40. Studies on Chromosomes Doubling of Tartary Buckwheat

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314 Materials and Methods In the spring of 1989, the three varieties oftartary buckwheat, namely, Eluowuqie, Shichee and Kuciqiao were cultivated in pots at the Agricultural Test Station of Xichang Agricultural College. Forty pots were planted for each variety. After the seeds sprouted, four plants were kept in each pot. The following method of treatment for the doubling of the chromosomes of Jiujiang tartary buckwheat was used [9, 10]. After 2-3 leaves appeared, absorbent cotton balls were placed on the growing point of the leafstalk. A solution mixture of colchicine (0.2%) and dimethyl sulfoxide (1.5%) was dropped on the growing point. This was done twice a day (one in the morning and the other in the evening) for six days. The following tasks were completed : the botanical characteristics were identified and the number ofchromosomes ofthe root tip cells were examined and counted. After the seeds of the above mentioned plants were obtained and treated, they were sowed in the Autumn ofthe same year. Good plants were selected when ripe. Each variety ofseed was sowed and harvested at the same times. In 1990, the seeds of the three varieties of autotetraploid tartary buckwheat and its diploid parent stock were respectively sowed in large fields in holes 35 cm apart. After sprouting, four plants were retained in each hole. During the seedling stage the peroxidase isozymes of their leaves were electrophoreticly analyzed and stained with benzidine diaminodiphenyl. Photographs were taken immediately [11]. The following tasks were completed: the botanical characteristics were identified and recorded ; leaf guard cells, pollen grains and the sizes of their root tip mitotic cells were examined, and measured during flowering period. The seeds were dried when they were ripe and the amounts of amino acids in the seeds of both the autotetraploid tartary buckwheat and its parent stock were measured with a Hitachi 835-50 High Rate Amino Acid Analyzer. The amounts of nutrients-crude proteins, fats, starches and vitamins-were also measured according to the related methods ofthe International Association ofSeed Testing. Results and Analyses 1. The Effect ofTreatment by the Solution Mixture ofColchicine and Dimentyl Sulfoxide Among the treated plants, some died ofpoisoning. In the surviving plants the variety SHICHEE proved to be the most successful. It's doubling percentage was 62.81%, and the effect of the treatment was also the best being 47.50. However, the doubling percentage and treatment effect ofthe variety KUCHIQIAO were relatively poor (see Table 1). The growing point on the main stalk ofthe successfully doubled plant expanded and stopped growing taller. 7-12 days after being treated, 2-5 shoots grew from the swollen knot and the plant appeared to be mosaic. Some shoots were creepers, and grew many wild roots from the knot. The plant was shorter, leaves became thicker, leaf colour became deeper and there was a marked change in the shape of the leaves. There were two types of flower on the plant. The diameter ofthe corolla on one flower being larger than the other, and the resulting seeds being larger from the larger flower. The small seeds from the small flower on the mosaic were similar
315 to the seeds from 'the parent stock (contrast) (see Table 2). After eXamination 'under a microscope, it was found that the number of chromosomes in the root tip cell ofthe'largerseed was 2n = 4x = 32. It was autotetraploid. The number ofchromosomes in. the root tip cell ofthe small seed on both the parent stock and the mosaic was 2n = 2x = 16. They were diploids (see Picture I, II) Table I. Survival rate and chromosomes-doubling ofdifferent plants. Variety Treated No. Survived No. Dead No, Successfully- Doubling-Rate Treatment Effect Doubled No. Eluowuqie 160 107 23 64 59.81 -<strong>40.</strong>00 Shichee 160 121 29 76 62.81 47.50 Kuochiqiao 160 110 34 61 55.45 38.13 Note: Any plant from which more than one doubled seed was harvested means that the plant was successfully doubled. Doubling Rate = Successfully doubled No. I Survived No, Treatment Effect =Successfully doubled No, I Treated No, Table 2. A comparison on flower and seed between doubled plants and CK plants. Variety Corolla Dia. (mm) Seed L.x W. (mm), Eluowuqie diploid (CK) 3.29 5.2 x 3.7 Eluowuqie mosaic 2x 3.27 5.4 x 3.6 4x 4.41 6.9 x4,9 Shichee diploid (CK) 3.38 5.8 x 3.2 Shichee mosaic 2x 3.34 5.7 x 3.0 4x 4.75 7.9 x 3.6 Kuciquiao diploid (CK) 3.16 5.0 x 4.7 Kuciquiao mosaic 2x 3.17 4.8 x 4.6 4x 4.59 7.1 x 5.9 2. Main Characteristics ofthe Tetraploid Tartary Buckwheat Compared with the diploid parent stock (CK), the tetraploid has a taller plant, thicker stalk, many shoots on the main stalk. less leaves but larger in size. The seed-forming rates of aU the tetraploid tartary buckwheat are decreased. The average seed-fonning rate of Eluowuqie tetraploid is 24.12%, 16.05% less than the contrast rate 28.73%. The average seed-fonni!1g rate of Shichee tetraploid is 27.1%, 10.56% less than the contrast rate. However, what merits attention. is that, because of the smaller fJowers of the single plant of tetraplo.id tartary buckwheat being notably increased (about 30-50%), its seeds from a single plant are still more than that from diploid parent stock. In addition, the se~ds of tetraploid' tartary buckwheat are remarkably enlarged. Thus the yield ofa single plant is higher than that of diploid tartary buckwheat (see Table 3).
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40. Studies on Chromosomes Doubling of Tartary Buckwheat

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