Correlation and variability analysis of yield and quality related traits in different peanut varieties across various ecological zones of China

Peanut cultivation in China spans various ecological zones, each with unique environmental conditions. Identifying suitable peanut varieties for these regions has been challenging due to significant phenotypic variations observed across environments. This study, based on a comprehensive analysis of 256 peanut varieties, selected nine representative varieties(Huayu23, Yuanza9102, Silihong, Wanhua2, Zhonghua6, Zhonghua16, Zhonghua21,Zhonghua215, Zhonghua24) for cultivation in five distinct ecological zones including Chengdu, Hefei, Nanjing,Shijiazhuang, and Wuhan. The yield and quality related phenotypic traits of these varieties were thoroughly assessed, revealing a complex interplay between genetic and environmental factors. Principal component analysis(PCA) effectively distinguished varieties based on yield and quality traits. Strong correlations were observed between specific traits, such as seed size and quality components. The G × E interaction was evident, as some varieties consistently performed better in certain environments. Varieties with lower coefficient of variation(CV)values exhibited stable trait expression, making them reliable choices for broad cultivation. In contrast, varieties with higher CV values displayed greater sensitivity to environmental fluctuations, potentially due to specific genetic factors. Two high oleic acid varieties, Zhonghua24 and Zhonghua215, demonstrated remarkable stability in oleic acid content across diverse environments, suggesting the presence of genetic mechanisms that buffer against environmental variations. Overall, this study underscores the importance of selecting peanut varieties based on their adaptability and performance in specific ecological zones. These findings provide valuable insights for peanut breeders and farmers, facilitating informed decisions for improved crop production and quality.

The quantity of OA and activity of cellulase and polygalacturonase are involved in variation of virulence in Sclerotium rolfsii

In order to understand the pathogenic mechanisms of Sclerotium rolfsii on peanut and to analyze the variation of virulence in S.rolfsii strains,the highly virulent strain(ZY2)and weakly virulent strain(GP3-1)were investigated under both in vivo and in vitro conditions.The results indicated that S.rolfsii directly infected peanut by producing infection cushions.ZY2 formed infection cushions earlier than GP3-1,and ZY2 produced a greater number of infection cushions compare to GP3-1.Both strains could utilize cellulose,xylose,or polygalacturonic acid in the Czapek medium.The activities of cellulase(CL)and polygalacturonase(PG)in the inoculated peanut stems increased significantly at 9 h after inoculation.The activities of CL and PG produced by ZY2 in the inoculated stems were significantly higher than that produced by GP3-1.Both strains could produce oxalic acid(OA),and the content of OA produced by ZY2 in the inoculated stems was higher than that produced by GP3-1.In summary,it suggested that S.rolfsii destroyed peanut cells through physical and biochemical factors by secreting a large amount of OA,CL and PG during the formation of infection cushions.The difference in OA content,activity of CL and PG produced by highly and weakly virulent strains played important roles in variation of virulence.

A systematic identification of cold tolerance genes in peanut using yeast functional screening system

Peanut(Arachis hypogaea L.)is a thermophilic crop,and low temperature leads to a significant reduction in annual yields.Despite a few cold tolerant germplasms or cultivars have been discovered and developed,molecular mechanisms governing peanut cold tolerance is poorly understood.Identification of keys genes involved in cold tolerance is the first step to address the underlying mechanism.In this study,we isolated and characterized 157 genes with potentials to confer cold tolerance in peanut by using a yeast functional screening system.GO(Gene ontology)and KEGG(Kyoto encyclopedia of genes and genomes)enrichment analysis of these genes revealed that ribosome and photosynthesis proteins might play essential roles in peanut cold response.Transcriptome results indicated that 60 cold tolerance candidate genes were significantly induced or depressed by low temperature.qRT-PCR analysis demonstrated that several candidate genes could be also regulated by salt or drought stress.Individual overexpression of two UDP-glycosyltransferases(AhUGT2 and AhUGT268)in transgenic yeast cells could enhance their tolerance to multiple abiotic stress.In conclusion,this study advances our understanding of the mechanisms associated with the cold stress responses in peanut,and offers valuable gene resources for genetic improvement of abiotic stress tolerance in crops.

Phenotypic identification of peanut germplasm for resistance to southern stem rot

Southern stem rot,caused by Sclerotium rolfsii Sacc.,is a destructive soil fungal disease of peanut in China and other countries.To evaluate resistant germplasm,a total of 256 peanut accessions were investigated on their resistance to southern stem rot in 3 environments by artificial inoculation.Variance analysis indicated that disease index was significantly influenced by environment,genotype and genotypeenvironment interactions.Peanut accessions of var.vulgaris type exhibited higher resistance to southern stem rot.Disease index was significantly negatively correlated with linoleic acid content,while positively correlated with oleic acid content.Six resistant accessions were identified,including Hua 28,Shandongzai,ICG 6326,Quanhua 7,Quanhua 9 and Guihua 836,with their disease indexes under 40 and mortality were less than 30%in the three environments.The identified resistant accessions showed the great potential to be applied in resistant peanut breeding,and would be good genetic resources for enhancing the resistance to southern stem rot.

Genetic diversity of atoxigenic Aspergillus flavus isolates from peanut kernels in China

Aflatoxin contamination in peanuts is a major threat to public health, especially in tropical and subtropical regions of the world. Recently, the use of atoxigenic Aspergillus flavus strains as biological control agents prove to be effective in reducing aflatoxin contamination in crops. A total of 208 atoxigenic A. flavus isolates, collected from peanut kernels, were grouped into 7 deletion patterns by quadruplex PCR products of nor-1, ver-1, aflR and omtA genes. 49 SNPs, found in 1254 bp fragment of omtA gene, showed genetic variation of omtA among different A. flavus isolates. These isolates were assigned to either MAT1-1 type or MAT1-2 type with primers for each MAT locus. Thus, rich genetic diversity was found in the atoxigenic A. flavus isolates of peanut in China. The results indicated that quadruplex PCR would be an effective method for rapid screening of atoxigenic isolates with gene deletion in aflatoxin biosynthetic cluster.

Biocontrol potential of reducing aflatoxin contamination by an atoxigenic strain of Aspergillus flavus. isolated from peanut

An Aspergillus section/Zam isolate （ NAFFHB396） was isolated from a peanut kernel. It was identified as Aspergillus flavus based on morphology and molecular characteristics. It produced yellow to green - colored conidia on CYA medium and colonies with bright orange in color on AFPA medium. NAFFHB396 was grouped with A. flavus NRRL21882 and NRRL3357 by phylogenetic analysis of partial calmodulin sequence data. It was found that 12 genes were absent in aflatoxin gene cluster in NAFF- HB396. HPLC result further showed that it was an atoxigenic isolate. Co - inoculation of NAFFHB396 with a high aflatoxin producer AF2202 at the ratio of 1：1 both on CYA medium and peanut kernel resul-ted in reduction of aflatoxin production by 88.7% and 99. 8% respectively. These results suggested that the atoxigenic NAFFHB396 obtained in this study had a great potential to be a biocontrol agent to reduce aflatoxin contamination of peanut in China.

Effect of non-aflatoxigenic strains of Aspergillus flavus on aflatoxin contamination of pre-harvest peanuts in fields in China

Aflatoxin contamination of peanuts is one of the most concerns in peanut production in China.Applying nonaflatoxigenic Aspergillus flavus strains,based on competitive exclusion,has been proved to be a promising strategy to reduce aflatoxin contamination in pre-harvest peanuts.Two non-aflatoxigenic A.flavus strains collected in China,which have been proved effectively reducing aflatoxin in the laboratory,were mixed with high aflatoxin producer to the soil in peanut growing season.The two non-aflatoxigenic strains significantly(P<0.05)reduced aflatoxin contamination in peanut kernels under both normal and drought stresses in two fields.Compared to control,the total aflatoxin(sum of aflatoxin B1 and B2)was reduced 26.7–99.12%in field 1,and 84.96–99.33%in field 2.The aflatoxin was reduced 84.96–99.33%under drought stress in two fields.The present study indicated the non-aflatoxigenic A.flavus strains could be potential biocontrol agents for reducing aflatoxin contamination under field condition.