SUCCESSFUL MICROSPORE REPROGRAMMING TOWARDS EMBRYOGENESIS OF BULGARIAN PEPPER VARIETIES AND EFFECTS OF STRESS TREATMENTS AND WHEAT OVARIES ON EMBRYO FORMATION

Androgenesis is a remarkable feature of the immature pollen grains to form totipotent cells that has the ability to leave the gamethophytic pathway of development and re-program toward sporophytic one. The result is formation of a complete new plant with a single set of chromosomes thus becoming the perfect material for genetic improvement of crop plants. The influence of the developmental stage of microspores as well as the effect of heat shock and starvation on androgenic induction in microspores from three Bulgarian pepper varieties was tested (Djolunska shipka, Hebar, and Kurtovska kapia). Pepper microspores were subjected to different time of heat shock (33 degrees C) treatment or starvation, and to a combination of heat shock and starvation. The cytological analysis during the 20 days of culture showed that the frequencies of dividing microspores and multicellular structures were higher when heat shock in combination with starvation was applied for 3 days in comparison with heat shock or starvation alone. After transfer to a rich medium high frequency of multicellular and callus structures was observed. The difference in microspore embryogenesis among the pepper genotypes was shown. The effects of carbohydrate source and wheat ovaries were tested for optimization of the protocol for embryo formation. The combination of maltose and wheat ovaries overcame the callus development and increased the frequency of embryo formation in varieties Djolunska shipka and Hebar.