广西木薯胚发育调查及幼胚离体培养

Investigation on embryo development of cassava in Guangxi and in vitro culture of immature embryo

[目的]调查广西3个木薯品种（系）果实、种子和胚的发育情况,进行幼胚离体培养,为广西木薯杂交育种提供参考.[方法]开花期采用开放式自然杂交进行授粉,11月采集3个木薯品种（系）果实约200粒,对果实、种子和胚等相关性状进行分类和测定,并进行相关性分析;通过对幼胚进行胚成熟培养、成苗培养、增殖培养和生根培养,获得幼胚再生植株,计算胚成熟率、成苗率及移栽存活率.[结果]在木薯果实趋于成熟时采收获处于不同发育时期的果实类型中,根据发育阶段可将种皮颜色分为黑色（A）、棕色（B）、棕黄两色（C）、黄色顶端带黑点（D）、黄色（E）和白色（F）6种;各发育阶段单果平均种子数均小于3粒.当3个木薯品种（系）种皮颜色为A、B、C型时,果实较重、直径较长,胚发育较好,平均胚长分别为6.53～8.40、7.31～8.28、4.50～7.10 mm.除NZ199的A、B型外,3个品种（系）胚长均随种皮颜色加深而变长,表现为：A＞B＞C＞D＞E＞F,胚长变化范围为0～10.66mm.可见胚率总体表现为：NZ199＞SC5＞J393;SC5和NZ199种皮为棕黄色时可见胚率最高,分别为66.7％和94.2％;至棕色时可见胚率分别降低至61.9％和80.6％;至黑色时SC5可见胚率降低至59.9％,NZ199则升高至85.2％;J393在种皮为黄色顶端带黑点时可见胚率为50.1％,至棕黄色、棕色时可见胚率分别降至48.8％和41.0％,以黑色种皮的可见胚率最高,为68.2％.3个木薯品种（系）果实重量与果实直径、可见胚率呈极显著正相关,胚长与果实重量、果实直径呈显著正相关.幼胚离体培养胚成熟率为89.3％,成苗率为62.7％,移栽存活率为71.9％.[结论]3个木薯品种（系）同一果实内或相同发育阶段的不同种子内胚发育不一致;通过木薯果实的重量和直径可初步判断胚的大小;宜选择种皮颜色为棕黄色或黄色顶端带黑点的种子进行幼胚离体培养.

[ Objective ]Fruit, seed and embryo development of three cassava varieties （lines） planting in Guangxi was investigated and immature embryo was cultured in vitro in order to provide references for cassava hybridization breeding in Guangxi. [ Method ]After natural p,311ination in open, about 200 fruits of 3 cassava varieties （lines） viz., NZ199, SC5 and J393 were collected in November to investigate and measure fruits, seeds and embryo traits, and conduct correlation analysis. Young embryo was used for mature culture, plantlet inducing culture, multiplication cul- ture and rooting culture, and maturing ratio and survival ratio of transplant were calculated. [ Result ]The collected fruits of 3 cassava varieties （lines）was at different developmental stages, and their seed coat color could be classified into 6 types of black （A）, brown （ B ） , brownk,,h yellow （ C ） , yellow with black spots at top （ D ）, yellow （E） and white （F）. Less than 3 seeds were found in different fruit types. When A, B and C types of seed coat color were found in 3 cassava varieties （lines）, the fruits were cheractered by heavier weight, longer diameter, and better development of embryo; their average embryo length were 6.53-8.40, 7.31-8.28 and 4.50-7.10 mm, respectively. Except for A and B types of seed coat color in NZ199, the embryo length of 3 cassava varieties（lines） was found to elongate with seed coat color getting deep, which presente,] as follows： A 〉B 〉C 〉D 〉E 〉F. The embryo length ranged from 0 to 10.66 ram. The visible embryo rate in differenL varieties was found to be NZ199〉SCS〉J393. SC5 and NZ199 present- ed the highest visible embryo rate （66.7% and 94.2%） in C type seed coat color, and they decreased to 61.9% and 80.6% in B type seed coat color. In A type seed coat color, the visible embryo rate of SC5 reduced to 59.9%, while that of NZ199 increased to 85.2%. The visible embryo rate of J393 was 50.1% in D type seed coat color, and 48.8% and 41.0% in C and B type seed coat color, respectively, while the highest one （68.2%） was found in A type seed coat color. As to 3 cassava cuhivars （lines）, fruit weight was very significantly correlated withfruit diameter and visible embryo rate, and embryo length was significantly correlated with fruit weight and diameter. For young embryo in vitro culture, the maturation rate of embryo was 89.3%, the plantlet inducing rate was 62.7%, and the transplanting survival rate was 71.9%. [Conclusion]The same fruit of three cassava cultivars （lines） or dif- ferent seeds with same developmental stage present unsynchronized development of embryo under environmental condi- tion of Guangxi. The embryo size could be judged by fruit weight and diameter of cassava. The young embryo in seed coat with brownish yellow or yellow with black spots at top was suitable for in vitro culture.