ความหลากหลายของเชื้อราสาเหตุโรคไหม้กับการพัฒนาข้าวต้านทานโรคไหม้

Abstract

Most farmers in rainfed lowland areas in the north and northeast Thailand grow three high quality aromatic rice varieties called Khao Dawk Mali 105, RD15 and RD6, which are very susceptible to rice blast disease. The disease caused by a fungus Magnaporthe grisea (Hebert) Barr. The objectives of this report were 1) to pyramid blast resistance genes, using a marker-assisted selection (MAS) technique, into KDML105 through a backcross breeding method and 2) to integrate the information from blast population characterization with fungal pathotype selection for a screening of breeding materials in order to obtain resistant lines. The fungal population was characterized into 552 pathotypes from 2,293 tested isolates. High diversity of the fungus was found in this study. Common pathotypes found less virulence than rare pathotypes. Good resistant genes detected were Pi k (Pi k, Pi kp, Pi kh), Pi 1 (Pi 1, Pi 1LAC, Pi 1TTP, Pi 1CL), and another group (Pi z-5, Pi ta2 , Pi 9). Combinations of resistant genes good for blast populations in Thailand were Pi kh – Pi 9, Pi ta2 – Pi 1CL, and Pi 1CL – Pi 9. Two resistance cultivars, Jao Hawm Nin (JHN) and DHL279, were used as donors and 5 lines from a cross between IR77955 and KDML 105 were used as recurrent parents. A backcross breeding method was used to develop blast resistant lines with good grain quality similar to KDML 105. Six blast resistant lines with early flowering date were obtained with good grain quality, aroma and cooking quality. These lines showed 11- 34% higher yield than RD15 under severe blast infection. Nine blast resistant lines with the same flowering date as KDML 105 were obtained. These lines showed 1.6 - 9% higher yield than KDML 105. It is expected that these blast resistant lines with similar grain quality as KDML 105 will be released as new cultivars for promoting in target areas in the near future.