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Fifty three accessions of lowland Black Glutinous Rice (BGR) and three
white rice varieties from Lao PDR were evaluated for variations in 2-acetyl-1-pyrroline
(2-AP), a main aroma compound present in fragrant rice and a 257 bp genomic
fragment associated with a gene encoding 2-AP. The objective of this study
was to characterize the variation in aromatic characters of Lao BGR by
using chemical and molecular techniques. Thirty six out of the 56 accessions
had aromatic properties, containing 2-acetyl-1-pyrroline (2-AP). The concentrations
of 2-AP in unpolished samples were about 50% higher than those of the
polished samples. The concentrations of 2-AP in BGR accessions were lower
than those of white aromatic rice varieties in which 2-AP was highest
in Kai Noi Leuang (0.688 ppm). Seventeen accessions and two of white rice
(Kai Noi Leuang and TDK5) had a common 355 bp allele corresponding to
that found in Calrose, a non-fragrant variety. A 257 bp allele was found
in the 36 varieties of BGR and a local aromatic white rice variety, Hom
Nang Nouan, sharing a common allele as in the fragrant variety KDML 105.
Surprisingly, Kai Noi Leuang, a popular Lao local aromatic rice variety
with the highest 2-AP concentration did not possess a 257 bp fragment
which has been identified previously as a fragrant allele. This is the
first study of the chemical and molecular aromatic properties of lowland
BGR varieties of the Lao PDR and the data obtained will be valuable in
screening other germplasm and in planning a breeding program in the country
geared towards fragrant rices with superior agronomic properties.
