ASSOCIATION BETWEEN SPOROPHYTIC REACTION TO ALTERNARIA-HELIANTHI AND GAMETOPHYTIC TOLERANCE TO PATHOGEN CULTURE FILTRATE IN SUNFLOWER (HELIANTHUS-ANNUUS L.)

Seven sunflower genotypes comprising of populations and hybrids showin g differential sporophytic reaction to Alter nai in leaf and stem blig ht were studied for their gametophytic reaction to pathogen culture fi ltrate. The sunflower pollen grains germinate well in the liquid mediu m and give good pollen tube growth in the absence of the culture filtr ate. The addition of increasing concentrations of culture filtrate to medium significantly reduced the pollen germination and tube growth in all the genotypes. The reduction in pollen germination and tube growt h in vitro due to culture filtrate was more in highly susceptible geno types L-101 and Morden than the moderately resistant genotypes Acc. no s. 1229, 180 and ISFH-306. Pretreating the stigma and style with the c ulture filtrate before pollination reduced the number of pollen grains germinating compared to untreated control suggesting toxin stress can be created on the stigmatic surface before pollination. There was cor respondence between pollen germination on stressed stigma (in vitro) a nd sporophytic reaction of the genotype suggesting pollen grain having resistance would germinate on the stressed stigma and fertilise the o vule achieving selective fertilisation. The correlation analysis indic ated that there is a negative relation between sporophytic per cent di sease index value and gametophytic parameters such as in vitro and in vivo pollen germination, culture filtrate required to inhibit 50% poll en germination and pollen tube growth. The association between pollen and the sporophytic reaction to the disease indicate the possibility o f rapid screening of a large number of genotypes by means of pollen as say as an alternate technique with regard to sporophytic disease index in sunflower. The study also indicate the possibility of pollen selec tion before fertilisation to achieve rapid improvement in disease resi stance.