The Screening And Evaluation Of Watermelon Rootstock Resources For Resistance To Meloidogyne Incognita

Root-knot nematode is one of the main diseases of watermelon, having brought increasingly serious harm. The most effective and economic way to control this disease is using the resistance germplasm breeding resistant root-stock or resistant watermelon. Therefore, this experiment aiming to screening watermelon resources for resistance to Meloidogyne incognita, in this experiment examined the growth indexes and resistant indexes of watermelon resources seedling which inoculated by M.incognita, applying multiple screening indexes and systems, furthermore, screened several resistant materials.The main results were as follows:1.The different relative growth indexes of different organs of watermelon resource seedling, different indexes of watermelon resource seedlings and the coefficient variances of them were different resulted from infection of M. incognita. The coefficient variances of GI,EI, RF,DI four resistant indexes were 27.31%-129.92%,but that of PH,SD,RFW,SFW,LFW five relative growth indexes were just 8.15%-21.56%.The result of clustering analysis with the gall index, which coefficient variance was the highest, was almost the same to that with four resistant indexes, but both the results could just evaluate resistance not the tolerance of watermelon resource seedling to M. incognita. Subordinate function could be used for evaluate the order of resistance (or tolerance) to M. incognita, but could not classify the watermelon resource by the capability of resistance (or tolerance). Therefore, this experiment applying multiple screening indexes and systems could accurately evaluate resistance (or tolerance) of watermelon resource to M.incognita. In view of the above, watermelon resource in the experiment could be classified into three groups, high susceptibility, susceptibility and low resistance. The resistance of Red-seed watermelon is the strongest, and the Zhongke No 1 is the weakest.2.The changes of the content of MD A, the activity of SOD, the activity of CAT, the activity of POD were determined after the root of watermelon resources inoculation by M.incognita. The result showed that the content of MDA in the root of Zhongke No 1 is higher than the Red-seed watermelon, this showed the M. incognita can hurt membrane of watermelon resources'root, the hurt to susceptible variety is serious; after inoculation 3 day to 22 day, the activity of SOD was lower than the watermelon resources which not inoculation, with the inoculation day going, the activity of SOD of Zhongke No 1 increased, and the peak appear at the 15th day, then showed downtrend, and increased again at the early stage of second infection. And the change of activity of SOD was bigger in red-seed watermelon, the peak appears at 15th day, then decrease, and the decrease degree was bigger than Zhongke No 1, the activity of SOD increased again at the early stage of second infection; the activity of CAT of Zhongke No 1was increased after inoculation, the peak appear at 15th day, then decrease, increased again at the early stage of second infection, the activity of CAT of Red-seed watermelon was suddenly decreased at 8th day, then increased and reached the peak at 15th day, then decrease and increased again at the early stage of second infection, the activity of POD in both red-seed watermelon and Zhongke No 1 inoculation is higher than that no inoculation, the activity of POD increased after inoculation 3 day to 22 day, and reached the peak at 22th day, then decreased increased again at the early stage of second infection. With the day going, the activity of POD increased in Red-seed watermelon and Zhongke No 1 which no inoculation.3.There was root-knot formation at the root tip of Zhongke No 1 after 4 days from inoculation, crosscutting showed the juvenile had invaded in the root, build feeding sites and develop into giant cell. The juvenile had developed female lOdays later. After 18 days inoculation, the female had development and maturation, the crosscutting showed that the nutrition in some giant cell had been absorbed by nematode and the giant cell become vacant giant cell. The root-knot appeared on the root tip of Red-seed watermelon 8days after inoculation.From the crosscutting, there were some giant cells,14days later the juvenile start to growing, and they were in the development at the 22th day, there had no vacant giant cell after inoculation 30days.4.The seedling investigation result showed that, the stem diameter of Citrullus lanatus var.citroides was 2.30 mm, which was significant difference with Zhongke No 1 and Mimei (4X)'1.58mm. The stem diameter of Red-seed watermelon seedling compare with Zhongke No 1, the different is significant. The result of three investigation after field planting showed that the stem diameter increase of PI299378 4.02mm was most obvious, the Red-seed watermelon took the second place, the stem diameter difference was significant between the two watermelon materials and Zhongke No 1. The result of twice growth vigor investigations in field showed that the growth vigor of Ningxia red-seed watermelon 15.04mm and 12.77mm was the strongest, the growth vigor difference between Red-seed watermelon and Ningxia red-seed watermelon was significant at the first investigation, but the difference was not significant at the second investigation. The growth vigor difference between Zhongke No 1 and Red-seed watermelon was significant. Ningxia red-seed watermelon and Red-seed watermelon could be used for the rootstock, and make a profound study.