Utilization of wild sunflower species for the improvement of cultivated sunflower

Abstract

Abstract The genus Helianthus is composed of 49 species and 19 subspecies with 12 annual and 37 perennial species. These diverse species represent considerable genetic variability which can be utilized for the improvement of cultivated sunflower. The taxonomy of Helianthus is somewhat confusing due to the complicated natural interspecific hybridization and different ploidy levels of several species. A germplasm collection of 2000 accessions, mostly annuals, has been assembled. Interspecific hybridization has become important as a means of introducing genetic variability into the cultivated sunflower. This has been facilitated by the use of embryo culture and chromosome doubling with colchicine to increase fertility. The wild species continue to serve as a source of cytoplasmic male sterility for cultivated sunflower. Molecular techniques of restriction endonucleases of mitochondrial DNA can be used to differentiate CMS sources. The greatest impact the wild species have made on cultivated sunflower has been in the area of genes for disease resistance and, to a lesser extent, resistance to insects. The recent discovery of genes for high tolerance to the disease Phomopsis/Diaporthe helianthi Munt. Cvet. is an excellent example. Considerable variability has been reported in oil content and fatty acid concentrations in the wild species as well as agronomic and morphologic traits of plant height, days to flowering and tolerances to stress, especially salt.