RESUMO

The soybean green stem and foliar retention syndrome (GFSR) [1], caused by Aphelenchoides besseyi, is reported in Brazilian fields located at the States of Mato Grosso, Pará, Amapá, Tocantins, and Maranhão, which correspond to warm climates with well-defined rainfall patterns when the air humidity is high during several consecutive days. Studies showed that the infection of plants by A. besseyi occurs in regions with a high frequency of rains and under temperatures higher than 28 °C, when the nematode founds adequate conditions to migrate from soil to shoot parts of plants to initiate its parasitism [2]. One of the challenges was the difficulty in simulating the natural conditions for the disease development, which needs luminosity, high temperatures, and moisture. These conditions can be reproduced using modern growth chambers, but these equipment are onerous and scarce in most Brazilian research centers. So, for the studies with A. besseyi and different plant hosts, it is difficult to reproduce the environmental conditions similar to those found in the field where this nematode is reported, especially under the operational and economic points of view. Considering these environmental conditions and the necessity in conducting studies under controlled environments with this pathossystem aiming a detailed investigation about the symptoms and the nematode parasitism, but also to isolate the effects due to exclusively the nematode parasitism instead of other effects that occur under field conditions, especially in crops like soybean, common bean, and cotton [1], [2], [3], [4], the objective of this project was to develop a growth chamber for the cultivation of these plants under controlled environmental, simulating the necessary conditions for the GFSR development. For this, we used an environmental chamber [5] as the base to our project, where we could find the important aspects that need to be adjusted to suit our purpose.•We developed a plant growth chamber to be used under greenhouse conditions for the studies with Aphelenchoides besseyi and different host plants.•The soybean green stem and foliar retention syndrome (GFSR) needs specific environmental conditions of humidity and temperature for the development of the characteristic symptoms and for the nematode multiplication in the parasitized plants.•This method simulates adequately the environmental conditions found in the field, since the chamber is installed inside a greenhouse, assuring the reliable observation of the plant behavior in relation to the pathogen and allowing the conduction of experiments of this nature in regions different from those where the disease naturally occurs.

RESUMO

Several species of nematodes are known to cause losses to cowpea (Vigna unguiculata) throughout the world. In Brazil, Aphelenchoides besseyi was described as causing damage on soybean, cotton, and common bean, but no report was found about the parasitism of this nematode in cowpea. This study aimed to verify the host reaction of cowpea cultivars to A. besseyi. The experiment was conducted under greenhouse conditions, using two A. besseyi populations as inocula, obtained from symptomatic soybean and cotton plants collected in naturally infested fields. Cultivars Imponente, Aracê, Guariba, Tumucumaque, Nova Era, and Tracuateua were inoculated with 500 A. besseyi of each population, separately, into soil, and after 30 days from the inoculation nematodes were extracted from shoot systems. Both populations were able to parasitize all the cowpea cultivars. Independently of the cultivar, cowpea plants exhibited symptoms of leaf deformation similar to those described for soybean, cotton, and common bean and, in addition, severe brooming was observed, with the interior of the stems being porous and necrotic. To our knowledge, this is the first report of parasitism by A. besseyi of cowpea in Brazil, under greenhouse conditions, increasing the list of hosts of this nematode.

Assuntos