Seleção dos genótipos de algodoeiros com base no crescimento compensatório dos botões florais em resposta ao dano ocasionado pelo bicudo

Abstract

The cotton boll weevil, Anthonomus grandis Boheman is the main pest of cotton, causing severe damage to production, if control measures are not adopted. The boll weevil can be controlled by the use of tolerant cotton cultivars. Cotton plants have developed a series of direct and indirect mechanisms contributing to their resistance and the ability to tolerate and/or compensate for injury caused by insect pests on their reproductive structures. The present research aims to select cotton genotypes based on the compensatory growth of cotton squares in response to the damage caused by the boll weevil. The first experiment aimed to select cotton genotypes with greater compensatory growth of the cotton squares artificially removed from the plant. The experimental design was randomized blocks, in a 4 x 2 factorial scheme, represented by the cotton genotypes FM975WS, TMG81WS, IMA6501B2RF and BRS432B2RF, with 100% removal of cotton squares at 50, 70 and 90 days after emergence of plants and by the types of production, passive (control, without removal) and active (with removal) of squares, with four replications. In the second experiment, the damage caused by the boll weevil on the genotypes TMG81WS and BRS432B2RF was evaluated, with greater and lesser compensatory growth of cotton squares after their removal at 50 days of age. The experimental design was randomized blocks, in a 2 x 2 factorial scheme, represented by the above-mentioned genotypes and by the sprayings with carbamate or without spraying (control). It was observed that the cotton genotype with the highest compensatory growth of cotton squares was TMG81WS, mainly after its artificial removal at 50 and 70 days of age. The compensatory growth of the cotton squares in genotypes increases steadily over the period of exponential of the cotton squares production and can be used to select genotypes tolerant to the damage caused by the boll weevil in areas of organic and/or agroecological cotton production.