Peyronellaea arachidicola is the causal agent of peanut (Arachis hypogaea L.) web blotch. Here, we report an assembled draft genome sequence of P. arachidicola strain YY187 obtained from the symptomatic leaf of peanut in China. The genome size is 47.3 Mb, consisting of 26 contigs (N₅₀= 2.2 Mb) with G+C content of 56.37%. This genome will provide a valuable foundation for further research on genetics and comparative genomics of P. arachidicola.

Peanut is an economical crop of global importance and grown widely in both tropics and subtropics. Currently, China is the largest peanut production, consumption and trade countries around the world. In August 2014, light-brown foliar spots with dark brown, irregular borders were found on peanut (Yuhua 22) at Xinyang in Henan province, China. Symptomatic leaf samples were collected, and surface-sterilized (75% ethanol, 30 s; 3% NaClO, 2 min), rinsed in sterile water for three times, air-dried, plated on potato dextrose agar (PDA) medium, and incubated at 25°C under a 12-h dark/light cycle. Colonies on PDA were initially gray, fluffy mycelium with unevenly distributed mycelial pellets, then becoming dark gray with age. Conidia were oblong, slightly curved, and light-brown with 6 to 10 septa. Conidial sizes (length × width) were 57.5 to 144.7×8.4 to 21.4 (average 102.0×13.8) μm. Pathogenicity tests were conducted with 6-week-old peanut plants. Ten 16×12-cm pots with six plants per pot were inoculated onto the peanut leaves, daubed evenly with mycelial suspension (due to low spore production) which was prepared from cultures grown on PDA medium for 7 days. Two additional pots were inoculated with sterile water to serve as controls. Peanuts were enclosed in a plastic bag for 72 hours to keep high humidity and incubated at 25°C. Then plastic bags were removed, and plants were incubated at 28°C with 60 to 70% relative humidity and a 12-h photoperiod of dark and light. Foliar spot symptoms appeared 10 to 14 days after inoculation, and were identical to those described in the original leaf samples, while no symptoms were observed on control plants. Koch’s postulates were fulfilled by reisolating the colonies with the same morphology as described above. Isolates were identified as Bipolaris species based on cultural and morphological characteristics (Manamgoda et al. 2012). To further confirm the identification, the ITS, GPD and EF1-α genes were amplified with PCR using primer pairs ITS1/ITS4, gpd1/gpd2 and EF983/EF2218R, respectively (Manamgoda et al. 2012). The PCR products were sequenced and the BLASTn search showed that: (1) sequences from the original isolate and the reisolated pathogen were identical; (2) isolates were identified as Bipolaris oryzae by the combined three-gene analysis (Manamgoda et al. 2014) of ITS, GPD and EF1-α sequences (GenBank accession no. KR738745, MF033264 and MF033265, respectively). So far, Bipolaris oryzae has been reported only on monocot hosts such as Oryza sativa, Zizania palustris, Panicum virgatum, Zea mays and Aechmea tayoensis et al. (Farr et al. 1989, Vu and Dee 2013, Sanahuja and Palmateer 2016). To our knowledge, this is the first report of B. oryzae found on peanut (dicot host) in China. Whether the isolate of B. oryzae in this report can infect other dicot hosts needs to be further investigated.

Didymella arachidicola is one of the most important fungal pathogens, causing foliar disease and leading to severe yield losses of peanuts (Arachis hypogaea L.) in China. Two main lesion phenotypes of peanut web blotch have been identified as reticulation type (R type) and blotch type (B type). As no satisfactory reference genome is available, the genomic variations and pathogenicity factors of D. arachidicola remain to be revealed. In the present study, we collected 41 D. arachidicola isolates from 26 geographic locations across China (33 for R type and 8 for B type). The chromosome-scale genome of the most virulent isolate (YY187) was assembled as a reference using PacBio and Hi-C technologies. In addition, we re-sequenced 40 isolates from different sampling sites. Genome-wide alignments showed high similarity among the genomic sequences from the 40 isolates, with an average mapping rate of 97.38%. An average of 3242 SNPs and 315 InDels were identified in the genomic variation analysis, which revealed an intraspecific polymorphism in D. arachidicola. The comparative analysis of the most and least virulent isolates generated an integrated gene set containing 512 differential genes. Moreover, 225 genes individually or simultaneously harbored hits in CAZy-base, PHI-base, DFVF, etc. Compared with the R type reference, the differential gene sets from all B type isolates identified 13 shared genes potentially related to lesion phenotype. Our results reveal the intraspecific genomic variation of D. arachidicola isolates and pathogenicity factors potentially related to different lesion phenotypes. This work sets a genomic foundation for understanding the mechanisms behind genomic diversity driving different pathogenic phenotypes of D. arachidicola.

Leguminous plants are critical global crops for food security, animal feed, and ecological sustainability due to their ability to establish nitrogen-fixing symbioses with rhizobia and their high nutritional value. Autophagy, a highly conserved eukaryotic catabolic process, mediates the degradation and recycling of cytoplasmic components through the fusion of autophagosome with vacuole/lysosome and plays essential roles in plant growth, stress adaptation, and cellular homeostasis. This review systematically summarizes current knowledge of autophagy in both Arabidopsis and leguminous plants. We first outline the conserved molecular machinery of autophagy, focusing on core autophagy-related (ATG) genes in Arabidopsis and key legume species such as Glycine max, Arachis hypogaea, Pisum sativum, Cicer arietinum, and Medicago truncatula. Furthermore, the review dissects the intricate molecular regulatory networks controlling autophagy, with an emphasis on the roles of phytohormones, transcription factors, and epigenetic modifications. We then highlight the multifaceted physiological functions of autophagy in these plants. Additionally, a preliminary analysis of the ATG8 gene family in peanut indicates that its members may be involved in seed development, biological nitrogen fixation, and drought resistance. Finally, it highlights key unresolved challenges in legume autophagy research and proposes future research directions. This review aims to provide a comprehensive theoretical framework for understanding the unique regulatory mechanisms of autophagy in legumes and to provide insights for molecular breeding aimed at developing stress-resilient, high-yielding, and high-quality legume cultivars.