Supressividade do inóculo rizosférico de Meloidogyne exigua no cafeeiro em alguns períodos do ano

Abstract

The suppressiveness of plant-parasitic nematodes occurs in the field due to the physical factors, organic matter and soil microbiota. On a stable rhizosphere as in coffee crop (perennial plant) the investigation of suppressive factors during the seasons of the year may bring about the damage and loss potentials to coffee by M. exigua rhizosphere inoculum. From representative samples (galled roots) taken from coffee rhizosphere at two municipalities (Lavras and Varginha) on Minas Gerais state, Brazil, it was evaluated gall and egg numbers per gram of root as well as second stage juvenile (J2 ) hatching and embryonic development. Although these parameters varied considerably among two sampling places and sampling periods, the number of galls and the egg production were consistently high (P ≤ 0.05) on coffee root in December, January, March and April. However, the J2 hatching percentage was highest on samples taken in June and July (56 to 60 %) followed by sampling on March and April (between 13.4 and 22 %). The number of eggs with developed juvenile was lower (P ≤ 0.05) on samples taken in September / October and December / January compared to the other sampling periods. In the non-hatched eggs occurred about 53 to 76 of the abnormal juveniles and 23 to 45 % of eggs with well developed juvenile. In the period of September to January, the antagonist microbiota to M. exigua may have been favored by good temperature and humidity conditions. This caused, consequently, low hatching percentage and reduced number of egg with developed juvenile which may, possibly, be the indication of M. exigua suppressiveness on coffee rhizosphere, which has already been observed in some plantations of Minas Gerais state.