The genotype × environment interaction and the stability of eight cotton lines and the standard variety were studied during 2014-2017. The years of the study appeared to be as different ecological environments. The stability variances (s2i and S2i) of Shukla (1972) and YSi index of Kang (1993) were calculated. It was found that the cotton genotypes tested interacted significantly with the environmental (year) conditions in terms of seed cotton yields, boll weigt, fiber length and lint persentage. For an effective selection of these traits, the genotypes had to be tested in different years at diverse environmental conditions and a calculation of the phenotypic stability parameters was necessary for a more precise selection. Based on Sukla’s variance stability parameters the breeding usefull stability was observed for all studed traits. Some lines were stable for more than one traits. Line 553 was found to be stable for the seed cotton yield, boll weight and lint percentage, lines 489 and 457 – for the boll weight and fiber length. These lines appeared to be very suitable for inclusion in crosses. According to Kang’s YSi index the complex breeding value (the average level of trait and stability) was found in: line 553 for the seed coton yield, boll weight, fiber length and lint percentage; line 489 for the boll weight, fiber length and lint percentage; line 535 for the seed coton yield and boll weight; line 449 for the boll weight and fiber length; line 457 for the fiber length. These lines are very suitable for the cotton breeding programs to create genotypes with a high expression and high stability of the traits.
Keywords: cotton, G. hirsutum L., genotype-environment interaction, phenotypic stability, economic traits.