Storage of cassava pollen for conservation of nuclear genetic diversity and overcoming hybridization barriers

The objective of the storing cassava pollen is to preserve the genetic material for the future use, to maintain their germination, vigour and genetic integrity by providing the optimal conditions. Non-synchronous flowering between parental lines, monoecious and protogynous nature, poor and irregular flowering poses difficulty in cassava breeding. Staggered and multiple planting can circumvent this limitation to some extent, however it consumed a lot of time, labour and space. Availability of stored viable pollen for hybridization can be of great help as the preserved pollen facilitates the easy exchange of genetic material among the researchers as also between the nations due to the less stringent restrictions on the transfer of stored pollen. Hence, cassava pollen storage was undertaken in present studies. Freshly opened male flowers of cassava variety Sree Padmanabha (SP) and Vellayani Hraswa (VH) were collected between 9.00 AM and 10.30 AM. Viability of the pollen was tested by acetocarmine staining and in vitro pollen germination tests. The results showed that after 45 days of storage in liquid nitrogen, the pollen staining was 59.1% and 63.9 % while pollen germination was 49.5% and 51.0% in SP and VH, respectively in the laboratory assessment. Hand pollination in the field was done using cryopreserved pollen and the normal fruit set was observed. These findings will form the base information in helping the breeders to plan hybridization programme in cassava and in easy conservation and exchange of the elite germplasm.