Tolerância de cultivares e linhagens de feijão-caupi ao herbicida diclosulam

Abstract

There are few options for chemical weed control in cowpea cultivation. The herbicide diclosulam would be an alternative for the control of weeds with broad and narrow leaves in crop pre-emergence. Thus, the aim of this study was to identify cultivars and lines of cowpea tolerant to the herbicide diclosulam. In trial 1, the application of three herbicide doses (0D, ½D and 1D, with D equivalent to 35 g ha-1 of diclosulam) in six cultivars (BRS Imponente, BRS Itaim, BRS Guariba, BRS Novaera, BRS Pajeú and BRS Tumucumaque) and 14 lines of cowpea (ten from the commercial class colors and four from the commercial class fradinho). The variables analyzed were: the number of plants at 7 and 35 days after application (DAA), shoot dry mass and leaf area of trefoils at 35 DAA and phytotoxicity at 7, 14 and 21 DAA. Test 2 was conducted in the field and, due to the low phytotoxicity observed in test 1, it was decided to evaluate only the six cultivars and three lines of the commercial color class, one with higher and two with lower tolerance to diclosulam at 14 DAA and , also, a lineage representing the fradinho commercial class. The variables analyzed were: phytointoxication at 7, 14, 21 and 28 DAA; stand at harvest time, pods per plant, grains per pod, weight of 100 grains and grain yield. The herbicide diclosulam provided reduced phytotoxicity (<15%) in both trials, in all evaluations. There was an interaction between genotype and herbicide doses only at 14 DAA with plant recovery in subsequent evaluations. The injuries observed in the plants were not enough to cause significant damage in the other variables analyzed in the two tests. The differences observed between cultivars and lines were not due to the effect of the herbicide, but rather due to the morphological and genetic differences of each genotype. Because, when the variables, with the exception of phytointoxication, were relativized to the corresponding control, there was no difference in tolerance to the herbicide between cultivars and lines. Thus, it was concluded that the evaluated lines and cultivars of cowpea are tolerant to the herbicide diclosulam.