National Bureau of Plant Genetic Resources, Pusa Campus, New Delhi-110 012.
1 USDA-ARS, Northern Crop Science Laboratory, P.O. Box 5677, Fargo, North Dakota, USA-S8105
One hundred forty-four accessions representing eight wild species of sunflower were collected from 124 sites in diverse habitats of the Central Great Plains of United States of America during September, 1991. A wide range of in-situ variability was observed for various morphological and economic characters including stress tolerance. The populations of H. annuus were observed to be highly variable and widely distributed in different habitats in the seven states surveyed. Helianthus pumilus which has low variability and limited distribution, was represented by only one sample in Colorado. Helianthus petiolaris ssp. petiolaris, the only source species of cytoplasmic male sterility was found, widely distributed and along sandy roadsides of highways. Helianthus pauciflorus ssp. subrhomboideus, H. nuttallii, H. grosseserratus and H. tuberosus were sparsely distributed in some specific habitats. Other species such as H. hirsutus, H. salicifolius and H. pauciflorus ssp. pauciflorus occur in this area but were not collected due to immature stage of seed growth.
