Genotypic control of pollen plant formation in Nicotiana tabacum L

Tobacco plants (Nicotiana tabacum L.) of four varieties ('Badischer Burley', 'White Burley', 'Techne', 'Kupchunos') were raised at different temperatures and daylengths and the effect of genotype on embryogenic pollen grain formation in situ and on pollen plant formation in anther and pollen cultures from these plants was studied. Genotype controlled embryogenic pollen grain and pollen plant formation by defining productivity under standard growth conditions (long days at 24 °C). 'Kupchunos' was the most productive variety, followed by 'White Burley', 'Techne', and 'Badischer Burley'. Furthermore, genotype defined which environmental factor was able to affect embryogenic pollen grain and pollen plant formation and also to which degree. In anther cultures, in addition to these effects, genotype controlled the formation of (an) inhibitory substance(s) in the anther wall in interaction with the plant growth conditions. In 'Badischer Burley' and 'Techne', inhibitor action could be prevented by isolation of the pollen after one week of anther culture. Finally, direct pollen cultures in 'Badischer Burley' and 'Techne' produced embryos were only when the pollen was isolated from nearly mature anthers, while in 'White Burley' and 'Kupchunos', embryos also produced at earlier stages and at higher yields. This indicated that genotype controls the time when the embryogenic pollen grains become ready to divide. The results are discussed in relation to strategies to overcome recalcitrance of species and genotypes.