Desenvolvimento e respostas fisiológicas de mudas de cafeeiro parasitado por Meloidogyne exigua e M. paranaensis / Development and physiological responses of seedlings of coffee parasitized by Meloidogyne exigua and M. paranaensis

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

27/05/2011

RESUMO

The nematodes of the genus Meloidogyne are responsible for the largest losses in coffee crop. M. exigua is the most widespread species in coffee area and causes large losses, but M. paranaensis, the most aggressive species, can derail the coffee crop in infested areas. Under field conditions has been observed that the coffee is more tolerant to M. exigua parasitism than M. paranaensis. It is believed that the physiological and biochemical alterations caused by both species on the coffee are different and can be influenced by the level of the nematode population. In this work we investigated the effect of M. exigua and M. paranaensis parasitism in physiological and biochemical processes, and on the growth of coffee plant in greenhouse and growth chamber conditions. Coffee plants were inoculated with different inoculum concentrations of M. exigua or M. paranaensis (0, 4000, 8000, 16000 and 32000 eggs/plant) in greenhouse and in growth chamber at 25 C, coffee plants were inoculated separately with 1500 J2 of each species. Soluble carbohydrates (soluble sugars and reducing sugars) and insoluble (starch) in the gall tissue and in uninfected tissue of inoculated plants, and the number of galls and eggs of M. exigua and M. paranaensis were evaluated in the roots of the coffee plants. In the greenhouse, there were reduction in height and number of leaves on coffee seedlings with increasing inoculum level of M. exigua, and the DW roots did not change significantly between treatments. The effect of M. paranaensis in these same variables was more pronounced at eight months after inoculation (MAI). There were reduction of 38.4% on DW of the roots when compared with uninoculated roots of plants. Both nematode species did not affect the photosynthetic rate, transpiration, stomatal conductance and water potential of coffee. There were reduction in concentration of soluble sugars, reducing sugars and starch with the increase in the level of inoculum of M. exigua. Most pronounced changes occurred at eight MAI in plants inoculated with 8000 eggs of M. paranaensis, where the plants showed higher amount these carbohydrates than the uninoculated plants, which did not occur in those plants inoculated with 32000 eggs. The two species of nematodes interfered on the foliar concentration of some nutrients and their concentration in inoculated plants was higher than in the not inoculated plants. In the experiment under controlled temperature at 25 C, both species caused a reduction in plant height, transpiration and stomatal conductance. With respect to photosynthetic rate and DW only the roots of plants inoculated with M. paranaensis were affected. In the gall tissues, the highest concentrations of reducing sugars were observed for M. exigua. However, both nematode species reduced the concentration of starch in the tissues of the galls and even in uninfected tissues of inoculated plants. For soluble sugars, no change was observed between the treatments. With respect to foliar concentration of nutrients, major changes were observed in the interaction of coffee with M. paranaensis, with the lowest values for K, Ca, Mn and Fe compared to control. The concentration of S was higher in plants inoculated with both species of nematode than the uninoculated plants. We conclude that both species of nematode interfered in the growth of coffee plants, in the biochemical processes and in the concentration of nutrients. However, the alterations on the physiological variables could only be verified in controlled temperature conditions.

ASSUNTO(S)

açúcares redutores fitopatologia coffea arabica nematóide de galhas nematode galls carbohydrates coffea arabica reducing sugars carboidratos

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