Respostas fisiológicas induzidas por estresse hídrico e infecção por Meloidogyne javanica (Treub) Chitwood em portaenxertos de Prunus spp

Abstract

The Rio Grande do Sul has the largest peach producing area of the country, but its productivity is still low when compared with other Brazil´s states. One of the problems related to low productivity are soils with poor drainage and low water storage capacity, mainly in the producing region of Pelotas, as well as the presence of root-knot nematodes (Meloidogyne spp.) on the orchards, whose damages have great importance because the novice action on the root system, affecting the nutrient and water absorption and translocation. These stresses can cause physiological changes in plants affecting fruit quality and productivity of orchards. The objective of this study was to evaluate the effects of these stresses on peach plants of rootstock cv. Capdeboscq, Flordaguard and plum rootstock cv. Mirabolano 29-C. The study was divided into two experiments. At first, we evaluated gas exchange and antioxidant enzymes activity of Prunus rootstocks submitted to the following stresses treatments: a) Waterlogging, for eight days; b) drought for eight days; and c) control, with regular plant watering. After the stresses period, plants returned to normal water regime. The Mirabolano 29-C rootstock shown to be more susceptible to drought than waterlogging, compared to the two peach rootstocks evaluated. On the other hand, Flordaguard and Capdeboscq shown more damages when the plants were subjected to waterlogging, verified by the higher rate of lipid peroxidation in relation to the control plants of these cultivars. The second experiment evaluated the effects of M. javanica plant-inoculation on the reproduction factor (RF) and gas exchange. 150 days after inoculation, the plants of cvs. Capdeboscq, Flordaguard, and Mirabolano C-29 were susceptible (FR = 1.77), resistant, and immune, respectively. In relation to gas exchange, only the inoculated plants of cv. Capdeboscq showed higher stomatal conductance, internal CO2 concentration and transpiration, and reduced efficiency in water use. For other genotypes there were no significant effects on the variables analyzed.