**Characterization of Quantitative Trait Loci for Germination and Coleoptile Length under Low-Temperature Condition Using Introgression Lines Derived from an Interspecific Cross in Rice**

**Mirjalol Akhtamov 1, Cheryl Adeva 1, Kyu-Chan Shim 1, Hyun-Sook Lee 1, Sun Ha Kim 1, Yun-A Jeon 1, Ngoc Ha Luong 1, Ju-Won Kang 2, Ji-Yoon Lee 2 and Sang-Nag Ahn 1,\***


**\*** Correspondence: ahnsn@cnu.ac.kr; Tel.: +82-42-821-5728

Received: 24 August 2020; Accepted: 9 October 2020; Published: 15 October 2020

**Abstract:** Previously, five putative quantitative trait loci (QTLs) for low-temperature germination (LTG) have been detected using 96 BC3F8 lines derived from an interspecific cross between the Korean *japonica* cultivar "Hwaseong" and *Oryza rufipogon*. In the present study, two introgression lines, CR1517 and CR1518, were used as parents to detect additional QTLs and analyze interactions among QTLs for LTG. The F2 population (154 plants) along with parental lines, Hwaseong and *O. rufipogon*, were evaluated for LTG and coleoptile length under low-temperature conditions (13 ◦C). Among five QTLs for LTG, two major QTLs, *qLTG1* and *qLTG3*, were consistently detected at 6 and 7 days after incubation. Three minor QTLs were detected on chromosomes 8 and 10. Two QTLs, *qLTG10.1* and *qLTG10.2*, showing linkage on chromosome 10, exerted opposite e ffects with the Hwaseong allele at *qLTG10.2* and the *O. rufipogon* allele at *qLTG10.1* respectively, in turn, increasing LTG. Interactions among QTLs were not significant, implying that the QTLs act in an additive manner. Near-isogenic line plants with the combination of favorable alleles from *O. rufipogon* and Hwaseong exhibited higher LTG than two introgression lines. With regard to coleoptile length, three QTLs observed on chromosomes 1, 3, and 8 were colocalized with QTLs for LTG, suggesting the pleiotropy of the single gene at each locus. According to the results, the introgression of favorable *O. rufipogon* alleles could hasten the development of rice with high LTG and high coleoptile elongation in *japonica* cultivars.

**Keywords:** low-temperature germinability; rice; interspecific cross; QTL; interaction
