A hybrid sterile locus leads to the linkage drag of interspecific hybrid progenies

Abstract

Interspecific hybridization plays an important role in rice breeding by broadening access to desirable traits such as disease resistance and improving yields. However, interspecific hybridization is often hindered by hybrid sterility, linkage drag, and distorted segregation. To mine for favorable genes from Oryza glaberrima , we cultivated a series of BC 4 introgression lines (ILs) of O. glaberrima in the japonica rice variety background (Dianjingyou 1) in which the IL-2769 (BC 4 F 10 ) showed longer sterile lemmas, wider grains and spreading panicles compared with its receptor parent, suggesting that linkage drag may have occurred. Based on the BC 5 F 2 population, a hybrid sterility locus, S20 , a long sterile lemma locus, G1-g , and a new grain width quantitative trait locus (QTL), qGW7 , were mapped in the linkage region about 15 centimorgan (cM) from the end of the short arm of chromosome 7. The hybrid sterility locus S20 from O. glaberrima eliminated male gametes of Oryza sativa , and male gametes carrying the alleles of O. sativa in the heterozygotes were aborted completely. In addition, the homozygotes presented a genotype of O. glaberrima , and homozygous O. sativa were not produced. Surprisingly, the linked traits G1-g and qGW7 showed similar segregation distortion. These results indicate that S20 was responsible for the linkage drag. As a large number of detected hybrid sterility loci are widely distributed on rice chromosomes, we suggest that hybrid sterility loci are the critical factors for the linkage drag in interspecific and subspecific hybridization of rice.

Introgression of tsv1 improves tungro disease resistance of a rice variety BRRI dhan71

“…Similar observations were also made in two populations derived from TW6 showing Mendelian segregation for tsv1 by phenotypic segregation and genotypic segregation based on the progeny test 8 . Segregation distortion and linkage drag associated with the genes/QTLs derived from distant species of cultivated rice and wild relatives are a major hindrance for their use in breeding 54 , 55 . The main advantage of backcross is to retain the most important traits of the recipient varieties, it has been established that 3–4 backcrosses are enough to recover most of the recipient parent genome and thereby most of its traits 43 , 44 , 49 .…”

Reap the crop wild relatives for breeding future crops

“…In these cases, marker technologies in combination with backcrossing have proven to be effective in eliminating linkage drag. More recently, Wang and coworkers [12] examined interspecific progenies of rice derived from crosses between Oryza glaberrima and Oryza sativa, and observed an association between the hybrid sterility locus, Box 2. Male sterility trait to boost hybrid technology Exploitation of heterosis or hybrid vigor is a key component of sustainable plant breeding.…”

Crop Wild Relatives (CWRs) a Genetic Pool for Crop Improvement: A Review

“…4. Furthermore, when CWR genetic material is introduced into cultivated germplasm, sterility issues can arise, most commonly at the F1 or BC1 generation (Wang et al 2020;Bohra et al 2022).…”