Dehydrogenase that can use N-acetyl-c-aminobutyraldehyde (NAGABald), gamma-guanidinobutyraldehyde (GGBald), betaine aldehyde (Bet-ald), gamma-aminobutyraldehyde (GAB-ald), acetaldehyde, 4-aminobutylaldehyde (AB-ald), 3-aminopropionaldehyde (AP-ald), 4-N-trimethylaminobutyraldehyde (TMAB-ald) and 3-N-trimethylaminopropionaldehyde (TMAP-ald) as substrates. Catalyzes the oxidation of GAB-ald more efficiently than Bet-ald. Mediates the conversion of GAB-ald into gamma-aminobutyric acid (GABA), and prevents the formation of 2-acetyl-1-pyrroline (2AP) which gives fragrant rice its aromatic properties. betaine aldehyde + H2O + NAD(+) = glycine betaine + 2 H(+) + NADH Amine and polyamine biosynthesis; betaine biosynthesis via choline pathway; betaine from betaine aldehyde: step 1/1. Homodimer. Present in a truncated form, mostly allele badh2.1, also called 'fgr' in fragrant rice varieties (e.g. basmati and jasmine rice). The loss of activity leads to accumulation of 2-acetyl-1-pyrroline (2AP) that confers the flavor of fragrant rice. Haplotype analysis suggests a single origin of the badh2.1 allele within the Japonica varietal group and demonstrates the introgression of this allele from Japonica to Indica (PubMed:18599581, PubMed:19706531). Belongs to the aldehyde dehydrogenase family.