A viral matchmaker
Lin's decision to study viruses that infect bamboo was influenced by the background and social milieu in which she grew up.
Lin's father, Lin Wei-chih, was a botanist who once headed the Liugui branch of the Taiwan Forestry Research Institute. From an early age, Lin watched her father study the taxonomy of bamboo, and as such she has a special sentiment for the plant. Furthermore, over 20 years ago, the Council of Agriculture made great efforts to promote bamboo shoots as a high-fiber, water-rich and low-maintenance crop, a prime summer vegetable that doesn't need pesticides. So, from among the various major crop disease affecting Taiwanese agriculture, Lin chose bamboo diseases as her life's work.
Yet Taiwan, whose people love bamboo shoots and where more than 90,000 hectares of the crop is grown, is the place where the bamboo mosaic virus poses the greatest threat in the world.
The earliest report of BaMV infection in Taiwan appeared in 1974. After infection, bamboo leaves start showing yellow and brown streaks, and brown or black spots appear on the shoots and stalks. At that time it was called "brown-spotted blight" by locals. The infection causes hardening of fibers within the shoots, and reduces yields by 50%.
Because bamboo plants are grafted asexually, once a parent plant is infected by the virus, it will be passed on to subsequent generations. Moreover, infections can be spread via hoes and other farming equipment during the harvest. As a result, virus infection became more serious, spreading throughout Taiwan. Lin says that around 1990, the Tainan District Agricultural Research and Extension Station (DARES) carried out an island-wide survey of Oldham's bamboo (Bambusa oldhamii) and Taiwan giant bamboo (Dendrocalamus latiflorus) plantations, finding a morbidity rate of over 90%. A decade later, in 2002, Tainan DARES re-investigated the Oldham's bamboo plantations in Tainan County, and found morbidity rates surpassing 98% in a number of townships.
"Once plants are infected with a virus, they are quite troublesome to deal with," says Hsu. Like those that affect mammals, such as the HIV and hepatitis B viruses, plant viruses depend on the host for replication. Since no insects have been found in bamboo forests that serve as a means of transmitting this virus, there is no suitable insecticide that can be applied. Currently it's possible to grow healthy, virus-free bamboo sprouts and mitigate the viral disease by the meristem-tip culture technique, but ultimately this problem has to be solved by developing disease-resistant plants or transgenic crops.
Though the bamboo mosaic virus weakened the quality and yield of bamboo shoot harvests, the importance of the bamboo industry started to decline after Taiwan's entry into the WTO in 2002, opening Taiwan to imports of agricultural products. Now, with the exception of those farmers raising virus-free bamboo through meristem-tip culture under the auspices of the Taoyuan and Tainan DARES, the majority of bamboo farmers are not aggressively planting new bamboo crops, seeing it as a waste of time.
Even though the issue of curing bamboo disease in Taiwan has lost its urgency, Lin and Hsu have not changed their tack, working to blaze new trails in the jungle of science as they continue focusing on BaMV.
The bamboo mosaic virus is a filamentous, single-stranded, positive-sense RNA virus, a potexvirus of the alphavirus superfamily. According to current knowledge, BaMV is the main filterable virus affecting bamboo.
Hsu and Lin teamed up with Chang Ban-yang of the Institute of Biochemistry at NCHU, as well as Meng Meng-hsiao and Tsai Ching-hsiu of the Agricultural Biotechnology Research Center at NCHU, to conduct research on the molecular biology of BaMV. In the past decade or so, the team members have followed a practical course, each working on their parts of the task, conducting basic research on pathogenic mechanisms and disease prevention, and investigating ways to modify the virus through genetic engineering so that it can serve as a vector for producing proteins and manufacturing vaccines. BaMV research in Taiwan has stepped into the international realm.
Bamboo plants are grafted asexually, and once a parent plant is infected, the virus will be passed on to subsequent generations. Therefore tissue cultures are utilized to raise healthy, virus-free shoots.