40. Studies on Chromosomes Doubling of Tartary Buckwheat

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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