Morphological and Genetic Characterization of Non‐Nodulating Peanut Recombinant Inbred Lines

Abstract

Peanut (Arachis hypogaea L.) nodulation is relatively diverged from other legumes. Further understanding of nodulation mechanisms would facilitate improvement of biological N fixation and yield in peanut. The objective of this study was to characterize the non‐nodulating (Nod−) peanut recombinant inbred lines (RILs) in comparison to their nodulating (Nod+) sister RILs morphologically and genetically. Two pairs of Nod− and Nod+ RILs were inoculated with rhizobia for morphological observation. Nodules and root hairs were absent in Nod− lines and present in Nod+ lines. The Nod− lines had a much smaller canopy with yellow leaves and fewer pods than Nod+ lines. Simple‐sequence repeat (SSR) marker genotyping of the two pairs of RILs and their parental lines revealed several chromosome regions differing between Nod− and Nod+ sister lines, which potentially harbor the genes controlling nodulation. Two F2 populations segregating for nodulation were constructed by crossing the two Nod− lines with their Nod+ sister lines. The segregation ratios of Nod−/Nod+ of the two populations followed 7:9 and 7:57, respectively, indicating that multiple genes were involved in controlling peanut nodulation. The results from this study provided important morphological and genetic information related to peanut nodulation, which paved the road for further mapping and cloning of peanut nodulation genes and for eventually developing peanut cultivars with improved N fixation efficiency.

Involvement of Root Hair during <i>Rhizobial</i> Invasion in Cultivated Peanut (<i>Arachis hypogaea</i> L.)

“…Therefore, they concluded that 'crack entry' mode of infection is used in the absence of root hair in L. japonicus. In another word, the root hair is not required for crack entry infection, which is in agreement with our findings, though many other studies indicated that infection of peanut only occurs in the presence of root hair at the base of the lateral roots [7] [13] [14] [15].…”

“…Liang and Harris [27] proposed that the tendency of legumes to form no-American Journal of Plant Sciences dules may be linked to a difference in ABA sensitivity. Since root hair formation and nodule development mechanisms in different legume species, M. truncatula and L. japonicas, share some phytohormones [26], it is highly possible that peanut nodule development and root hair formation mechanisms share the same phytohormones, thus the closely linked or co-segregation relationship observed between nodulation and RoH formation in our study and other reported studies [13] [14] [15]. Further genetic and molecular studies on peanut root hair formation and nodulation need to be conducted to test the relationship between RoH, nodulation, their genetic and hormonal controls.…”

“…showed that RoH was almost completely co-segregating with nodulation. In another word, RoH is only present in nodulating peanut while absent in non-nodulating peanut plants [15]. These observations signal a close relationship between RoH and peanut nodulation, though previous reports indicated that peanut root infection by Bradyrhizobia is not through root hair because Bradyrhizobia enter the plant at epidermal ruptures [6].…”

Comparison of SNP Calling Pipelines and NGS Platforms to Predict the Genomic Regions Harboring Candidate Genes for Nodulation in Cultivated Peanut

“…They are also parental lines for two F 2 mapping populations (E4 × E5 and E6 × E7) for genetic mapping of nodulation genes. The morphological and genetic characterizations of the RILs were previously described (Peng et al, 2018). The genomic DNA of the six genotypes was extracted by using the CTAB method (Rogers and Bendich, 1994).…”

“…A transcriptome study using root samples from two sets of recombinant inbred lines (RILs) with Nod+ and Nod− phenotype revealed hundreds of differentially expressed genes (DEGs) upon infection with rhizobia (Peng et al, 2017a). In addition, the same materials were morphologically and genetically characterized to initiate studies on peanut nodulation genes (Peng et al, 2018). A total of 188 simple sequence repeat (SSR) markers were used for genetic characterization, and only a few polymorphic SSRs were obtained between the RILs due to their high genetic similarity.…”