Quite a few markets in Central Asia seem to be emerging. For example, Uzbekistan wasn’t exporting more than USD 7 million before 2018. In 2019, exported almost USD 70 million, almost cracking into the top 10 exporters in the world. Pakistan similarly went from exporting USD 12 million to 67 million in the same period, while Afghanistan suddenly jumped to USD 38 million in 2019 having not recorded any export values in previous years. While none of it is necessary major markets, it may only be a matter of time.
Otherwise, the top five exporters are the Netherlands, China, India, Mexico, and the United States. The latter three countries have seen varying but relatively stable export values since 2010, while the Netherlands and China, outside of a few outlier years, have been growing in export values, reaching the highest values in 2019.
Here’s a graph based on ITC Trade Map Information concerning the export values of the top 10 exporters of onions:

And here’s a graph based on more ITC Trade Map Information concerning the overall change in total exports since 2010:
