Chongqing - A team of graduate students from the Citrus Research Institute of Southwest University has turned an academic experiment into an online sensation, selling out 5,000 boxes of a newly developed hybrid citrus variety in just seven days.

The fifth-generation hybrid citrus variety “Sunshine No.2,” developed by Cao Li after more than a decade of research. (Photo provided by the interviewee)

It all started when Li Shunxin, a graduate student under researcher Cao Li, and four classmates formed a small “sales team” on October 15. They began promoting “Sunshine No.2,” the fifth-generation hybrid citrus developed by Cao after more than a decade of research, across social media platforms such as WeChat, Xiaohongshu, and Douyin. Within a week, their posts went viral, orders poured in from all over China, and the fruit quickly sold out.

“We really didn’t expect this,” said Cao, who has been breeding hybrid citrus for years. “I wanted my students to gain practical experience beyond the lab — to understand the market, interact with consumers, and learn how science connects to real life.”

Li explained that the sales project began as a way to earn some living expenses and practice communication and management skills. “Professor Cao always tells us that graduate students shouldn’t just write papers — we should learn how to apply our strengths in real-world contexts,” Li said.

A Scientific Variety That Won the Market

“Sunshine No.2” is the latest in a long line of carefully bred hybrids, descending from well-known varieties such as mandarin, grapefruit, navel orange, and satsuma. Priced at 58.8 yuan for 2.5 kilograms, the fruit is slightly more expensive than common tangerines, but customers praised its rich flavor and refreshing sweetness, driving overwhelming demand.

Cao’s research team has previously developed “Golden Autumn Sugar Mandarin,” China’s first commercially promoted hybrid citrus, and “Sunshine No.1,” a grapefruit-mandarin hybrid known for its balanced flavor. “Golden Autumn” is now sold in major supermarkets across Chongqing, while “Sunshine No.1” is expected to enter the market this December.

The fifth-generation hybrid citrus variety “Sunshine No.2,” developed by Cao Li after more than a decade of research. (Photo provided by the interviewee)

“Our citrus groves are carefully managed by experts and strictly follow green, pesticide-free standards,” Cao noted. “We don’t use high-toxicity pesticides or ripening agents — everything is grown naturally.”

From Online Buzz to Long-Term Vision

After media reports of their viral success, the research group found themselves inundated with phone calls and online messages asking when new batches would be available. Yet amid the frenzy, Cao reminded his students of the core value of scientific research: patience.

“Breeding a new variety takes at least ten years from the first fruit to full commercialization,” he explained while inspecting trees at a test base in Jiangjin District. “Every variety has strengths and weaknesses. Some can be improved, others cannot. We must ensure stability and consistency before promotion.”

The Jiangjin base, managed in collaboration with Chongqing Guilai Fruit Industry Co., Ltd., spans 300 mu (20 hectares) and currently grows nearly 250 tons of “Sunshine No.1.” In contrast, the earlier viral “Sunshine No.2” was planted on only 20 mu, explaining its limited supply.

Cao Li (center) and his graduate students examine the growth of citrus trees. (Photo/Zheng Yu)

Cao emphasized that breeding excellence requires time, testing, and perseverance. “A hit product doesn’t change the nature of science,” he said. “As agricultural researchers, we must learn to be friends with time — testing our varieties across different regions, climates, and soil types to deliver the best results for farmers.”

Cao added that the team plans to relaunch sales in late November when “Sunshine No.1” ripens for harvest. “We’re thrilled by everyone’s enthusiasm,” he said, “but more importantly, we’re learning how to connect research, innovation, and practice in a meaningful way.”