Brown planthopper, bacterial leaf blight and rice blast disease are identified as devastating stresses of rice cultivation. Developing host plant resistance is considered an effective and environmentally friendly management strategy. In Sri Lanka, limited studies have been carried out to assess the genetic basis of disease resistance. Bph3, Pikh and Xa21 genes convey significant resistance against biotic stresses. The current study was conducted to identify whether markers linked to Bph3, Pikh and Xa21 genes can facilitate the identification of resistant varieties. A total of 34 varieties were selected for the study and their morphometric and marker allelic data were subjected to descriptive and statistical analyses. Moderate height varieties depicted high yield. Most of the varieties showed significant moderate resistance against stresses. Molecular marker analysis yielded polymorphic banding patterns for all markers. RM 589 marker linked to Bph3 dominant gene provides overlapping banding patterns for the cultivars with different resistance levels making it impossible to discriminate resistant and susceptible cultivars. RM 206 marker linked to gene pikh provided the expected PCR product size for RM 206 marker is 147 bp. The resistant varieties gave band lengths of 140 bp, 170 bp and susceptible or moderately susceptible varieties produced band lengths of 160 bp and 155 bp. pTA 248 marker linked to Xa21 locus produced bands length of 670 bp, 740 bp and 930 bp. The 930 bp band was observed only in IRBB 60 variety. IRBB60 amplified 930 bp fragment confirms the possession of the resistant allele of Xa21 in its background. Presence of 730 bp indicates the susceptible allele. None of the Sri Lankan varieties carries a resistant allele for Xa21 as they have 730 bp allele for pTA 248. The rice varieties such as Bg251, Bg455, Bg450, Bg305, At402, At308 and At354 contain high yielding traits but need to improve for the pest and disease resistance.
Rice provides a balanced diet, and regular rice consumption helps maintain a healthy life and prevents many common illnesses. Amylose content and gelatinization temperature are considered major physicochemical factors which significantly affect the nutrition and cooking quality of rice. The Waxy (Wx) gene controls the synthesis of amylose in the endosperm and the ALK gene controls the gelatinization temperature of rice. Both genes are present on chromosome 6. Improving the rice traits is crucially essential to the cultivators and the consumers to overcome the increasing demand for high-quality and nutritionally rich rice. Many studies have been successfully conducted to improve the agronomical traits of rice. However, the concern for improving nutrition and cooking quality-related traits of rice is less common among the breeders. Therefore, considering the current trends, introducing consumer-friendly novel varieties that can fulfill the nutritional requirements is essential to face the increasing domestic demand for high-quality rice. In the present study, we used frequently grown 54 local rice varieties and carried out a markerbased genetic analysis for three traits: amylose content, gelatinization temperature, and yield. Then statistical analysis was carried out using quantitative data of different agronomical and physicochemical traits to identify the correlation and potential to improve such essential traits. The level of amylose content is significantly associated with the gelatinization temperature indicating that AC and GT have a positive correlation. The DNA markers SSIIa and Seq1-2 markers showed monomorphic patterns indicating the narrow genetic basis of the rice varieties tested. This study revealed that existing high-yielding rice varieties could be successfully employed to increase the amylose content while decreasing the level of gelatinization temperature through breeding strategies to make nutritionally rich consumer-friendly novel varieties.
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