Screening and identification of cellulose/lignin-degrading strains against plant pathogenic fungi

Abstract:

[Background] While improving soil fertility and nutrients, straw returning faces the challenge of slow straw degradation and threat of pathogenic fungi. [Objective] To screen efficient straw-degrading strains against the fungi from samples in areas with long-term straw returning. [Methods] The isolation by dilution in liquid, aniline blue staining, and Congo red staining were used to screen the efficient straw-degrading strains and the strains were identified based on 16S rRNA gene sequencing and phylogeny analysis. The inhibition of the screened straw-degrading strains on Setostphaeria turcica, Alternaria kikuchiana, Alternaria solani, and Alternaria alternate aCCC38230 and aCCC38231 was examined by the confrontation assay. Moreover, the ability of the metabolites of the antagonistic strains against S. turcica was determined, and the influence of the strains on conidial germination and hypha growth of S. turcica was detected with crude extract of antagonistic strains. [Results] Three efficient cellulose/lignin-degrading strains were screened out and named as JY122, ZY133, and JY215, which all belong to Bacillus. Phylogeny analysis revealed 99.4% similarity between JY122 and Bacillus cereus, 100% similarity between ZY133 and Bacillus subtilis, and 99.1% similarity between JY215 and Bacillus velezensis. The three had strong inhibitory effect on pathogenic fungi of different species with the inhibition rate in the range of 43.74%-67.54%. In addition, the metabolites of them showed antifungal activity and strong thermal stability, as the antifungal activity was still high after treatment at 95 ℃. [Conclusion] JY122, ZY133, and JY215 show high efficiency in degrading cellulose/lignin and inhibit the growth of a variety of plant pathogenic fungi. The metabolites of the three have strong antifungal ability and high thermal stability. This study provides strain resources for returning maize straw and a method for tackling the challenges in straw returning.