Abstract:

In this study，‘Jinpeng 14-6’tomato cultivar was used as the material，and total six treatments according to two air relative humidity levels（high humidity：80%-95%;low humidity：65%-80%）and three soil relative water content levels（low water content：60%-70%;middle water content：70%-80%;high water content：80%-90%）were set out to investigate their effects on the development of tomato gray mold. The results showed that the tomato gray mold appears earlier and developed more severely and faster in the high humidity conditions than in the low humidity ones;the disease severity under high humidity conditions was as follows：high water content > middle water content > low water content;under low humidity conditions，the disease severity developed slower in middle water content treatment. In the low humidity middle soil water content treatment，the appearance of Botrytis cinerea hyphae was seven days later than the high humidity high soil water content treatment and the damage of the mesophyll cells occurred milder and later. In the early stage of gray mold（one day after B. cinerea inoculation），the thickness of every leaf tissue structures（except the upper and lower epidermis）displayed an escalating trend with an increase of soil relative water content;in the late stage of gray mold（5-10 days after inoculation），under high humidity conditions，the thickness of every leaf tissue structures were significantly lower in high soil water content treatment than other treatments and under low humidity conditions，they were larger in middle soil water content treatment compared with others. With the development of B. cinerea infection，the content of reactive oxygen species and the activity of antioxidant enzymes were relatively more active. In the high humidity conditions，the photosystemⅡ（PSⅡ）maximum photochemical efficiency F_v/F_m and fruit quality were significantly lower than treatments under low humidity conditions. The highest yield was acquired in low humidity middle soil water content treatment and the lowest one was acquired in high humidity high soil water content. The impact of tomato gray mold on the yields under the treatments were air relative humidity > soil relative water content > interactions between them. The low humidity middle soil water content conditions in the tomato cultivation facilities to some extent inhibited the B. cinerea infection，delayed the disease appearance，reduced the disease severity and the impact of the disease on tomato fruit quality and yields.

Key words: tomato, humidity, Botrytis cinerea, tissue structure, antioxidant system, yield