CO2 Exchange, Cytogenetics, and Leaf Anatomy of Hybrids between Photosynthetically Distinct Flaveria Species 1

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Hybrids between the C4-like species, Flaveria brownii, A. M. Powell and the C3-C4 intermediate species Flaveria linearis Lag., Flaveria floridana Johnston, and Flaveria oppositifolia (DC.) Rydb. exhibited bivalent chromosome pairing during meiosis and stainability of pollen was high, ranging from 51 to 95%. An F2 population produced from an F. brownii × F. linearis F1 hybrid, exhibited bivalent chromosome pairing and high pollen stainability indicating a high degree of fertility in the hybrid. Oxygen inhibition of apparent photosynthesis averaged 6.8% for F. brownii and 22.2% for the C3-C4 species (in two experiments), and F1 hybrids exhibited inhibitions which were intermediate to their parents. Values of carbon dioxide compensation concentration determined at low irradiance were 4.0, 34.0, and 6.5 microliters per liter for F. brownii, F. linearis and their F1 hybrid, respectively. The mean value at low irradiance for 33 F1 plants was 6.8 microliters per liter, and individual values ranged only from 3.7 to 11.7 microliters per liter. Anatomical characteristics for the F1 hybrid leaves were intermediate to those of the parents, and there was considerable variation among F2 plants derived from F. brownii × F. linearis. In the F2 population δ13C values ranged from −27‰ to −20‰. The expression of more C4-like characteristics by the F1 hybrids in this study and their apparent high fertility make them promising specimens for producing segregating populations for use in C4 inheritance studies.

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