2.2. Comparison between anther and pollen culture

Anther culture is an easy, quick and practicable approach. Anther walls act as conditioning factors and promote culture growth. Thus, anther cultures are reasonably efficient for haploid production. The major limitation is that the plants not only originate from pollen but also from other somatic parts of the anther. This results in the development of plants at different ploidy levels viz., haploids, diploids, aneuploids, as a result of which the final tissue, derived, may not be of purely gametophytic origin. Moreover, the plants arising from an anther would constitute a heterogenous population. It has been observed in some species that anther cultures show asynchronous pollen development, the older grains may suppress the androgenic potential of younger grains by releasing toxic substances . The disadvantages associated with anther culture can be overcome by pollen culture as it offers the following advantages:

• •  Undesirable effects of anther wall and associated tissues can be avoided.

•  Androgenesis, starting from a single cell, can be better regulated.

•  Isolated microspores (pollen) are ideal for various genetic manipulations like transformation, mutagenesis etc.

•  The yield of haploid plants is relatively higher.

 

2.3. Pathways of development

The early divisions in responding pollen grains may occur in any one of the following four pathways (Figure 9.3):

i)  Pathway I - The uninucleate pollen grain may divide symmetrically to yield two equal daughter cells both of which undergo further divisions e.g. Datura innoxia .

ii)  Pathway II - In some other cases e.g. N.tabacum, barley, wheat etc., the uninucleate pollen divides unequally. The generative cell degenerates, callus/embryo originates due to successive divisions of the vegetative cell.

iii)  Pathway III - But in few species, the pollen embryos originate from the generative cell alone; the vegetative cell either does not divide or divides only to a limited extent forming a suspensor like structure.

iv)  Pathway IV - Finally in few other species e.g. Datura innoxia, the uninucleate pollen grains divide unequally, producing generative and vegetative cells, but both these cells divide repeatedly to contribute to the developing embryo/callus.