Malaysian Rice Cultivars Research Articles

Transgressive variants for red pericarp grain with high yield potential derived from Oryza rufipogon × Oryza sativa: Field evaluation, screening for blast disease, QTL validation and background marker analysis for agronomic traits

Five transgressive variants (advanced breeding lines from BC 2F 5 and BC 2F 6 generation) were derived from a cross between the wild relative, O. rufipogon Griff. and O. sativa L. subsp. indica cv. MR219, a popular high yielding Malaysian rice cultivar. The aim of the study was to evaluate the pericarp colour of the grains along with yield potential and to validate quantitative trait loci (QTLs) for agronomic traits. The variants were screened against blast disease. Background marker analysis was also done for the promising variants. The field trials were carried out at a single location (due to containment purposes) over two seasons using randomized complete block design (RCBD) with three replications. A trait-based marker analysis was used to identify QTLs for validation in BC 2F 5 generation. Analysis of variance (ANOVA) showed that the seasonal factors influenced different agronomic traits. Variant G33 produced significantly ( p < 0.05) higher yield (5.20 t/ha) than the control, MR219 (4.53 t/ha). Eighteen QTLs for different agronomic traits were identified in BC 2F 2 population in a previous study. Among them 14 QTLs were found in BC 2F 5 population of the present study. The yield of variant G33 was influenced by several QTLs viz. qGPL-1, qSPL-1-2, qSPL-8 and qYLD-4, which were introgressed from the donor parent revealed by background marker analysis using BC 2F 7 generation. Percentage (99%) of red pericarp grain of G33 and G34 in BC 2F 5 and BC 2F 6 generations indicated the stability of pericarp colour which was transferred from the wild relative. Variant G33 showed resistance against two pathotype of blast disease ( Magnaporthe oryzae). Among the evaluated variants, G33 could be considered for inclusion in the cultivar development program for red rice with high yield potential and resistance to blast disease. This study demonstrated that the alleles from wild relative could improve the yield and yield related traits through allelic interaction, even though the phenotypic traits were inferior to the recurrent parent.

Responses of the antioxidative enzymes in Malaysian rice (Oryza sativa L.) cultivars under submergence condition

The potential involvement of activated oxygen species by submergence stress was studied in two Malaysian rice cultivars, MR219-4 and MR219-9, and cultivar FR13A that is known to be tolerant to submergence. Seedlings of these three rice cultivars were subjected to different submergence periods (4, 8, and 12 days). Under 8 days of complete submergence, FR13A cultivar showed higher lipid peroxidation in terms of malondialdehyde level and activities of antioxidative enzymes, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) when compared to the MR219-4 and MR219-9 cultivars. MR219-9 showed higher SOD, APX, and GR activities after 12 days of submergence. The levels of SOD activity indicated that detoxification of O 2 ·− to H2O2 was maintained at a stable level throughout the submergence stress until up to 8 days and increased rapidly at 12 days of submergence. The results indicated that tolerance to submergence in rice is associated until 8 days submergence for MR219-4 and FR13A cultivars. These findings suggested that tolerance to submergence stress in rice might be proven by increased the capacity of antioxidative system. In addition, CAT activity has much higher affinity for scavenges H2O2 than APX. Therefore, ascorbate glutathione cycle might be more efficient to scavenge H2O2.

Physiological and Morphological Responses of Locally Grown Malaysian Rice Cultivars (Oryza Sativa L.) to Different Ozone Concentrations

Malaysian rice (Oryza sativa L.) cultivars MR84 and MR185 were grown in greenhouse chambers and exposed to four different levels of ozone from 28th August, 2001 to 22nd January, 2002. Four ozone levels were selected in close relation to the Malaysian peri-urban ambient level (approximately 30 ppb, 8 hr mean), the Malaysian guideline level (approximately 60 ppb) and possible future higher ozone levels (approximately 90 ppb). Both morphological and physiological parameters showed distinctive impacts of ozone treatments. The plants treated with the highest ozone concentration showed different morphological development, probably induced by severe foliar injury and physiological adaptation of the plants to the ozone stress. The physiological measurements revealed a high sensitivity at the early and late vegetative stages. It was concluded that MR84, which was found to be physiologically sensitive, responded to ozone relatively quickly and altered its morphology to compensate for effects on growth and yield, while MR185, found to be physiologically insensitive, responded to ozone stress slowly which resulted in more severe impacts on growth and yield parameters. Slight growth stimulation was observed at the lowest (30 ppb) ozone level for MR185, whilst negative impacts on growth occurred at both of the higher ozone levels. The study provided useful insights into the earlier findings of an open-top chamber filtration study on the same cultivars in the field at a peri-urban site in Malaysia. The present study proved that yield could be reduced substantially when other parameters associated with grain yield were affected, which was accompanied by increasing yellowing of leaves and premature senescence.

Optimization of Aging Time and Temperature for Four Malaysian Rice Cultivars

Aging is a process that can develop rice-cooking quality. Specially, it helps to increase kernel elongation rate during cooking time. We have aged four popular Malaysian rice cultivars in different time and temperature conditions and we have observed that maximum good kernel elongation ratio for Mahsuri and Mahsuri Mutant are 100 C for 5 hours. In 9192, maximum kernel elongation ratio was observed at 110 C o o