Overview of the presence of nematodes in irrigated rice in southern Brazil

Worldwide production of rice (Oryza sativa L.) reaches 700 million tons annually. In Brazil, the states of Rio Grande do Sul and Santa Catarina stand out as the largest producers, contributing to over 85% of the national production of this cereal, covering an area of over 1 million hectares for irrigated rice cultivation. Various phytosanitary issues have the potential to limit the productive potential of the crop. Among these factors, plant-parasitic nematodes stand out in the rice scenario. These microorganisms specialize in infecting and harming the growth of plant root systems. One of the main groups involved in this process is the root-knot nematodes, considered of major economic importance in agriculture worldwide.

Meloidogyne graminicola nematode is the most prevalent and capable of causing significant damage to the crop in different parts of the globe

Despite the great diversity within this group and the various species that can attack irrigated rice, Meloidogyne graminicola is the most prevalent and capable of causing significant damage to the crop in different parts of the globe. Estimates have indicated that the impact caused by this nematode in irrigated rice fields ranges from 10% to 80%. The symptoms related to the infection caused by Meloidogyne vary according to the nematode’s population density, the management practices used in the fields, and the plant’s resistance.

Symptoms of Meloidogyne graminicola nematodes

However, symptoms generally begin with the formation of galls at the tips of the roots, significantly impairing the development of the root system, as well as the development of the aboveground parts of the plants. This process directly interferes with the absorption and transport of water/nutrients by the plant, leading to symptoms in the aboveground parts such as stunting, chlorosis, loss of vigor, delayed maturation, and reduced tillering. It should be noted that these symptoms are usually not very significant due to the application of nitrogen fertilization, which ends up concealing or even reducing such symptoms, allowing the problem to persist.

Another aspect that also hinders the observation of symptoms in the field is the fact that these microorganisms are not visible to the naked eye. The main initial symptoms of the issue occur in the plant’s root system, an “underground” environment that is difficult to visualize.

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