| Arbuscular mycorrizal fungi can exist in many type of soil and live with80%of terrestrial plant in mutualistic symbiosis. AM fungi invade and extenden in the plant roots to formed AM. AM symbiosis is a widespread phenomenon in nature. It is well-known that AMF play important roles in expanting the scope of roots absorption, promoting plant growth, improving resisitance ability and absorption of nutrients, increasing production and increasing the quality. In the present study, we have investigated the effects of different strains on the growth of watermelon by using watermelon variety “Zhongxuan12” as model plant. Meanwhile, we screened the best strain and inoculation density on watermelon seedlings. After that, the role and mechanism of AM fungi against Rhizoctonia solani were discussed. The results have significance on watermelon seedling. The main findings are as follows:1．Mycorrhizal fungi could promote plant growth, which showed a certain selectivity of host. The8strains made a different role in improving growth of watermelon seedlings. The height, stem diameter, dry weight, photosynthetic rate and chlorophyll content were all showed a distinct difference. Among the eight differents strains, Mycorrhiza for vegetable (VT) showed the best effect; Furthermore, the root activity of G．intradices SAR/G. intradices BEG140/G. microageregatum BEG/G. Claroideum BEG210(HH) behaved the best effects; Different strains varied greatly in the absorption of mineral nutrition. VT showed the best effect in overall comparison. In summary, VT was the best strain on seedling growth among the eight strains, which was more suitable for mycorrhizal watermelon seedling.2．In this experiment,4different spore numbers were inoculated in watermelon seedlings respectively. Each hole were600(A),300(B),150(C) and (D)50spores respectively. Control (E) was without inoculation. After sowing23d, we observed response of watermelon seedlings with different arbuscular mycorrhizal fungi inoculation quantity. The results showed that the roots of all treatments are effective by impregnation. The infection rate improved with the increase of spore density. Compared with the control, each treatment can significantly promote the growth of plant height and stem diameter, increase the dry weight matter. Comparing different spore density, B processed the best effect. And the mycorrhizal dependency is the largest among all the treatments. Pn, chlorophyll A, chlorophyll B, carotenoid content, root activity, IAA, ABA and ZR, of treatment B were increased by28.2%,22.00%,16.84%,22.00%,20.70,55.12%,160.83%and19.28%compared with control. In addition, B, C and D did not showed significantly different effects in GA3content. Insummary,300spores per hole is the best mycorrhizal inoculum in watermelon seedling.3．It can significantly enhance the resistance ability of watermelon seedlings inculated with arbuscular mycorrhizal fungi. After inoculated Rhizoctonia solani, the incidence rates of AMF seedlings and non-AMF seedlings were18.4%and45.7%respectively.The incidence rates of watermelon seedling inoculated with AMF was27.3%lower than the control.4．AM fungi can enhance disease resistance, which was closely related to the promotion of growth of watermelon. Inoculation with AM fungi promoted the growth of watermelon seedlings in plant height, stem diameter, improve the dry weight and fresh weight of the shoot and root part, activated the activities of antioxidant enzymes SOD, POD, CAT, and reduced the MDA content in roots... |
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