Allelic variations in aroma gene in cultivated rice varieties

Abstract

Germplasm is a valuable source of genetic diversity that supports crop improvement efforts in any breeding programme but it must first be fully characterised for economically valuable traits before it can be effectively utilised. In rice (Oryza sativa), the development of new varieties with improved aroma requires correct phenotyping and prior knowledge of the available genes and alleles governing the aroma trait in the gene pool. Correct phenotyping and genotyping can be achieved using sensory methods and functional markers associated with polymorphisms that define the aroma genes. The objective of this study was to evaluate the aroma status of rice accessions and to assess for the various alleles of badh2 gene using functional markers. A total of 56 rice accessions were evaluated at National Crops Resources Research Institute (NaCRRI) in Uganda for their aroma using sensory methods and a molecular marker to differentiate between aromatic and non- aromatic accessions. The aromatic accessions were then evaluated for variations within the betaine aldehyde dehydrogenase2 (badh2) gene responsible for aroma in rice using functional markers. Sensory evaluation of aroma identified 23 accessions to be aromatic; while 33 were non-aromatic. Molecular results identified 20 accessions as aromatic; while 36 accessions were non-aromatic. Functional marker analysis indicated the presence of badh2-E7 allele in 20 aromatic accessions within this collection that could be employed in the breeding programme for the rice aromatic trait.
 Key words: badh2 alleles, functional markers, Oryza sativa

Screening for aroma in rice genotypes with African and Asian backgrounds

“…The level of aroma expression perceived by the evaluators varied among the tested genotypes. The current results agree with other recent studies that found differences in the strength of aroma among rice genotypes (Akwero et al., 2020; Ocan et al., 2019). As the evaluated genotypes were grown in the same field and handled in the same way after harvesting, these differences in level of aroma expression can mostly be explained by the genetic background of each genotype (Ndikuryayo et al., 2022; Ocan et al., 2019).…”

“…The scores for taste were significantly different among the tested genotypes. This result agrees with other research findings that revealed significant differences in sensory scores among the evaluated rice genotypes (Akwero et al., 2020; Kwak et al., 2015; Ocan et al., 2019). In a study conducted by Kwak et al.…”

“…Each leaf was directly put in one labeled envelop inside the ice container. These samples were taken to the laboratory where they were punched and kept in wells of plates at −80°C (Akwero et al., 2020) for 14 h. Each plate was also labeled. Samples were later transferred to a lyophilizer for 48 h for drying (Kanyange et al., 2019).…”

“…These compounds include hexanal, octanal, nonanal, (E)‐2‐octenal, decanal, 1‐heptanol, and 1‐octanol (Zhao et al., 2020). However, aroma is mainly induced by high concentration of 2‐acetyl‐1‐pyrroline (2AP), an N‐heterocycle compound that is produced by a mutation in the betaine aldehyde dehydrogenase ( BADH 2 ) gene (Akwero et al., 2020; Ocan et al., 2019; Wang et al., 2016; Withana et al., 2020). That mutation is responsible for accumulation of 4‐aminobutanal, its acetylation, and cyclization (Daygon et al., 2017).…”

Inheritance studies of grain shape and aroma traits of rice genotypes in Uganda rice germplasm

“…In regards to presentational qualities, some grain attributes of rice from Uganda including grain length were suggested to have met the market requirement specification (Lamo et al, 2017), but grain aroma which was also reported to be associated with the grain shape (MAAIF, 2020) was not one of the attributes for the recently released varieties in Uganda. Furthermore, despite of some efforts being directed at identification of aromatic rice varieties in Uganda (Akwero et al, 2020), the issue of adaptability has affected use of primary introduction as a breeding strategy and yet deliberate study on inheritance of aroma trait has so far been limited. One of the main problems faced by plant breeders for improving varieties is to select good parents and better insights on the combining abilities of the parents as pre-requisite for developing progenies for trait selection.…”