TABLE CONTENTS

Mapping Nematode Resistance in Rice
Shrestha, R., F. Uzzo, M.J. Wilson & A.H. Price
Institute of Biological and Environmental Sciences, University of Aberdeen, UK AB243UU
The root knot nematode Meloidogyne graminicola is an obligate biotrophic parasite and a
major pest of rice for which resistant varieties are not available in Oryza sativa L.. Six O.
sativa varieties displayed differing degrees of nematode susceptibility, while an O.
glaberrima variety was resistant. Nematode infection in two O. sativa varieties (Bala and
Azucena) was investigated in a time course experiment. M. graminicola consistently caused
more galling and had higher reproductive success in Azucena compared with Bala.
Quantitative trait loci for partial resistance to M. graminicola were identified using the Bala x
Azucena mapping population of recombinant inbred lines. Gall numbers were estimated for
144-156 RILs two and four weeks after inoculation. A total of five and two significant or
putative QTLs (LOD score ≥ 3.2 or ≥2.4 respectively) for nematode resistance were detected
in the two experiments. The five QTLs in the two-week experiment were on chromosomes 1,
2, 6, 9 and 11 and explained 5.2 – 9.0 % of the total phenotypic variation. In the four-week
experiment, two QTLs were detected on chromosomes 6 and 7, explaining 9.6 and 10.3% of
variation. The QTL on chromosome 6 was detected in both experiments. For two of the
QTLs detected, Azucena was the donor of the resistant alleles, suggesting it will be possible
to breed plants with greater resistance than the more resistant parent. Partial resistance genes
are thought to be non-specific and effective against all races of pathogens and therefore are
valuable for development of durable resistant varieties.
5 th International Congress of Nematology, 2008 245