Anatomical characteristics correlated to peg strength in Arachis

Authors: LEVINSON, C - University Of Georgia; CHU, Y - University Of Georgia; LEVINSON, M - University Of Georgia; MARASIGAN, K - University Of Georgia; STALKER, H - North Carolina State University; Holbrook, Carl - Corley; OZIAS-AKINS, P - University Of Georgia

Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2021
Publication Date: 11/15/2021
Citation: Levinson, C.M., Chu, Y., Levinson, M., Marasigan, K., Stalker, H.T., Holbrook Jr, C.C., Ozias-Akins, P. 2021. Anatomical characteristics correlated to peg strength in Arachis. Peanut Science. 48:97-112. https://doi.org/10.3146/PS21-1.1.
DOI: https://doi.org/10.3146/PS21-1.1

Interpretive Summary: Peanut variety improvement is limited by a narrow genetic base. Our peanut pre-breeding program seeks to overcome this obstacle by incorporating genetic variability from wild, diploid peanut species through interspecific hybridizations. However, wild peanut species also have undesirable traits such as weak peg strength. Weak peg strength results in yield loss during harvest. To enable breeders to effectively utilize these wild species, we sought to characterize peg strength and anatomical characteristics correlated with peg strength in seven Arachis species, as well as four allotetraploids, six (cultivated peanut lines x allotetraploid) F1 hybrids, and two cultivated peanut breeding lines. Peg strength comparable to the peanut breeding lines was recovered in the F1 hybrids suggesting that few backcrosses would be needed to select against weak peg strength. Furthermore, there may be positive alleles for peg strength in some wild species. Peanut breeders should be encouraged that the weak peg strength of Arachis species should not hinder the introgression of beneficial alleles from wild species into peanut cultivars.

Technical Abstract: Wild, diploid Arachis species are a great source of biotic and abiotic stress resistances and tolerances for peanut breeding programs; however, these species also have undesirable characteristics such as small seed size, low yield, and weak peg strength. Peg strength has been shown to have a positive, linear relationship with yield in cultivated peanut. Therefore, the weak peg strength in Arachis species could be detrimental to yield and needs to be selected against when introgressing useful alleles from wild species. To enable breeders to effectively utilize these wild species, we sought to characterize peg strength and anatomical characteristics correlated with peg strength in seven Arachis species, as well as four allotetraploids, six (cultivated peanut lines x allotetraploid) F1 hybrids, and two cultivated peanut breeding lines. For each genotype, five mature pegs were tested for peg strength and subsequently cross-sections for three of the five pegs were taken and analyzed for peg anatomical characteristics including total peg cross-section area, average bundle cap area, total bundle cap area, bundle cap area, total distance between bundle caps, and tannin cell count. Genotype was a significant indicator for peg strength and all the anatomical characterization parameters (P<0.05). Peg strength was positively and highly correlated with peg area, average bundle cap area, total bundle cap area, and bundle cap number. Peg strength comparable to that of peanut breeding lines was recovered in the F1 hybrids. Because weak peg strength in the wild species appears to be recessive, strong peg can easily be selected during the process of introgression.