Fermentation Optimization Of Photorhabdus Luminescens And Its Activity Against Banana Fusarium Wilt

Photorhabdus luminescens is a symbiotic bacteria of Photorhabdus and Heterorhaditis nematodes.It can secrete hydroxystibenes,anthraquinone,bacteriocin and chitinase,and inhibit a variety of plant pathogens,which is a kind of new biological resources with the development potential and application prospect.In view of the devastating soil borne disease banana fusarium wilt without special agents and disease-resistant varieties,this study is aimed to determine the control effect of Photorhabdus luminescens Hb1029 strain on Fusarium oxysporum f.sp.Cubense(Foc4),and optimize fermentation condition of Hb1029 strain that has a high inhibition activity to Foc4.These can provide a theory and practice basis for Hb1029 strain application in the biological control of banana fusarium wilt.The main results of this study are as follows:The symbiotic strain Hb1029 was identified by molecular biology.Its 16 S r DNA full-length sequence was obtained by PCR amplification,with a length of 1283 bp,and was identified as Photorhabdus luminescens by the BLAST analysis.The Hb1029 strain had a good inhibitory activity against the growth and spore germination of pathogen Foc4.The activity tests showed that its fermentation broth and aseptic filtrate had obvious inhibition zones to Foc4,with a diameter of 22.6 mm and 19.8mm,respectively.The spore germination rate of Foc4 was only 36.17 % after Hb1029 strain treatment,and the difference was significant(P<0.001).Treatments with Hb1029 strain before or after banana seedlings transplanting could significantly reduced the incidence index of banana fusarium wilt,and the control efficiencies were 82.3 % and85.1 %,respectively.The Hb1029 strain could effectively inhibit banana fusarium wilt.Field trials showed that the incidence rate of banana in the control group reached 28.89 %,while the incidencerate of Hb1029 strain treatment group was only 5.53 %,and the difference between the two groups was significant(P<0.001).The control efficiencies of Hb1029 strain treatment group increased with the processing time,and the maximum reached 80.86 %.The optimal fermentation conditions of Hb1029 strain were as follows: NA medium with p H 7.2,and fermental cultivation at 28 ℃ and 180 rpm/min for 48 h,Hb1029 strain grew best with a high bacteria density,and exhibited the strongest inhibition activity to Foc4 spore germination.To sum up,Photorhabdus luminescens Hb1029 has a significant inhibitory activity against pathogen Foc4,and can effectively inhibits the banana fusarium wilt in the field,which shows that Hb1029 strain has a potential application prospect.