Hybrid vigor and its deterioration in intraspecific populations of upland cotton

Abstract

Seven lines (‘VH-292’, ‘VH-259’, ‘Bt-802’, ‘Sadori’, ‘Shahbaz’, ‘CRIS-342’, and ‘Bt.ZZ.NL-370’), and three testers (‘VH-291’, ‘FH-113’, and ‘IR-3701’) of upland cotton (Gossypium hirsutum L.) were crossed through line-by-tester mating to produce 21 F1 hybrids. The lines, testers, and their F1 and F2 populations were grown in a randomized complete block design with three replications at Sindh Agriculture University, Tandojam, Pakistan, in consecutive cropping seasons. Analysis of variance revealed that the genotypes (including parental lines, testers, and their 21 F1 and F2 populations) and parent vs. hybrids differed significantly for all the studied traits, except for plant height in the F2 population and sympodial branches plant−1 in the F1 and F2 populations. Lines ‘VH-292’ and ‘VH-259’ and testers ‘VH-291’ and ‘FH-113’ exhibited higher plant height, sympodial branches, bolls plant−1, and boll weight than other genotypes and were identified as suitable parental genotypes for hybridization. The F1 and F2 populations of ‘VH-292’ × ‘VH-291’ and ‘VH-292’ × ‘FH-113’ produced more sympodial branches, bolls plant−1, and seed cotton yield plant−1 than other crosses. The F1 hybrid of ‘Bt-802’ × ‘VH-291’ and the F2 population of the ‘Sadori’ × ‘VH-291’ cross produced higher boll weight than other genotypes. Overall, the mean performance of the F1 hybrids for all the traits was better than that of their parents and the F2 populations likely due to heterotic effects in the F1 populations and inbreeding depression in the F2 populations. The significant mean squares for parental genotypes, crosses, and parents vs. crosses indicated that the data obtained in this work are valuable for determining parental performance, hybrid evaluation, heterotic effects, and inbreeding depression. Significant mean squares due to parents vs. crosses revealed the good scope of heterotic effects in the F1 populations for all the traits.