Genetic Enhancement of Resistance to Alternaria Leaf Blight in Sunflower through Cyclic Gametophytic and Sporophytic Selections
2007
Rani, T Shobha | Ravikumar, R. L.
Only partial resistance has been reported so far in Helianthus species for leaf blight caused by Alternaria helianthi (Hansf.). Therefore, in the present study one to two cycles of recurrent selection based on sporophytic and gametophytic selection was effected to increase resistance to leaf blight in the base population. The base population was synthesized by random mating five diverse early generation breeding lines. The gamete selection was practiced by applying pathogen culture filtrate to stigma and style 1 h before pollination. The selection response was measured by recording observations on percent disease index (PDI) at flowering, 15 d after flowering and at physiological maturity. In both gametophytic and sporophytic selection cycles significant reduction in PDI was observed. The populations improved through gametophytic selection were more promising as the pollen selection could allow high selection intensity and absence of dominance effects. In sporophytic selection the rare favorable allelic combination is hardly detected. The progress in resistance in two cycles of selection was not very high for their use in crop improvement. There is a need to increase the number of cycle of selection to maximize the desirable alleles to achieve high level of resistance. The gametophytic selection combined with the conventional sporophytic selection can be considered as an effective tool in improving populations for partial resistance.
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