| Fusarium head blight and wheat crown rot,caused by Fusarium graminearum and Fusarium pseudograminearum species complex,are both worldwide destructive fungal diseases of wheat.In recent years,climate change and farming systems changes(such as straw returning,wheat-maize rotation,etc.)have promoted the accumulation of pathogens in the field,which further aggravated the prevalence of these two diseases.At present,there is a lack of disease-resistant wheat varieties,and the prevention and control mainly rely on chemical pesticides.Although chemical pesticides have irreplaceable advantages,inappropriately use of chemical pesticides may bring about“3R problems”.In this condition,efficient and green biological control method is particularly important.Clonostachys spp.is one of the biocontrol factors of plant diseases with high biocontrol potential among antagonistic microorganisms.Previous laboratory studies have found that C.chloroleuca 620strain can be ingrowed into the roots of wheat,which has significant growth promotion and resistance induction effects.Wheat seeds soaked with spores solution of strain C.chloroleuca 620 has significant biocontrol effects on wheat scab and stem rot in the field.Based on this,this study aims to expand the use of C.chloroleuca 620 seed soaking by coating and fertilizing,so as to further deepen the application research of strain 620.In order to better solve the green prevention and control of wheat scab and stem rot,this paper studied the fermentation conditions,the storage conditions of spores,the preliminary research and development of the seed coating agent of C.chloroleuca 620 and the effect evaluation.The results are as follows:1.The fermentation conditions of C.chloroleuca 620 were optimized and the storage conditions of spores were explored.Through the orthogonal experimental design of fermentation temperature,p H and rotational speed,the spores production were measured.The theoretical optimal temperature was 23.7℃,the rotational speed was 153.3 rpm,the PH was 6.6,and the maximum spores production was 1.51×10~8cfu/ml.The actual test showed that the upper limit of spores production was 1.32×10~8cfu/ml,and the average spore yield was 1.11×10~8cfu/ml(lower than the theoretical maximum),which was more than twice of the maximum sporulation yield of 3.03×10~7cfu/ml before optimization meaning the amount of spores obtained was significantly improved.The dynamic spores production curve was measured under the optimum conditions,and the optimum culture time was 8 days,and the average spore yield was increased to 1.21×10~8cfu/ml.After exploring the storage conditions,it is known that the spore liquid can be stored at low temperature for three days for a short time,while for long-term storage,the spores should be dehydrated before being stored at low temperature.2.The C.chloroleuca 620 seed coating agent was preliminary developed and its effect was evaluated.According to the characteristics of suitable p H and water solubility for the growth and development of C.chloroleuca,the inactive ingredients,sodium carboxymethylcellulose,wetting dispersant and emulsifying thickening agent xanthan gum for the production of C.chloroleuca 620 seed coating agent were preliminatively screened.The proportion and dosage of seed coating agents were screened from the perspective of seed coating forming time,seed coating uniformity,seed coating shedding rate and effect on spores survival rate,and finally it was determined that 0.4 g carboxymethylcellulose,4 g nekal and 0.4g xanthan gum should be added to every 100 ml seed coating agent.The growth promotion and control effects of C.chloroleuca seed coating were tested in greenhouse pot experiment.The results showed that C.chloroleuca seed coating promoted the growth of wheat,the plant height of wheat seedlings was significantly higher than that of the control group,and the control effect on wheat stem base rot reached 62.50%,which significantly reduced the incidence of wheat crown rot.There was no difference between the growth promotion and control effects of C.chloroleuca seed coating and soaking treatment.The control efficiency of C.chloroleuca seed coating agent and Cruiser chemical seed coating agent was compared.It was found that the control efficiency of C.chloroleuca seed coating agent was 57.15%,which was lower than that of Cruiser chemical coating agent71.43%.The results showed that the control efficiency of C.chloroleuca seed coating agent should be further optimized to enhance the effect.3.The C.chloroleuca 620 fertilizer was preliminary developed and its effect was evaluated.Based on the prevalence of wheat-maize rotation mode,corn straws were selected as the substrate for the production of C.chloroleuca 620 fertilizer.According to the changes of C.chloroleuca on corn straws,the production process was divided into four stages:initial culture,middle culture,late culture and final culture.After the fertilizer was broken and sifted,the concentration of effective viable bacteria was higher than 4×10~7cfu/g.After 90days,the concentration of effective viable bacteria was higher than 1×10~7cfu/g.Potted experiment with this fertilizer showed that the plant height of wheat fertilized with this fertilizer was significantly higher than that of the control group,and the control effect of this fertilizer on stem base rot of wheat reached 62%,while the incidence of this fertilizer increased by 33%.The results showed that the conversion of corn straws to C.chloroleuca could significantly reduce the incidence of wheat crown rot,and the control effect of bacterial fertilizer fertilization was better than that of seed soaking treatment.However,the growth promotion effect of bacterial fertilizer fertilization is weaker than that of seed soaking treatment,so the way of seed soaking or seed coating can be combined with the application of bacterial fertilizer,to achieve better growth promotion and biological control effect.This study successfully explored the high efficiency fermentation conditions of C.chloroleuca(Temperature was 23.7℃,rotational speed was 153.3 rpm,p H value was 6.6)and spores storage conditions(Low temperature,drying and vacuuming treatment),and obtained the seed coating agent and bacterial fertilizer of C.chloroleuca with good growth promotion and biocontrol effects in greenhouse experiment.Good methods and ideas were provided for the green prevention and control of Fusarium head blight and wheat crown rot. |
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