Inoue H, Nakamura M, Mizubayashi T, Takahashi A, Sugano S, Fukuoka S, Hayashi N.

Rice (N Y). 2017 Dec;10(1):36. doi: 10.1186/s12284-017-0175-0. Epub 2017 Aug 1.

Abstract

BACKGROUND:

Rice blast is the most serious disease afflicting rice and there is an urgent need for the use of disease resistance (R) genes in blast tolerance breeding programs. Pb1 is classified as a quantitative resistance gene and it does not have fungal specificity. Pb1-mediated resistance develops in the latter stages of growth. However, some cultivars, such as Kanto209 (K209), cultivar name Satojiman, despite possessing Pb1, do not exert resistance to rice blast during the reproductive stage.

RESULTS:

We found that the expression of WRKY45 gene downstream of Pb1 was weakly induced by rice blast inoculation at the full heading stage in K209. Genetic analysis using the SNP-based Golden Gate assay of K209 crossing with Koshihikari Aichi SBL (KASBL) found at least four regions related to the resistance in the rice genome (Chr8, Chr9, Chr7, Chr11). Mapping of QTL related to Chr7 confirmed the existence of factors that were required for the resistance of Pb1 in the 22 to 23 Mbp region of the rice genome.

CONCLUSION:

We clarified how the K209 cultivar is vulnerable to the blast disease despite possessing Pb1 and found the DNA marker responsible for the quantitative resistance of Pb1. We identified the QTL loci required for Pb1-mediated resistance to rice panicle blast. Pb1 was negatively dependent on at least three QTLs, 7, 9 and 11, and positively dependent on one, QTL 8, in the K209 genome. This finding paves the way for creating a line to select optimal QTLs in order to make use of Pb1-mediated resistance more effectively.

See https://www.ncbi.nlm.nih.gov/pubmed/28766258

Figure 1: Development of panicle blast on Pb1-mediated resistance gene cultivars. Rice blast index of cultivars grown in an experimental paddy field at the Aichi Agricultural Research Center field in 2014. The cultivars, Aichi67, Tsukinohikari, Hoshijirushi, K209 and Kanto HD2 were evaluated in the field. The resistances of Tsukinohikari and Aichi 67 were stronger than that of Kanto 209 and Hoshijirushi in the full heading stage. The heading date of Aichi67, Tsukinohikari, Hoshijirushi, K209 and Kanto HD2 were 21st, 20th, 20th, 19th and 22nd of August, 2013, respectively. The Kanto HD2 cultivar was the negative control for the rice panicle blast resistance.