| Yam is one of the most important agricultural products in the world. However, yam production has been restricted due to long-term monoculture system. Root/stem rot of yam is one of the most destructive diseases in China. No breeding of cultivates with resistance and chemical strategy can effectively control this disease. Thus, it is necessary and urgent to find a better way to ensure yam industry. Biocontrol has been proven to be economical and environment-friendly for overcoming soil-borne disease such as root/stem rot.A pathogen (Fusarium solani) of yam root/stem rot disease was isolated from the infected yam plants, and then two high efficient antagonists were selected and fermented with organic fertilizer to prepare a bio-organic fertilizer. A series of laboratory and field experiments were conducted to investigate the growth-promotion and disease-suppressive effects of the special bio-organic fertilizer on the yam plants. The results were as follows:1. The field plot experiment was carried out to study the effect of application of BIO organic fertilizer on the suppression of root/stem rot of yam and plant growth. The results indicated that the BIO organic fertilizer could control the disease of root/stem rot of yam by reducing the length and the percentage of disease spot. The length of the disease spot of yam tuber in the treatments T1(CK+450 kg/hm2 BIO), T2(CK+750 kg/hm2 BIO) and T3(CK+1050 kg/hm2 BIO) were reduced by 65.1%,77.2%, and 78.0%, and the percentage of disease spot were reduced by 67.6%,80.0%, and 81.7% respectively compared with CK. Otherwise, application of BIO organic fertilizer could promote the growth of yam. The fresh weight of yam tuber in the treatments T1, T2 and T3 were increased by 15.2%,32.0%, 37.1%; the length of yam tuber were increased by 6.0%,11.3%,19.5%; the diameter of yam tuber were increased by 10.9%,23.6%,50.9%; the yield of yam were also raised by 15.3%,32.2%,37.3% respectively compared with CK. In addition, the soil microbial environment was improved with the application of bio-organic manure. The research showed that the amounts of soil bacteria and actinomyces in the treatments T1, T2 and T3 were increased by 1.04,1.31,1.41 times and 1.09,1.18,1.71 times, while the number of soil fungi were decreased by 21.9%,46.9%,50.0% respectively compared with CK.2. Nine fungi strains isolated from the rot yam tuber were inoculated on yam both in lab and field, and the result showed that the strain T4 was responsible for the disease. The pathogen was identified as F solani based on morphological characteristics and rDNA-ITS molecular analysis.3. The research of biological characteristics of the pathogen T4 showed that the optimal temperature and pH for its colony growth were 30 ? and 8 respectively; the pathogen could utilize many kinds of carbon sources but fructose; nitrogen nutrient could affect the growth of the pathogen significantly, and nitrate-nitrogen was suitable for its growth, but ammonium-nitrogen was not appropriate; the conidia lethal temperature is 57 ?,10 minutes lasted.4. Two strains Trichoderma harzianum SQR-T037 and Bacillus amyloliquefaciens QL-18, which obtained from our laboratory showed high antifungal activity against F. solani. Organic fertilizer were inoculated with strains SQR-T037 and QL-18 for a second solid fermentation to produce bio-organic fertilizer, which was applied to soil to further investigate the effects of controlling root-stem rot on yam through field experiments. Yam specific bio-organic fertilizer could significantly reduce yam root/stem rot incidence, among which BOF base fertilizer (600 kg/hm2+dressing 900 kg/hm2) is the best in terms of prevention effect, the controlling percentage was up to 68.4%. Application of biological fertilizer could improve soil microbial community structure by increasing the number of bacteria and actinomyces but reducing the amount of fungi and pathogen.5. Application of yam special bio-organic fertilizer on yam had apparent stimulative effect. At the growth period, the SPAD value of T3 was maximum of 53.1, which was increased by 25.1% compared with CK. At the harvest period, the effects of T3 were the best. The tuber fresh weight, length and diameter were 3.54 kg/strain,159.0 cm and 5.30 cm respectively, and the stem diameter of shoot was 0.77 cm, the yield of yam was 114 667 kg/hm2. Compared with CK, the tuber fresh weight, length, diameter and the stem diameter of shoot, the yield were increased by 37.8%,20.7%,38.4%,36.0% and 28.8% respectively.6. Application of yam special biological organic fertilizer could promote the decomposition, transforming and releasing of nutrients in soil and fertilizer. At the harvest period, the effects of T3 were the best of all treatments:the ammonium nitrogen content was 27.2 mg/kg, which was increased by 61.2% compared with CK; the nitrate nitrogen content was 101.8 mg/kg, which was increased by 46.3% compared with CK; the available phosphorus content was 7.8 mg/kg, which was increased by 53.4% compared with CK; the available potassium content was 78.9 mg/kg, which was increased by 36.5% compared with CK.In conclusion, the specific bio-organic fertilizer used in this study effectively suppressed yam root/stem rot, promoted plant growth, improved the yam rhizosphere microbial diversity, and increased soil fertilities. |
PDF Full Text Request