Genome-wide association analysis of 101 accessions dissects the genetic basis of shell thickness for genetic improvement in Persian walnut (Juglans regia L.)

Abstract

Background Understanding the underlying genetic mechanisms that drive phenotypic variations is essential for enhancing the efficacy of crop improvement. Persian walnut (Juglans regia L.), which is grown extensively worldwide, is an important economic tree fruit due to its horticultural, medicinal, and material value. The quality of the walnut fruit is related to the selection of traits such as thinner shells, larger filling rates, and better taste, which is very important for breeding in China. The complex quantitative fruit-related traits are influenced by a variety of physiological and environmental factors, which can vary widely between walnut genotypes. Results For this study, a set of 101 Persian walnut accessions were re-sequenced, which generated a total of 906.2 Gb of Illumina sequence data with an average read depth of 13.8× for each accession. We performed the genome-wide association study (GWAS) using 10.9 Mb of high-quality single-nucleotide polymorphisms (SNPs) and 10 agronomic traits to explore the underlying genetic basis of the walnut fruit. Several candidate genes are proposed to be involved in walnut characteristics, including JrPXC1, JrWAKL8, JrGAMYB, and JrFRK1. Specifically, the JrPXC1 gene was confirmed to participate in the regulation of secondary wall cellulose thickening in the walnut shell. Conclusion In addition to providing considerable available genetic resources for walnut trees, this study revealed the underlying genetic basis involved in important walnut agronomic traits, particularly shell thickness, as well as providing clues for the improvement of genetic breeding and domestication in other perennial economic crops.

The shape and volume of air, kernels and cracks, in a nutshell

“…Multiple-pronged strategies have been proposed and developed to unravel the underlying mechanisms that regulate shell thickness, shape, and strength. Through genome-wide association studies (GWAS), transcription factors and pathways that affect the shell and seal formation have been identified (Sideli et al, 2020; Wang et al, 2022). Walnut shell physics have been explored with numerical simulations, where walnuts are modeled as thin spheres and biophysical mechanical properties are tested under unidirectional loads based on finite-element analyses (Bao et al, 2022; Koyuncu et al, 2004).…”

The potential of non-traditional walnut shells waste for the production of antioxidant reach extracts intended for the food industry

“…According to the maximum value, the catechin content is 169.92 mg/dm 3, and that of quercetin is 100.98 mg/dm 3 . Given that all antioxidants protect the body from damage by harmful free radicals -toxins that enter from the environment and damage healthy cells, leading to inflammatory processes, it is worth noting the significant role of the flavonoid composition of the walnut shell as one of the components [36], [37] in identifying the further direction of research.…”