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Improved rice lines were developed frome three parents with the resistance or tolerance to bacterial leaf blight, blast and drought stress, respectively, using single-, double- and three-way crosses. The improved lines were assessed for agro-morphological and yield traits under non-drought stress (NS) and reproductive-stage drought stress (RS) treatments. The mean comparison of traits measured between parent plants and progenies (improved lines) were similar, and there were significant and non-significant differences among the parents and improved lines (genotypes) under NS and RS. Smilarly, there was significant and non-significant differences in the interaction among both parent varieties and improved lines for NS and RS. Cluster and 3D-model of principal component analysis did not generate categorical clusters according to crossing methods, and there were no exclusive crossing method inclined variations under the treatments. The improved lines were high-yielding, disease resistant, and drought-tolerant compared with their parents. All the crossing methods were good for this crop improvement program without preference to any, despite the number of genes introgressed.

Bacterial leaf blight (BLB) and blast are among the most destructive diseases of rice. In order to develop new varieties that can resist various races of the pathogens Xanthomonas oryzae pv. oryzae (Xoo) and Magnaporthe oryzae, which cause these two diseases, respectively, it is important to identify suitable markers and a marker-aided selection strategy. Seventeen foreground microsatellites associated with resistance against BLB and blast were screened for polymorphism for possible adoption in a breeding program for resistant cultivar development. A total of 472 background simple sequence repeats (SSRs) were also screened for polymorphism in order to recover the recurrent parent genome. All 72 F1 progenies were also analysed with the 17 foreground and 472 background markers in comparison to the alleles of their parents. The markers were validated using 218 BC2F2 plants. The result revealed six tightly linked polymorphic foreground markers (Xa21FR, pTA248, Xa13prom, MP, RM21 and RM13) associated with resistance against Xoo pathotype P7.7 and two microsatellites (RM6836 and RM8225) associated with resistance against blast pathotype P7.2. A total of 79 polymorphic background markers were identified for recovering the recurrent parent genome. The result also showed that the markers had goodness of fit (blast resistance) to 1:2:1 ratio for single gene model in BC2F2 progenies. These genetically confirmed microsatellite markers were recommended for use in marker-assisted backcross breeding and other marker-assisted selection of BLB and blast resistance genes in order to develop varieties with durable and broad spectrum resistance against the two major rice diseases.

Exploring the genetic aspects of germplasm using genotypic and phenotypic analysis is more reliable for the development of rice varieties that could lead to the attainment of food security. This is because genetic variations provide a space for recombinants, which is an important factor in new varietal development. This study was conducted to evaluate genetic variability and diversity among 32 coloured rice accessions using agro-morphological characteristics and simple sequence repeats (SSR) markers. Quantitative traits (morphological, grain quality and antioxidant properties) and 34 SSR molecular markers were used as tools for determining cultivar identities and genetic diversity. Most of the quantitative traits showed significant differences (p ≤ 0.01) among all rice accessions. Clustering analysis from quantitative traits categorised the accessions into four groups. Similarly, the 32 accessions were grouped into 4 cluster groups based on the analysis of 34 SSR markers. The accessions YTM15, Pulut Merah 3, Padi Randau, Ringan Bawang, DNJ128 and DV 107 can be potentially selected for development of new varieties for local cultivation. Finally, these accessions can be used as parents in further breeding programmes.

Breeding for disease resistant varieties remains very effective and economical in controlling the bacterial leaf blight (BLB) of rice. Breeders have played a major role in developing resistant rice varieties against the BLB infection which has been adjudged to be a major disease causing significant yield reduction in rice. It would be difficult to select rice crops with multiple genes of resistance using the conventional approach alone. This is due to masking effect of genes including epistasis. In addition, conventional breeding takes a lot of time before a gene of interest can be introgressed. Linkage drag is also a major challenge in conventional approach. Molecular breeding involving markers has facilitated the characterization and introgression of BLB disease resistance genes. Biotechnology has brought another innovation in form of genetic engineering (transgenesis) of rice. Although, molecular breeding cannot be taken as a substitute for conventional breeding, molecular approach for combating BLB disease in rice is worthwhile given the demand for increased production of rice in a fast growing population of our society. This present article highlights the recent progress from conventional to molecular approach in breeding for BLB disease resistant rice varieties.

Marker-assisted selection and gene pyramiding are very important breeding strategies for conferring broad spectrum and durable resistance against diseases causing yield loss in rice. One such disease causing major set backs in rice production is bacterial leaf blight (BLB) caused by the pathogen Xanthomonas oryzae pv. oryzae. Molecular markers are very essential in both marker-assisted selection and pyramiding of genes, hence, many molecular marker techniques have already been developed. Presently, the most commonly used ones are DNA-based markers also known as molecular markers. The molecular markers are classified into two major categories based on the techniques used for detecting them. These are hybridization and polymerase chain reaction-based markers. Other types of markers available include the morphological (traditionally based) and biochemical (enzyme-based) markers. Host plant/varietal resistance is the most suitable means for controlling BLB disease of rice. Marker-assisted gene pyramiding has the potential to accelerate the breeding programmes and guarantee the durability of resistance conferred in the host plant. Therefore, this paper uncovers the utilization, economic importance, limitations and future prospects of marker-assisted selection and gene pyramiding for resistance to BLB disease of rice.

High kernel elongation (HKE) is one of the high-quality characteristics in rice. The objectives of this study were to determine the effects of ageing treatments, gene actions, and inheritance pattern of kernel elongation on cooking quality in two populations of rice and determine the path of influence and contribution of other traits to kernel elongation in rice. Two rice populations derived from crosses between MR219 × Mahsuri Mutan and MR219 × Basmati 370 were used. The breeding materials included two F1 progenies from the two populations, and their respective parents were grown in four different batches at a week interval to synchronize the flowering between the female and male plants. Scaling tests and generation means analysis were carried out to determine ageing effects and estimate additive-dominance gene action and epistasis. The estimation of gene interaction was based on quantitative traits. Path coefficient analysis was done using SAS software version 9.4 to determine the path of influence (direct or indirect) of six quantitative traits on HKE. Results obtained showed that nonallelic gene interaction was observed in all traits. The results before ageing and after ageing showed significant differences in all traits, while the gene interaction changed after ageing. The HKE value improved after ageing, suggesting that ageing is an external factor that could influence gene expression. The epistasis effect for HKE obtained from the cross Mahsuri Mutan × MR219 showed duplicate epistasis while that obtained from a cross between Basmati 370 × MR219 showed complimentary epistasis. Besides, the heritability of HKE was higher in Basmati 370 × MR219 compared to that obtained in Mahsuri Mutan × MR219. The path analysis showed that the cooked grain length and length-width ratio positively significantly affected HKE. It was concluded that ageing treatment is an external factor that could improve the expression of HKE. The findings from this study would be useful to breeders in the selection and development of new specialty (HKE) rice varieties.