Host-parasite relationship between Aphelenchoides besseyi and soybean

Abstract

Aphelenchoides besseyi is a concern to Brazilian agriculture, since the losses caused by the green stem and foliar retention syndrome in soybean, especially in hot and humid climates, could reach high levels. However, limited information is available regarding the host-parasite relationship. The objective of this study was to evaluate the capacity of A. besseyi to penetrate soybean roots and its movement in soybean tissues until reaching the top parts. Plants inoculated with 1000 A. besseyi were evaluated for root penetration from 1-28 days after inoculation (DAI), and post-penetration and movement inside tissues by staining them with acid fuchsin. Plant development, chronology of the symptoms and the number of pods were also evaluated at 60 DAI. Aphelenchoides besseyi was found in the cortex and xylem vessels of roots from 1 DAI. During the experimental period, the number of nematodes from roots to shoots increased more than 123, 330 and 430%, respectively, for roots, stems + petioles + inflorescences, and leaves, demonstrating the ascendent movement of A. besseyi. Necrotic lesions in young leaves and apical tissues were observed from 8 DAI; the typical symptom of ‘amachamiento’ was observed from 10 DAI, with enlargement of nodes and lesions in inflorescences and, at 30 DAI, stunted plants were detected. At 60 DAI, inoculated plants had lower numbers of pods and exhibited severe symptoms including abortion of flowers and tissue splitting and cortical lesions in a few pods and roots. These observations emphasise the importance of A. besseyi for Brazilian soybean production.