Abstract: Nucleo-cytoplasmic hybrid wheat NC4 is resistent to a number of stresses and produces high yield. It was obtained by crossing Aegilops squarrosa (♀) with Triticum aestivum ( ♂ ), and several back crossings. The rbcLs (the gene of large subunit of Rubisco ( rihulose-1, 5-bisphosphate carboxylase/oxygenase )) cloned from NC4 and T. aestivum have been sequenced, and the result showed that the rbcL of NC4 was originated from Ae. squarrosa. The ratio of carhoxylase activity to oxygenase activity, Vco2/Vo2, of hybrid NC4 Was lower than that of Ae. squarrosa, but higher than that of T. aestivum. This difference may be accounted for the higher yield of NC4 than that of T. aestivum. Sequence analysis showed that three nucleotides in the rbcL of NC4 which were different from those of T. aestivum, corresponded to the No. 14, 86 and 95 amino acid residues of rbcL.

Key words: Rubisco, Nucleo-cytoplasmic hybrid wheat, Sequence of rbcL, Ratio of carboxylase activity to oxygenase activity