Viability, production and morphology of pollen grains for different species in the genus Manihot (Euphorbiaceae)

Lívia De Jesus Vieira,Fernanda Vidigal Duarte Souza,Alfredo Augusto Cunha Alves,Taliane Leila Soares,Francisco De Assis Ribeiro Dos Santos,Mônica Lanzoni Rossi

doi:10.1590/s0102-33062012000200011

Abstract

The objective of this work was to characterize the viability, production and morphology of pollen for different species in the genus Manihot. Floral buds from Manihot accessions were collected from two germplasm banks at Embrapa Cassava & Fruits. The viability of the pollen was assessed via colorimetric, in vitro and in vivo assays. The diameter of the pollen grains was determined by measuring the transversal length of the grain. The experimental design was entirely randomized. Studies on pollen ultrastructure were performed via scanning electron microscopy. Pollen viability was high in the colorimetric tests and intermediate in vivo tests; there was no germination in the in vitro tests. The average production for all accessions was 1,253 pollen grains per floral bud. The size of the pollen grains varied from 132 to 163 µm in the wild accessions, and 129 to 146 µm in the cultivated accessions. The pollen grains for all accessions were very large, apolar, spherical as well as inaperturate, with an exine ornamented with pila organized in a Croton pattern. The wild accessions, in general, produced more and larger pollen grains compared with the cultivated accessions.

Highlights

Cassava (Manihot esculenta Crantz), a species originally from the American continent, is a halophyte and a perennial shrub that belongs to the Euphorbiaceae
All of the accessions had a high level of pollen viability when evaluated using the colorimetric techniques (Table 1)
The results presented here corroborate those discussed in the literature about cassava, where the pollen viability rate in species of Manihot was above 60% (Silva et al 2001; Vidal et al 2008)

Summary

Introduction

Cassava (Manihot esculenta Crantz), a species originally from the American continent, is a halophyte and a perennial shrub that belongs to the Euphorbiaceae. It is drought tolerant and can adapt to a wide range of soil and climate conditions. The wild cassava species are essential for a breeding program because they have a high level of variability, can adapt to a broad spectrum of conditions, and they offer many traits for developing more productive plants, such as resistance to pests and disease, as well as a higher tolerance to abiotic stresses (Horsfall & Abia 2003; Nassar et al 2007 a,b). Primary problems using wild Manihot species in improvement programs include a lack of synchrony during the flowering periods, as well as difficulty with the propagation and maintenance of these species in the field (Ceballos et al 2002). There is little information regarding pollen grain fertility for wild cassava species, despite their potential use in crosses for hybrid production

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