Composição do meio de cultura e condições ambientais para germinação de grãos de pólen de porta-enxertos de pereira

Abstract

In order to support the works with genetic improvement for pear rootstocks and adjust the pollen germination protocol for intra and inter species polinization, this study aimed to adjust the culture medium basic compounds and environmental conditions for the realization of in vitro pears pollen grains germination and viability tests of 'Taiwan Nashi-C' (Pyrus calleryana) e 'Taiwan Mamenashi' (P. betulaefolia) pear rootstock. Thus, five experiments were performed: 1) Sucrose concentrations (0, 30, 60 and 90g L-1) and agar (4, 6, 8 and 10g L-1); 2) calcium nitrate (0, 200, 400 and 800mg L-1) and boric acid (0, 400, 800 and 1200mg L-1); 3) pH (4.0; 4.5; 5.0; 5.5; 6.0 and 6.5); 4) temperatures (20; 25; 30 and 35 ) and 5) emission time of the pollen tube (1, 2, 3, 4, 5, 6 and 12 hours after inoculation), which were assembled sequentially. The use of 10g L-1 of agar combined with 90g L-1 sucrose for the rootstock 'Taiwan Mamenashi' and 47.78g L-1 for the 'Taiwan Nashi-C', with 795 to 838mg L-1 of boric acid, under absence of calcium nitrate and pH between 5.2 and 5.8 and temperature of 28 °C, provided the best conditions to the germination of the pollen grains. The maximum percentage of germinated pollen is obtained with eight hours after inoculation for 'Taiwan Nashi-C' and twelve hours for 'Taiwan Mamenashi'.