Early Development of Direct Embryos in the Cultured Anthers of Manihot esculenta Crantz.

Lakmali Dissanayake,Manosha Jayawardhana,Thilak Attanayaka,Erwin Heberle,Prasanthi Perera

doi:10.3390/plants9101315

Lakmali Dissanayake, Manosha Jayawardhana + Show 3 more

Open Access

https://doi.org/10.3390/plants9101315

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Abstract

Cassava is one of the most important sources of energy. To meet the growing demand, genetic improvement is of utmost importance. Its cross-pollinating nature limits the opportunity of exploitation of hybrid vigor and demands the development of homozygous lines through doubled-haploid technologies. The problems in callus-mediated embryogenesis, such as longer processing time and genetically unstable nature, can be overcome by direct embryogenesis. Conditions to produce embryos directly from microspores in cultured anthers were optimized. The optimum stress pretreatment condition was 40 °C for 6 h after culturing the anthers into the induction medium. For proembryo formation, 2% sucrose and 5 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) or 1 mg/l 1-naphthaleneacetic acid were optimum. Globular embryos were formed by subculturing proembryos into the medium with 0.5 mg/l 2,4-D and 5 mg/l 6-benzylaminopurine after two weeks of culturing. Light microscopy of cultured anthers demonstrated the formation of multicellular structures and their further development into proembryos. Microscopic studies showed proembryos emerging through the damaged anther wall. Monoallelic banding in simple sequence repeat (SSR) analysis indicated homozygous or haploid states in some of the originated embryos. The conditions optimized in this study were effective in the early development of direct embryos after two weeks of culture initiation. This is the first report of the formation of direct embryos in cultured anthers of cassava.

Highlights

The biological nature of cassava, including drought tolerance, ability to grow in diverse climatic conditions and in depleted soils, its fast recovery from damage caused by pests and diseases, etc. [1,2], makes it a crop with increasing demand, under the global issues of food security and climate change [3]
The present study revealed that direct embryogenesis occurred much more rapidly, i.e., already after two weeks of culturing
The study revealed that direct microspore embryogenesis is possible in cultured anthers

Summary

Introduction

The biological nature of cassava, including drought tolerance, ability to grow in diverse climatic conditions and in depleted soils, its fast recovery from damage caused by pests and diseases, etc. [1,2], makes it a crop with increasing demand, under the global issues of food security and climate change [3]. [1,2], makes it a crop with increasing demand, under the global issues of food security and climate change [3]. Starch produced from cassava is amenable for use in various applications, both dietary and industrial [4]. The latter, including pharmaceutical uses, the production of bioethanol and of modified starches for a variety of commercial purposes, caused cassava to transform into the status of a cash crop. In order to fulfill the emerging global demand, improvements have to be made in the genetic aspects. The genetic improvement of cassava is hampered by the heterozygous nature created by its crossbreed behavior, while the availability of homozygous lines will accelerate the production of. It is of the utmost importance to develop efficient protocols for Plants 2020, 9, 1315; doi:10.3390/plants9101315 www.mdpi.com/journal/plants

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