Viability and longevity of pollen of Nothofagus species in South Chile

Abstract

The reproductive success of some Nothofagus species from South Chile is poor. Although self‐incompatibility is known to occur, seed set by out‐crossing pollination is still low. Therefore, in this study we focused on the pollen physiology of these species. Using direct and indirect methods, the viability and longevity of pollen grains from young and mature individuals of the species N. antarctica, N. obliqua, N. dombeyi, and N. betuloides were assessed. Pollen germination in vivo was evaluated in hand‐pollinated and naturally pollinated receptive stigmas of both categories. To assess pollen viability indirectly, in vitro germination on a sucrose‐agar culture medium was performed. Alexander's procedure (an indirect method) was used to evaluate viability immediately after pollen collection and longevity after 3, 6, and 12 months of storage. Pollen germination in vivo ranged from 52 to 74% in young individuals and 68 to 84% in mature trees. In vitro germination ranged from 46 to 71 % in young individuals and 49 to 85 % in mature trees. Fresh pollen dyed with Alexander's stain reached 91–100% viability. Similar values were obtained after three months of storage. After 6 months, pollen viability reduced to 66% and after one year of storage, viability had dropped to 21 to 50%, with mature individuals showing the highest loss of viability. The relevance of these findings to breeding programmes and pollination studies is discussed.