Antagonism And Mechanism Of Trichothecium Roseum Against Several Important Plant Pathogenic Fungi

Trichothecium roseum is an important plant pathogenic fungus causing many plant diseases, but on the other hand, it has a great potential in biological control and healthy function. Based on the screening of the medium suitable for mycelium growth of T. roseum, the inhibitory activities of isolates of the fungus from different hosts against several important plant pathogenic fungi were tested, and the antagonism and mechanism of T. roseum against plant pathogenic fungi were probed in this dissertation for master degree.The main results obtained were as follows.1. To screen out the medium suitable for mycelium growth of T. roseum, 6 isolates of the fungus from different hosts were inoculated and incubated on the tested different nutrient media at 25℃in dark for 3 d. The results showed that the isolates of T. roseum growed normally on different media, but there was obvious difference in growth rate among different media and among different isolates. For isolate TrB, Hami melon medium was the best for mycelial growth, with the colony diameter of 4.6 cm at 3 d, next was PDA medium. TrC strain growed the best on Hami-melon medium, with the colony diameter of 8.2 cm at 3 d, better on carrot medium. For isolate TrA, PDA+VB medium was the best for mycelial growth, with the colony diameter of 5.3 cm at 3 d, next was PDA medium. For isolate TrM, Hami melon medium was the best for mycelial growth, with the colony diameter of 4.85 cm at 3 d, next was carrot medium. For isolate TrG, Hami melon medium was the best for mycelial growth, with the colony diameter of 6.8 cm at 3 d, next was PDA+VB medium, with the colony diameter of 5.55 cm at 3 d. For isolate TrP, Hami melon medium was the best for mycelial growth, with the colony diameter of 5.55 cm at 3 d, next was pear medium. Analysis of variance showed that there were very significant difference (α=0.01) among the colony diameters of six T. roseum strains on different culture media. Hami melon medium was the best for mycelial growth of most isolates tested. The formulation of Hami melon medium is: Hami melon slices 200 g, agar 20 g, water (added to) 1000 mL.2. The resuls of dual cultivation test indicated that among the 6 tested isolates of T. roseum, TrC had the greatest inhibition against the mycelial growth of Bipolaris maydis isolate, with inhibitory rate of 47.43%. But its inhibition against the mycelial growth of Gibberella zeae isolate was the least, with inhibitory rate of 10.49%. It was revealed variation. The activity of F-D-3 was gradually enhanced in the 2 days ,4days and 6 days , microscopically that the hyphae of TrC enwinded the hyphae of Rhizoctonia cerealis, Gibberella zeae and Bipolaris maydis. It was also observed that the hyphae of TrC penetrated and broke the hyphae of Fusarium oxysporum f. sp. niveum and Alternaria alternata. It was suggested that TrC parasitized the pathogens.3. The results of cup-plate test showed that both the fermentation filtrate and inactivated fermentation filtrate of TrC were obviously inhibitory against the mycelial growth of five kinds of plant pathogenic fungi. The inhibitory rates increased with the concentration of the fermentation filtrate. Among five pathogenic fungi, the mycelial fermentation filtrate of TrC had the highest inhibitory effectiveness against Rhizoctonia cerealis. When the volume of added fermentation filtrate of TrC was 1mL, 2mL, 4mL, the relative inhibition rates was 35.63%, 48.75%, 67.50%, respectively. Next was inhibitory effectiveness of the mycelial fermentation filtrate of TrC against Bipolaris maydis. When the volume of added fermentation filtrate of TrC was 1mL, 2mL, 4mL, the relative inhibition rates was 16.98%, 37.74%, 50.00%, respectively. When the volume rate of added fermentation filtrate of TrC against Gibberella zeae was 6.25% and 25%, the relative inhibition rates was 14.55% and 40%, repectively. The inhibition of 3 concentrations of ferment filtrate of TrC against Alternaria alternate was almost the same as that against Fusarium oxysporum f. sp. Niveum. When the volume rate of added fermentation filtrate of TrC was 25%, their relative inhibition rate was 14.55% and 40% in turn, repectively.The inhibitory rates increased with the concentration of the inactivated fermentation filtrate. Among five pathogenic fungi, the mycelial inactivated fermentation filtrate of TrC had the highest inhibitory effectiveness against Rhizoctonia cerealis. When the volume of added inactivated fermentation filtrate of TrC was 1mL, 2mL, 4mL, the relative inhibition rates was 28.13%, 36.88%, 52.50%, respectively. Next was inhibitory effectiveness of the mycelial inactivated fermentation filtrate of TrC against Bipolaris maydis. When the volume of added inactivated fermentation filtrate of TrC was 1mL, 2mL, 4mL, the relative inhibition rates was 16.67 %, 25.00 %, 38.89 %, respectively. When the volume rate of added inactivated fermentation filtrate of TrC against Gibberella zeae was 6.25% and 25%, the relative inhibition rates was 8.86% and 24.05%,repectively. The inhibition of 3 concentrations of inactivated fermentation filtrate of TrC against Alternaria alternate was almost the same as that against Fusarium oxysporum f. sp. Niveum. When the volume rate of added inactivated fermentation filtrate of TrC was covered by the formation of confrontation. This indicated 25%, their relative inhibition rate was 12.50% and 22.81% in turn, repectively.It was suggested that the mycelial fermentation filtrate of TrC contained a certain hot- stable substance inhibitory to the tested pathogenic fungi.4. The sclerotia of Rhizoctonia cerealis were transplanted and incubated on the PDA amended with the mycelial fermentation filtrate of TrC at 25℃in dark for 3 d to observe the sclerotial germination. Test result showed that the average germination rate of sclerotia in the treatment group was 46.25%, while the average germination rate of sclerotia was high to 95.83% in the control group (the PDA with no filtrate). The germination rate of treatment group was far less than that of the control group, suggested that the mycelial fermentation filtrate of T. roseum TrC has a strong inhibition agaist germination of sclerotia of Rhizoctonia cerealis, the pathogen of wheat eyespot.5. To probe farther the inhibitory mechanism to pathogenic fungi, the inhibition the mycelial fermentation filtrate of TrC against spore germination of Bipolaris maydis was investigated. The results indicated that at 2h, 4h, 8h, 12h and 24h after treating, the germination rate of the pathogen spores was 37.5%, 53.33%, 66.15%, 55.56% and 50.65%, respectively, with the germination rate at 8h after treating the highest. In addition, it was observed that the tubes of the germinated spores in the treatment were shorter, thicker and abnormal.