Flood proofing of Ranjit, a popular variety of North-Eastern India through transfer of Sub1 rice QTL by modified marker-assisted backcross breeding

Abstract

Flooding is one of the major constraints of rice production in the rainfed lowland rice ecosystem. To cope with the frequent flooding in the climate change regime, tolerant cultivars are urgently needed to protect the paddy crop from flash floods. With the help of molecular markers, a major QTL for submergence tolerance "Sub1" was introgressed into a rainfed lowland mega variety Ranjit of N.E. India, by backcrossing followed by two generations of selfing. In this modified marker-assisted backcrossing (MABC), a gene based marker Sub1BC 2 and 50051 SNPs were used for foreground and background selection, respectively, in backcrosses between a Sub1 donor, Swarna-Sub1 and the recipient variety, Ranjit. The recombinant selection was skipped and background selection was deferred to BC 2 F 2 generation. The size of the donor fragment was found to be 1.65Mb. The introgression of this small segment was possible due to large population and strict selection in segregating generations for the recurrent parent with the help of 62 DUS characters. Ranjit-Sub1, a selection in BC 2 F 2 generation, showed background recovery of 96.54% and submergence tolerance similar to the tolerant donor parent. Yield, yield-components and grain physico-chemical properties showed successful recovery of these traits in Ranjit-Sub1, with yield potential ranging from 6.5 to 7.0 t/ha, not significantly different from the recurrent parent, Ranjit. Therefore, Ranjit-Sub1 has been recommended for Zone III for submergence stress conditions in India. The study demonstrates a rapid and highly precise strategy adopted to introgress a major QTL by BC 2 F 2 generation into a modern rice variety using a modified MABC.

Effect of Submergence Stress on Agro-Morphological and Physiological Traits in Rice (Oryza Sativa L.) Genotypes

“…Frequent occurrence of flash flooding and pathogenic dynamics with varying levels of genetic diversity and virulence renders their management extremely challenging (Kumar et al, 2021). There are plenty of suitable rice cultivars are available but stress due to submergence threatens rice productivity under RSL and deep water ecosystem (Chetia et al, 2018).…”

“…FR13A is utilized as donor of Sub1 in many rice improvement programs (Pradhan et al, 2015 and. Popular rice varieties, Swarna (Neeraja et al, 2007), Ranjit (Chetia et al, 2018), IR64 (Singh et al, 2015), Chehrang (Singh et al, 2015), CO3 (Rahman et al, 2018), CR 1009 (Singh et al, 2015), BRRI dhan52 (Kabir et al, 2017), Aiswarya (Nair et al, 2021) etc. have been pyramided with Sub1 through MAS/MAB approach.…”

Farmers’ Rice Yield in Fallow - T. Aman Rice - Fallow Cropping Pattern Due to Variability in Genotype And Management

“…However, in stressed area such as in the Northern Region (Dinajpur, Rajshahi and Rangpur) the adoption of Swarna-type varieties was 7 to 16 times higher than BRRI dhan49 (BRRI, 2020). It may be noted that Swarna-Ranjit is a mega variety for low land in rainfed rice system in Assam, India, covering 50% area (Chetia, 2018).…”

Mechanism of anoxic tolerance in backcross lines developed through Jyothi x Swarna-Sub 1 under submergence stress.

“…Finally, at the BC 3 F 2 generation, progenies with Sub1 introgressed region in the homozygous state and maximum recurrent parent genome percentage were selected. Similar strategies were followed by plant breeders to select the progenies for crossing during the introgression of Sub1 QTL into the genetic background of popular rice varieties (Chetia et al 2018;Bhandari et al 2019). Germinated seedlings 40 each of the selected 20 BC 3 F 2 plants along with donor and recurrent parents were sown in pots in Completely Randomized Design with 3 replications.…”