A cytological indicator allows rapid assessment of microspore maturity, leading to improved in vitro anther response in Indica rice (Oryza sativa L.)

The inadequate response of Indica rice (Oryza sativa L.) to anther culture hinders the utility of this technique for rice crop improvement. This study focused on intensifying the in vitro anther response of selected varieties from Sri Lankan germplasm by precisely targeting the most effective maturity stage of microspores for culture. Analysis of five varieties responsive to anther culture ("At 303", "Bw 272-6B", "Dahanala", "Dikwee", and "Herath Banda"), revealed that the microspore development stage at the time of culture was crucial for fine-tuning the callus induction response. The external guide used to determine microspore maturity which was the internode distance between the last two leaves of the panicle, could not be applied equally for all rice varieties. Anther response could be improved by, at least, four- to sixfold by precisely targeting anthers with late uninucleate microspores for culture. Close correlation was demonstrated between the stage of nuclear division in the microspores and the degree of starch accumulation. Therefore, the degree of starch deposition in the microspores can be used as an effective cytological marker, which can be applied more rapidly and reliably to assess microspore maturity, in place of the internode distance.