Fitonematoides endoparasitas associados à cana-de-açúcar : interações e novo assinalamento

Abstract

Meloidogyne incognita and Pratylenchus zeae are two of the most damaging nematodes of sugarcane, which are commonly present in Brazilian sugarcane fields causing severe losses. Another nematode widely known as damaging for the Brazilian agribusiness is the Meloidogyne enterolobii, which, recently, was reported as naturally occurrring in sugarcane field from Pernambuco and Rio Grande do Sul states. Aphelenchoides sp. despite being considered as a shoot parasitic nematode it is often associated with sugarcane rhizosphere, and some reports indicate its association with groundnut and some grasses which can damage these plants. This work aimed to evaluate the multiplication of M. incognita and M. enterolobii in both isolated and joint inoculation with P. zeae, to examine the effect of these interactions in initial sugarcane growing and to register the presence of Aphelenchoides spp. in sugarcane roots. Four experiments were performed, from which three were performed in parallel. In the first experiment, three different population densities of M. incognita and M. enterolobii were inoculated on both RB867515 and RB92579 sugarcane varieties. The second experiment followed the same experimental design at the first, but with previous infection of P. zeae (initial population=2000). The third experiment consisted of a prior inoculation de P. zeae followed by M. incognita and M. enterolobii inoculations in both sugarcane varieties. In the fourth experiment, roots were stained with acid fucsin and dissecated, then fixed, dehydrated, included in resin, sectioned e colored with toluidine blue. Meloidogyne enterolobii did not develop well in both sugarcane varieties even after 120 days of inoculation. Meloidogyne incognita reached high population levels when in single infections, but its population was reduced when in mixed infections with P. zeae. The mixed infections of P. zeae and M. incognita reduce both fresh and dried shoot weight. In mixed infectons P. zeae and M. incognita suppress each other. We also report Aphelenchoides sp. inside the roots in microscopy mount and histopathological sections under optical microscope, but this nematode did not induce any symptom of infection on plant.