Modern industrialised farming systems rely on mono cropping. This type of farming has resulted in a rapid decline of agro-biodiversity in China. In order to reverse this, agricultural systems that encourage farmers to plant traditional varieties are being encouraged by both scientists and farmers alike. This is an important complement to ex-situ conservation (collecting, handling and management of germplasm 'off-site' - see box below) of crop varieties by plant breeders or scientists.
Agro-biodiversity under threat
With the advent of modern ‘industrialised’ agriculture, many traditional crop varieties world-wide have been replaced by a few high-yielding ones; a result of apparently ‘efficient’ crop breeding and intensive cultivation practices adopted on a massive scale. This has caused a rapid decline of local crop diversity e.g. rice, in China.
Conservation of traditional crop varieties ex-situ, mainly through seed collections, is widely spread in gene banks around the world. However, there are several restrictions to this method. It is static in evolution terms, because there is no genetic adaptation to the changing environment and it is difficult to work with seeds that may lose their ability to germinate shortly after ripening.
Hence, encouraging farmers to interplant traditional varieties of market value with modern crops, will then engage farmers to participate in-situ conservation. This is considered as an important complement to ex-situ conservation (maintenance of the diversity present in habitats 'on site'– see box below.) This system of farming has proven to be effective in pest & disease management, reducing chemical use; raising farmer's income and on-farm conservation of crop diversity. Thus fully illustrating the principles of sustainability.
Choosing varieties for inter-planting
In the past, farmers in China practiced different types of inter-planting in their fields. Researchers now only need to study the right combinations of crops, determine an appropriate cultivation model and then share their results with farmers. By engaging farmers to join a participatory experiment they will then be able to manage the technique themselves.
Normally, there are criteria for selecting the traditional varieties for inter-planting. The selected traditional varieties should have good market demand, high quality and palatability. In most cases, the genetic dissimilarity coefficient between the traditional crop and hybrid crop selected for mixed planting should be greater than 70%, as measured by the resistant gene analogue finger-printing technique. In the case of mixed rice farming system, the selected traditional variety should be taller than the hybrid variety by at least 30cm. In addition, the difference in time of maturity should be less than 10 days. The hybrid variety selected should be high yielding and short.
An important role for farmers
The role of farmers in conserving agro-biodiversity should be emphasized. Traditionally, farmers play an important role in conserving agro-biodiversity by their crop selection. Scientists in remote gene banks consider in-situ conservation of crop varieties in their original habitats on farms, through agricultural practices, as an important complement to ex-situ conservation.
It emphasizes the role of farmers for two reasons: Firstly, crop varieties are the result not only of natural factors, such as mutation and natural selection, but also, and particularly, of human selection and management; and secondly, farmers' decision ultimately determine whether these populations are maintained or abandoned.
Success
Yunnan, the Center of Genetic Diversity in China has achieved significant success with this approach. The bio-diversity in Yunnan is extremely rich, half of the bio-diversity in China can be found there. Since the initiation of the crop diversity program in 1997 by Phytopathology Laboratory of Yunnan Agricultural University, a remarkable result has been achieved. 20 local rice varieties, which were formerly locally extinct, have been restored to agriculture communities and the area of cultivation has been expanded rapidly. Reports from the provincial government authorities indicate the area of cultivated rice under diversity management has expanded to about 460,000 hectares in the Yunnan, Sichuan and Guizhou Provinces in the last few years. The approach has been promoted to use for conserving other crop species including wheat, fava bean, potato, maize and oil rape.
Ex-situ 'off-site' conservation
Ex-situ conservation involves the collecting, handling and management (including research) of germplasm, its storage, regeneration, characterization/evaluation, documentation and dissemination to users.
In-situ 'on-site' conservation
In-situ conservation of involves the maintenance of the diversity present in and among populations of the many species used directly in agriculture, or used as sources of genes, in habitats where such diversity arose and continues to grow. It concerns entire agroecosystems, including immediately useful species (such as food crops, forages, and agro-forestry species), as well as their wild and weedy relatives that may be growing in nearby areas.
