| In this reserch, the impact of root-knot nematodes and temperature stress for greenhouse grafted watermelon were studied. In order to clarify the root-knot nematode resistance mechanism, the grafted watermelon growth index and its physiological and biochemical changes were measured after nematode infection in greenhouse. The grafted watermelon growth index and its physiological and biochemical changes after temperature stress were also measured in order to clarify the temperature stress resistance mechanism. Two watermelon varieties,"jinxing"and"chunxiu", were used as scion in this experiment;"bodajiajiewang","qingzhenyihao","black seed pumpkin","black pumpkin","bottle gourd","bigcalabash 12hao","baizisigua","quanengtiejia","laizhenyihao"and"shengzhenyihao"were used as rootstock. The main conclusions are as follows.1 Screening of watermelon rootstocksAs rootstock, laizhenyihao, black seed pumpkin, quannengtiejia, big calabash12hao and shengzhenyihao had better performance after a comprehensive analysis of the grafted survival, growth potential and fruit traits.2 Effects of root-knot nematode infection on grafted watermelon seedlingsAfter root-knot nematode infection, PAL activity, TAL activity, PPO, O2-.content, SOD and CAT activity and total phenol of grafted watermelon root were higher than self-root seedlings. Slightly difference were found in different rootstock scion combinations. After root-knot nematode infection, MDA content in root tissue continued to increase, but the increment of self-root seedlings was highest. In the 60 days after root-knot nematode infectted, gall index of grafted-root seedlings was lower than self-root seedlings. Nematode infection can lead to plant height, leaf number, leaf area, fruit weight, total sugar, VC and free amino acid content decreased; soluble protein content increased in watermelon.3 Effects of watermelon root exudates on root-knot nematode eggs hatchingNon-vaccinated nematode, the impact of self-rooted and grafted watermelon root exudates on root-knot nematode eggs hatching cuold be ignored. The root exudates of self-rooted watermelon, with root-knot nematode infection, had a clear stimulation to root-knot nematode eggs hatching. The root exudates of grafted watermelon, with root-knot nematode infection, had a significant inhibition to root-knot nematode eggs hatching.4 Effects of temperature stress on grafted watermelon seedlingsAfter heat stress, different scion and rootstock combinations showed different heat resistance capacity. In this study the sequence from high to low were shengzhenyihao/jinxing > laizhenyihao/jinxing > black seed pumpkin/jinxing>bigcalabash12hao/jinxing> quannengtiejia /jinxing > jinxing; shengzhenyihao/chunxiu > black seed pumpkin/chunxiu > big calabash12hao/chunxiu>laizhenyihao/chunxiu>quannengtiejia/chunxiu>chunxiu.After low temperature stress, different scion and rootstock combinations showed different cold resistance capacity. In this study the sequence from high to low were quannengtiejia/jinxing >laizhenyihao/jinxing>blackseedpumpkin/jinxing>shengzhenyihao/jinxing>bigcalabash12hao/jinxing>jinxing,quannengtiejia/chunxiu>laizhenyihao/chunxiu>shengzhenyihao/chunxiu>black seed pumpkin/chunxiu>big calabash12hao/chunxiu>chunxiu. The"laizhenyihao"was the best rootstock in this study through a comprehensive consideration. It can better improve the grafted watermelon resistance capacity to temperature stress. |
