ASSESSMENT OF POLLEN VIABILITY IN GUAVA GENOTYPES

Abstract

Pollen viability is significant for plant breeding as an indicator of fecundation and fertilization efficiency of the male gamete. The present work aimed at evaluating the pollen viability of 19 guava genotypes, from five localities in the south of the State of Espirito Santo, and from Caparao, in the State of Minas Gerais, Brazil. For this end, staining and in vitro (pollen germination) methods were applied. Estimation of pollen viability by staining employed Lugol solution 1%, and acetic orcein 2%. Three slides were evaluated with each dye per plant, and an average of 500 pollen grains was counted per slide. Pollen tube germination was assessed in pollen grains distributed onto petri dishes, containing culture medium consisting of 10 g/L sucrose and 2% agar. The dishes were incubated in a germination chamber at 28°C, for 2 h. Three replications were carried out, and an average of 500 pollen grains was evaluated per dish. The observations were made using an optical microscope with 40x magnification. Analysis of variance was applied, and the means were compared by Tukey test (P<0.05). Differences in pollen viability were observed among the analyzed locations with both staining methods, even though all genotypes showed high viability (above 70%). The observation of significant differences between genotypes within the species indicates the existence of genetic variability for the evaluated characteristic. Viability, as tested by germination of the pollen tube, was inferior to that found by staining, presenting low index of germinated pollen, except for CCA1 and CCA3 genotypes from CCA locality of Espirito Santo, with 91.8 and 72.7%, respectively). According to these observations, viability obtained by staining methods seems to express the germination potential, but not its occurrence, as showed by in vitro method.