Contents - Faperta

Physico-Chemical and Molecular Markers for Resistance to Insect Pests 173
rice lines possessing both early maturity and insect resistance (Tsuji, Saka, and Izawa,
2003). The indica genotype was maintained in the upstream region of the Grh3(t) gene
located on chromosome 6 of Aichi 66. Four genes condition resistance in rice to N. cincticeps.
Gene Grh1 (green rice leafhopper) from the cultivar Norin-PL2 (Kobayashi et al., 1980), is
located on rice chromosome 5 (Tamura et al., 1999). Grh3 is located on chromosome 6, and
Grh4 on chromosome 3 (Saka et al., 1997; Fukuta et al., 1998; Yazawa et al., 1998). QTLs identifi
ed by Fujita, Yoshimura, and Yashi (2003) coincide with each of these four resistance
genes. The Grh5 gene located on the distal region of the long arm of chromosome 8 is
tightly linked to markers RM3754 and RM3761, and can be used in MAS to breed for resistance
to this insect (Fujita et al., 2006). The QTLs for Nephotettix virescens (Dist.) resistance
on chromosomes 3 and 11 are very near to Grh2 and Grh4. The near-isogenic lines (NIL)
containing both Grh2 and Grh4 express resistance to N. virescens (Wang et al., 2003, 2004).
RFLP markers have been used to identify resistance genes in pairs of near-isogenic lines
(NIL), each containing a single gene for resistance to the whitebacked planthopper, Sogatella
furcifera (Horvath) or to Xanthomonas oryzae pv. oryzae (Ishiyama), and 78 F 3 families from
the cross, TN1/IR36, segregating for fi ve single resistance genes (McCouch, Khush, and
Tanksley, 1991). Location of the resistance genes in NIL pairs was confi rmed by using RFLP
markers from putative positive regions as probes on segregating F 2 populations from
crosses involving resistant isoline susceptible recurrent parent. Two RFLP markers were
linked to Wbph1 for resistance to the S. furcifera, although the chromosomal location of
the gene was unclear, since both linked markers were detected using multiple-copy clones
as probes.
Wheat
Monosomic analysis has been used to locate a single, dominant, Hessian fl y, M. destructor,
resistance gene (H13) in the D genome of common wheat germplasm KS81H1640HF
derived from Aegilops squarrosa L. (Gill, Hatchett, and Raupp, 1987). Telocentric analysis
was used to map the H13 gene on 6Dq (long arm) 35.0 ± 8.0 recombination units from the
centromere. Dweikat et al. (2004) used a set of near-isogenic wheat lines, each carrying a
resistance gene at 1 of 11 loci (H3, H5, H6, H9, H10, H11, H12, H13, H14, H16, or H17). These
were developed by backcrossing to Hessian fl y susceptible wheat cultivar “Newton.”
Eleven RAPD markers linked to the 11 resistance genes were identifi ed. Several of these
markers can be used to determine the presence/absence of specifi c Hessian fl y resistance
genes in wheat lines that have 1 or more genes for resistance. Linkage relationships among
genes on wheat chromosome 5A that condition resistance to M. destructor have been identifi
ed (Ohm et al., 1995). Testcross analyses indicated that six of these genes appear to
occupy a single linkage block on wheat chromosome 5A in the order H9 to H15, H10, H17,
H16, and H12. Gene H14 did not appear to be within the linkage block H9 to H12. Linkage
analysis identifi ed one sequence tagged site (STS) marker, STS-Pm3, and eight microsatellite
markers (Xbarc263, Xcfa2153, Xpsp2999, Xgwm136, Xgdm33, Xcnl76, Xcnl117, and
Xwmc24) near the H9 locus on the distal region of the short arm of chromosome 1A, contrary
to the previously reported location of H9 on chromosome 5A (Kong et al., 2005).
Locus Xbarc263 was 1.2 cM distal to H9, which itself was 1.7 cM proximal to loci Xcfa2153,
Xpsp2999, and Xgwm136. Marker alleles at loci Xgwm136, Xcfa2153, and SOPO05 909 were
shown to be specifi c to H9 and not diagnostic to several other Hessian fl y resistance genes,
and therefore should be useful for pyramiding H9 with other Hessian fl y resistance genes
in a single genotype.