| Budget Amount *help |
¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1999: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
1. Somaclomnal variation obtained from short term culture of rice calli. Somaclonal variation obtained from tissue culture regenerants in expected for crop improvement. We obtained 10 regenerated plants from seed calli of japonica variety, Reimai. The plants were grown in green house until mature stage and analyzed agronomic traits. Out of 10 regenerants, 3 plants were 8-10 cm shorter that Reimei and other regenerated plants. While, one regenerated plant showed fewer ripened grains and lower ripening percentage. The other characters were almost the same. From these results, It should be clear the genes controlling the culm length in these regenerated plants.
2. Detection of genomic change at molecular level coused by long term culture of rice calli. Chloroplast DNA (ctDNA) alteration of long term callus cultures derived from rice seeds was easily detected when rice chloroplast DNA fragment BamHI-1 was used as a probe. Chloroplast DNA (ctDNA) molecules of two callus lines out of 12 callus lines cultured for 36 months were deficient in large regions of the rice chloroplast genome. Maps of deleted ctDNA molecules were constructed using a seventeen hybridization probes. In the callus lines of T36-1 and T36-2, small sizes of ctDNA molecules (58.5 and 7.5 kb) were mapped. When these two callus lines were further cultured on the MS maintenance medium for more six months, further deletion (about 0.5 kb) was occurred in one callus line (T42-2). From the restriction maps of the deleted derivatives of ctDNA, callus lines of T36-1 and T42-1 lost both large inverted repeat sequences, together with the intervening small single copy region. On the other hand, callus lines of T36-2 and T42-2 lost rbcL and most of the large single copy region. These ctDNA molecules commonly retain only about 20 kb that encode tm gene cluster and rpo genes. These results suggests that this region of rice chloroplast genome contains at least one functional origin of replication.
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