Abstract
The rice variety ‘Swarna’ is highly popular in the eastern region of India. The farmers of eastern India cultivate mainly rainfed rice and face the adverse effects of climate change very frequently. Rice production in this region is not stable. Swarna variety is highly susceptible to bacterial blight (BB) disease and flash floods, which cause a heavy reduction in the yield. Transfer of five target genes/QTLs was targeted into the variety, Swarna by adopting marker-assisted backcross breeding approach. Direct markers for Sub1A, OsSPL14, and SCM2 QTLs and closely linked markers for xa5 and Xa21 BB resistance genes were screened in the backcross progenies. Swarna-Sub1, CR Dhan 800, and Swarna–Habataki near-isogenic lines (NILs) were used as donor parents in the breeding program. True multiple F1 plants were identified for backcrossing, and 796 BC1F1 seeds were generated. Foreground selection detected all the five target genes in six progenies in BC1F1 generation. The progeny containing all the target genes and more similar with the recipient parent was backcrossed, and a total of 446 BC2F1 seeds were produced. Foreground screening detected four BC2F1 plants carrying the five target genes. A total of 2,145 BC2F2 seeds were obtained from the best BC2F1 progeny. Screening of the progenies resulted in one plant with all five desirable genes, three plants with four, and another three progenies carrying three genes in homozygous conditions. The pyramided lines showed higher BB resistance and submergence tolerance than the recipient parent, Swarna. Culm strength of the pyramided lines showed higher breaking force than the recipient parent, Swarna. The pyramided line, SSBY-16-68-69 yielded the highest grain yield of 7.52 t/ha followed by the lines SSBY-16-68-511 (7.34 t/ha) and SSBY-16-68-1633 (7.02 t/ha). The best-pyramided line showed a yield advantage of 18% over the recipient parent and 6.8% over the yield component donor parent. Seven pyramided lines showed higher yield than the recipient parent, while five lines were better yielders than the yield component donor parent. The pyramided line SSBY-16-68-69 produced 365 grains/panicle, while the recipient had 152. The main morphologic and grain quality features of the recipient parent were retained in the pyramided lines.
Highlights
Rice, the queen of cereals, is the livelihood of millions of the world’s inhabitants
Single cross F1 plants produced from the cross of Swarna-Sub1 with CR Dhan 800 carrying Sub1A, xa5, and Xa21 were validated for the presence of the genes, and the true crossed plant was hybridized with the third donor parent, i.e., Swarna–Habataki NIL for combining the two yield component QTLs, SCM2, and
We detected many desirable genes individually, but when it came to the combination of genes with all the three different traits, we found six plants out of 796 which carry all the five genes/QTLs viz., OsSPL14, SCM2, Sub1A, xa5, and Xa21
Summary
The queen of cereals, is the livelihood of millions of the world’s inhabitants. India needs to increase its rice production to fulfill the ever-growing need of the people of the country. The target of additional rice production is about 2–3 million tons of milled rice per year. This increase in production should be achieved from less land, less labor, fewer chemicals, and less water in the coming years which will be a challenging task (Pradhan et al, 2019). The crop is cultivated in about 161 million ha of global area, and 45% of rice area is under rainfed ecology, which gives low production due to many biotic and abiotic stresses. Resilient rice varieties against biotic and abiotic stresses producing high grain yield are needed for the eastern region to meet the climate change-related effects in this part of the country
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