Ploidy Manipulation and Introgression of Resistance to Alternaria Helianthi from Wild Hexaploid Helianthus Species to Cultivated Sunflower (H. annuus L.) Aided by Anther Culture

Abstract

The present investigation discusses the scope for transferring of resistance to leaf spot disease incited by Alternaria helianthi from two hexaploid wild species (H. tuberosus and H. resinosus) to diploid cultivated sunflower. Interspecific hybrids produced between sunflower and these two hexaploid species were partially fertile with tetraploid chromosome status. Backcrosses of these interspecific hybrids with cultivated sunflower resulted in the formation of sterile triploid plants. To overcome the problem of sterility and facilitate backcrosses with cultivated sunflower, anther culture of the tetraploid interspecific hybrids was carried out to bring down their chromosome number to diploid status. Anthers from both interspecific hybrids were cultured on basal Murashige and Skoog media supplemented with varying concentrations of organics and the growth regulators benzyladenine and naphthaleneacetic acid. Anthers of interspecific hybrids involving H. resinosus responded well and regenerated through an embryogenic route at a frequency of 98.7%. But in interspecific hybrids with H. tuberosus, anthers formed callus and subsequently regenerated shoots through an organogenic pathway. DNA ploidy analysis of anther culture plants of interspecific hybrids derived from H. tuberosus crosses was carried out to identify plants with desired diploid status. In vitro screening of parents, interspecific hybrids and anther culture plantlets against A. helianthi showed resistance in 68.5% of the anther culture plants of interspecific hybrids from H. tuberosus and in 24.3% of the plants derived from interspecific hybrids involving H. resinosus.