The Pyricularia grisea Strain MT-2 is Effective in Inhibiting Digitaria sanguinalis Growth and Inducing Rice Resistance to Blast Fungus

Purpose Based on the infection capability of Digitaria sanguinalis isolates against D. sanguinalis and their inducibility of resistance to rice blast, this study aimed to explore Pyricularia strains that could simultaneously achieve D. sanguinalis control and rice blast management, thereby providing resource reserves and technical support for the biological control of both weed infestation and rice blast disease in upland rice production systems.

Methods Taking the isolate MT-2 derived from D. sanguinalis as the research subject, its taxonomic status was determined by morphological observation and multi-gene phylogenetic tree constrction. Its pathogenicity to D. Sanguinalis and its ability to induce resistance to rice blast were assessed using artificial inoculation under greenhouse conditions. Furthermore, the effects of strain MT-2 on inhibiting D. sanguinalis growth and enhancing rice blast resistance was evaluated under rice-D. sanguinalis co-growth conditions.

Results The conidia of strain MT-2 were obpyriform or fusiform, mostly consisting of three cells, with a size of (19.8±1.5) μm×(8.1±0.4) μm. Multi-gene phylogenetic analysis showed 100% sequence identity with P. grisea strains. Artificial inoculation assays demonstrated that MT-2 possessed strong pathogenicity to D. sanguinalis, but was avirulent to the rice cultivar CO39, which was highly susceptible to blast fungi. Pretreatment of CO39 seedlings with the MT-2 conidial suspension significantly enhanced their resistance to the virulent rice blast isolate Guy11. Under rice-D. sanguinalis co-growth conditions, foliar application of MT-2 conidial suspension effectively controlled D. sanguinalis and simultaneously enhanced rice blast resistance.

Conclusion The pathogenic strain MT-2 isolated from D. sanguinalis was identified as P. grisea. It exhibits strong pathogenicity to D. sanguinalis but is avirulent to rice. Treatment with MT-2 conidial suspension significantly enhances rice resistance to the blast fungus. Therefore, MT-2 shows potential for controlling D. sanguinalis and simultaneously preventing rice blast disease occurrence in upland rice fields.