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 Sriprakhon^c and Chanakan Vongsaprom^c

 
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.