ScienceAsia 32 (2006): 133-142 |doi: 10.2306/scienceasia1513-1874.2006.32.133
QTL Mapping for Leaf and Neck Blast Resistance
in Khao Dawk Mali105 and Jao Hom Nin
Recombinant Inbred Lines
Apichart Noenplab,a Apichart Vanavichit,b Theerayut Toojinda,c* Pattama Sirithunyad,d Somvong
Tragoonrung,e Saengchai Sriprakhonc and Chanakan Vongsapromc
ABSTRACT: Blast disease caused by a fungus called Pyricularia grisea Sacc. (perfect stage = Magnaporthe grisea Sacc.) is one of the most devastating rice diseases in the world. To date, the genetic relationship of leaf and
neck blast is not well understood. Some rice cultivars known to carry leaf blast resistance genes are susceptible
to neck blast. Five hundred eighty-seven recombinant inbred lines (RILs) derived from a cross between Khao
Dawk Mali105 (susceptible) and Jao Hom Nin (resistant) cultivars were developed by single seed descent
and used as rice materials to identify quantitative trait loci (QTL) associated with leaf and neck blast
resistance. Rice materials were assayed for both leaf and neck blast resistance using three selected blast
isolates, designated THL191, THL318 and THL899. Correlation coefficients between leaf and neck blast
resistance were low (0.28-0.56), suggesting the presence of two different pathosystems. A chi-square (2) test
fitted a ratio of approximately 3:1, reflecting the presence of at least 2 resistance QTL functioning against leaf
and neck blast. Fourteen QTL were identified and mapped on three chromosomes: 1, 11 and 12. The QTL for
resistance against leaf and neck blast on chromosome 1 were coincidentally mapped to the RM5-RM104
interval for all isolates. Jao Hom Nin contributed all resistant QTL alleles. QTL were detected on chromosome
11 with high LOD values for both leaf and neck blast resistance against THL191 and THL899. Three major
genes, Pi 7(t), Pi 1 and Pi lm2, have been reportedly located within the vicinity of these QTL. Jao Hom Nin
contributed all resistant QTL alleles. QTL on chromosome 12 showed a race-specificity for leaf and neck blast
against THL318 and THL899. The peak of resistance QTL on chromosome 12 was located between the
RM179 and RM309 markers. Jao Hom Nin contributed resistant QTL alleles against THL899, while Khao
Dawk Mali 105 contributed resistant QTL alleles against THL318. QTL interactions behaved additively for
both leaf and neck blast resistance. Coincident, QTL on three chromosomes revealed the presence of resistance
gene clustering in these genomic regions. Three QTL were detected by QTL analysis while 2 QTL were
obtained from the chi-square test for THL899, which suggested that the RIL population used was large
enough that even a small QTL could be detected. The coincident locations of leaf and neck blast resistance
QTL on chromosomes 1 and 11 and associations of molecular markers with QTL will be useful information
for marker assisted selection.
a Phitsanulok Rice Research Center, Amphur Wang Thong, Phitsanulok 65130, Thailand.
b Rice Gene Discovery Unit, National Center for Genetic Engineering and Biotechnology, Kasetsart
University Kampaengsaen Campus, Nakhon Pathom 74130, Thailand.
c Center of excellence for rice molecular breeding and product development, National Center for
Genetic Engineering and Biotechnology, Kasetsart University, Kampaengsaen Campus, Nakhon
Pathom 74130, Thailand.
d Lampang Agricultural Research and Training Center (LARTC), P.O. Box89, Muang, Lampang 52000,
e DNA-Technology Laboratory, National Center for Genetic Engineering and Biotechnology, Kasetsart
University, Kampaengsaen Campus, Nakhon Pathom 74130, Thailand.
* Corresponding author, E-mail: email@example.com
Received 4 Oct 2005, Accepted 6 Feb 2006