甘薯两次嫁接法诱导开花和结实的研究

甘薯是短日照植物,在我国北方秋季日照较长,一般品种不能开花。用大牵牛花为砧木,天然开花的品种为中间砧木,杂交亲本为接穗,经过两次嫁接后,能诱导甘薯一般品种在北方地区自然开花,且效果显著。应用此法可更广泛地进行甘薯有性杂交育种。接穗品种约在嫁接后12天左右开始现蕾,30天左右开始开花,80天左右个别品种开始停止开花,到100天左右全部品种停止开花。接穗品种间现蕾,开花两期差异较小,现蕾最早者比最晚者早6天,开花最早者比最晚者早2天。停花期各品种之间差异显著,最早者比最晚者提前20天。各接穗品种盛花期在8月10日～9月4日之间,结实盛期在8月30日～9月18日之间,在上述两期中,一般开花越多,结实率越高,接穗品种开花数目和结实率因品种不同而异;开花较多者(蓬尾),平均每株为292.3朵,较低者(华北553),平均每株为90.3朵;结实率较高者(徐薯18),为53.7%,较低者(蓬尾),为24.3%。开花数目与结实率呈反比关系,开花越多,结实率越低。

STUDIES ON FLOWERING AND SEED PRODUCTION OF SWEET POTATO INDUCED BY THE TWICE-GRAFTING METHOD

The sweet potato (Ipomoea batatas Lam.) is a short-day plant. General varieties fail to flower in the north area of China, because there are long days in autumn. Through the twice-grafting method using great morning-glory as the basic stock, varieties with natu- rally flowering habit as the middle stock and cross parents as the scion, the general varie- ties could be induced effectively to flower under the natural conditions of northern China. In this way, cross-breeding of sweet potato could beconducted casily. After the second grafting, scion varieties began to squar in 12 days, to flower in 30 days, to stop flowering in 100 days and only a few stopped flowering in 80 days. All scion varie- ties reaching the squaring and flowering stages differed a little. The last variety began to squar only 6 days later than the earliest one. The first variety began to flower only 2 days earlier than the last one. However, there was much variation in the length of flowering pe- riod for every scion variety. The earliest variety stopped flowering 20 days earlier than the last one. The full blooming stage of scion varieties was between August 10 and September 4 while the full fruiting stage was between August 30 and September 18. At the above two stages, the more flowers were blooming, the more seeds were setting. The flowering number and the rate of seed production of scion varities were different. The highest flowering variety was Peng Wei with an average of 292.3 flowers per plant. The least productive flowering variety was Hua Bei 553 with an average of 90.3 flowers per plant. The highest rate of seed production of scion variety was 53.7 percent (Xu Shu no. 18), and the least only 24.3 percent (Peng Wei). There was a negative relationship between the flowering number and the rate of seed production.