| Echinochloa damo is a Japanese millet variety of Echinochloa, with high photosynthetic efficiency, strong resistance, wide adaptability, and non-shattering and other characteristics, which is an excellent plant resource. It is difficult to use polyploidization to overcome the problems of non-affinity and non-pregnancy of hybrids in distant hybridization, because of the unclear photo-thermal characteristics in Guangzhou and the limit of this research. In the present study, the mature seeds of Echinochloa damo were used to observe its characteristics of photo-thermos reaction by setting different sowing dates,established optimization system of the tissue culture response, and polyploidized of Echinochloa damo by colchicine treatment. The main results are as follows:1. The characteristic of photo-period and temperature in Echinochloa damo. Several characteristics of Echinochloa damo including survival rate, plant height, tiller number, the number of kernel per plant and growth cycle, which sowed on different dates, were observed. In the results, the optimal sowing date was from January 23 rd to May 10 th. The peak of kernel per plant which nearly 2300 were sowed on the May 10 th, and the second highest were on April 20 which took near to 2200. Meanwhile, its growth period was about55 to 75 days, while others were 45 to 75 days. Therefore, the end of April to the middle of May was the optimal sowing date in Guangzhou.2. Optimization of tissue culture system of Echinochloa damo. We found that the mature embryos produced the highest induction frequency and better quality of calli on N6+ 3.0mg/L 2, 4-D(p H5.4~5.8), which added organic substance. The optimal medium for subculture multiplication was composed of N6 + 2.0mg/L 2, 4-D + 0.05mg/L 6-BA(p H5.4~5.8), adding organic matter. The favorable shoot inducing medium was 1/2MS +1.0mg/L 6-BA + 0.5mg/L NAA + 0.3g/L CH(p H5.4~5.8) and the differentiation frequency was 99.33%. The proper culture medium of rooting was 1/2MS without plant hormone,with a rooting percentage more than 90%.3. Induction of autopolyploid Echinochloa damo. There was no polyploid plant derived from multiple shoot, on the callus as material by impregnation method and co-culture method were able to induce polyploidy. There were derived polyploidy with impregnation method,and the colchicine treatment combinations were 200 mg / L(24, 48 h), 300 mg / L(24h), 800 mg / L(24h), with the polyploid induction rate 6.67%, 10%, 3.33% and 3.33%.In co-culture conditions, the highest polyploid induction rate was 6.67%.4. Morphological characteristics in autopolyploid of Echinochloa damo. Cytological studies on Echinochloa damo, its diploid chromosome number is 54, and the autoteraploidy chromosome number is 108. There are obvious Morphologic changes of autopolyploid plants compared with the original seed of Echinochloa damo, which include more green leaf color, wider leaf, and coarser stem, more dwarf plant height, reduced tiller number,decreased seed setting rate etc. These features can be the primary screening index for polyploidy induction. Microscopic observation of blade surface showed that the stomatal density was decreased, and the stomatal size of the plants was increased comparisted with the controls’. The autopolyploidy ploidy of the root tip cell of Echinochloa damo are variable, with some reverse mutation, while the materials in co culture condition, whose autopolyploid progenies’ percentage were 83.33%.The research above demonstrated the optimal sowing date, established autotetraploid induction system of Echinochloa damo, and obtained autopolyploid Echinochloa damo,which is hopeful to lay the foundation for further use of Echinochloa damo beneficial genes for crop improvement. |
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