Phytophthora boehmeriae Sawada is an important pathogenic oomycete, and causes Phytophthora blight of cotton and ramie, which are main limiting factors to the production of cotton and ramie in China. The aggressiveness and fitness of the metalaxyl-resistant (MR) mutants of P. boehmeriae obtained by inducing on LBA amended with sublethal dose (10 µg·mL −1 ) of metalaxyl were studied in this paper. The results showed that there were no significant differences between the MR mutants and their metalaxyl-sensitive (MS) wild-type parents in temperature for mycelial growth, zoosporangium production, sensitivity to malachite green, and the pathogenicity to cotton seedlings. However, the oospore productions of the mutants were much lower than those of their MS parents. The growth rates and the colony morphology of MR mutants and their MS parents all displayed obvious variation or separation, and were inherited unsteadily in their single-zoospore and single-oospore progenies. At the same time, the homothallic character of MR mutants could inherit steadily as well as that of the MS wild-type isolates did in asexual and sexual progenies. It was suggested that the MR mutants of P. boehmeriae possessed equal aggressiveness and fitness with their MS parental isolates, and would develop the MR population easily in a short time as long as the MR mutants formed. Thereby, there would be a high risk of development of metalaxyl resistance in populations of P. boehmeriae in the field, when metalaxyl was long and continuously applied for the control of the diseases caused by P. boehmeriae.

Phytophthora sojae can cause soybean phytophthora blight, and greatly reduce soybean production. It is helpful to understand the pathogenic mechanism of P. sojae to prevent soybean phytophthora blight and ensures food security. Glycosyl hydrolases (GHs) disintegrate plant cell walls for nutrition and invasion, and they may act as an important virulence factor during P. sojae infection. To reveal the role of GHs in the main stages of P. sojae life cycle, we measured the expression level of genes, which encoded GHs, and constructed P. sojae transformants for biological function verification by the gene editing technology CRISPR-Cas9. In this study, four genes, encoded special GH proteins, with conserved glycine-rich were identified in the P. sojae genome, and their sequences were similar to those of the TOS1 family genes. One of them, the xp_009520987.1, was named PsGRGH, and was significantly upregulated during the germination of spores and in the early infection stages. The results revealed that PsGRGH was involved in the growth and mycelial morphology regulation in P. sojae, and was essential for its sporangium development and virulence. In addition, PsGRGH is localized on the cell membrane and plays an important role in tolerance toward Bacillus and abiotic stress.

本文从被侵染的大豆根茎及土壤中分离了5株病原真菌,在V8培养基上能较好的生长菌落呈现白色绒毛状松散.5株病原菌均能产生卵孢子和孢子囊,孢子囊低温诱导释放游动孢子,它们趋向性侵染大豆根部.利用特异性引物ITS6和ITS8扩增其保守序列区域,经测序比对与NCBI发布的大豆疫霉菌株序列同源性为100％;根据形态学和分子生物学结果鉴定为大豆疫霉.5株大豆疫霉的生长速率和致病力存在差异,其致病力与生长速率以及致病基因的表达成正相关关系.

Metalaxyl is one of the main fungicides used to control pepper blight caused by Phytophthora capsici. Metalaxyl resistance of P. capsici, caused by the long-term intense use of this fungicide, has become one of the most serious challenges facing pest management. To reveal the potential resistance mechanism of P. capsici to fungicide metalaxyl, a metalaxyl-resistant mutant strain SD1-9 was obtained under laboratory conditions. The pathogenicity test showed that mutant strain SD1-9 had different pathogenicity to different host plants with or without the treatment of metalaxyl compared with that of the wild type SD1. Comparative transcriptome sequencing of mutant strain SD1-9 and wild type SD1 led to the identification of 3845 differentially expressed genes, among them, 517 genes were upregulated, while 3328 genes were down-regulated in SD1-9 compared to that in the SD1. The expression levels of 10 genes were further verified by real-time RT-PCR. KEGG analysis showed that the differentially expressed genes were enriched in the peroxisome, endocytosis, alanine and tyrosine metabolism. The expression of the candidate gene XLOC_020226 during 10 life history stages was further studied, the results showed that expression level reached a maximum at the zoospores stage and basically showed a gradually increasing trend with increasing infection time in pepper leaves in SD1-9 strain, while its expression gradually increased in the SD1 strain throughout the 10 stages, indicated that XLOC_020226 may be related to the growth and pathogenicity of P. capsici. In summary, transcriptome analysis of plant pathogen P. capsici strains with different metalaxyl resistance not only provided database of the genes involved in the metalaxyl resistance of P. capsici, but also allowed us to gain novel insights into the potential resistance mechanism of P. capsici to metalaxyl in peppers.

With the improper application of fungicides, Phytophthora sojae begins to develop resistance to fungicides, and biological control is one of the potential ways to control it. We screened two strains of Bacillus; Bacillus amyloliquefaciens JDF3 and Bacillus subtilis RSS-1, which had an efficient inhibitory effect on P. sojae. They could inhibit mycelial growth, the germination of the cysts, and the swimming of the motile zoospores. To elucidate the response of P. sojae under the stress of B. amyloliquefaciens and B. subtilis, and the molecular mechanism of biological control, comparative transcriptome analysis was applied. Transcriptome analysis revealed that the expression gene of P. sojae showed significant changes, and a total of 1616 differentially expressed genes (DEGs) were detected. They participated in two major types of regulation, namely "specificity" regulation and "common" regulation. They might inhibit the growth of P. sojae mainly by inhibiting the activity of ribosome. A pot experiment indicated that B. amyloliquefaciens and B. subtilis enhanced the resistance of soybean to P. sojae, and their control effects of them were 70.7% and 65.5%, respectively. In addition, B. amyloliquefaciens fermentation broth could induce an active oxygen burst, NO production, callose deposition, and lignification. B. subtilis could also stimulate the systemic to develop the resistance of soybean by lignification, and phytoalexin.

Fuzhuan brick-tea (FBT) is unique for a fungal fermentation stage in its manufacture process and is classified in dark tea. A new acylated flavonol glycoside, kaempferol 3-O-[E-p-coumaroyl-(→2)][α-l-arabinopyranosyl-(1→3)][α-l-rhamnopyranosyl(1→6)]-β-d-glucopyranoside, which was trivially named as camellikaempferoside A (1), was isolated from FBT along with camelliquercetiside C (2). Their structures were unambiguously elucidated by combination of spectroscopic and chemical methods. Compound 1 showed anti-proliferative activity against MCF-7 and MDA-MB-231 cells with IC50 values of 7.83 and 19.16 μM, respectively.