Isolation,screening and identification of rotting fungi and antagonistic bacteria of postharvest melon in Xinjiang
[Objective]The main spoilage microorganisms in postharvest melon were isolated and identified,and the antagonistic strains with the best preservative effect were screened to enrich the antagonistic bacteria resources for postharvest preservation of melon.[Method]In the study,the tissue block separation method was used to isolate the spoilage bacteria in the rotting melon fruit,and the gradient dilution method was used to isolate the antagonistic bacteria from the soil of the melon planting area.The biocontrol bacteria with strong antagonistic effect were screened by the plate confrontation method,and the species were determined by morphological observation,physiological and biochemi-cal determination and biological identification.The effect of antagonistic bacteria on mycelial growth and conidia germination was determined to clarify the control effect of antagonistic bacteria on spoilage bacteria.[Result]In the study,a major pathogen CH-3 was isolated.Through BLAST alignment and phylogenetic analysis of ITS,tef and tub gene sequences,combined with the observation of colony morphological char-acteristics,the pathogen CH-3 was identified as Fusarium oxysporum.67 strains of bacteria were isolated from the soil of muskmelon planting area.Three strains of antagonistic bacteria with strong antibacterial activity were obtained by antagonistic test,which were BG-1,BG-2 and BG-3,respectively.BG-2 with better antibacterial effect was selected as the test strain.Combined with physiological and biochemical determi-nation,colony and bacterial morphological characteristics observation and 16S rDNA,gyrB and rpoB gene sequence analysis results,the antag-onistic bacteria BG-2 was identified as Bacillus velezensis.The results of pathogenicity test showed that the pathogenic fungus CH-3 was patho-genic to melon.The relative inhibition rates of BG-2 on spore germination and mycelial growth of F.oxysporum CH-3 were 90.00％and 60.11％,respectively.[Conclusion]An antagonistic strain BG-2 with the best antagonistic effect is obtained and identified as B.velezensis.A main spoilage fungus CH-3 of melon is isolated and identified as F.oxysporum.B.velezensis BG-2 has a strong antagonistic effect on F.oxyspo-rum CH-3,and the spoilage fungus CH-3 is pathogenic to melon.The antagonistic bacteria BG-2 can effectively inhibit the spore germination and mycelial growth of F.oxysporum CH-3,and the higher the concentration of antagonistic bacteria,the better the inhibitory effect on spore germination.It has potential application value in postharvest storage and biological preservation of melon.
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