Calotropis gigantea (L.) W.T. Aiton is well known for its aesthetic, medicinal, fodder, biodiesel, and fiber production potential. Unfortunately, this plant species is still undomesticated, and the genetic information available for crop improvement is limited. It is extensively distributed in Bangladesh and China (Sichuan, Yunnan, Guangxi, Guangdong, and Hainan provinces), where the species is broadly used in traditional medicine. Both countries have high human-mediated pressure and current threats such as habitat loss, fragmentation, and over-harvesting of the plant might impact the levels of genetic diversity in these areas. Therefore, it is urgent need to know the population genetics estimates of this key plant. 

To identify the genetic diversity and population structure of C. gigantea, Md. Rabiul Islam, a PhD candidate from Wuhan Botanical Garden conducted an investigation under the supervision of Prof. WANG Qingfeng and Associate Prof. CHEN Lingyun. They sampled young leaves of 21 natural populations including 379 individuals from Bangladesh and China that covering the mainland and island distribution ranges and genotyped those using nine nuclear microsatellite markers.  

Genetic diversity was higher in Bangladesh than that observed in Chinese populations. The mainland populations showed slightly higher genetic diversity than island populations, but differences were not statistically significant. Overall, a moderate level of genetic diversity, strong population structure with higher gene flow was observed. 

Some populations may have experienced recent demographic bottlenecks and therefore, this study provides a baseline for exploitation of the genetic resources of C. gigantea in domestication and breeding programs as well as some insights into the germplasm conservation of this valuable plant. 

The project was financially supported by National Natural Science Foundation of China and CAS-TWAS President’s PhD Fellowship Program, University of Chinese Academy of Sciences, China. Results have been published in Biochemical Genetics entitled “Population Genetics of Calotropis gigantea, a Medicinal and Fiber Resource Plant, as Inferred from Microsatellite Marker Variation in two Native Countries”.