Study On Evaluation For Resistance To Meloidogyne Incognita And The Resistant Mechanism Of Eggplant Rootstocks

Root knot disease could inhibit growth and development and decrease quantity and quanlity, therefore, it has been made one of serious diseases in eggplant. Recently, grafting clutivation using resisitant rootstock could prevent effectively eggplant from this disease. As a result, this experiment aiming to evaluate eggplant rootstock for resistance to Meloidogyne incognita, examined growth and resistant indexes of eggplant rootstock seedlings inoculated by M. incognita and established integrated evaluation system applying multiple screening indexes and systems, futhermore, screened several resistant materials. Physiological and biochemical mechanisms of resistance to M. incognita with different resistant eggplant rootstock(Solanum torvum and Solanum integriflium) were studied. The main results were as follows:1. The different relative growth indexes of different organs, different resistant indexes of eggplant rootstock seedlings and their coefficient variances were different resulted from infection of M. incognita. Coefficient variances of four resistant indexes (GI,EI,RF,DI) were 40.30%~101.22%, but that of five relative growth indexes (PH,SD,RFW,SFW,LFW) were only 8.29%~18.85%. The result of clustering analysis with gall index, which coefficient variance was higher, was the same to that with four resistant indexes, but both results could just evaluate resistance not the tolerance of eggplant rootstocks to M. incognita, and results had a little different with that of clustering analysis with five relative growth indexes and relative root fresh weight.Subordinate function could evaluate the order of resistance (or tolerance) to M. incognita, but could not classify the eggplant rootstocks by capability of resistance (or tolerance). Therefore, applying multiple screening indexes and systems could accurately evaluate resistance (or tolerance) of eggplant rootstocks to M. incognita. In view of the above, eggplant rootstocks in the experiment could be classified four groups, i.e. high resistance, tolerance, moderate susceptibility and high susceptibility. The sequence of resistance (or tolerance) from strong to weak successively was: Solanum torvum, Tuotuosijia, Shengtuosi, Solanum surattense, Beinongqiezhen, Solanum daidaro, Solanum sisybriiflium, Solanum integriflium, Taibyo VF, Solanum muricatum, Qiongyeqie.2. Whether the seedling roots were infected by M. incognita or not, the activities of phenylalanine ammonia lyase (PAL), tyrosine ammonia lyase (TAL) and polyphenol oxidase (PPO) and the content of total phenolic and lignin in S. torvum were significantly higher than those in S. intergrifolium. Though the contents of phenylpropanes and activities of relative enzyme in seedling roots of two different resistant varieties infected with M. incognita both increased, the activities of PAL, TAL, PPO and contents of total phenolic and lignin in S. torvum increased higher than those in S.intergrifolium, and the highest increasing extention of those indexes in S.torvum was 67.87%, 82.13%, 32.19%, 62.14%, 20.91% higher than the control, but only 47.13%, 45.52%, 18.08%, 35.38%, 14.86% higher than the control in S.intergrifolium, respectively. During the process of infection, intensive resistant reaction was discovered in S.torvum, but the resistant reaction in S.integrifolium was weak except for at the earlier stage of first infection, especially, the resistance to second infection was remarkably lower than first infection. The results suggested that the metabolite of phenylpropanes and their key enzymes were closely related to resistance of eggplant rootstock to Meloidogyne incognita.The production rate of superoxide anion radical (O2-·), the content of hydrogen peroxide (H2O2) and the activity of superoxide dismutase (SOD), catalase (CAT), chitinase (CHT) andβ-1,3-glucanase (GLU) in S. torvum, the high resistant variety to M. incognita, were significantly higher than those in S.integriflium, which was susceptible variety. However, the activity of peroxidase (POD) in S.integriflium was higher. At the early stage of first infection, the production rate of O2-·, the content of H2O2 and the activity of CHT and GLU in both varieties rapidly increased, and the increasing rate of S.torvum's was significantly higher than that of S.integriflium's, but the above four indexes decreased at the later stage of first infection, then increased again at the early stage of second infection, but the increasing rate, especially the S.integriflium's was lower comparing with that of the first infection. Nevertheless the activity of SOD and CAT in roots infected by M.incognita was significantly decreased, and the decreasing rate of S.torvum's were higher than that of S.integriflium's at the early stage of infection circle, but increased at the later stage of infection circle. The changes of activity of POD were contrary to that of SOD and CAT at the whole infection circle. Infection by M.incognita also caused persistent increase of malondialdehyde content in roots, and S.integriflium's was higher, which suggested that the infection aggravated the extent of membrane lipid peroxidation in roots, especially in the root of susceptible variety.3. Root diffusates from 2 eggplant rootstocks had less effects on egg hatching. At 8 and 33 days after inoculation, the hatching rate in root diffusates of S.integriflium were always higher than that in control. However, the hatching rate in root diffusates of S.torvum were always lower than that in contral. Root diffusates from S.integriflium had stimulated egg hatching, but in S.torvum, the inhibitory effects were found. At 15 and 26 days after inoculation, root diffusates of 2 eggplant rootstocks had less effects on egg hatching. From whole process of hatching, root diffusates of S.integriflium could stimulate egg hatching of nematode.4. Inoculation of M.incognita resulted in the increase in nematode quantity. From whole process of inocubation, nematode quantity and the number of juveniles fluctuated significantly in S.integriflium, while in S.torvum, the dynamic changes of nematode group was relatively steady. However, nematode quantity in S.integriflium was significantly more than that in S.torvum.At the early age of infection(1 to 8 days after inoculation), in root of 2 eggplant rootstock, nematode quantity and the number of juveniles changed relatively stable. At the middle age of infection(8 to 22 days after inoculation), nematode quantity and the number of the second (J2)and third(J3) stage of juveniles reached to the maximum, moreover, the number in S.integriflium was significantly more than that in S.torvum. At the end age of infection(22 to 26 days after inoculation), because J2 in S.integriflium developed into J3 and J4, therefore, the number of J2 in S.torvum was significantly higher than that in S.intergriflium, the number of J4 in S.integriflium reached to the maximum and was significantly more than that in S.torvum, indicating that M. incognita could grow normally in S.integriflium and be inhibited in S.torvum. Nematode sex differentiation of 2 eggplant rootstock was studied and results showed that the number of female was relatively more in S.integriflium, but in S.torvum, the number of male was relatively more.These indicated that M. incognita in S.integriflium could propagated normally, but in S.torvum, it was dificult for M.incognita to propagate.