Stunt Nematode Found in Irrigated Lowland Rice Fields in North‐Central Brazil

ABSTRACT

Brazil is a major global rice producer. Among the problems affecting the crop, nematodes cause significant damage, but studies on rice nematodes in the country are still considered insufficient. Commercial rice crops in lowland regions of rice‐producing municipalities in the state of Tocantins, Brazil, were examined following reports of stunted plants with underdeveloped roots. Comparing the areas cultivated with irrigated rice, a reduction of 1050 kg/ha was observed, putatively due to nematode infestation. Nematodes were extracted from soil samples using the centrifugal flotation method with sugar, revealing the presence of a phytophagous species. The morphometry of adult females was carried out. Subsequently, species‐level identification was performed through molecular analysis of the 28S sequences of the nematode populations PV962688 and PX206795. The sequences showed 100% identity with the Tylenchorhynchus annulatus sequences deposited in GenBank. The pathogenicity was confirmed experimentally, and 50 days after soil infestation, nematode specimens identical to T. annulatus were recovered from stunted and chlorotic plants in the infested pots. This is the first report of T. annulatus infecting roots of flood‐irrigated rice in Brazil.