In a processing shop of Chongqing Huida Lemon Technology Group, located in Chongqing's Tongnan district, workers are busy packing boxes of fresh lemons that will soon find their way to Russia.

Tongnan, located at the conjunction of Sichuan province and Chongqing, has an average temperature of 17.9 C and vast, fertile alluvial plains. It is one of the most famous vegetable bases in western China as well as one of the world's top lemon-producing areas.

According to the data processing website Atlasbig.com, more than 20 million metric tons of lemons are produced worldwide per year, and of that, China produces 2.7 million tons, ranking behind only India.

"Tongnan produces nearly half of the country's lemons, and more than 30 percent of the district's yield is exported overseas to more than 30 countries and regions, including Russia, Kazakhstan, Indonesia and Singapore," said Fu Qiang, director of the Lemon Industry Development Bureau at the Tongnan Agriculture Science and Technology Promotion Center.

He said that the average annual income of the over 600 households involved in lemon planting in the district has increased by 6,000 yuan ($870).

Lemon planting in Tongnan district dates back to the 1970s, but large-scale and standardized lemon growing began in 2000. The district's lemon-growing area covers 21,300 hectares, second only to Anyue county in Sichuan province, said Zhang Yuhong, an official in charge of agriculture from Tongnan district.

Thanks to the smooth trade and logistics routes including the New International Land-Sea Trade Corridor and the Chongqing-Xinjiang-Europe international railway, more than 100,000 tons of fresh lemons worth 1 billion yuan ($148 million) were exported last year to over 30 countries and regions in eastern Europe, the Middle East and Southeast Asia, according to Huida.

In addition to fresh lemon exports, fruit of low-grade quality will go through soaking, cleaning and scanning, and enter a deep-processing phase－using all parts of the fruit.

Via deep processing, the lemons are turned into over 300 products including lemon juice, beverages, essential oil, liquid aromas and facial masks, said Dai Xiaoqiang, general manager of Huida Group.

With the fast development of over 10 leading lemon companies based in Tongnan district like Huida, the district is striving to become the "lemon capital of the world", boasting the National Protection and Demonstration Zone for Ecological and Original Lemon Product and National Modern Agriculture (Lemon) Industrial Park.

The annual lemon output of 280,000 tons is worth more than 5 billion yuan, according to Ni Biao, deputy director of the Tongnan Agriculture Science and Technology Promotion Center.

"We have built a whole industrial chain of planting, processing, marketing, research and tourism related to lemons in Tongnan," he said.

"By 2025, the total output value of Tongnan lemons is expected to reach 12 billion yuan," Ni said.

Liao Chengbin, one of the largest lemon growers in Baizi town, the core base of the district's lemon industry, moved from Anyue to Tongnan 11 years ago to start a lemon planting business. Now he owns a lemon farm of 53.3 hectares.

"In the bumper harvest season every October to November, another 40 workers are needed to help out at the farm, to ensure the delivery time for the clients," the farmer said.

But the bumper harvest never comes easy.

In 2017, the devastating disease called "lemon cancer" struck Tongnan. Tremendous numbers of lemon trees were cut down to control the spread of the disease.

In order to achieve sustainable development in the industry by making lemon plants more resistant to the disease, a lemon seedling detoxification center was established in the district in the same year, said Han Guohui, chief expert of the lemon innovation team at the Chongqing Academy of Agricultural Sciences.

The center can breed at least 500,000 lemon seedlings in over 40 varieties like Eureka lemon, Dulce lemon and citron each year, Han said.