Host response of drought-tolerant aerobic Asian rice genotypes to infection of the rice root-knot nematode Meloidogyne graminicola

Twenty-five progenies (either F4 or F6) derived from crosses between the drought-tolerant Indian upland rice cv. Vandana and the drought-sensitive Indonesian upland rice cv. Way Rarem (both Asian rice) were examined for their host response to Meloidogyne graminicola infection under aerobic conditions in a field experiment at IRRI, Los Barios, Philippines. The host response was compared with the host response of the susceptible references UPLRi-5 and IR64 (both Asian rice), and the resistant reference CG14 (African rice). None of the aerobic progenies was classified as resistant. Compared with UPLRi-5 on the basis of the number of second-stage juveniles (J2) (root system)(-1), 22 progenies were classified as partially resistant and three as susceptible. Based on the number of J2 (g roots)(-1), 13 progenies were classified as partially resistant and 12 as susceptible. Compared with IR64 and based on both J2 (root system)(-1) and J2 (g roots)(-1), 13 progenies were classified as partially resistant and 12 as susceptible. The aerobic progenies showed a wide variation in terms of tolerance to M graminicola infection. Fresh root weight was the plant growth trait most affected and percentage filled grains per panicle the yield-contributing trait most affected. On the basis of percentage reduction in yield/plant, seven progenies were classified as tolerant (< 10% yield reduction), nine progenies as less sensitive (10-20% yield reduction), eight progenies as sensitive (21-30% yield reduction) and one genotype as highly sensitive (36% yield reduction). Of the eight progenies classified as tolerant, three progenies (IR84984-83-15-862-B, IR90019:6-86 and IR90020:22-265) were also partially resistant. Cultivar Vandana was partially resistant and less sensitive, whilst cv. Way Rarem was partially resistant/susceptible and tolerant to M. graminicola infection.