| Bacillus subtilis can produce endogenous spores,and has high resistance to adverse conditions,and can take control of many kinds of plant diseases,such as verticillium wilt, rice blast,wheat take-all,tobacco bacterial wilt and so on.While controlling the diseases, many bacterial strains can promote growth and increase production,and meanwhile do little harm to the environment and the animals.Zhang zhi yuan isolated endogenous bacteria from branch of the good plants of large tangerines,oranges,and shaddocks in Meizhou GuanDong,Beipei Chongqing,and Shimen Hunan,which had the antagonistic effect on Sclerotinia sclerotiorum.The biological characters and colonization of the isolated YS-45 are studied in this paper:using aseptic seedlings and potted seedlings in seedling stage of the rape by the diproots in inoculum.The main results are the following:1.Rape seed has high rate of the endogenous germ,so it is not suitable for it to bring up directly aseptic seedling.Instead,we should choose the rape samples which have low bacterial rate and less bacterial numbers to cultivate aseptic seedlings,along with the -1% per liter mercury explantation sterilizing disinfection.The results showed that the other breeds reached up to 55.0%～85.0%in the endogenous germ's bacterial rate of the rape seed except M004,which was lower,only 30.0%;the M004 seed's bacterial numbers was also lower,1.5×10~5cfu/g,the most was 98C04,6.0×10~5cfu/g.2.The research result of the YS-45 growing property showed that the pH value of the most suitable growth for its bacterial strain was 7.0 and the optimal temperature was 30℃. The YS-45 bacterial strain grew slowly by shining of the 20W ultraviolet lights at various times,and along with the long time for cultivation,its total bacterial strain numbers were increasing continuously and were stable after 36h which its viable counted attain the peak value,and after that,decreased considerably.So the YS-45 bacterial strain grew stably during 24h～36h.3.For colonization study,a Kanamycin resistant YS-45 mutants,YS-45,was selected that could grow stably in 70μg/ml Kanamycin without changes in colony shape and the antagonism of Sclerotinia sclerotiorum.The results showed that 1.2×10~9cfu/ml of YS-45 could invade the colonizing rape's aseptic seedlings by the method of watering root with the suspension YS-45 and the bacteria numbers of the aseptic seedlings were 1.3×10~5 cfu/g.4.The potted seedling had better effect on resisting Sclerotinia sclerotiorum than the aseptic seedling for the colonization of YS-45.The incidence of a disease and disease index were respectively 76.1%and 47.4 when Sclerotinia sclerotiorum was inoculated by the aseptic seedling of the colonizing YS-45 in budding stage,compared with the incidence of a disease and disease index were 95.7%and 80.6.The control effect for its aseptic seedling was 41.2%and it was low disease incidence;the incidence of a disease and disease index of the potted seedling for the YS-45 which had 1.2×10~9cfu/ml density for the colonization in seedling stage were lowest,only 61.4%and 16.3,and the second for the potted seedling of the colonizing YS-45 having 0.6×10~9cfu/ml density,compared with 84.7%and 44.2.And the controlling effect of the potted sprout of the colonizing YS-45 which had 1.2×10~9cfu/ml density and which had 0.6×10~9cfu/ml density were 63.0%and 54.3%,and lower disease incidence.YS-45 had the most power of the bacteriostatic activity to Sclerotinia sclerotiorum and can entered the rape plants inner colonization,So it is a very optimal biocontrol fungus. |
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