Effect of moisture stress on combining ability variation for bird resistance traits in sunflower (Helianthus annuus L.)

Experiments on sunflower were carried out under 2 moisture level in the field to study their effect on phenotypic expression and combining ability of bird resistant traits i.e, degree of head shape (DHS), degree of achene compactness (DAC), degree of stem orientation (DSO) and degree of head orientation (DHO). Genotypes indicated substantial shift in their relative morphology for all traits related to bird resistance over moisture regimes. All traits exhibited larger proportion of non additive gene action under both conditions and showed an increase in proportion of non-additive genetic variation under moisture stress condition. Intermating and recurrent selection procedures could be useful breeding procedures for accumulating favorable genes responsible for better bird resistance traits and may produce superior recombinants in segregating progenies under both conditions. Under moisture stress condition, only drought tolerant parents showed peculiar morphology of traits leading to bird attack resistance. Relative sensitivity of these traits to the moisture stress has indicated their potential of acting as morphological marker for selection of drought tolerant genotypes. Among bird resistant traits, degree of head shape showed significant negative relationship with achene yield suggesting the possibility of improving yield through selection of highly concave genotype under drought stress condition.