Decoding the Grain Aroma in Rice (Oryza sativa L.): Current Progress and Prospects for Improvement

Le résumé fourni par la source

Aromatic rice is a distinct category of rice because of its pleasant fragrance. Basmati and Jasmine are the most popular types of aromatic rice in the global market. Short-grain aromatic rice cultivars of South and Southeast Asia are also popular but still need to be fully explored. Many researchers have attempted to explore the origin of aromatic rice, but it is still being clarified. Researchers depicted that evolutionarily aromatic rice demonstrates a close association with the Japonica-type gene pool and could be evolved in the Himalayan foothills through a natural hybridization between domesticated Japonica and wild rice. Genetics and environment intricately interact to control the formation and accumulation of aromatic compounds in rice grain. Although several candidate gene/QTLs for grain aroma have been identified, the fgr gene mapped on chromosome 8 as BETAINE ALDEHYDE DEHYDROGENASE 2 (BADH2) encoding an oxidoreductase enzyme betaine aldehyde dehydrogenase, which oxidizes γ-aminobutyraldehyde (GAB-ald) and produces γ-aminobutyric acid (GABA), is considered as the major gene for grain aroma in rice. The loss of function of BADH2 inhibits the GABA production and enhances the conversion of GAB-ald into 2-acetyl-1-pyrroline (2AP). 2AP is considered as one of the major fragrance components in rice grain. Being a volatile component, 2AP accumulation in rice grain is highly influenced by the environmental factors and crop management practices as well. Cool temperature and low humidity are good for the accumulation of volatile fragrance components in rice grain. Low yield, lodging and disease susceptibility are major constraints in commercial cultivation. Improving the agronomic performance and disease resistance are the major breeding objectives of aromatic rice breeding. Combining conventional, mutation, and molecular breeding methods could be a better solution to develop lodging-resistant and higher-yielding aromatic rice varieties. This review focused on the current progress in aromatic rice research and prospecting the future research programs.

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