Marker-assisted introgression of wild chromosome segments conferring resistance to fungal foliar diseases into peanut (Arachis hypogaea L.)

Colonization of Serendipita indica enhances resistance against Phoma arachidicola in Arachis hypogaea L

The endophytic fungus Serendipita indica (Si) could suppress Phoma arachidicola (Pa) and control peanut web blotch disease. The study evaluated its growth-promoting and disease-resistant effects in two peanut cultivars, Luhua11 and Baisha1016. In vitro experiments and microscopy analysis demonstrated that S. indica suppressed the growth of P. arachidicola. Additionally, scanning electron microscopy illustrated that S. indica adversely affected the pathogen's hyphae. LSi treatment showed the highest stem height (35 cm), root length (15.533 cm), shoot fresh weight (9.33 g), shoot dry weight (1.30085 g), root dry weight (0.1990 g), and chlorophyll a (1.3253) and b (1.8316), while BPa had the lowest values of these parameters. The highest MDA value was observed at 96 h for BPa with (3.14598 nmol/g), and the highest proline value was observed at 72 h for LSi-Pa with (56.42851 µmol/g). Antioxidant enzymes, catalase, peroxidase, ascorbate peroxidase, and phenylalanine ammonia-lyase, increased significantly after 48 h in cultivar L. The most significant result is observed in salicylic acid with LSi-Pa at 72 h (702.10 µg/mL), showing a consistent significant difference. RNA-seq analysis revealed more pronounced transcriptomic changes in cultivar L, with enriched pathways related to flavonoid biosynthesis and defense responses. The LSi-Pa treatment significantly upregulated gene expression at 96 h, with AhNPR1 (0.05807), AhNPR10 (0.10536), AhPAL1 (4.30831), and Ahcapx (0.22074), demonstrating a strong regulatory effect. These results demonstrate that S. indica enhances peanut plant growth and resilience against P. arachidicola, mainly through modulation of oxidative stress and immune responses.

Calcium enhanced the resistance against Phoma arachidicola by improving cell membrane stability and regulating reactive oxygen species metabolism in peanut

BACKGROUND

Peanut (Arachis hypogaea), a vital oil and food crop globally, is susceptible to web blotch which is a significant foliar disease caused by Phoma arachidicola Marasas Pauer&Boerema leading to substantial yield losses in peanut production. Calcium treatment has been found to enhance plant resistance against pathogens.

RESULTS

This study investigates the impact of exogenous calcium on peanut resistance to web blotch and explores its mechanisms. Greenhouse experiments revealed that exogenous calcium treatment effectively enhanced resistance to peanut web blotch. Specifically, amino acid calcium and sugar alcohol calcium solutions demonstrated the best induced resistance effects, achieving reduction rates of 61.54% and 60% in Baisha1016, and 53.94% and 50% in Luhua11, respectively. All exogenous calcium treatments reduced malondialdehyde (MDA) and relative electrical conductivity (REC) levels in peanut leaves, mitigating pathogen-induced cell membrane damage. Exogenous calcium supplementation led to elevated hydrogen peroxide (H2O2) content and superoxide anion (O2∙-) production in peanut leaves, facilitating the accumulation of reactive oxygen species (ROS) crucial for plant defense responses. Amino acid calcium and sugar alcohol calcium treatments significantly boosted activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in peanut leaves. Activation of these antioxidant enzymes effectively scavenged excess ROS, maintaining ROS balance and mitigating cellular damage.

CONCLUSIONS

In summary, exogenous calcium treatment triggered ROS production, which was subsequently eliminated by the activation of antioxidant enzymes, thereby reducing cell membrane damage and inducing defense responses against peanut web blotch.

Genetic diversity, disease resistance, and environmental adaptation of Arachis duranensis L.: New insights from landscape genomics

The genetic diversity that exists in natural populations of Arachis duranensis, the wild diploid donor of the A subgenome of cultivated tetraploid peanut, has the potential to improve crop adaptability, resilience to major pests and diseases, and drought tolerance. Despite its potential value for peanut improvement, limited research has been focused on the association between allelic variation, environmental factors, and response to early (ELS) and late leaf spot (LLS) diseases. The present study implemented a landscape genomics approach to gain a better understanding of the genetic variability of A. duranensis represented in the ex-situ peanut germplasm collection maintained at the U.S. Department of Agriculture, which spans the entire geographic range of the species in its center of origin in South America. A set of 2810 single nucleotide polymorphism (SNP) markers allowed a high-resolution genome-wide characterization of natural populations. The analysis of population structure showed a complex pattern of genetic diversity with five putative groups. The incorporation of bioclimatic variables for genotype-environment associations, using the latent factor mixed model (LFMM2) method, provided insights into the genomic signatures of environmental adaptation, and led to the identification of SNP loci whose allele frequencies were correlated with elevation, temperature, and precipitation-related variables (q < 0.05). The LFMM2 analysis for ELS and LLS detected candidate SNPs and genomic regions on chromosomes A02, A03, A04, A06, and A08. These findings highlight the importance of the application of landscape genomics in ex situ collections of peanut and other crop wild relatives to effectively identify favorable alleles and germplasm for incorporation into breeding programs. We report new sources of A. duranensis germplasm harboring adaptive allelic variation, which have the potential to be utilized in introgression breeding for a single or multiple environmental factors, as well as for resistance to leaf spot diseases.

Development and evaluation of the utility of GenoBaits Peanut 40K for a peanut MAGIC population

Population and genotype data are essential for genetic mapping. The multi-parent advanced generation intercross (MAGIC) population is a permanent mapping population used for precisely mapping quantitative trait loci. Moreover, genotyping-by-target sequencing (GBTS) is a robust high-throughput genotyping technology characterized by its low cost, flexibility, and limited requirements for information management and support. In this study, an 8-way MAGIC population was constructed using eight elite founder lines. In addition, GenoBaits Peanut 40K was developed and utilized for the constructed MAGIC population. A subset (297 lines) of the MAGIC population at the S2 stage was genotyped using GenoBaits Peanut 40K. Furthermore, these lines and the eight parents were analyzed in terms of pod length, width, area, and perimeter. A total of 27 single nucleotide polymorphisms (SNPs) were revealed to be significantly associated with peanut pod size-related traits according to a genome-wide association study. The GenoBaits Peanut 40K provided herein and the constructed MAGIC population will be applicable for future research to identify the key genes responsible for important peanut traits.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01417-w.