Genome-wide association mapping for component traits of drought tolerance in dry beans (Phaseolus vulgaris L.)

Understanding the genetic basis of traits of economic importance under drought stressed and well-watered conditions is important in enhancing genetic gains in dry beans (Phaseolus vulgaris L.). This research aims to: (i) identify markers associated with agronomic and physiological traits for drought tolerance and (ii) identify drought-related putative candidate genes within the mapped genomic regions. An andean and middle-american diversity panel (AMDP) comprising of 185 genotypes was screened in the field under drought stressed and well-watered conditions for two successive seasons. Agronomic and physiological traits, viz., days to 50% flowering (DFW), plant height (PH), days to physiological maturity (DPM), grain yield (GYD), 100-seed weight (SW), leaf temperature (LT), leaf chlorophyll content (LCC) and stomatal conductance (SC) were phenotyped. Principal component and association analysis were conducted using the filtered 9370 Diversity Arrays Technology sequencing (DArTseq) markers. The mean PH, GYD, SW, DPM, LCC and SC of the panel was reduced by 12.1, 29.6, 10.3, 12.6, 28.5 and 62.0%, respectively under drought stressed conditions. Population structure analysis revealed two sub-populations, which corresponded to the andean and middle-american gene pools. Markers explained 0.08-0.10, 0.22-0.23, 0.29-0.32, 0.43-0.44, 0.65-0.66 and 0.69-0.70 of the total phenotypic variability (R2) for SC, LT, PH, GYD, SW and DFW, respectively under drought stressed conditions. For well-watered conditions, R2 varied from 0.08 (LT) to 0.70 (DPM). Overall, 68 significant (p < 10-03) marker-trait associations (MTAs) and 22 putative candidate genes were identified across drought stressed and well-watered conditions. Most of the identified genes had known biological functions related to regulating the response to drought stress. The findings provide new insights into the genetic architecture of drought stress tolerance in common bean. The findings also provide potential candidate SNPs and putative genes that can be utilized in gene discovery and marker-assisted breeding for drought tolerance after validation.Bruce Mutari, Julia Sibiya, Admire Shayanowako, Charity Chidzanga, Prince M. Matova, Edmore Gasur

Geological effects on water quality: a review of issues and challenges in Malaysia

Malaysian source of water for household and industrial use is derived mainly from surface sources. The increasing demand for quality water for household consumption and industrial use has posed a great challenge to the otherwise abundant but scarce natural resources. This paper examines the important challenges associated with the deteriorating water quality in Peninsular Malaysia. Quality water enhances one’s good health. Therefore, evaluating health risk as a result of heavy metals introduction through drinking water from various geological activities like the ex-mining ponds in Klang Valley is worthy to note. Heavy metals which are one of the sources of contaminants, due to their solubility are transported from their source (mining, agricultural, and industrial) to groundwater. There is a linkage between land-use change (activities) such as logging, agriculture, urbanization, mining, and industrial activities as a potential source of contaminants, this is further conflated by the hydrogeology of the areas which show a shallow aquifer system predominantly associated with alluvial and carbonate. Also, microbial contamination had affected water sources. Given that more of the aquifer systems in Peninsular Malaysia are shallow, this makes it very easy for groundwater sources around Malaysia to be contaminated. The industrialisation and urbanisation in Malaysia, as well as the growing population, posed a great challenge to water quality. This paper highlights the key challenges and possible solutions to water quality management in Malaysia