Polygenic Genetic Analysis of Principal Genes for Yield Traits in Land Cotton

Objective: Yield traits are crucial for cotton breeding. Analyzing the yield traits of terrestrial cotton and exploring their genetic mechanisms through a primary gene + multigene hybrid genetic model provide a theoretical basis for selecting high-quality cotton varieties and identifying associated molecular markers. Methods: Completing the construction of the six populations (P1, P2, F1, F2, B1, B2) using Xinluzhong 37 as the female parent and Xinluzhong 51 as the male parent. Six yield traits were assessed: single boll weight, boll number per plant, lint yield per plant, seed cotton per plant, lint percentage, and seed index. Data were tested for normal distribution, and the inheritance patterns of yield traits were analyzed through combined primary gene + polygenic analysis. Results: The coefficients of variation for the six yield traits ranged from 37.368% to 53.905%, 33.335% to 58.524%, 34.132% to 57.686%, 8.721% to 12.808%, 1.842% to 6.283%, and 8.783% to 12.580%, respectively. These traits displayed either normal or skewed normal distributions. The optimal genetic model for single boll weight and seed index was PG-ADI, while MX2-ADI-AD best fit the traits of boll number per plant and lint percentage. For lint yield per plant and seed cotton per plant, the 2MG-ADI model was optimal. The polygenic heritability for single boll weight was 29.58%; for boll number per plant, main gene heritability was 25.19%, with 0% heritability for polygenes; for lint yield per plant, the heritability of the main gene was 23.47%. For seed cotton per plant, the heritability of main genes was 15.38%, with lint percentage showing 63.25% heritability for main genes and 0.08% for polygenes, and seed index with 45.93% heritability due to polygenes. Overall, single boll weight and seed index were predominantly polygenic, while boll number per plant and lint percentage were largely controlled by main gene inheritance. The inheritance of lint yield per plant and seed cotton per plant was also primarily governed by main genes.