Development of Cross Compatible Near-Isogenic Lines Using Marker-Assisted Selection in Radish (Raphanus sativus L.)

Numerous F₁ hybrids have been released using the self-incompatibility (SI) system in radish. As the SI blocks seed production of parental inbreds, breeders have to use artificial bud pollination or CO₂ treatment to avoid SI. In order to produce parental seeds efficiently, double-crossed (DC) varieties were developed. To increase the seed uniformity of DC hybrid, it was recommended that using near-isogenic lines (NILs) as parental materials. Using DNA markers to identify the S-haplotypes in Brassica crops, we tried to develop cross compatible NILs through selecting SI heterozygotes in every segregating generations.

Two hybrids of ‘Gwandong yeoreum’ having S₁S₁₀ haplotypes of class-I and ‘Pyeongji yeoreum’ having S₄S₅ haplotypes of class-II, were chosen for the population-I. For the population-II, hybrids of ‘Kingkong’ and ‘Haryeong’, which were distantly located in randomly amplified polymorphic DNA (RAPD) dendrogram and having S₈S₂₆ and S₂₁S₃₀ genotypes, respectively, were selected.

In population-I, the primer pairs of RPS5+RPS15 and RPS3+RPS21 were applied for amplification of class-I and class-II SLG gene, respectively. The individuals PCR amplified with two primers sets were considered as SI-heterozygous. In population-II, the primer pairs of SRK3+SRK5 and RPS3+RPS21 were used to amplify the class-I SRK and class-II SLG genes, respectively.

Following this, a total of 318 SI heterozygotes were identified at the F₄ generation. Each F₄ inbred lines showed great difference in horticultural traits between inbreds but uniform within inbred. Some selected inbreds produced 1,253 seeds per plant using bee pollination. These results indicate that these NILs could reduce hybrid seed production cost in radish.