Drought Stress Modified Genetic Components and Combining Ability of Cotton Genotypes 

Abstract Background: Gene action and combining ability of the genotypes are two important components in crop breeding and may be influenced by environmental stresses which sometimes mislead the selection process. Therefore, an experiment was conducted to assess the behavior of genetic parameters of cotton (Gossypium hirsutum) under drought stress during the year 2017-19. Initially, 50 genotypes of cotton were screened for drought stress tolerance potential by subjecting them to 4 week long drought stress (at 20% field capacity). Based on physiological parameters, 5 drought tolerant and 4 drought susceptible genotypes (lines and testers respectively) were selected and hybridized using Line × Tester technique to develop F1 crosses. In the next year, 9 parents and their 20 F1 hybrids were evaluated in field under normal irrigation and drought stress (at 50% field capacity). Results: Stronger specific combining ability effects observed for seed cotton yield, number of bolls, boll weight and lint percentage (%) indicated active role of non-additive genes operating in the direction of lower parents with the exception for number of bolls where dominance worked towards superior parents. Best varietal combinations identified under water stress for number of bolls and boll weight were CIM-496 × NF-801-2-37, DPL-26 × NF-801-2-37, B-557 × NF-801-2-37, B-557 × MNH-129. Variety B-557 was found to be good general combiner followed by BOU-1724 for number of bolls, boll weight and lint % under drought. Conclusion: Combining ability analysis indicated critical role of non-additive component in total variation suggesting weak heritability for all the traits. Direct selection in this material is therefore not advisable. Drought had suppressed variability and restricted the expression of yield characters, however, best identified varietal combinations for seed cotton yield, number of bolls and boll weight may be exploited for the development of hybrid to be grown in drought hit areas of Pakistan.