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They have germ pore on their thick walls. In Figure 1-6, the focus section of the conjugated pollen grains shows the structure of opening very clearly. Figure 1-7 shows the same conjugation opening as in Figure 1-6, but the chromonema is just Migrating through the conjugation opening. It is suggested that a gene system of P. huashanica also controls conjugation opening formation in this hybrid as well as in those previously reported hybrids of R. ciliaris x P. huashanica (Yen et al. 1993), T. aestivum x P. huashanica (Sun et al. 1993b) and Ae. tauschii x P. huashanica (Sun et al. 1992). The result indicates that the Nh genome of P. huashanica has a gene system for controlling this process, because this kind of behavior appears in all the hybrids which are derived from P. huashanica.

The chromatin mirgation may cause coenocytes. If a coenocyte has synchronized nuclei, the chromosome number could be doubled or redoubled by nuclei fusion and a unified high level polyploid nucleus could be formed, although in some cases nuclei may not remain fused in coenocytes. This might be a way in which spontaneous chromosome doubling occurs. It is one way of natural polyploid formation, especially high level alloautopolyploid. If the transfer of a nucleus into a neighboring cell is not complete, aneuploid PMCs will appear. A loss or gain of one or more chromosomes has two obvious possibilities: firstly extremely deficient gametes will not survive and they will be eliminated; and secondly, those gametes which contain chromosome numbers different from the normal and are able to survive. In hybrid descendants of R. tsukushiensis with P. huashanica, polyploids and aneuploids which contain two different gene pools of R. tsukushiensis and P. huashanica may be obtained. Thus, it is possible to transfer drought resistance from P. huashanica into R. tsukushiensis by backcrossing F1 hybrid with R. tsukushiensis.


References

Sun GL, Yan J and Yang JL, (1992) Cytogenetic investigation of the hybrid between Aegilops tauschii and Psathyrostachys huashanica. J Sichuan Agric Univ 10(4): 603-611.

Sun GL, Yan J and Yang JL, (1993a) A biosystematic study on hybrids between Psathyrostachys huashanica and two species of Roegneria. Acta Phytotaxonomica Sinica 31(5): 393-398.

Sun GL, Yen C and Yang JL, (1993b) intermciocyte connections and cytornixis in intergeneric hybrids II: Triticum aestivum x Psathyrostachys huashanica. Wheat Inf Ser No. 77 13-18.

Yen Q Yang JL and Sun GL, (1993) Intermeiocyte connections and cytornixis in intergeneric hybrid of Roegneria ciliaris (Trin.) Nevski with Psathyrostachys huashanica Keng. Cytologia, 58:187-193.

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