Comparison of migration, penetration, development and reproduction of Meloidogyne graminicola on susceptible and resistant rice genotypes

Migration, penetration, development and reproduction of the rice root-knot nematode, Meloidogyne graminicola, in the resistant African rice genotypes TOG5674, TOG5675, CG14 and RAM131, and in the susceptible Asian rice genotypes IR64 and UPLRi-5 were studied and compared. The number of second-stage juveniles (J2) that had migrated horizontally and vertically towards the rhizosphere at 48 h after inoculation was comparable in both resistant and susceptible rice genotypes. Penetration of J2 was significantly lower in the resistant rice genotypes compared with the susceptible rice genotypes at 3 and 7 days after inoculation (DAI). Nematode development in the resistant rice genotypes was slower than in the susceptible rice genotypes. Nematode reproduction was significantly lower in the resistant rice genotypes, which supported fewer eggs per g of roots and eggs per female. A significantly higher percentage of egg-laying females was found in the susceptible rice genotypes. Mature females that had developed in the resistant rice genotypes were significantly smaller than the ones in the susceptible rice genotypes. The resistant rice genotypes had significantly fewer galls than the susceptible rice genotypes. © 2012 Koninklijke Brill NV, Leiden.status: publishe

Host response of Oryza glaberrima and O. sativa rice genotypes to the rice root-knot nematode Meloidogyne graminicola in a hydroponic system under growth chamber

© 2016 Taylor & Francis. The host response of 25 rice genotypes belonging to Oryza glaberrima and Oryza sativa to Meloidogyne graminicola infection was examined in a hydroponic system. The M. graminicola can build up high population densities in a hydroponic system. Resistance to this nematode species was found in O. glaberrima genotypes which supported significantly lower nematode numbers per plant and per unit root than O. sativa genotypes. The M. graminicola-infected O. sativa genotypes showed a higher root galling index than the O. glaberrima genotypes. The hydroponic system is efficient and reliable method to examine the host response of rice genotypes to M. graminicola infection, and can be useful for the fast screening of high numbers of rice genotypes for the selection of M. graminicola-resistant rice germplasm for breeding purposes.status: publishe

Histopathology of the rice root-knot nematode Meloidogyne graminicola on Oryza sativa and O. glaberrima

The root-knot nematode, Meloidogyne graminicola, can cause substantial rice yield losses. Understanding the mechanisms of resistance to this nematode species in known resistant rice genotypes may help to improve rice genotypes, aiming at developing and implementing environment-friendly and cost-effective nematode management strategies. Using susceptible and resistant rice genotypes, a comparative analysis of histological response mechanisms was made during two phases of the nematode colonisation: i) root penetration; and ii) subsequent establishment and development by M. graminicola second-stage juveniles (J2). Two types of defence response mechanisms could be distinguished in the resistant rice genotypes. The early defence response consisted of a hypersensitive response (HR)-like reaction in the early stage of infection characterised by necrosis of cells directly affected by nematode feeding. This HR-like reaction was observed only in the M. graminicola-resistant Oryza glaberrima genotypes and not in the M. graminicolasusceptible O. sativa genotypes. The late defence response took place after the induction of giant cells by the J2. Giant cells usually collapsed and degenerated before J2 developed into adults. Structural features of the roots of the susceptible O. sativa showed greater root and stele diam. and cortex thickness than the resistant O. glaberrima genotypes. Desired features of plants with resistance to M. graminicola elucidated in this study can be used for selection of plants for breeding programmes. © Koninklijke Brill NV, Leiden, 2014.status: publishe