Studies On Cross Compatibility Of The Intergeneric Hybridization Between B.chinensis And C. Abyssinica And Investigation Of Cytogenetics In The Hybrid

An intergeneric hybrid between Brassica chinesis and Crambe abyssinica was obtained by Sichuan agricultural university rapeseed research center. In this paper, Brassica chinesis, Crambe abyssinica and the intergeneric hybrid F₁ were used to study the cross compatibility between the two parents and the cytogenetics studies of the hybrid F₁. Main aspects studied include: (1) Compatible studies by means of treating stigmas of Brassica chinesis with different chemicals: a. Observing of the germination of pollen grains of Crambe abyssinica on the stigmas of B. Chinensis with scanning electron microscope. b. Observing of growth of pollen tubes of Crambe abyssinica in the styles of B. Chinensis by fluorescence microscope. (2) Cytogenetical studies of the hybrid: Observing the chromosome numbers of the hybrid in root tip cells, and PMC meiosis process. In addition, the viability of pollen grains were observed. The main results are the following:With treatment of stigmas with gibberellins, at one hour after hand pollination, a small number of pollen grains could adhere to the stigmas. Six hours later, the number of pollen adhering to stigmas reached the climax, averaged at over 52. Twenty-four hours later, the number of adhering pollens was 32. Three hours later, some pollen grains began to germinate and callose could be seen in papillose cells. Germination climax appeared after 6-8 hours, about 4-9 pollen grains geminated per stigma, one or two pollen tubes could penetrate into the papillose cells, while most pollen tubes failed to penetrate the papillose cells. However, the behavior of pollen tube growth was abnormal, forming twist, coil, screw, etc. Twenty-four hours later, pollen tubes continued to grow and reached the style, a few pollen grains began to shrink, and many still failed to germination. It was indicated that gibberellins had a good effect on germination of pollen grains and growth of pollen tubes.When stigmas were treated with glycin, at one hour after hand pollination, a big amount of pollen grains adhered to the stigmas, averaged at 75, a lot of callose was produced in the stigma papillose cells. At three to eight hours later, the amount of pollen grains adhered to stigmas was reduced. Twenty-four hours later, the amount of pollen grains averaged 57. Six hours later, very few pollen grains were seen germinated. Eight hour later, 1-3 pollen grains could be seen germinated, however, large amount of callose had been produced in thepapillose cells. No pollen tubes penetrated papillose cells and entered the style. Twenty-four hours later, no pollen tubes were seen in the style. In most cases, pollen tubes continued to creep on the stigma. Their behavior was abnormal, producing twist, coil or screw, etc. It was observe that glycin could facilitate pollen grains adhering to stigmas, but not facilitate the germination of pollen grains and the growth of pollen tubes. So effects of glycin were limited in overcoming in- compatibility of intergeneric hybridization in rapeseed.The intergeneric hybrid Fi between Brassica Chinensis and Crambe abyssinica showed a chromosome number of 2n=55 in the early progenies. After several generations of planting and in-vitro propagation by tissue culture, the chromosomes in the intergeneric hybrid were reduced, to about 26, varying from 25 to 28.In the meiosis of PMC in the hybrid, the average configuration of chromosomes was 0.06 III+l 1.26 II+3.80 I .The number of bivalents varied from 8 to 13. The majority of PMC cells showed 1011,11 II or 12II bivalents. The frequencies were 24.58%, 23.91% and 30.98% respectively. The number of univalents varied from 0 to 8. The big decrease of chromosome number in the hybrid and high bivalent number were possibly due to the reasons that chromosome of Crambe abyssinica were mostly eliminated and the chromosomes of Brassica Chinensis remained and were doubled in the hybrid cells. Some cells with triads, chromosome lagging, and chromosome bridges were observed in anaphase II.The viability of pollens of the hybrid F( was 63.04%. It was 98.04% for the normal B.napus reference ZhongShuang 4. It is obvious that the viability of pollen grains of the generic hybrid was markedly lower than that of the normal B.napus cultivar. However, the viabilility of pollens in the intergeneric hybrid was still high. This may be related to the doubling of chromosomes in the hybrid.