Mapping QTLs for plant phenology and production traits using indica rice (Oryza sativa L.) lines adapted to rainfed environment.

Drought is a major abiotic stress limiting rice production and yield stability in rainfed ecosystems. Identifying quantitative trait loci (QTL) for rice yield and yield components under water limited environments will help to develop drought resilient cultivars using marker assisted breeding (MAB) strategy. A total of 232 recombinant inbred lines of IR62266/Norungan were used to map QTLs for plant phenology and production traits under rainfed condition in target population of environments. A total of 79 QTLs for plant phenology and production traits with phenotypic variation ranging from 4.4 to 72.8% were detected under non-stress and drought stress conditions across two locations. Consistent QTLs for phenology and production traits were detected across experiments and water regimes. The QTL region, RM204-RM197-RM217 on chromosome 6 was linked to days to 50% flowering and grain yield per plant under both rainfed and irrigated conditions. The same genomic region, RM585-RM204-RM197 was also linked to harvest index under rainfed condition with positive alleles from Norungan, a local landrace. QTLs for plant production and drought resistance traits co-located near RM585-RM204-RM197-RM217 region on chromosome 6 in several rice genotypes. Thus with further fine mapping, this region may be useful as a candidate QTL for MAB, map-based cloning of genes and functional genomics studies for rainfed rice improvement.

Beneficial role of naringin, a flavanoid on nickel induced nephrotoxicity in rats.

This study was conducted to investigate the beneficial role of naringin on nickel induced nephrotoxicity. Nickel (Ni) (20mg/kg body weight (b.w.) was administered intraperitoneally (i.p.) for 20 days. Naringin was administered orally (20, 40 and 80 mg/kg b.w.) with i.p. administration of Ni. Ni administration increased the levels of serum urea, uric acid and creatinine with a significant decrease in creatinine clearance and decreased levels of urea, uric acid and creatinine in urine. The levels of lipid peroxidation markers and nickel concentration in blood and kidney were also increased. While, the activities of enzymic and non-enzymic antioxidants were decreased. Treatment with naringin attenuated the alterations in the renal and urine markers, decreasing lipid peroxidation markers, increasing the antioxidant cascade and decreasing the nickel concentration in blood and kidney. All these changes were supported by histopathological observations. These findings demonstrate that naringin exerts a protective effect against nickel toxicity.

Fine mapping QTL for drought resistance traits in rice (Oryza sativa L.) using bulk segregant analysis.

Drought stress is a major limitation to rice (Oryza sativa L.) yields and its stability, especially in rainfed conditions. Developing rice cultivars with inherent capacity to withstand drought stress would improve rainfed rice production. Mapping quantitative trait loci (QTLs) linked to drought resistance traits will help to develop rice cultivars suitable for water-limited environments through molecular marker-assisted selection (MAS) strategy. However, QTL mapping is usually carried out by genotyping large number of progenies, which is labour-intensive, time-consuming and cost-ineffective. Bulk segregant analysis (BSA) serves as an affordable strategy for mapping large effect QTLs by genotyping only the extreme phenotypes instead of the entire mapping population. We have previously mapped a QTL linked to leaf rolling and leaf drying in recombinant inbred (RI) lines derived from two locally adapted indica rice ecotypes viz., IR20/Nootripathu using BSA. Fine mapping the QTL will facilitate its application in MAS. BSA was done by bulking DNA of 10 drought-resistant and 12 drought-sensitive RI lines. Out of 343 rice microsatellites markers genotyped, RM8085 co-segregated among the RI lines constituting the respective bulks. RM8085 was mapped in the middle of the QTL region on chromosome 1 previously identified in these RI lines thus reducing the QTL interval from 7.9 to 3.8 cM. Further, the study showed that the region, RM212-RM302-RM8085-RM3825 on chromosome 1, harbours large effect QTLs for drought-resistance traits across several genetic backgrounds in rice. Thus, the QTL may be useful for drought resistance improvement in rice through MAS and map-based cloning.

Prevalence of peripheral artery disease in urban high-risk Malaysian patients.

Atherosclerosis is a progressive, disseminated condition that affects all the vascular beds. Peripheral arterial disease (PAD), a manifestation of atherosclerosis, measured non-invasively in the legs by ankle-brachial index (ABI) is associated with increased cardiovascular morbidity and mortality. Though several studies in the western industrialised countries have shown that PAD is widely prevalent in the general older population at risk, not much data are available in the South East Asian developing countries. We have conducted an epidemiological survey on the prevalence of PAD in high-risk patients at an urban hospital in Malaysia. A total of 301 consecutive patients aged 32-90 years were recruited during their follow-up clinic visits for established cardiovascular disease, ischaemic stroke or diabetes mellitus > or = 5 years. All participants underwent ABI measurement and were subjected to the Edinburgh claudication questionnaire to assess leg symptoms. The prevalence of PAD in our high-risk population was 23%, of which only 27% were symptomatic with the classical intermittent claudication. All the patients with PAD were diagnosed at the time of the study. PAD was found in 33% of patients with pre-existent cardiovascular disease, 28% in patients with ischaemic stroke and 24% in diabetic patients. PAD was also highly prevalent among the younger patients. Our study has shown that PAD is highly prevalent among high-risk Malaysian patients and is not necessarily a disease of older age. Only 27% of these patients were symptomatic. All the subjects with PAD were diagnosed at the time of the study, which would suggest it is an unrecognised and underdiagnosed condition, even in patients with atherosclerotic risk factors.

Ethnicity and drug therapy for hypertension.

Physiological and pharmacological responses may be influenced by ethnicity as a result of genetic factors, environmental factors and/or their interaction. This review is divided into 2 parts. Firstly, there will be overview of ethnicity as a determinant of drug metabolism and response with reference to antihypertensive agents. The concept of ethnicity has been applied extensively to the study of hypertension especially in American blacks in whom the hypertension is more common and more aggressive. Thus, the second part of this review will then focus on examining the black-white differences in physiological responses to pharmacological challenge that may provide a link between these models and known ethnic differences in drug responses. We will discuss the hypertension studies that have examined the relative effectiveness of different classes of antihypertensive agents including several recent cardiovascular outcome trials that either have a high proportion of blacks or were conducted entirely in black subjects.