甜瓜属一新物种(双二倍体)合成及定性

Synthesis and Preliminary Characterization of A New Species (Amphidiploid) in Cucumis

采用胚胎拯救方法 ,首次成功实现了栽培黄瓜 (Cucumis sativus L.,2 n=1 4)与同属野生种 C.hystrix Chakr.(2 n=2 4 )间可重复的种间杂交。杂交 F1植株形态一致。其中多分枝、密棕茸毛 (尤其是在花瓣和雌蕊上 )、桔黄色花冠及卵圆形果实这些特征与亲本 C.hystrix相似 ,而第一雌花节位则与亲本黄瓜 (C.sativus)相似。其它性状如株径、节长、叶和花的形状和大小等都介于双亲之间而呈中间型。将杂种 F1植株自交并与两亲本进行回交 ,结果表明 F1杂种的雄蕊和雌蕊都是不育的。这可能是由于杂种染色体数目为奇数 (2 n=1 9,其中 7条来自黄瓜 ,1 2条来自野生黄瓜 ) ,缺乏同源性而导致减数分裂不正常。利用体细胞无性系突变方法 ,对杂种的染色体数进行了加倍。流动细胞计量仪测定表明 ,加倍的 F1植株 (双二倍体 )占再生植株的 7.3 %,形态一致 ,其 DNA含量为 2 .3 5 pg,而 F1(二倍体 )的含量为 1 .1 7pg。新合成的双二倍体植株能释放花粉 ,并且能形成含种子的果实。对生长和发育、营养价值及抗性等方面初步研究表明 ,这一新物种可望成为一新型作物种 ,在未来农业中占有一席之地。通过不同杂交可形成两种类型的果实 :一种为腌渍类型 ,该株系每株可着生 3 0多个大约 1 0 cm长的果实 ,可一次性采收 ;

The first repeatable interspecific hybridization between cucumber (C.sativus L., 2n=14) and a wild Cucumis species,C.hystrix Chakr.(2n=24) was successfully made through embryo rescue.The hybrid plants were morphologically uniform.While the multiple branching habit,densely brown hairs (especially on corolla and pistil),orange-yellow corolla,and ovate fruit of F 1 hybrid plants were similar to that of the C.hystrix parent,appearance of the first pistillate flower was more similar to that of C.sativus parent.The diameter and internode length of stem,shape and size of leaves and flowers were intermediate when compared to that of the parents.Self-pollination and backcrossing of the F 1 hybrid plants to either parent indicated that the original hybrid was both male- and female-sterile,probably due to meiotic abnormalities caused by lack of homology and the odd chromosome number 2n=19 (including 7 from cucumber and 12 from C.hystrix).The chromosome number in the hybrid was doubled with somaclonal mutation to restore the fertility.Pollen grains were released from the synthetic amphidiploid and fruits set with viable seeds on the fertility-restored plants.The results from flow cytometry indicated that,on average,7.3% of the regenerants with unique morphology were chromosome-doubled F 1 hybrids.The 2C DNA content of the original F 1 hybrid was 1.17 pg,and the 4C DNA content was 2.35 pg.This new species was preliminarily characterized in growth and development,nutrition value,and disease resistance.The results suggested it a possible place to be a new Cucumis crop in future agriculture.Two types of fruits produced in our first season of crosses included a potential pickling variety that produces multiple uniform fruits at a single node with the 1∶3 length/width ratio for once over harvest.A second cross produces long slender fruits,nearly seedless with the ability to grow in partially shaded conditions,which may be the suitable varieties for greenhouse production.Results from nutrition analysis indicated that the synthetic species has higher protein (0.78%) and mineral (0.35%) content compared to the normal pickling cucumber (0.62% and 0.27%,respectively).A screen for root-knot nematode resistance revealed a high level of resistance existed in C.hystrix,and the resistance was partially transmitted to the F 1 and the chromosome-doubled F 1 when the reciprocal hybrid was made.