Introgression and inheritance of charcoal rot (Macrophomina phaseolina) resistance from silver sunflower (Helianthus argophyllus Torr. & A. Gray) into cultivated sunflower (Helianthus annuus L.)

Charcoal rot is a devastating disease of sunflower causing significant yield losses. There is a lack of high-level resistance in cultivated germplasm for this disease. The purpose of this study was to incorporate resistance against charcoal rot into cultivated sunflower lines. The study indicated that sunflower elite cultivated germplasm was susceptible which showed complete stunting of growth and wilting when compared with wild accessions of Helianthus argophyllus. H. argophyllus was identified as immune for charcoal rot and has the potential to diversify the initial source of disease resistance in sunflower elite germplasm. The segregating ratios in the F₂ generation showed the presence of two major genes having an epistatic interaction to control immunity while a single gene was found to control disease resistance or partial resistance. Stem color showed the highest correlation with disease scoring which may be used to differentiate resistant and susceptible plant progenies. The F₃ progenies selected on the basis of this trait resulted in the selection of all types of resistance in the F₄ generation with an immune class having a minimal reduction in or deterioration of morphological traits. Stem color also correlated with stem toughness (r = 0.46**), and as a result, plant genotypes with tough stems were selected. The selected progenies will be registered as a source of charcoal rot resistance.