IN VITRO GERMINATION OF PYRUS CALLERYANA DECNE. POLLEN: ADJUSTING A PROTOCOL

In general, temperate fruit genetic improvement in the Instituto Agronômico (IAC), Brazil is realized by using controlled hybridization and posterior selection of the best materials generated. However, to have success in breeding it is indispensable to know the pollen germination viability of potential parents. In this context, this work had the objective of determining protocol adjustments for in vitro pollen germination of the pear tree rootstock cultivars ‘Taiwan Nashi-C’ and ‘Taiwan Mamenashi’; this information will be used to help the genetic improvement of this culture in Brazil. Two experiments were conducted to define the best agar, sucrose, calcium and boron concentrations in the germinating solution. In a first experiment, different agar (4, 6, 8 and 10 g.L^-1) and sucrose (0, 30, 60 and 90 g.L^-1) concentrations were tested. From these results, further work was initiated comparing the addition of various calcium nitrate (0, 200, 400 and 800 mg.L^-1) and boric acid (0, 400 e 800 and 1200 mg.L^-1) concentrations. It was shown that the best results for germination and pollen viability were obtained in culture media with 10 g.L^-1 of agar, 90 g.L^-1 of sucrose and 838 mg.L^-1 of boric acid for ‘Taiwan Mamenashi’ and 10 g.L^-1 of agar, 47,78 g.L^-1 of sucrose and 795 mg.L^-1 of boric acid for ‘Taiwan Nashi-C’. The results showed also that the addition of calcium nitrate had a negative effect on in vitro pollen germination, for the pear rootstock cultivars used in this work.