KUBO Nakao Kyoto Prefectural Univ., Agriculture, Associate professor, 農学研究科, 助教授 (60347440)
TERABAYASHI Satoshi Kyoto Prefectural Univ., Agriculture, Associate professor, 農学研究科, 助教授 (70155472)
MATSUMOTO Satoru National Inst.Veg. & Tea Science, Head of laboratory, 生物系特定産業技術研究機構・野菜茶業研究所, 研究室長 (00355629)
鈴木 徹 農業, 生物系特定産業技術研究機構・野菜茶業研究所, 研究室長 (10272155)
|Budget Amount *help
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2004: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2003: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2002: ¥7,700,000 (Direct Cost: ¥7,700,000)
Clubroot disease is caused by an obligate parasite, Plasmodiophora brassicae, and is one of the most serious diseases of Brassica crops worldwide. The resting spore infect root of crucifer crops, and caused clubs. Upon the decay of the clubs, numerous resting spores are released into the soil, where they can survive for many years.
Four clubroot resistance loci were found in Brassica rapa through genetic analysis using molecular markers. Two of which, Crr1 and Crr2 were found in Siloga, a fodder turnip. Crr3 was found in a turnip, Milan White. Gelria R, a European turnip was found to have a locus CRb, which has recently been reported from a Korean research group.
An SSR-based linkage map was constructed in Brassica rapa. It includes 113 SSR, 87 RFLP, and 62 RAPD markers. It consists of 10 linkage groups with a total distance of 1005.5 cM and an average distance of 3.7 cM. The number of the linkage groups was matched to the haploid chromosome number of this species. SSRs are distributed t
hroughout the linkage groups at an average of 8.7 cM. Synteny between B.rapa and a model plant, Arabidopsis thaliana, was analyzed. A number of small genomic segments of A.thaliana were scattered throughout an entire B.rapa linkage map. This points out the complex genomic rearrangements during the course of evolution in Cruciferae. A 282.5 cM region in the B.rapa map was in synteny with A thaliana. Of the three QTLs (Crr1, Crr2, and Crr4) for clubroot resistance identified, synteny analysis revealed that two major QTL regions, Crr1 and Crr2, overlapped in a small region of Arabidopsis chromosome 4. This region belongs to one of the disease resistance gene clusters (MRCs) in the A.thaliana genome. These results suggest that the resistance genes for clubroot originated from a member of the MRCs in a common ancestral genome, and subsequently were distributed to the different regions they now inhabit in the process of evolution. On the other hand Crr3 region showed homology to chromosome 3 of Arabidopsis. Therefore, clubroot resistance loci of Brassica rapa may originate at least two independent regions of the ancestral genome.
Linkage markers found in the present study are now disclosed, they may be useful genetic markers in marker-assisted breeding of clubroot resistant Chinese cabbage and the other vegetable crops in Brassica rapa.
In addition, a preliminary linkage map of Raphanus sativus was constructed. Less