Genetic differentiation of peg strength and analysis of major influencing factors in peanut germplasm

Peanut (Arachis hypogaea L.) is an important oil crop in China. Due to its unique biological characteristic of “aerial flowering and subterranean fruiting”, it faces a high pod drop rate during harvesting—especially under mechanized conditions—which significantly reduces production efficiency and leads to yield losses. Variations in peg strength among peanut germplasm are a key determinant of pod drop rate during digging operations. Systematically uncovering the variation patterns in peg strength and identifying its primary influencing factors will provide valuable germplasm and technical support for breeding pod drop-resistant varieties. In this study, peg strength and related traits—including peg thickness, lignin content, and cellulose content—were evaluated across 241 representative peanut germplasm accessions. The results showed that the coefficients of variation for the breaking force at both the stem-peg and pod-peg junctions exceeded 30%, indicating substantial phenotypic diversity. Eleven elite germplasm accessions with superior peg strength were identified. Significant differences in peg strength were observed among botanical types, with Valencia and Multigrain types exhibiting significantly higher values than others, suggesting that genetic background has a notable influence on peg strength. Further correlation analysis, principal component analysis, and multiple linear regression revealed a strong positive correlation between peg strength and cellulose content. To validate this, four accessions with extreme phenotypes were selected, and cellulose and lignin contents were measured at four developmental stages of the peg. Accessions with high peg strength consistently exhibited significantly higher cellulose content across all stages compared to those with low peg strength, confirming that cellulose content is a key factor influencing peg strength. This study clarifies the phenotypic variation in peg strength among peanut germplasm and highlights the critical role of cellulose content, providing a theoretical basis for the genetic improvement of peg strength and the development of peanut varieties suitable for mechanized harvesting.