Pollination and fertilization under in vitro conditions offer an opportunity for producing hybrid embryos among plants that cannot cross by conventional methods of plant breeding. In nature, Intergeneric or Interspecific hybridization occurs less frequently. This is due to barriers hindering the growth of the pollen tube on the stigma or style. In such cases the style or part of it can be excised and pollen grains either placed on the cut surface of overy or transferred through a hole in the wall of ovary. This technique, called intraovarian pollination, has been successfully applied in such species as Papaver sommiferum , Eschscholtiza California, Argemone Mexicana and Argemone ochroleuca. Another approach to overcome the barrier to pollen tube growth is direct pollination of cultured ovules or excised ovules together with placenta. This technique was developed at university of Delhi in papaveracea and solanaceae. Various other techniques developed to overcome the prezygotic barriers to fertility include: a) Bud pollination, b) Sub pollination, c) Heat treatment of style, d) Irradication and e) Mixed pollination.
The development of seed through in vitro pollination of exposed ovules has been described as ‘test-tube fertilization’ whereas the process of seed formation following stigmatic pollination of cultured whole pistils has been referred to as ‘in vitro pollination’. Considering the fact that male gametes in plants do not float freely and are delivery by pollen tube, a general terms ‘in vitro pollination has been used for ovular pollination, overian pollination, placental pollination and stigmatic pollination under in vitro conditions.
The vitro pollination can be accomplished by procedure by following appropriate sterilization procedure, suitable nutrient medium and selection of suitable explant.
Application of in Vitro Pollination:
In plant breeding the technique of in vitro pollination has potential applications in at least three different areas, viz, a) overcoming self-incompatibility b) overcoming cross-incompatibility, c) haploid production through parthenogenesis.