| Post-harvest diseases of tomato have been a big problem to perplex the development of tomato industry. The extensive usage of synthetic fungicides exists the chemical residues, environment pollutions, fungicide-resistant by pathogens, etc. many malpractices. Recently, biological control proved to be an effective alternative to synthetic fungicides and has been an emerging method to utilize antagonistic microorganisms to control post-harvest diseases.This study isolated 240 yeast strains from the surface epiphytes of several fruits by the theory of plant mini-ecology system. By using screening methods in vitro and fruits inoculating test in vivo, isolates L-1-6 and H-2 exhibited preferable inhibitory activity to Alternaria solani and Rhizopus nigricans respectively, and evidently decrease post-harvest rot in tomato. Tomato storage test with the two yeast isolates was done in detail to evaluate antiseptic and quality holding effect. The growth dynamic of antagonism yeast L-l-6 on tomato fruits surface and wound was studied, as well as the effect of calcium ions. Main result is as follows:1. By the method of dish screening (in vitro), 11 yeast isolates exhibited inhibitory activity to Alternaria solani. The tests of equivalent volume mix of each yeast isolate and Alternaria solani suggested 7 of 11 yeast isolates at the three concentration of 106, 107 and 108CFU/mL can totally restrain the growth of Alternaria solani at the three concentration of 105 104and 103spores/mL. The yeast isolate L-l-6 was found to be highly antagonistic to Alternaria solani on three varieties tomato by fruits inoculating test in vivo and the average percentage of controlling got to 77.78%.2. By the method of dish screening (in vitro), 9 yeast isolates exhibited inhibitory activity to Rhizopus nigricans. The tests of equivalent volume mix of each yeast isolate and Rhizopus nigricans suggested 7 of 9 yeast isolates at the concentration of 108CFU/mL can totally restrain the growth of Rhizopus nigricans at the concentration of 105spores/mL; and 5 of them, PG2-5, F-2-2, PG2-3, PG2-4 and H-2-1, at the concentration of 107CFU/mL can totally restrain the growth of Rhizopus nigricans at the concentration of 104spores/mL. The yeast isolate H-2 was found to be highly antagonistic to Rhizopus nigricans on 'Xiyou 5' tomato by inoculating yeast isolate and Rhizopus nigricans test in vivo, and the average percent decay was 33.33%, which is distinctly lower than that of control and other yeast isolates.3. A yeast isolate exhibiting preferable inhibitory activity in vitro to a certain pathogens, does not necessarily express the good inhibitory activity in vivo, and vice versa. Therefore, the screening in vivo is more important than the screening in vitro during screening post-harvest Antagonism yeast.4. Haifen 901 tomato fruits harvested at the mature green stage were dipped in antagonist suspension at the concentration of 1.0 X 106CFU/mL for 2 min, and were stored for 20 days in RT. The result suggested: Both antagonist L-1-6 and antagonist H-2 suspension can delay the rot occur, evidently decrease the percentage of rot, dehydration and total loss. The percentage of good fruit of them is 80% and 58.3% respectively, while only 40% in control; The equivalent volume nux of antagonist L-1-6 and antagonist H-2 suspension at the concentration of 1.0 X 106CFU/mL happened to increase the rot occur. It was found using antagonist L-1-6 or H-2 did not exerted bad influence to nutrient components and edible quality of fruit.5. Antagonism yeast L-1-6 under the room temperature can quickly settle in tomato fruit wound and on the fruit surface. Tomato fruit wound was incubated 20 u L antagonism yeast L-1-6 at the concentration of 3.0 x 106CFU/mL, After 45h the wound antagonism yeast' CFU increase 541 times. And the surface antagonism yeast' CFU increase 11.2 times after 45h when tomato fruit was dipped in antagonism yeast L-1-6 suspension at the concentration of 2.0X105CFU/mL . 2%CaCL2 matching antagonism yeast L-1-6 in the two conditions can both... |
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