The application of marker-assisted selection (MAS) in breeding programs hastened the development of lines containing the desired trait/s. In this study, the traditional KDML105 popularly grown in rainfed lowland areas in Thailand is intolerant to flash flooding and brown planthopper damage. Two major QTL namely m>Sub1m> and m>Qbph12m> were incorporated into KDML105 by marker-assisted backcrossing. Homozygous lines containing m>Sub1m> and m>Qbph12m> were pyramided using marker-assisted selection coupled with stringent phenotypic selection in developing KDML105 breeding lines with submergence tolerance and brown planthopper resistance. The study displayed the success in combining QTL/gene into a popular rice background that is suitable in areas frequently damaged by flash flooding and brown planthopper attack. Once again, marker-assisted selection has been an indispensable tool in rice breeding program.

The study also dealt on the maintenance of grain quality and yield stability as revealed by multi-location trials in elite lines with KDML105 background aside from the incorporation of submergence tolerance and brown planthopper resistance. Thailand has been number one exporter of premium rice and therefore quality based on physical and chemical aspects of the grain are important traits in breeding rice particularly in the rainfed lowland areas where very aromatic and palatable KDML105 is produce. Moreover, yield was improved in the elite lines as tested in three locations in the northeast Thailand. With the increase in yield and addition of new traits the elite lines while maintaining the grain cooking and eating quality has high impact to rice farmers in the area.