Effects of Meloidogyne spp. on growth, nodulation and nitrogenase activity of siratro ( Macroptilium atropurpureum (DC) Urb.)

Abstract

Top growth of Siratro ( Macroptilium atropurpureum (D.C.) Urb.) was not significantly altered by infestation with several Meloidogyne spp. Root-nodule weight and nitrogenase activity in nematode-infected plants were significantly increased compared with nematode-free plants. Nitrate reductase of nodule-cytosol was 10 times higher in nematode-infested nodules compared with nematode-free nodules. Nematode infestation did not significantly influence enzyme activity levels that govern fixed N transformations within nodules. However, enzume activity governing ureidoglycolate transformations and glyoxylate metabolism were greatly decreased by nematode infestation. Ureide and pyruvate contents of nematode-free nodules were significantly greater than those nodules of nematode-infested plants. Nitrate and amine-amide contents of noninfected nodules were significantly less than those in nematode-infected nodules. Nodule cytosol contents of α-ketoglutarate, nonconjugate P, K, Ca, Mg and Na were not changed by nematode infestation. Nematode infestation reduced fibrous root growth and caused galls on both roots and nodules. Nematode invasion of nodules induced development of giant multinucleate cells in the peripheral parenchyma adjacent to vascular bundles, the absence of lipophilic vacuoles in rhizobial engorged cells, and the predominance of rod-shaped rather than pleomorphic bacteroids.