Establishment of growth medium and quantification of pollen grains of olive cultivars in Brazil's subtropical areas

Luiz Fernando De Oliveira Da Silva,Adelson Francisco De Oliveira,Rafael Pio,Carolina Ruiz Zambon,Emerson Dias Gonçalves

doi:10.1590/1678-4499.213

Luiz Fernando De Oliveira Da Silva, Adelson Francisco De Oliveira + Show 3 more

Open Access

https://doi.org/10.1590/1678-4499.213

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Abstract

Pollen grain germination in vitro indicates viability and consequently provides information related to fruit set. It also assists in the development of hybrids. Along with a suitable species, a standard culture medium is essential for evaluating pollen viability. It should contain a gelling agent consisting of carbohydrates and enhancer elements as well as have the correct pH, temperature, and incubation time. The objective of this study was to optimise the culture medium, determine the pollen germination capacity, and quantify the number of pollen grains per flower of certain olive tree cultivars. A basic sequential culture medium for pollen grain germination was determined, always utilizing the best result from the previous experiment to continue the sequence.The factorial treatment arrangement was: 1) agar versus boric acid; 2) pH versus sucrose; 3) calcium nitrate versus magnesium sulfate. After determining the culture medium components, two experiments were conducted evaluating temperature and incubation time. Another experiment evaluated both the germination percentage and the number of flower pollen grains of 28 cultivars. The culture medium should be composed of 4 g∙L-1 of agar, 90 g∙L-1 of sucrose, and 400 mg∙L-1 of boric acid with a pH adjusted to 5.79 and an incubation time of 60 h at 28 °C. The Manzanilla 215 cultivar had the highest germination rate while Ascolano 315 presented the highest number of pollen grains per flower.

Highlights

Despite the high quality of olive oil produced in Brazilian subtropical conditions, olive cultivation is still not a viable economic activity due to difficulties in adapting cultivars to the country’s climate (Silva et al 2012a)
After the release of the pollen grains, three factorial experiments were conducted to determine the ideal components of the culture medium: 1) agar (4, 6, 8 and 10 g∙L–1) versus boric acid (0, 400, 800 and 1,200 mg∙L–1); 2) pH (3.5, 4.5, 5.5 and 6.5) versus sucrose (0, 30, 60 and 90 g∙L–1); and 3) calcium nitrate (0, 200, 400 and 800 mg∙L–1) versus magnesium sulfate (0, 0.5, 1.0 and 1.5 mg∙L–1)
The concentrations of 4 g∙L–1 of agar and 400 mg∙L–1 of boric acid promoted a greater germination of the pollen grains (28.94%) (Figure 1)

Summary

Introduction

Despite the high quality of olive oil produced in Brazilian subtropical conditions, olive cultivation is still not a viable economic activity due to difficulties in adapting cultivars to the country’s climate (Silva et al 2012a). Self and inter-incompatibility are determined by the presence of an allelic series in the haploid genome of the pollen. This allelic series controls the development of the pollen tube in the pistil (Rapaport 1999). The lack of an efficient pollinator cultivar may explain losses caused by low fruit set. This position is still controversial, there is recognition that cross pollination might increase the fruit set rate (Cuevas et al 2009; Shemer et al 2014)

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