Development and Genetic Characterization of Peanut Advanced Backcross Lines That Incorporate Root-Knot Nematode Resistance From Arachis stenosperma

Abstract

Crop wild species are increasingly important for crop improvement. Peanut (Arachis hypogaea L.) 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 Arachis cardenasii, which could be overcome as a result of the emergence of virulent nematode populations. Therefore, new sources of resistance may be needed. Near-immunity has been found in the peanut wild relative Arachis stenosperma. The two loci controlling the resistance, present on chromosomes A02 and A09, have been validated in tetraploid lines and have been shown to reduce nematode reproduction by up to 98%. To incorporate these new resistance QTL into cultivated peanut, we used a marker-assisted backcrossing approach, using PRKN A. stenosperma-derived resistant lines as donor parents. Four cycles of backcrossing were completed, and SNP assays linked to the QTL were used for foreground selection. In each backcross generation seed weight, length, and width were measured, and based on a statistical analysis we observed that only one generation of backcrossing was required to recover the elite peanut’s seed size. A populating of 271 BC3F1 lines was genome-wide genotyped to characterize the introgressions across the genome. Phenotypic information for leaf spot incidence and domestication traits (seed size, fertility, plant 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. Finally, PRKN resistance was validated in BC3F3 lines. We observed that the QTL in A02 and/or large introgression in A09 are needed for resistance. This present work represents an important step toward the development of new high-yielding and nematode-resistant peanut cultivars.

A study of pod constriction in a peanut population with mixed wild and cultivated genetics

“…Within the BC 3 F 2 plants, the score was on average 3.66 ± 0.64, with six plants having a score of 5, same as the control cultivars (Figure 3a; Table 1; Table S1). The contribution of wild genome throughout all chromosomes of these progenies was determined using the SNP data and is displayed in the field map showing a wide variation of wild introgressions (between 1.1% and 19.1%, Ballén‐Taborda et al., 2022) (Figure S1b).…”

“…The output was analyzed using custom shell scripts (modified from Ballén‐Taborda et al. (2022)) to recover polymorphic SNPs between BatSten1 and Runner‐886 and to retrieve only A. stenosperma ‐specific and A. batizocoi ‐specific markers present in the genetic map in Ballén‐Taborda et al. (2019).…”

“…The induced allotetraploid BatSten1 PI 695418 ([ A. batizocoi ‘PI298639/K9484’ × A. stenosperma ‘PI666100/V10309’] (2 n = 4 x = 40) ) (D. Bertioli et al., 2021) was used as a donor to produce a BC population (herein called RBS, where RBS is A. hypogaea ‘Runner‐886’ × ‘BatSten1’ backcross population). An F 2 population was created from a cross between BatSten1 and A. hypogaea ‘Runner‐886’ with the purpose of incorporating resistance loci against RKN from A. stenosperma (Ballén‐Taborda et al., 2022). Using four selected F 2 plants, a BC scheme was designed, and three recurrent parents (TifGP‐2, 5‐646‐10, and 13‐1014) were used (Ballén‐Taborda et al., 2019, 2021).…”

“…While this breeding population was originally selected to incorporate RKN resistance, non‐targeted wild segments were introgressed, in different lineages, throughout the genome. This introduced variations of other important traits, including seed size, plant architecture, flower color, and leaf spot incidence (Ballén‐Taborda et al., 2022). This study focused on the pod and seed characteristics of peanut lineages of mixed cultivated and wild pedigrees, with a primary focus on PC (Patil et al., 2018).…”

Sustaining yield and nutritional quality of peanuts in harsh environments: Physiological and molecular basis of drought and heat stress tolerance

“…Efforts are underway to apply genomic selection (GS) for predicting the phenotypes by studying their genotypic architecture in multi-environment breeding trials (Pandey et al, 2020), but study of GS related to abiotic stress tolerance is not yet defined in peanut. Marker-assisted breeding has successfully introduced resistance to nematodes, rust and leaf spot and improved oil quality in peanuts (Varshney et al, 2014;Bera et al, 2018;Ballén-Taborda et al, 2022). Ascorbate peroxidase (APX), an antioxidant enzyme, contributes to ROS scavenging by decreasing hydrogen peroxide (H 2 O 2 ) under environmental stresses.…”