Cytoplasmic diversity in alloplasmic common wheats with cytoplasms of Triticum and Aegilops revealed by photosynthetic and respiratory characteristics

Photosynthetic and respiratory characteristics were surveyed to evaluate cytoplasmic diversities in alloplasmic common wheats in which a nuclear genome of common wheat (Triticum aestivum L. cv. Chinese Spring (CS)) was combined with cytoplasms of Triticum and Aegilops species. The photosynthetic capacity (PSC) was measured based on the 13CO2-assimilation rate by infrared absorption spectrophotometry. A significant variation was found in PSC. The alloplasmic line with a cytoplasm of T. monococcum ssp. boeoticum which is unique in causing severe growth depression and male sterility when combined with CS nuclei showed more than 30% higher PSC than the euplasmic CS. A negative correlation was found between PSC and growth vigor of the euplasmic and alloplasmic lines. Respiratory electron flows and the cytochrome c oxidase (COX) activity were measured polarographically by an oxygen electrode. The cytochrome path activity, the COX activity and the alternative path capacity showed significant variations among the lines, irrespective of plant tissues studied. The alloplasmic line with T. monococcum cytoplasm showed chracteristic respiration in the alloplasmic line: It significantly increased the alternative path capacity and the COX activity in roots and leaves of 2-week-old plants. Moreover, the COX activity in the roots was negatively correlated with growth vigor among the lines. The results suggested that the aberrantly high COX activity might be related to the growth depression of the alloplasmic CS with T. monococcum cytoplasm.