| Modern sugarcane cultivars have shown a sharp decline in gentic diversity. Hybridization between cultivated sugarcane and wild sugarcane germplasm is the most common means to enrich the genetic variation. In recent decades, the studies and utilization of wild sugarcane resources have focused on Erianthus arundinacius (E. arundinacius) and Saccharum spontaneum L. (S. spontaneum). GXAS07-6-1, an intergeneric hybrid of E. arundinaceus and S. spontaneum L. has the advantages of its parents, which exists higher vigor, comprehensive agronomic characters and tolerance. In this study, the cytological smear technique was used for staining to observe the meiosis and chromosome behavior of pollen mother cells in GXAS07-6-1, and genomic in situ hybridization (GISH) technique was used to reveal the chromosome composition and transmission in GXAS07-6-1 and the progeny of crosses of sugarcane (Saccharum spp.) and GXAS07-6-1. The main results were as follows.1) The chromosomes of pollen mother cells of GXAS07-6-1 showed univalents, bivalents and trivalents in diakinesis. A few lagged chromosomes appeared in every other phase of meiosis. Abnormal cell morphology and mis-orientated chromosomes were observed in Metaphase II, the daughter cell chromosomes in dyad were out of sync separation, and micronucli occurred at dyad stage. Triads, different sized tetrads and micronuclis were aslo observed at tetrad stage, and the triads accounted for a low proportion, while high frequency of micronucli accounted for 70%. The split index of GXAS07-6-1 was 30%, which suggested that a low genetic stability; and the pollen fertility was 72.79%, maybe the decrease in pollen fertility was due to the abnormal behaviors in meiosis.2) Methods for sugarcane root culture and pretreatment were studied and the results showed that the roots of GXAS07-6-1 was very difficult to grow in sand culture under 28℃ but easy to grow in pot culture. For GXASF108-2-17, GXASF108-2-22 and GXASF108-2-32, many strong roots could be obtained from the both cultures. The root tips were thicker and stronger from pot culture, which is good for enzymolysis, but it is relatively more rapid and convenient to get the roots from seedcane culture in sand under stable temperature (28℃), so latter way was selected in this study. It was found that pretreatment for 3 h with p-dichlorobenzene solution was the best; it resulted in good chromosome morphology and straight scattering with rich middle split phase, which was suitable for observation.3) The genetic composition of the GXAS07-6-1 somatic cells was identified by GISH. It was found that the chromosome number of GXAS07-6-1 was 58-62, consisting of 27-30 E. arundinaceus chromosomes from GXA87-36 and 30-34 S. spontaneum chromosomes from GXS79-9, indicating n+n transmission. The results of karyotype analysis showed that the karyotype of GXAS07-6-1 was primitive 1B type.4) The chromosome number of GXASF108-2-17, GXASF108-2-22 and GXASF108-2-32 showed 75 to 84, and 69-73 chromosomes were derived from the complex of sugarcane GT01-53 and S. spontaneum GXS79-9, and 7-11 derived from E. arundinaceus GXA87-36. The results revealed that the three F1 clones had n+n transmission, but showed chromosomes missing, and most of the lost chromosomes were from E. arundinaceus GXA87-36. The somatic chromosome karyotypic type of GXASF108-2-17 belonged to the primitive 2B type, and that of GXASF108-2-22 and GXASF108-2-32 belonged to the primitive 1B type. For all of them, the absolute lengths of chromosomes from E. arundinaceus were longer than those from Saccharum spp. |
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