Experimental modelling for phenotyping soybean host reaction to Aphelenchoides besseyi

Abstract

Summary The nematode causing the green stem and foliar retention syndrome of soybean, Aphelenchoides besseyi, is a concern to Brazilian growers, especially in warm and humid climates, where losses can reach 60% of the yields. Management options have not yet been studied properly, but apparently genetic variability is found in soybean genotypes in the resistance to this nematode. However, the correct phenotyping of soybean genotypes is compromised by the scarcity of studies of this pathosystem. Therefore, the objective of this study was to evaluate the inoculum densities of A. besseyi and the plant ages at inoculation to obtain the correct phenotyping of soybean genotypes. Experiments were conducted under glasshouse conditions with the soybean ‘Elite’, using a completely randomised design and a factorial scheme (five nematode population densities: 150, 300, 600, 1200 and 2400 nematodes plant−1, and three plant ages at inoculation: 7, 12 and 17 days after planting). Evaluations were performed 35 days after inoculation, extracting nematodes from soil, roots and shoot parts of plants to obtain the final population of the nematodes of each replicate. The inoculum of 150-300 A. besseyi specimens per plant is the most suitable to assess the reaction of soybean genotypes to this nematode as it resulted in the greatest reproduction factors. Population densities higher than 1500 nematodes per plant could lead to misclassification of the host reaction because of the inconsistent reproduction factors obtained.