ThePi40Gene for Durable Resistance to Rice Blast and Molecular Analysis ofPi40-Advanced Backcross Breeding Lines

Abstract

Rice blast severely reduces production in both irrigated and water-stressed upland ecosystems of tropical and temperate countries. Nearly 50 blast resistance genes have been identified and some of those are incorporated into several rice cultivars. However, most of the resistance genes break down in a few years because of their race specificity and the rapid change in pathogenicity of the blast fungus (Magnaporthe grisea). The objective of this study was to analyze advanced backcross breeding lines (ABL) possessing the gene Pi40 for durable rice blast resistance. In all, 4 resistant genotypes, 4 japonica cultivars, and 10 monogenic differential rice genotypes with some known resistance genes were bioassayed in the greenhouse using seven sequential plantings and 29 virulent M. grisea isolates of Korea. The genotypes with the Pi40 gene had <3% diseased leaf area, which was significantly below the disease threshold level of 40% considered for durable blast resistance. Moreover, the genotypes with the Pi40 gene expressed compatibility with only two to three virulent M. grisea isolates supporting durability of resistance, in contrast to susceptible cultivars with >50% diseased leaf area and 10 compatible isolates. Of the 10 known resistance genes tested, Piz-t, Piz-5, and Pi9 showed differential reactions to the pathogen isolates in seven plantings. Genotyping of the ABL with 260 simple sequence repeat (SSR) markers revealed rapid conversion toward recurrent parent genotypes with fewer donor chromosomal segments (5.3 to 14.5%). Our study based on a sequential testing and background selection of breeding lines with the resistance gene Pi40 provided valuable information for durable blast resistance breeding in rice.

Inheritance patterns and identification of microsatellite markers linked to the rice blast resistance in BC2F1 population of rice breeding

“…Using other foreground markers none of plants were found as heterozygous condition which indicates that some blast resistant gene disappeared due to the backcrossed with MR219. This statement is more coincide with the findings of Suh et al (2009) who found that some genes were lost during the recombination process in segregating generations of advanced backcross lines. The two polymorphic (RM6836 -238bp and RM8225 -212bp) linked markers were used to evaluate BC 2 F 1 progenies.…”

“…Rice blast caused by Magnaporthe oryzae (M. oryzae) is the most devastating diseases of rice worldwide (Khush & Jena, 2009;Liu et al, 2010). Rice blast severely reduces production in both irrigated and water stressed upland ecosystems of tropical and temperate countries (Suh et al, 2009). The incorporation of blast resistance genes into cultivars is the most preferential strategy in rice breeding program to prevent this disease.…”

Identification of Blast Resistance in a Core Collection of Foxtail Millet Germplasm

“…Many pathogenic races have been identified in M. grisea infecting rice, and this variability has been cited as the principal cause for the frequent breakdown of resistance in rice varieties (25). Although pathogenic variations in the M. grisea populations adapted to rice, wheat, foxtail millet, finger millet, pearl millet, and several weed hosts have been reported (12,13,21,26), there is no infor- Table 3 a Resistant = ≤10% head blast incidence, ≤3.0 score on a 1-to-9 scale, and ≤2.0 score on a 1-to-5 scale; moderately resistant = 11 to 30% head blast incidence, 3.1 to 5.0 score on a 1-to-9 scale, and 2.1 to 3.0 score on a 1-to-5 scale; susceptible = 31 to 50% head blast incidence, 5.1 to 7.0 score on a 1-to-9 scale, and 3.1 to 4.0 score on a 1-to-5 scale; and highly susceptible = >50% head blast incidence, >7.0 score on a 1-to-9 scale, and >4.0 score on a 1-to-5 scale.…”

Field Performance and SSR Analysis of Drought QTL Introgression Lines of Rice

“…Genomic DNA was extracted from the fresh frozen leaves of the rice cultivars by a modified CTAB method (Rogers and Bendich, 1988). The procedure used in the PCR assay was as described by Suh et al (2009). The PCR products were detected using 4% denaturing polyacrylamide gel electrophoresis with silver staining.…”