Cultivo de mamona no controle do nematoide Meloidogyne javanica e o cultivo de soja em sucessão à mamona

Abstract

The castor bean plant (Ricinus communis L.) is an oilseed with high economic potential. The castor bean, in addition to its economic potential, presents plants with aggressive taproot, tolerance to climate water stress and it is considered resistant, not host, to nematode species such as M. javanica. In general, there is a lack of more frequent investigations on the interaction of castor bean plants with nematodes and few studies have evaluated their resistance to nematode species and the possibility of using castor bean crops in a crop rotation program. Therefore, this work sought to deepen the knowledge of the interaction of castor bean plants with the nematode M. javanica and the relation of cultivate soybean in succession to the cultivation of castor bean. Four experimental trials were installed in greenhouses, with planting in ceramic pots. In trial 1, penetration (color test) of the nematode M. javanica to the roots of castor bean plants in infested and inoculated soil and soybean in inoculated soil was evaluated, as well as the reproduction factor (RF) of nematodes in the crops. The results induced that soybean is poorly resistant to nematode penetration into its roots. Castor bean proved to be more resistant to root penetration and infection in both types of soils. It was observed that the RF of the crops was increased in the evaluation period from 30 days after the emergency (DAE) to 60 DAE of the crops and decreased in the evaluations at 90 DAE. However, the results observed in the castor bean crop were very low and in sterile inoculated soil the value was below 1, which is peculiar to a non-multiplier crop of the nematode. In trials 2, 3 and 4, the cultivation of soybean was analyzed in succession to castor bean, corn, crotalaria and soybean in sterile, inoculated and infested sterile soils. Thus, the evaluation of the reproduction factor of the nematode M. javanica in castor bean, soybean, corn, crotalaria and the dry and fresh mass in soybean were performed. Castor bean, corn, crotalaria and soybean were cultivated up to 60 DAE and then the plants were cut, and the soybean sown in the same pot with subsequent inoculation with M. javanica. The best results were observed when soybean was sown after crotalaria. Regarding the control of nematodes by castor bean, it was understood that the crop needs an interaction greater than 60 DAE within the nematodes to control and provide all the benefits linked to it and that can benefit the cultivation of soybean in succession to castor bean.