AUTHOR=Pan Zuxian , Munir Shahzad , Li Yongmei , He Pengbo , He Pengfei , Wu Yixin , Xie Yan , Fu Zongwei , Cai Yongzhan , He Yueqiu 

TITLE=Deciphering the Bacillus amyloliquefaciens B9601-Y2 as a Potential Antagonist of Tobacco Leaf Mildew Pathogen During Flue-Curing

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.683365

DOI=10.3389/fmicb.2021.683365

ISSN=1664-302X

ABSTRACT=<p>Tobacco leaf mildew caused by <italic>Rhizopus oryzae</italic> (<italic>Mucorales, Zygomycota</italic>) is an important and devastating post-harvest disease during flue-cured tobacco period, and also is known to cause diseases of fruits and vegetables. In this study, assessment of several candidate biological control agents were first tested <italic>in vitro</italic> to determine their antifungal activities and potential strains were further applied to tobacco leaves to prevent pathogen colonization during the tobacco-curing process. <italic>In vitro</italic> screening of 36 bacteria and the isolates of one fungus were performed for their antifungal activities against <italic>R. oryzae</italic> using dual culture method. Potential five isolates viz. <italic>Bacillus amyloliquefaciens</italic> B9601-Y2 (Y2), <italic>B. amyloliquefaciens</italic> YN201728 (YN28), <italic>Pseudomonas</italic> sp. (Pb), and <italic>B. amyloliquefaciens</italic> YN201732 (YN32) and <italic>T. harzianum</italic> B (Th-B) from total screened isolates have shown remarkable results for controlling the mycelial growth of <italic>R. oryzae</italic>. Finally, out of these five isolates, <italic>B. amyloliquefaciens</italic> B9601-Y2 potentially reduced the mycelial growth of fungal pathogen with great inhibitory effect. In order to get a better understanding of the biocontrol effect of B9601-Y2 in a flue-curing barn, various suspension density tests with two application methods involving spraying and soaking were examined. Two application methods of <italic>B. amyloliquefaciens</italic> B9601-Y2 had 98.60 and 98.15% control effects, respectively. In curing barn, the incidence in the treatment group was significantly reduced and tobacco leaves did not get mildew. Altogether, the study demonstrated that candidate bacterial strain <italic>B. amyloliquefaciens</italic> B9601-Y2 is a potential antagonist for the management of tobacco leaf mildew during flue-curing.</p>