Black Rice Developed Through Interspecific Hybridization (O. sativaxO. rufipogon): Origin of Black Rice Gene from Indian Wild Rice

Abstract

Rice (Oryza sativa L.) is a most important staple food grain consumed by more than half of the world’s population. Wild rice (O. rufipogon Griff.) is considered as the immediate ancestral progenitor of cultivated rice O. sativa, evolved through the process of domestication. Most of the cultivated rice produced grains with white pericarp, but can also produce grains with brown, red and black (or purple rice) pericarp. Red rice pericarp accumulates proanthocyanidin whereas black rice contains anthocyanin, both have antioxidant activity and health benefits. Black pericarp is predicted to be regulated by alleles of three genetic loci- Kala1, Kala3, and Kala4. Recombinational and insertional genetic rearrangement in the promoter region of Kala4 is crucial for the development of black pericarp in rice grain. In the present study, we report first time in the breeding history that aromatic black rice lines were developed through interspecific hybridization and introgression in the genetic background of O. sativacv. Badshabhog, Chenga and Ranjit. Badshabhog and Ranjit is white grain rice but Chenga is red rice category. Common Asian wild rice O. rufipogon is used as donor parent (red grain) and source of black rice gene. Several possible genetic explanations have come up for the creation of black rice pericarp in the progeny lines. Possible reason may be the rearrangement and insertion of LINE1 in the promoter region of Kala4 allele through recombination mechanism leading to ectopic expression of Kala4 gene for the accumulation of anthocyanin and resulted in black rice formation. Other genes and regulatory factors may be induced and become functional to produce black pericarp. Black pericarp colour appeared in F2 populations in the wide crosses (Badshabhog x O. rufipogon and Chenga x O. rufipogon) but not in the cross with (Ranjit x O. rufipogon). Black pericarp trait inherited in F4 and F5 population with segregation phenotypes.This is a first report in the history of rice genetics and pre-breeding research, that black rice has been created through wide crossing and introgression by combining wild rice O. rufipogon in the genetic background of O. sativa. Present experimental evidence provides a new model of black rice origin. Thus, black rice (indica type) of Indian subcontinent originated independently through natural out crossing and artificial selection in the course of domestication.

Uncovering Genomic Regions Regulating the Superoxide Dismutase, Flavonoids, Anthocyanins, Carotenoids, γ-Oryzanol and Antioxidant Activity in Rice Through Association Mapping

“…The QTLs for anthocyanin and proanthocyanin content in rice was reported by earlier researchers 23,35,39,62 . In the present investigation, the QTLs for total anthocyanin content were detected on chromosome 1, 3, 5 and 12.…”

“…The genetic analyses for identi cation and ne mapping of genes and QTLs for pericarp pigmentation in rice have been published by using various mapping populations 10,25,35,37,39,40 . However, few reports on QTL mapping are available on gamma-oryzanol, total phenolics content (TPC), total avonoids content (TFC), ABTS (Azinobis 3-ethyl benzothiazoline-6-sulfonic acid) and SOD (Super oxide dismutase) activity in rice.…”

“…However, a recent study reported that A1 (Kala1/Rd/OsDFR), C1(OsC1) determine purple colour of the grain and pattern of anthocyanin pigmentation is determined by the allelic status of A1, C1, and S1 (OsANS1) 31 . Kala 4/OsB2/Pb gene was mainly responsible for black pigmentation in rice pericarp 32,33,34,35,36 . Although several genes responsible for pericarp pigmentation have already been identi ed but possibility of additional genes and variants associated with these traits exist and need to be discovered.The genetic analyses for identi cation and ne mapping of genes and QTLs for pericarp pigmentation in rice have been published by using various mapping populations 10,25,35,37,39,40 .…”

“…Kala 4/OsB2/Pb gene was mainly responsible for black pigmentation in rice pericarp 32,33,34,35,36 . Although several genes responsible for pericarp pigmentation have already been identi ed but possibility of additional genes and variants associated with these traits exist and need to be discovered.The genetic analyses for identi cation and ne mapping of genes and QTLs for pericarp pigmentation in rice have been published by using various mapping populations 10,25,35,37,39,40 . However, few reports on QTL mapping are available on gamma-oryzanol, total phenolics content (TPC), total avonoids content (TFC), ABTS (Azinobis 3-ethyl benzothiazoline-6-sulfonic acid) and SOD (Super oxide dismutase) activity in rice.…”

“…Attempts have been made to develop few pigmented rice varieties like'Rubi' and 'Onix' of Brazil 45 and 'Rice berry" of Thailand 46 . Also, some advanced breeding lines are available 33,36,47,48,49 .Though several studies reported about genes for these antioxidant traits of which some genes have been ne mapped in certain cases (Rc, Rd,Pb) and each adopted a different gene coding system which is still confusing for which more rm genes/loci should be identi ed to explain these complex traits 19 . There by development of trait-speci c markers will accelerate the efforts to breed high yielding pigmented rice varieties.…”