Yield stability of four cotton (Gossypium hirsutum L.) genotypes was studied following the Eberhart & Russel method, based on 13 experiments carried out at growing areas of the State of São Paulo and Goiás, Brazil, in the 1992/93 season. In some of these trials, one or more of the following adversities were present: Fusarium wilt (Fusarium oxysporum f. vasinfectum (Atk.) Snyder & Hansen); nematodes (Meloidogyne incognita, Pratylenchus brachyurus, Rotylenchulus reniformis and Helicotylenchus sp.); ramulose (Colletotrichum gossypii South var. cephalosporioides A.S. Costa) and mosaic virus. Considering the parameters involved in the model, the best results were obtained by two breeding lines coming from the program of multiple resistance to diseases and nematodes conducted by the Instituto Agronômico at Campinas, State of São Paulo, Brazil. The second best result was shown by the cultivars IAC 20. The less stable genotype was Deltapine Acala 90, a cultivars that showed the lowest production mean and was the unique to present a regression coefficient (1.333) significantly different of 1. By comparing the most and the least productive genotypes, losses of 33% and 50%, due, respectively, to Fusarium wilt and nematodes were observed. Considering all environments involved, the yield reduction was about 28%. Taking into account the diversity and dissemination of these parasites in the considered areas, it is pointed out that multiple resistance or tolerance must be introduced in the cultivars to be delivered for planting.
cotton; Gossypium hirsutum L.; yield stability; multiple resistance to diseases