Recent Advances in Onion Genetic Improvement

Christopher S Cramer,Suman Sharma,Subhankar Mandal,Ivette Guzman,Irwin Goldman,Seyed Shahabedddin Nourbakhsh

doi:10.3390/agronomy11030482

Christopher S Cramer, Suman Sharma + Show 4 more

Open Access

https://doi.org/10.3390/agronomy11030482

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Abstract

Onions are one of the most important vegetable crops worldwide. However, their production faces many challenges. Genetic improvement is one mechanism to address those challenges. In this review, we discuss recent research pertaining to the diseases Fusarium basal rot and Iris yellow spot, the insect pest onion thrips, onion pungency, and dormancy. Recent research for screening onion bulbs for Fusarium basal rot resistance has resulted in improved screening techniques and germplasm exhibiting less disease when inoculated with the disease-causing pathogen. Improved screening methods have resulted in germplasm exhibiting fewer and less severe Iris yellow spot symptoms when onion thrips and conducive environmental conditions are present. Onion germplasm with less and differing compositions of epicuticular wax on their leaves have shown a nonpreference for thrips feeding and have the potential for developing thrips tolerant cultivars. Conventional breeding efforts and genetic manipulation of the genes producing alliinase and lachrymatory factor synthase has resulted in low pungency, tearless onions. In long-day onions, an annual generation time has been achieved by artificially breaking bulb dormancy early while ensuring proper vernalization has been completed. Genetic improvement of these and many other onion traits will continue and result in better production in the future.

Highlights

Onion (Allium cepa L.) is one of the most important vegetable crops worldwide
Onions decline in vigor when self-pollinated and will suffer inbreeding depression visualized through smaller bulbs, fewer flowering scapes, smaller umbels, and lower seed production after several cycles of self-pollination [2,4]
This review will focus on recent research to improve resistance to Fusarium basal rot (FBR), to improve resistance to Iris yellow spot (IYS) disease, to improve tolerance to onion thrips, and to further understand onion pungency and dormancy

Summary

Introduction

Onion (Allium cepa L.) is one of the most important vegetable crops worldwide. Of the total vegetable production worldwide, onion accounts for around 24% of the total [1]. Since onions are a biennial plant species that results in a generation time of two years, seed production for research requires more time and effort than annual crops. To achieve a generation time of one year, onion dormancy must be broken early while ensuring proper vernalization occurs [3]. To accelerate the process in temperate environments, onion flowering and seed production must occur in a controlled environment to ensure that seed is ready in time for planting the generation [3]. Onions decline in vigor when self-pollinated and will suffer inbreeding depression visualized through smaller bulbs, fewer flowering scapes, smaller umbels, and lower seed production after several cycles of self-pollination [2,4]. Onions face many insects, fungal, bacterial, viral, and nematode pests. This review will focus on recent research to improve resistance to Fusarium basal rot (FBR), to improve resistance to Iris yellow spot (IYS) disease, to improve tolerance to onion thrips, and to further understand onion pungency and dormancy

Fusarium Basal Rot

Iris Yellow Spot and Onion Thrips

Pungency

Bulb Dormancy and Vernalization

Findings

Conclusions