was adopted for all treatments. In the second experiment, a 3 x 3 factorial scheme was adopted, with 9 treatments and 4 repetitions. The treatments consisted of 2 factors: position of the tuber segments (apical segment; medial segment and basal segment), weights (200, 100 and 50 g). The experiments lasted 45 days. The evaluated variables were presence or absence of roots, number of shoots, length of branches, dry mass and green mass of branches and green and dry mass of roots. The results showed that the apical and medial segments presented good results in the weights of 200 and 100g regarding the production of shoots and development of the branches, as well as to produce green and dry mass of the aerial part. In the weight of 50g, only the apical segment presented significant numbers regarding the production of shoots and development of the branches, with that it is concluded that it is not indicated to use this weight in the segments coming from the medial and basal positions.

Palabras-claves: Dioscorea alata; propagation; tuber-seeds.