Characterization of functional trait diversity among Indian cultivated and weedy rice populations

Hybrid Rice Production: A Worldwide Review of Floral Traits and Breeding Technology, with Special Emphasis on China

Rice is an important diet source for the majority of the world's population, and meeting the growing need for rice requires significant improvements at the production level. Hybrid rice production has been a significant breakthrough in this regard, and the floral traits play a major role in the development of hybrid rice. In grass species, rice has structural units called florets and spikelets and contains different floret organs such as lemma, palea, style length, anther, and stigma exsertion. These floral organs are crucial in enhancing rice production and uplifting rice cultivation at a broader level. Recent advances in breeding techniques also provide knowledge about different floral organs and how they can be improved by using biotechnological techniques for better production of rice. The rice flower holds immense significance and is the primary focal point for researchers working on rice molecular biology. Furthermore, the unique genetics of rice play a significant role in maintaining its floral structure. However, to improve rice varieties further, we need to identify the genomic regions through mapping of QTLs (quantitative trait loci) or by using GWAS (genome-wide association studies) and their validation should be performed by developing user-friendly molecular markers, such as Kompetitive allele-specific PCR (KASP). This review outlines the role of different floral traits and the benefits of using modern biotechnological approaches to improve hybrid rice production. It focuses on how floral traits are interrelated and their possible contribution to hybrid rice production to satisfy future rice demand. We discuss the significance of different floral traits, techniques, and breeding approaches in hybrid rice production. We provide a historical perspective of hybrid rice production and its current status and outline the challenges and opportunities in this field.

Morphological Variations of Weedy Rice (Oryza sativa ssp.) In Selected Rice Fields of Peninsular Malaysia

Weedy rice or locally known as ‘padi angin’ has been infesting rice granary areas in Malaysia for the last 20 years. The outbreak of weedy rice in the country started during the late 1980s in Projek Barat Laut Selangor (PBLS) due to the adoption of direct-seeding practices. Weedy rice can be characterized by its early maturing and easy-shattering traits. The objective of this study was to determine the morphological variations of weedy rice in selected granary areas located in Peninsular Malaysia. A total of 110 weedy rice accessions were collected from nine locations in three granary areas in Peninsular Malaysia (the Western, Eastern, & Northern regions). The collected weedy rice accessions were planted under greenhouse conditions to study their morphological features. Results of the present study indicated that 73.6% of weedy rice accessions were awnless while the remaining 26.4% produced awn. Selected traits such as plant height, flag leaf length, culm length, number of tillers, number of panicles, and panicle length were included in the Principal Component Analysis (PCA). The weedy rice accessions were grouped into three different clusters mainly Cluster 1: cultivated rice and awnless populations, Cluster 2: brown and red pericarp awnless populations, and Cluster 3: awned populations. The findings of this study may be used as guidance for farmers and researchers for designing sustainable weedy rice management in the future.

Whole-genome sequencing reveals uniqueness of black-hulled and straw-hulled weedy rice genomes

Both SH and BHA weedy rice genotypes evolved independently and have distinct genomic composition. Different genetic mechanisms may be responsible for their competitiveness and adaptation to diverse environmental conditions. Two major types of weedy rice are recognized in the USA based on morphology: straw-hull (SH) and black-hull awned (BHA) weedy rice. We performed whole-genome resequencing of a SH weedy rice 'PSRR-1', a BHA weedy rice 'BHA1115', and a japonica cultivar 'Cypress' to delineate genome-wide differences and their relevance to genetics and evolution of weedy attributes. The high-quality reads were uniformly distributed with 82-88% genome coverage. The number of genotype-specific SNPs and InDels was highest in Cypress, followed by BHA1115 and PSRR-1. However, more genes were affected in BHA1115 compared with other two genotypes which is evident from the number of high-impact SNPs and InDels. Haplotype analysis of selected genes involved in domestication, adaptation, and agronomic performance not only differentiated SH from BHA weedy rice and supported evolution of weedy rice through de-domestication, but also validated the function of several genes such as qAn-1, qAn-2, Bh4, Rc, SD1, OsLG1, and OsC1. Several candidate genes were identified for previously reported seed dormancy and seed shattering QTLs. The SH and BHA weedy rice have distinct genomic composition, and the BHA weedy rice likely diverged earlier than SH weedy rice. The accumulation of plant development, reproduction, and defense-related genes in weedy rice possibly helped them to compete, survive, and spread under a wide range of environmental conditions by employing novel and diverse mechanisms. The genomic resources will be useful for both weed management and rice improvement by exploring the molecular basis of key agronomic, adaptive, and domestication attributes.