Abstract
To support breeding programs of pear tree, on the selection of cultivars to subtropical area in Brazil, the objective of this research was to adjust the growth medium basic to pollen grain germination. The pollen grains of 'D'Agua' cultivar were spread on the surface of Petri dishes containing 20 ml of culture medium in accordance with the following sequential experiments: 1) agar (4; 6; 8 and 10 g L-1) and pH (3,5; 4,5; 5,5 and 6,5); 2) sucrose (0; 30; 60 and 90 g L-1); 3) calcium nitrate (0; 200; 400 and 800 mg L-1); 4) boric acid (0; 400; 800 and 1200 mg L-1); 5) temperature of incubation (15; 20; 25 e 30 oC) and 6) emission time of the pollen tube (0; 1; 2; 3; 4; 5 and 6 hours after inoculation). After incubation, the germination rate of pollen grains of nine pear cultivars ('Rocha', 'Abate Fetel', 'Packham's Triumph', 'Atago', 'Hosui', 'Primorosa', 'Triunfo', 'Seleta' and 'D'Agua') was evaluated, and number of stamens, the number of pollen grains per anther and per flower. The protocol for germination of pollen grains of pear tree consist in the culture medium have to be solidified with 10 g L-1 agar, being the pH measured to 5,2 , added with 90 g L-1 sucrose, 145 mg L-1 calcium nitrate and 700 mg L-1 boric acid, with incubation temperature of 23 oC. The readings germination percentage should be performed after five hours of incubation. The pollen grain 'Rocha' cultivar showed higher germination percentage.
Highlights
The production of pears in Brazil is fairly insignificant, being around 20,000 t per year
Despite the pear being a fruit from temperate climates, there are some cultivars adapted to a subtropical climate (BETTIOL NETO et al, 2014; TECCHIO et al, 2011); the cultivation of this fruit in regions with mild winters is possible due to hybrid cultivars (Pyrus communis x P. pyrifolia) known as hardy pears
The most sensible strategy in programs for genetic improvement of the pear in regions with mild winters, which seek the quality of European pears with the lower cold requirement of Asian pears (BARBOSA et al, 2007), would be to use the cultivar Packham’s Triumph as one of the parent plants, as this has a lower cold requirement compared to other European pears (BARBOSA et al, 2008)
Summary
The production of pears in Brazil is fairly insignificant, being around 20,000 t per year. Due to increased imports of higher quality pears like ‘Rocha’ and ‘Abate Fetel’, breeding programs need to be improved in order to obtain better quality cultivars adapted to the subtropical conditions of Brazil. If this is so, the most sensible strategy in programs for genetic improvement of the pear in regions with mild winters, which seek the quality of European pears with the lower cold requirement of Asian pears (BARBOSA et al, 2007), would be to use the cultivar Packham’s Triumph as one of the parent plants, as this has a lower cold requirement compared to other European pears (BARBOSA et al, 2008). To select this cultivar as the male parent, it needs to produce viable pollen grains in high quantities; this information is not found in the literature
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