Cytoplasmic-Nuclear Gene Interaction for Plant Vigor in Helianthus Species
Genetic diversity provided by of wild sunflower (Helianthus spp.) has not been exploited. This field and greenhouse study determined the inheritance and characterized a unique type of cytoplasmic-nuclear interaction involving major genes affecting plant vigor. Reduced vigor (RV) plants with pale-green leaves and stunted growth were obtained when back crossing inbred line HA 89 into cytoplasms of five perennial Helianthus species: H. mollis Lam., H. maximiliani Schrader, H. grosseserratus Martens, H. divaricates L., and H. angustifolius L. Reduced-vigor plants produced only RV progenies, either through back crossing or self-pollination. Crossing normal backcross (BC) progenies with HA 89 resulted in a segregation ratio of one normal to one RV, suggesting that each of the five species has a single dominant nuclear gene capable of restoring normal plant vigor. Progeny of diallel crosses among normal plants in advanced BC generations in the five cytoplasms segregated three normal to one RV plants, indicating similarities among these perennial cytoplasms and among their restoration genes. Compared with normal plants, the RV plants had significantly reduced plant height, head diameter, seed weight, percent seed set, net photosynthesis, total leaf chlorophyll, and delayed flowering. Effects of H, maximiliani cytoplasm were less extreme. These perennial species may have shared a common evolutionary origin, and their utilization as sources of genetic variability for sunflower improvement should not be affected by the described cytoplasmic-nuclear interaction.
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