Resistance to the rice nematodes Heterodera sacchari, Meloidogyne graminicola and M-incognita in Oryza glaberrima and O-glaberrima x O-sativa interspecific hybrids

Rice species Oryza glaberrima and O. sativa and interspecific hybrids produ ced at the West African Rice Development Association in Cote d'Ivoire, were screened for resistance to Heterodera sacchari, Meloidogyne graminicola an d M. incognita R2. H. sacchari screening was done in field and pot experime nts in Cote d'Ivoire. Non-indigenous species were screened in glasshouse te sts in the UK. All O. glaberrima genotypes were resistant to H. sacchari fr om Cote d'Ivoire and Ghana, M, graminicola from the Philippines and M. inco gnita R2. In pot tests, the number of females which developed on these geno types was zero for H, sacchari and < 3 for both species of Meloidogyne. Wit hin lines of O. saliva, variation in female numbers (P less than or equal t o 0.05) was observed, but all were susceptible both to H, sacchari and to M . graminicola. However, six cultivars and lines of O. sativa were less susc eptible (P less than or equal to 0.05) to M incognita R2 than the check cul tivar IDSA 6. Of 14 progeny from O. sativa cv. WAB56-104 x O.glaberrima lin e CG14, two WAB450-I-B-P-105 and WAB450-I-B-P-160, were resistant to H. sac chari from Cote d'Ivoire. These lines and two others were also less suscept ible (P less than or equal to 0.01) to M. graminicola than the O. sativa pa rent. The susceptibility of some of the progeny to both H. sacchari and M. graminicola and M. incognita was the same as that of the O. sativa parent. Of ten further progeny, screened against H. sacchari from Ghana, WAB450-25- 1-10 was resistant. The expression of resistance in the interspecific proge ny suggests that resistance to H, sacchari is qualitative, whilst that to M eloidogyne graminicola is quantitative. Resistance to M incognita R2 was fo und in O, glaberrima, O. sativa and in one hybrid progeny. None of the spec ies or progeny was resistant to Pratylenchus zeae and there were no signifi cant differences in field population densities of P. zeae, Mesocriconema on oensis or Helicotylenchus dihystera.