Agricultural Genetics And Genomics – The New Salt-Tolerance Breeding Strategy In Rice (Oryza Sativa L.)

Ching-Chu Yen^1,2*

¹Yun-Lin County Dou-Nan Senior High School, (TAIWAN)
²No.212, Zhongshan Rd., Dounan Township, Yunlin County 63044, (TAIWAN)

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ABSTRACT – DOI: https://dx.doi.org/10.47204/EBR.2.1.2021.009-014

To develop elite salt-tolerant varieties suitable for salinized areas, Yen (2011) and Yen and Lin (2011) performed the experiments on screening, inheritance and linkage marker analyses of salt tolerance in mutated scented japonica rice and Yen (2021) performed the analyses of mapping tightly linked markers of a single dominant heat-tolerance gene in indica rice variety, TCS17. Yen (2011), Yen and Lin (2011) and Yen (2021) treated the seedlings of 1005 mutated scented japonica rice lines^[4,21] at the six true leaf stage with 300 mM NaCl for three days^[15,19]. Only the salt-tolerant line, SM61, survived. F₁, F₂ and F₃ populations were obtained from the cross between a salt-tolerant and heat-susceptible japonica line, SM61^[25-27], and a salt-susceptible and heat-tolerant indica variety, TCS17^{[11,13,25-27]}. After culture with 200 mM NaCl for five days and 30/20°C (day/night), SM61 and F₁ (SM61×TCS17; TCS17×SM61) plants survived (R) while TCS17 plants did not (S). The R to S ratio in 513 F₂ plants showed a good fit to the Mendelian 3 : 1 segregation ratio by a Chi-square test indicating that the salt-tolerance of SM61 was governed by a single dominant gene (TABLE 1). With 35/25°C (day/night) and 200 mM NaCl for five days, the salt-tolerant and heat-tolerant surviving (R) to salt-sensitive or heat-sensitive non-surviving (S) ratio in 290 F₂ plants showed a good fit to the Mendelian 3 : 13 segregation ratio by a Chi-square test indicating that the salt-tolerance of SM61 was governed by a single homozygote-semidominant gene and the heat-tolerance of TCS17 was governed by a single dominant gene (TABLE 3). The mutated salt-tolerance gene explained close to 100% of the total phenotypic variation, and was tightly linked to RM223 (marker) located on chromosome 8; the heat-tolerance gene explained close to 100% of the total phenotypic variation, and was tightly linked to C61009 (marker) located on chromosome 4 (TABLE 2). These are the first reports of mapping tightly linked markers of a single dominant mutated salt-tolerance gene and a single dominant heat-tolerance gene. For the production of salt-heat-tolerant lines with superfine agronomic traits, to selecte salt-heat-tolerant lines like SM61 and TCS17 and RIL (the A genotype of the RM223 marker and the B genotype of the C61009 marker) will provide the new breeding sources of salt tolerance in rice in the field^[25-27]. This new breeding strategy and key breakthrough will bring solutions to human food shortages.