EFFECT OF DIFFERENT LEVELS OF DEFOLIATION ON PRODUCTIVITY OF COMMON BEANS (Phaseolus vulgaris L. CV. PEROLA)

Studies to evaluate artificial defoliation are very useful, mainly to simulate damages to plants, such, as the ones caused by insects or hail. Experiments with bean plant, indicated that the results are higly dependent on the cultivars used, and preponderant climatic conditions. The purpose of this study was to evaluate yeld reduction due to the reduction on the leaf area at different stages of growth of bean crop of Perola cultivar under environmental conditions of Rio Branco, Acre. The experiment was conducted at the Experimental Station of Embrapa Acre. The experiment was arranged as a split-plot in a randomized block design, with four replications. The main plots consisted of five plant development stages: V3= first trifoliate leaf, V4= third trifoliate leaf, R6= initiation of flowering, R7= pod formation and R8= pod maturation, and the sub-plots were the four defoliation levels (0%, 33%, 66% and 100%). At harvest an average of 480 plants of the four central lines of each sub-plot were evaluated. It was determined the number of pods per plant, number of seeds per pod and yeld (kg/ha). In order to determine the average leaf area, 50 plants were randomily harvested in each development stage. The results demonstrated that defoliation levels starting from 33%, in the stages V3, V4 and R7, reduced the number of pods per plant. The number of seeds per pod was not affected by the level of defoliation of the plants. The seed weight was significantly reduced as the plants were submitted to increasing levels of defoliation. The flowering stage (R6) presented the highest yeld reduction with defoliation of the plants.