关于甘薯属甘薯组中 A 群和 B 群之间可交配性的研究

A Study on the Crossability of Species between Group A and B in the Section Batatas of Genus Iponoea

用对甘薯组 A 群的种 I.tiliacea 和 I.gracilis 与 B 群的种 I.trifida 和 I.littoralis 杂交观察授粉后的胚胎发生的情况,发现授粉后7小时,花粉粒均能在柱头上发芽,花粉管也能通过花柱到达胚珠。在授粉后两天的子房内,可看到已受精、正受精、未受精等受精过程的各个阶段。此时以 B 群 K_(233-1)为母本的卵细胞受精率可达80%以上,而极核的受精率普遍较低。授粉后4天,极核的受精率则普遍提高。但没有发现一个受精卵细胞的分裂和分化,而是细胞大量退化。受精卵和胚乳核发育上的不协调,导致授粉后子房的早期变黄和脱落,这是两群种间杂交不亲和在胚胎发生上的表现。对授粉后两天的子房或胚珠进行离体培养可望获得群间杂种。

In general successful crossing between different groups of section Batatas is impossibleunder natural conditions.It is necessary to ascertain the cause of sterility by anatomical ob-servations.Four species were used:I.trifida(4x)(K 300-5)and I.littoralis(4x)(K 233-1)of group B,I.tiliacea(4x)(K 270-5)and I.gracilis(4x)(K 134-1)of group A.Pollinations were made as follows:K 300-5×K 270-5,K 300-5×K 134-1,K 233-1×K 270-5,K 233-1×K 134-1.Based on the observations of these mate-rials,some useful points could be summarized.1.Pollen grain could germinate on the stigma,pollen tubes could pass through theconducting tissue and the male nuclei could fertilize the egg cell and polar nuclei.WithK 233-1 as the female parent,the percentage of fertilization was up to over 80%,but theprocess of fertilization was going on very slowly.Moreover,various stages of fertilizationcould be observed at a certain time after pollination.These facts suggest that the situationis very complex.2.4 days after pollination,none of the fertilized egg cells had divided and differenti-ated but a large number of egg cells degenerated.At this time,the percentage of polarnuclei fertilization in each combination was high,especially in the K 233-1×K 134-1.It was up to 66.7%,whereas the rate of degenerated egg cells in this combination evenreached 74.0%.Incoordination of development between fertilized egg cell and endospermnuclei was one of the reasons that caused sterility of hybrid.3.Most of the materials from in vitro culture shrivelled and degenerated,and thatvery a few were just being fertilized.measures to overcome these difficulties,are cited,andit is suggested that the ovary/ovule culture might be started 2 days after pollination.