An investigation of genetic and biochemical characters of aroma in traditional indian rice landraces and its larger ecological role In plants

Abstract

Rice aroma is one of the major economically important rice crop traits which are culturally selected during domestication. The compound underlying this much-acclaimed perceptible aroma of rice is 2-acetyl-1-pyrroline (2-AP). Probing into the genetic basis of aroma in rice revealed badh2 to be the candidate gene for expression of aroma. It is situated on chromosome 8 and codes for the enzyme betaine aldehyde dehydrogenase homologue 2 (BADH2),thekeytuning the 2-AP formation pathway. An 8-bp deletion in badh2 gene also called badh2.1 is reported as the major cause of fragrance in different aromatic rice. However, those studies were focussed on mostly japonica rice samples. Very few of those studies have included the enormous untapped genetic diversity of Indian aromatic rice landraces involving indica, japonica and aus sub-populations. I investigated the genetic underpinnings of aroma in a set (55) of rare aromatic indica rice landraces. The occurrence of this functional mutation badh2.1 was diagnosed in 80% of aromatic indica rice landraces thereby refuting the notion of its occurrence in mainly tropical japonica rice. Moreover, 11 rice landraces which were found to be aromatic during the qualitative assessment, lacked 8-bp deletion in badh2 gene indicating the presence of mutation other than badh2.1. None of the wild rice samples examined in the study had this deletion. My study rekindles the questionregarding the origin of aroma insubsp. indica landraces. The occurrence of a large numberof aromatic landraces,without badh2.1 allele, evokes an alternate origin hypothesis which is deep-rooted in two primary lines of evidence.Firstly,most of the previous