Influence of pollen selection for Alternaria helianthi resistance on the progeny performance against leaf blight in sunflower (Helianthus annuus L.)

Seven genotypes of sunflower, including populations and hybrids, showing differential susceptibility to Alternaria leaf and stem blight were crossed to CMS 234A with pollen selection and without pollen selection. The pathogen culture filtrate was used as selective pressure at stylar tissue by applying it 1 h before pollination. Distilled water applied to stigmas and styles served as control. Two sets of seven hybrids, one set from selective and the other from non-selective fertilization, were evaluated for reaction to Alternaria leaf and stem blight during the rainy season under natural epiphytotic conditions. Selection for resistant pollen on the stigmatic surface resulted in a corresponding increase in progeny resistance. The study demonstrates the transmission of the selected trait from the pollen generation to progeny. Further, it was observed that the effect of pollen selection was high in the progenies of moderately resistant parents compared to progenies of highly susceptible parents. The effect of successive pollen selection was studied by backcrossing the progeny derived through selective fertilization to the fertile parent using selective fertilization. Successive pollen selection further improved disease resistance of progeny. However, the improvement was not very great. Hence, repeated cycles of selection are required to achieve a useful level of resistance in the case of sunflower, since resistance is polygenetically controlled. Received: 17 May 1999 / Revision accepted: 13 September 1999