การคัดแยกบาซิลลัสจากดินป่าชายเลนที่เป็นสารควบคุมทางชีวภาพสำหรับยับยั้งราก่อโรคพืช

Abstract

Plant diseases are among the most serious threats that cause preharvest and postharvest losses of agricultural products. Therefore, the control of disease is very important. The aim of this study is to isolate Bacillus sp. from mangrove soil that produces biocontrol agent against phytopathogenic fungi under optimal conditions. A biological agent from bacteria has the potential to inhibit plant pathogenic fungi. Out of 98 isolated bacteria from the mangrove soil, 36 isolated bacteria are gram positive bacteria that include rod or bacilli shape. After the biochemical test, it was found that there were only 18 isolated bacteria similar to Bacillus species. All of 18 isolated bacteria were also tested for antifungal activity against F. solani, F. moniliforme, F. proliferatum, P. palmivora and C. gloeosporioides by dual culture method. The results showed that 6 isolated can inhibit fungal pathogens. After the antifungal activity test by using culture filtrate, found that VIMSH06 can inhibit F. solani at 71.622.21%. VIMSH06 was highly similar to Bacillus at the pairwise similarity 99.93%. The appropriate conditions of VIMSH06 for the best inhibition of F. solani was to culture bacteria in Nutrient Broth (NB) pH 7 at 37°C for 21 h. The pH and temperature stability test demonstrated that the active substance in the culture filtrate was stable for at least 20 min at pH 2 to 10 and at 20 to 121°C. The hypha and tip of F. solani showed the abnormality when treated with culture filtrate of VIMSH06 under microscopy. In vivo test, the result revealed that the corn seedling roots were infected with conidia of F. solani and culture filtrate of VIMSH06 can protect the corn seedling from F. solani. Thus, the bacterial isolate VIMSH06 may be applied to a new approach for inhibition of fungal plant pathogens in sustainable agriculture.