Aroma volatile analyses and 2AP characterization at various developmental stages in Basmati and Non-Basmati scented rice (Oryza sativa L.) cultivars

Abstract

BackgroundRice plant growth is comprised of distinct phases, such as vegetative, reproductive, grain filling and maturity phases. In these phases synthesis and availability of primary and secondary metabolites including volatile organic compounds (VOC’s) is highly variable. In scented rice, aroma volatiles are synthesized in aerial plant parts and deposited in mature grains. There are more than 100 VOCs reported to be responsible for flavor in basmati rice. It will be interesting to keep track of aroma volatiles across the developmental stages in scented rice. Therefore, the aroma volatiles contributing in aroma with special reference to the major compound 2 acetyl-1-pyrroline (2AP) were screened at seven developmental stages in scented rice cultivars Basmati-370 and Ambemohar-157 along with non-scented rice cultivar IR-64 as a control following HS-SPME-GC-MS method. In addition, the expression levels of key genes and precursor levels involved in 2AP biosynthesis were studied.ResultsThe study indicated that volatilome of scented rice cultivars is more complex than non-scented rice cultivar. N-heterocyclic class was the major distinguishing class between scented from non-scented rice. A total of 14 compounds including, 2AP were detected specifically in scented rice cultivars. Maximum number of compounds were synthesized at seedling stage and decreased gradually at reproductive and maturity. The seedling stage is an active phase of development where maximum number green leaf volatiles were synthesized which are known to act as defense molecules for protection of young plant parts. Among the 14 odor active compounds (OACs), 10 OACs were accumulated at higher concentrations significantly in scented rice cultivars and contribute in the aroma. 2AP content was highest in mature grains followed by at booting stage. Gene expression analysis revealed that reduced expression of betaine aldehyde dehydrogenase 2 (badh2) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and elevated level of triose phosphate isomerase (TPI) and Δ1-Pyrolline-5-carboxylic acid synthetase (P5CS) transcript enhances 2AP accumulation.ConclusionsMost diverse compounds were synthesized at seedling stage and OACs were accumulated more at flowering followed by seedling stage. Distinct accumulation pattern exists for 2AP and other aroma volatiles at various developmental stages. The study revealed the mechanism of 2AP accumulation such that 2AP in mature grains might be transported from leaves and stem sheath and accumulation takes place in grains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0113-6) contains supplementary material, which is available to authorized users.

Volatile compounds profile of Brazilian aromatic brown rice genotypes and its cooking quality characteristics

“…Twenty‐three volatile compounds consisting of four alcohols, nine aldehydes, one furan, six ketones, and three terpenes were identified in brown rice samples of aromatic and non‐aromatic genotypes by GC‐MS (Table ). As reported by Hinge, Patil, and Nadaf (), the main groups of volatile compounds in mature rice grains were aliphatic aldehydes (27%), alcohols (21%), alkane (12%), and ketones (14%). Other groups such as aromatic aldehydes, furan, n ‐heterocyclic, phenol‐containing, alkenes, carboxylic acids, and aromatic hydrocarbons represent <6%.…”

Insight of aroma in brown rice through chemical assessment of 2‐Acetyl‐1‐pyrroline (2AP) in aromatic germplasm of India

“…Apart from fragrant rice genotypes, 2AP was also noticed in nonfragrant rice; however, its concentration is much lower than the former (Widjaja et al., ). More 2AP was noticed in scented rice than nonscented rice (Hinge et al., ; Maraval et al., ). 2AP content observed for Khao Dawk Mali 105 was similar Mahatheeranont et al.…”

“…() in seven rice varieties of Sri Lanka. A total of 14 compounds including nonanal, hexanal, indole, and 2AP was studied in three rice cultivars at seven developmental stages, seedling to mature grain, and reported high 2 AP content in matured grains (Hinge et al., ).…”

“…Hexanal, 2AP, benzyl alcohol, and indole were reported by Liyanaarachchi et al (2014) in seven rice varieties of Sri Lanka. A total of 14 compounds including nonanal, hexanal, indole, and 2AP was studied in three rice cultivars at seven developmental stages, seedling to mature grain, and reported high 2 AP content in matured grains (Hinge et al, 2016). During sensory evaluation, nasal receptors play important role in the identification of aromatic rice.…”

“…So far, rice aroma analysis was performed with varied number of varieties viz., only one variety (Mahatheeranont, Keawsa-ard, & Dumri, 2001), five (Maraval et al, 2008), 13 (Limpawattana, Yang, Kays, & Shewfelt, 2008), three (Hinge, Patil, & Nadaf, 2016;Wilkie, Wootton, & Paton, 2004), seven (Liyanaarachchi, Kottearachchi, & Samarasekera, 2014), 40 (Hien, Yoshihashi, Sarhadi, & Hirata, 2006), 548 (Kovach, Calingacion, Fitzgerald, & McCouch, 2009), and 478 (Fitzgerald, Sackville Hamilton, Calingacion, Verhoeven, & Butardo, 2008) genotypes and many of them only analyzed 2AP. Hence, the present investigation aimed in analyzing large number of aromatic genotypes for 2AP and other aromatic compounds using nonaromatic genotypes as control.…”