Optimized Protocol for In Vitro Pollen Germination in Yam (Dioscorea spp.).

Jean M. Mondo,Paterne A. Agre,Asrat Asfaw,Malachy O. Akoroda,Robert Asiedu

doi:10.3390/plants10040795

Abstract

Yam (Dioscorea spp.) plants are mostly dioecious and sometimes monoecious. Low, irregular, and asynchronous flowering of the genotypes are critical problems in yam breeding. Selecting suitable pollen parents and preserving yam pollen for future use are potential means of controlling these constraints and optimizing hybridization practice in yam breeding programs. However, implementing such procedures requires a robust protocol for pollen collection and viability testing to monitor pollen quality in the field and in storage. This study, therefore, aimed at optimizing the pollen germination assessment protocol for yam. The standard medium composition was stepwisely modified, the optimal growth condition was tested, and in vivo predictions were made. This study showed that the differences in yam pollen germination percentage are primarily linked to the genotype and growing conditions (i.e., medium viscosity, incubation temperature, and time to use) rather than the medium composition. The inclusion of polyethylene glycol (PEG) in the culture medium caused 67–75% inhibition of germination in D. alata. Although the in vivo fertilization was dependent on female parents, the in vitro germination test predicted the percentage fruit set at 25.2–79.7% and 26.4–59.7% accuracy for D. rotundata and D. alata genotypes, respectively. This study provides a reliable in vitro yam pollen germination protocol to support pollen management and preservation efforts in yam breeding.

Highlights

The yam is a multispecies crop belonging to the genus Dioscorea and provides food, medicine, and income in tropical and subtropical areas of America, Africa, Asia, the Caribbean, and Oceania [1]
We discovered that the established culture medium for D. rotundata was unsuitable for D. alata
Our study showed a positive correlation trend between pollen germination percent and the fruit set in field after hand pollination for both D. rotundata and D. alata genotypes

Summary

Introduction

The yam is a multispecies crop belonging to the genus Dioscorea and provides food, medicine, and income in tropical and subtropical areas of America, Africa, Asia, the Caribbean, and Oceania [1]. Six African countries, namely Nigeria, Ghana, Côte d’Ivoire, Benin, Togo and Cameroon, account for more than 90% of the annual global yam production [3]. In these countries, yam is a food and income security crop; it is an integral part of the people’s socio-cultural and religious belief systems. Most popular yam species are predominantly dioecious, with male and female flowers borne on separate individual plants. Successful hybridization depends primarily on the pollen germination ability (viability) of the male parent and the stigma receptivity of the female under favorable weather conditions [6]. Two aspects of pollen viability are discussed: the pollen’s germination ability tested in the laboratory, and its ability to fertilize a female flower after hand pollination [7]

Objectives

Methods

Results

Conclusion