Bacterial leaf blight (BLB) is one of the major rice diseases in Malaysia. This disease causes substantial yield loss as high as 70%. Development of rice varieties which inherited BLB resistant traits is a crucial approach to promote and sustain rice industry in Malaysia. Hence, this study aims were to enhance BLB disease resistant characters of high yielding commercial variety MR219 through backcross breeding approach with supporting tool of marker-assisted selection (MAS). Broad spectrum BLB resistance gene, Xa7 from donor parent IRBB7 were introgressed into the susceptible MR219 (recurrent parent) using two flanking markers ID7 and ID15. At BC3F4, we managed to generate 19 introgressed lines with homozygous Xa7 gene and showed resistant characteristics as donor parent when it was challenged with Xanthomonas oryzae pv. oryzae through artificial inoculation. Recurrent parent MR219 and control variety, MR263 were found to be severely infected by the disease. The improved lines exhibited similar morphological and yield performance characters as to the elite variety, MR219. Two lines, PB-2-107 and PB-2-34 were chosen to be potential lines because of their outstanding performances compared to parent, MR219. This study demonstrates a success story of MAS application in development of improved disease resistance lines of rice against BLB disease.

Genetic based information of different traits plays important role in varietal improvement of rice. Twenty rice accessions (Oryza sativa L.) obtained from National Rice Gene Bank were evaluated during main season 2015/2016 to estimate heritability, genetic variability and genetic advance for seven grain physical properties. Among the traits, milled grain length/width ratio, milled grain length, milled grain length after cooking and grain length exhibited high estimates of phenotypic coefficient of variation (PCV), and genotypic coefficient of variation (GCV). Highest broad sense heritability and genetic advance was obtained for grain length (98.66% and 62.25%), milled grain length (98.95% and 67.31%), milled grain length/width ratio (98.50% and 80.41%) and milled grain length after cooking (98.93% and 65.44%) which suggest these traits are most probably controlled by additive gene action and hence they can be fixed by selection. However, kernel elongation ratio showed lowest value of broad sense heritability and genetic advance (11.76% and 1.38%, respectively) and may suggest non-additive gene action in their inheritance and selection of this trait may difficult due to high environmental influences. Therefore, improvement of high quality rice with kernel elongation ability may require molecular marker application as it is highly affected by environment for precise selection.