Microsporogenesis and pollen formation in Zingiber officinale Roscoe

Abstract

Zingiber officinale Roscoe, the common ginger, is an invaluable horticultural crop cultivated majorly in China, India, Brazil, Jamaica and Nigeria. Its pungent aromatic rhizome is used all over the world as a spice, culinary herb, condiment, home remedy and medicinal agent. This species does not produce seeds and so is difficult to breed its new genotypes through sexual hybridization. Despite the economic and genetic value, ginger has not been subjected to detailed cytogenetic research, which could lead to a better understanding of its reproduction for future genetic improvement. Therefore, the present work is undertaken for the first time to study microsporogenesis and pollen formation in Z. officinale. Pre-meiotic stages were observed under light microscope using anther squashes and staining by either acetocarmine or carbol fuchsin, whereas, the post meiotic stages were visualized under fluorescence microscope using either isolated microspores or pollen grains stained by 4′, 6′-diamidino-2-phenylindole. The combination of these two different cytological techniques allowed the study of the complete microsporogenesis and pollen formation processes step by step starting from pollen mother cells (PMCs) stage to mature pollen grain. Assessment of meiotic behavior was also performed by evaluating all possible PMCs on each slide and at all stages of meiosis. Cytological analysis revealed that only anthers from flowers of small spikes presented appropriate PMCs to analyze meiotic irregularities. The present paper enriches the database of cytology and pollen viability estimations for supporting sexual hybridization. The present study demonstrated a good relationship between the development stage of microspore and the size of the spike. This basic information will hopefully allow the development of protocol for production of androgenic haploids to accelerate breeding and genetic improvement of ginger. Further, research is under progress for evaluation of several media and other cultural factors to achieve microspore embryogenesis and plant regeneration in this species.