Guoping Ma

Fusarium crown rot (FCR) has become one of the most serious diseases affecting wheat production worldwide. To date, many Fusarium species associated with wheat FCR disease have been reported. To gain a deeper understanding of Fusarium species diversity associated with wheat FCR, extensive research was conducted to identify different Fusarium species. A total of 194 diseased wheat samples were collected from Dezhou, Heze, Jining, Linyi, Qingdao, Rizhao, Weihai, and Zaozhuang cities of Shandong Province, China. A total of 1,512 Fusarium isolates were obtained from collected samples and identified using sequence analysis of the translation elongation factor-1α (TEF-1α), RNA polymerase II largest subunit (RPB1), and RNA polymerase II second largest subunit (RPB2) gene sequences. Of these Fusarium isolates, 1,082 were identified as Fusarium pseudograminearum, and the remaining isolates were identified as F. graminearum (n = 338), F. asiaticum (n = 41), F. proliferatum (n = 17), F. sinensis (n = 8), F. oxysporum (n = 7), F. acuminatum (n = 6), F. verticillioides (n = 5), F. nanum (n = 3), F. sulawesiense (n = 2), F. fujikuroi (n = 1), F. odoratissimum (n = 1), and F. reticulatum (n = 1). Among the 13 Fusarium species, F. verticillioides, F. nanum, F. sulawesiense, F. fujikuroi, F. odoratissimum, and F. reticulatum were obtained from wheat FCR samples for the first time and were considered six new record species. Pathogenicity tests of all the six newly recorded Fusarium species on the major wheat cultivar ‘Jimai 22’ revealed that all the tested isolates caused FCR disease. This is the first report of F. fujikuroi, F. nanum, F. odoratissimum, F. reticulatum, F. sulawesiense, and F. verticillioides causing wheat FCR worldwide.

Wheat is a vital global food crop, yet it faces challenges in saline–alkali soils where Fusarium crown rot significantly impacts growth. Variations in wheat growth across regions are often attributed to uneven terrain. To explore these disparities, we examined well-growing and poorly growing wheat samples and their rhizosphere soils. Measurements included wheat height, root length, fresh weight, and Fusarium crown rot severity. Well-growing wheat exhibited greater height, root length, and fresh weight, with a lower Fusarium crown rot disease index compared to poorly growing wheat. Analysis of rhizosphere soil revealed higher alkalinity; lower nutrient levels; and elevated Na, K, and Ca levels in poorly growing wheat compared to well-growing wheat. High-throughput sequencing identified a higher proportion of unique operational taxonomic units (OTUs) in poorly growing wheat, suggesting selection for distinct fungal species under stress. FUNGuild analysis indicated a higher prevalence of pathogenic microbial communities in poorly growing wheat rhizosphere soil. This study underscores how uneven terrains in saline–alkali soils affect pH, nutrient dynamics, mineral content, wheat health, and rhizosphere fungal community structure.

The acetylation of histone lysine residues regulates multiple life processes, including growth, conidiation, and pathogenicity in filamentous pathogenic fungi. However, the specific function of each lysine residue at the N-terminus of histone H3 in phytopathogenic fungi remains unclear. In this study, we mutated the N-terminal lysine residues of histone H3 in Fusarium pseudograminearum, the main causal agent of Fusarium crown rot of wheat in China, which also produces deoxynivalenol (DON) toxins harmful to humans and animals. Our findings reveal that all the FpH3^K9R, FpH3^K14R, FpH3^K18R, and FpH3^K23R mutants are vital for vegetative growth and conidiation. Additionally, FpH3K14 regulates the pathogen’s sensitivity to various stresses and fungicides. Despite the slowed growth of the FpH3^K9R and FpH3^K23R mutants, their pathogenicity towards wheat stems and heads remains unchanged. However, the FpH3^K9R mutant produces more DON. Furthermore, the FpH3^K14R and FpH3^K18R mutants exhibit significantly reduced virulence, with the FpH3^K18R mutant producing minimal DON. In the FpH3^K9R, FpH3^K14R, FpH3^K18R, and FpH3^K23R mutants, there are 1863, 1400, 1688, and 1806 downregulated genes, respectively, compared to the wild type. These downregulated genes include many that are crucial for growth, conidiation, pathogenicity, and DON production, as well as some essential genes. Gene ontology (GO) enrichment analysis indicates that genes downregulated in the FpH3^K14R and FpH3^K18R mutants are enriched for ribosome biogenesis, rRNA processing, and rRNA metabolic process. This suggests that the translation machinery is abnormal in the FpH3^K14R and FpH3^K18R mutants. Overall, our findings suggest that H3 N-terminal lysine residues are involved in regulating the expression of genes with important functions and are critical for fungal development and pathogenicity.

Mycoviruses are widespread in all major groups of plant-pathogenic fungi. So far, only one mycovirus has been reported to be associated with Fusarium pseudograminearum, the causal agent of Fusarium crown rot of wheat. In this study, a double-stranded RNA (dsRNA) segment was isolated from F. pseudograminearum strain JW2-1, and the sequence of its full-length cDNA (3077 nucleotides) was determined. Sequence analysis using the fungal mitochondrial genetic code (UGA coding for tryptophan) indicated that a single large open reading frame (ORF) is present on the positive strand of this dsRNA segment. The ORF encodes a putative RNA-dependent RNA polymerase (RdRp) of 748 amino acids (aa) with a molecular mass of 83.46 kDa. BLASTp analysis revealed that its aa sequence was 28.49–44.03% identical to those of viruses of the family Mitoviridae, with the most similarity to the corresponding RdRp sequences of Ophiostoma mitovirus 1c (44.03% identity) and Ophiostoma mitovirus 1b (40.33% identity). Phylogenetic analysis showed that this mycovirus, designated as "Fusarium pseudograminearum mitovirus 1" (FpgMV1), should be classified as a member of a new species in the earlier proposed genus "Duamitovirus" within the family Mitoviridae. To our best of our knowledge, this is the first report of a mitovirus infecting F. pseudograminearum.

Watermelon is an economically important crop in China and is commonly affected by Alternaria-like leaf blight that can result in significant economic losses. In this study, 830 Alternaria isolates, recovered from symptomatic watermelon leaves, were identified based on morphological traits, pathogenicity, and multilocus sequence analyses of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone 3 (HIS3), the internal transcribed spacer of ribosomal DNA (rDNA ITS), and the RNA polymerase II second largest subunit (RPB2). Watermelon isolates grouped to five Alternaria species and one unclassified Alternaria species. They were A. tenuissima, A. alternata, A. cucumerina, A. infectoria, A. gaisen, and Alternaria sp. Notably, A. tenuissima was the most prevalent (73.5%) of the six isolated species, followed by A. alternata (25.0%), A. cucumerina (1.1%), Alternaria sp. (0.2%), A. infectoria (0.1%), and A. gaisen (0.1%). Pathogenicity tests demonstrated that all six Alternaria species could produce brown necrotic lesions on detached leaves of watermelon. The average disease incidence (75.1%) and average disease index (60.8) of watermelon resulting from inoculation of leaves with A. cucumerina were significantly higher than levels resulting from A. alternata (52.9% and 37.2) and A. tenuissima (47.5% and 30.8). Inoculation with Alternaria sp. resulted in a disease incidence (70.0%) and disease index (51.5), which were lower than those of A. cucumerina. The disease incidence and disease index in watermelon leaves inoculated with the one isolate of A. infectoria and the one isolate of A. gaisen present in the inoculated leaves were 28.9% and 16.4, and 48.9% and 31.4, respectively. Results of the study indicate that Alternaria species associated with watermelon leaf blight in China are more diverse than that has been previously reported. This is the first report globally of A. infectoria, A. gaisen, and an unclassified Alternaria species as causal agents of leaf blight on watermelon.

Potato leaves with symptoms of foliar diseases were collected from eight different geographical areas in southern China. A total of 109 Alternaria isolates were recovered and identified to three species according to morphological characteristics, nucleotide sequencing and PCR-RFLP analysis. Three Alternaria species were recovered, of which A. tenuissima was the most common, followed by A. alternata and A. solani. Pathogenicity tests indicated that all species caused foliar symptoms on potato cultivar ‘Favorite’. Compared with earlier results reported in 2010–2013 in northern China, the proportion of A. alternata isolates was notably increased, while the number of A. solani isolates was lower. This study provides a survey of the Alternaria species composition associated with potato foliar diseases in southern China.