Influence of Meloidogyne javanica parasitism on soybean development and chemical composition

Soybean is a major economic crop worldwide, but its yield and quality are greatly affected by root-knot nematode infection. This study aimed to assess the effects of Meloidogyne javanica parasitism on soybean growth, yield, and quality. Soybean plants were inoculated with 0, 1000, 2000, or 4000 eggs + second-stage juveniles (J2) of M. javanica and evaluated for vegetative and nematode parameters. Grains from each treatment were analyzed for yield, proximate composition, total phenolic content, total flavonoid content, isoflavone profile, and antioxidant capacity. Plants free of nematodes had lower vegetative growth and higher yield than nematode-infected plants. The maximum estimated reproduction factor was 34.85, achieved by inoculation of 2433 eggs + J2. Moisture, fiber, and protein contents decreased with increasing inoculum levels. Lipid content increased with inoculum level until reaching 22.59 g 100 g−1 of sample. Total phenolic and flavonoid contents decreased with increasing inoculum level up to about 2000 eggs + J2 and then increased until reaching 219.20 mg gallic acid equivalents 100 g−1 of sample and 121.67 mg quercetin equivalent 100 g−1 of sample, respectively, at 4000 eggs + J2. A similar behavior was observed for antioxidant capacity determined by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging, superoxide radical scavenging, and ferric reducing antioxidant power assays. The highest contents of malonylgenistin (539 mmol g−1), acetylglycitin (106 mmol g−1), and genistin (87 mmol g−1) were found in grains from plants inoculated with 4000 eggs + J2. M. javanica inoculum level affected soybean development, grain production, yield, composition, and antioxidant capacity.