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Natural rubber is an important national strategic and industrial raw material. The leaf anthracnose of rubber trees caused by the Colletotrichum species is one of the important factors restricting the yields of natural rubber. In this study, we isolated and identified strain Bacillus velezensis SF334, which exhibited significant antagonistic activity against both C. australisinense and C. siamense, the dominant species of Colletotrichum causing rubber tree leaf anthracnose in the Hainan province of China, from a pool of 223 bacterial strains. The cell suspensions of SF334 had a significant prevention effect for the leaf anthracnose of rubber trees, with an efficacy of 79.67% against C. siamense and 71.8% against C. australisinense. We demonstrated that SF334 can lead to the lysis of C. australisinense and C. siamense mycelia by causing mycelial expansion, resulting in mycelial rupture and subsequent death. B. velezensis SF334 also harbors some plant probiotic traits, such as secreting siderophore, protease, cellulase, pectinase, and the auxin of indole-3-acetic acid (IAA), and it has broad-spectrum antifungal activity against some important plant pathogenic fungi. The genome combined with comparative genomic analyses indicated that SF334 possesses most genes of the central metabolic and gene clusters of secondary metabolites in B. velezensis strains. To our knowledge, this is the first time a Bacillus velezensis strain has been reported as a promising biocontrol agent against the leaf anthracnose of rubber trees caused by C. siamense and C. australisinense. The results suggest that B. velezensis could be a potential candidate agent for the leaf anthracnose of rubber trees. [ABSTRACT FROM AUTHOR]

Colletotrichum siamense causes rubber tree anthracnose and significant losses for the natural rubber industry. Here, actinomycete strains YQ-33, QZ-9 and WZ-2 were isolated, found to have high antagonistic activity against C. siamense and preliminarily identified as Streptomyces sp. Millet broth was the optimal medium for all strains to produce antifungal metabolites against C. siamense, and the millet broth culture filtrate from each strais greatly inhibited conidial germination and appressorial formation of C. siamense. Of the three strains, QZ-9 had relatively broad antifungal activity; its culture filtrate provided inhibition rates over 80% against mycelial growth of seven plant pathogenic fungi. Culture filtrates of QZ-9 and WZ-2 also reduced lesion size on rubber tree leaves and are promising candidates for control of rubber anthracnose. [ABSTRACT FROM AUTHOR]

• CsAtf1 affects the regulation of fludioxonil resistance. • CsAtf1 deletion attenuates the virulence of C. siamense. • CsAtf1 deletion mutants showed slightly retarded mycelial growth, small conidia, slow spore germination, and abnormal appressorium formation. In phytopathogenic fungi, the HOG MAPK pathway has roles in osmoregulation, fungicide sensitivity, and other processes. The ATF1/CREB-activating transcription factor Atf1 is a regulator that functions downstream of the HOG MAPK pathway. Here, we identified a gene, designated CsAtf1 , that encodes a bZIP transcription factor in Colletotrichum siamense , which is the main pathogen that causes Colletotrichum leaf fall disease in rubber trees in China. CsAtf1 localizes to the nucleus. Its mRNA expression correlates positively with that of CsPbs2 and CsHog1 in the HOG MAPK pathway in response to activator (anisomycin), inhibitor (SB203580) and fludioxonil treatments. The CsAtf1 deletion mutant showed slightly retarded mycelial growth, small conidia, slow spore germination, and abnormal appressorium formation. This mutant showed the increased spore germination rate after fludioxonil treatment and more resistance to the fungicide fludioxonil than did the wild-type fungus. However, unlike deletion of Pbs2 or Hog1 , which resulted in greater sensitivity to osmotic stress, the CsAtf1 deletion induced slightly increased resistance to osmotic stress and the cell wall stress response. The ΔCsAtf1 strain also exhibited significantly reduced virulence on rubber tree leaves. These data revealed that CsAtf1 plays a key role in the regulation of fludioxonil sensitivity and in pathogenicity regulation in C. siamense. [ABSTRACT FROM AUTHOR]