Viability of pollen grains of tetraploid banana

Abstract

Obtaining banana tetraploid cultivars from triploid strains results in total or partial reestablishment of fertility, allowing the occurrence of some fruits with seeds, a feature that is undesirable from a marketing perspective. The objective of this study was to assess the viability of pollen of 12 banana tetraploid hybrids (AAAB) by means of in vitro germination and two histochemical tests (acetocarmine and 2,3,5-triphenyltetrazolium chloride). The pollen tube growth was evaluated by germinating grains in three culture media — M1: 0.03% Ca(NO3∙4H2O, 0.02% Mg(SO4)∙7H2O, 0.01% KNO3, 0.01% H3BO3 and 15% sucrose; M2: 0.03% Ca(NO3)∙4H2O, 0.01% KNO3, 0.01% H3BO3 and 10% sucrose; and M3: 0.015% H3BO3, 0.045% Ca3(PO4)2 and 25% sucrose. The acetocarmine staining indicated high viability (above 80%), except for the genotypes YB42-17 and Caprichosa, which were 76 and 70%, respectively. However, the in vitro germination rate was lower than 50% for all the genotypes, except for the hybrids YB42-17 (M1) and YB42-47 (M1). The medium M1 provided the greatest germination percentage and pollen tube growth. Among the genotypes assessed, YB42-47 presented the highest germination rate (61.5%) and tube length (5.0 mm). On the other hand, the Vitória cultivar had the lowest germination percentage (8.2%) in medium M1. Studies of meiosis can shed more light on the differences observed in the evaluated tetraploids, since meiotic irregularities can affect pollen viability.