Application Of Plant Growth Regulators In Controlling Verticillium Wilt And Interaction With Fungicides

In this study, 9 plant growth regulators were employed to enhance the resistance of cotton seedlings to verticillium wilt. Their effects on the growth of verticillium dahliae and effects on the incidence of verticillium wilt after treatment with them were tested. 5 fungicides were evaluated both in vitro and in vivo to verticillium dahliae for screening the effective ones. The combination of the fungicides and the regulators were applied to control the development of verticillium wilt, and the synergistic effects and extents of plant growth regulator to different fungicides were made out. The primary studies on the mechanism of induced resistance were also undertaken. The results could be summarized as flollows:Through treated with plant growth regulators and succedent inoculated with verticillium dahliae to cotton seedlings in vivo, it indicated that some plant growth regulators could induce the cotton seedlings'resistance to verticillium wilt, the incidence and grade of the disease were also reduced. The control effects were different with different growth regulators and different cotton breeds. The effects of SA,PDJ, NAA were better than others, the best effect of all the concentrations on Zhongmian 12 and Simian 3 was more than 40% and 20%, respectively.The action of SA,PDJ,NAA on verticillium dahliae in vitro indicated that there lied certain inhibitions of NAA on conidia germination of V.dahliae, PDJ on the growth of its mycelia,some concentrations of PDJ and the higher concentrations of SA and PDJ on microsclerotio formation. Other disposals can either promote the growth of V.dahliae or had very small inhibition. Generally speaking, the induced effects of cotton to verticillium wilt by NAA, SA, PDJ have no evident relation with their effects on V.dahliae.The control effects of carbendazim with irrigating and spraying method,tricyclazole with irrigating method could be observed. The action of these two fungicides on verticillium dahliae in vitro indicated that they can inhibit growth of verticillium dahliae.The joint effects of NAA, PDJ, SA incorporated with carbendazim and tricyclazole were evaluated. The results indicated that NAA mixed with every fungicide showed addictive activities; PDJ,SA mixed with two fungicide showed synergistic activities. So plant growth regulator mixed with fungicide can be used as an approach in plant protection.The primary investigations on the physical and biochemical mechanism of cotton's induced resistance to verticillium wilt by plant growth regulators were also studied. The results showed that they could lead to the dynamic changes of activities of SOD,PAL,PPO,POD,CAT and the content of lignin and MDA. Those changes may have certain relation with cotton's resistance, but the detailed mechanism needed to be studied.