Development and genetic characterization of peanut advanced backcross lines that incorporate root-knot nematode resistance from Arachis stenosperma

Authors: BALLEN-TABORDA, C - University Of Georgia; CHU, Y - University Of Georgia; OZIAS-AKINS, P - University Of Georgia; Holbrook, Carl - Corley; Timper, Patricia - Patty; JACKSON, S - University Of Georgia; BERTIOLI, D - University Of Georgia; LEAL-BERTIOLI, S.C.M. - University Of Georgia

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2021
Publication Date: 1/17/2022
Citation: Ballen-Taborda, C., Chu, Y., Ozias-Akins, P., Holbrook Jr, C.C., Timper, P., Jackson, S.A., Bertioli, D.J., Leal-Bertioli, S. 2022. Development and genetic characterization of peanut advanced backcross lines that incorporate root-knot nematode resistance from Arachis stenosperma. Frontiers in Plant Science. 12:785358. https://doi.org/https://doi.org/10.3389/fpls.2021.785358.

Interpretive Summary: Peanut root-knot nematode (PRKN) is a serious pathogen on peanut. The cultivated peanut species (Arachis hypogaea) is highly susceptible to this nematode. Resistant peanut cultivars have been developed using a gene for resistance from a related peanut species (Arachis cardenasii). The identification of additional genes for resistance would be valuable incase the nematode overcomes the resistance from cardenasii. Near-immunity has been found in the peanut wild relative A. stenosperma. The two genes controlling the resistance present in chromosomes A02 and A09 have been validated and have been shown to reduce nematode reproduction by up to 98.2%. We also identified molecular markers for these genes so that breeders can use marker assisted breeding to rapidly develop nematode resistant peanut cultivars using the new genes for resistance.

Technical Abstract: Crop wild species have been used, and are increasing in importance, for crop improvement. Peanut (Arachis hypogaea) wild relatives comprise a diverse genetic pool that is being used to broaden its narrow genetic base. Peanut is an allotetraploid species extremely susceptible to peanut root-knot nematode (PRKN) Meloidogyne arenaria. Current resistant cultivars rely on a single introgression for PRKN resistance incorporated from the wild relative A. cardenasii, that could be overcome as a result of the emergence of new nematode populations. Thus, new sources of resistance may be needed. Near-immunity has been found in the peanut wild relative A. stenosperma. The two loci controlling the resistance present in chromosomes A02 and A09 have been validated in tetraploid lines and have been shown to reduce nematode reproduction by up to 98.2%. With the goal to incorporate this new resistance QTL into cultivated peanut, we used a marker-assisted backcrossing approach. Here, five elite breeding lines were used as recurrent parents, and PRKN resistant lines derived from A. stenosperma were used as initial donor parents. Four cycles of backcrossing were completed and KASP SNP assays linked to QTL were used for foreground selection. In each backcross generation seed weight, length and width were measured, and based on statistical analysis we observed that at least one generation of backcrossing was required to recover the elite peanut’s seed size. Furthermore, the advanced backcross population of 271 BC3F1 lines was genome-wide genotyped with the aim to characterize the introgressions across the genome. Phenotypic information for leaf spot incidence and domestication traits (seed size, fertility, architecture and flower color) were recorded. Correlations between the wild introgressions in different chromosomes and the phenotypic data allowed us to identify candidate regions controlling these domestication traits. Furthermore, resistance was confirmed on BC3F3 lines. This present work represents an important step towards the development of new high-yielding and nematode-resistant peanut cultivars with added molecular information for genotypic selection.