Crop wild relatives, which include crop ancestors and other closely related species, have been used for crop improvement for centuries. Modern cultivars of most crops contain some genes that are derived from a wild relative.
Crop wild relatives have been used to improve resistance against pests and diseases such as wheat curl mite, late blight in potato, and grassy stunt disease in rice, and to improve crop tolerance to stressful abiotic conditions such as drought in wheat and acid sulfate soils in rice. They have also raised the nutritional contents of crops, including protein in durum wheat, calcium in potato, and Provitamin A in tomato.
Genes with immense value
The commercial value of crop wild relatives is impressive. The desirable traits of wild sunflowers (Helianthus spp.) are worth an estimated US$267 million to US$384 million annually to the sunflower industry in the United States; one wild tomato variety has contributed to a 2.4 percent increase in solids contents worth US$250 million; and three wild peanuts have provided resistance to the root knot nematode, which cost peanut growers around the world US$100 million each year.
In addition to their use in breeding, crop wild relatives are also used in their wild state. A number of wild cowpea species (Vigna spp.) in Africa contribute directly to food security through consumption of their tubers, fruit and seeds. Wild yams (Dioscorea spp.) are an important source of carbohydrates and incomes in Madagascar, and wild fruits such as apple, pistachio and sea buckthorn are harvested for food in Central Asia and the Caucuses. CWR species also provide other invaluable products such as animal fodder, building materials and medicines.
Maintaining genetic diversity
The increasing genetic uniformity of crop varieties combined with climate change effects makes crops more vulnerable to stress. The potato famine of the 1840s was caused by large-scale crop failures as a result of genetic vulnerability to the late potato blight epidemic – a large proportion of the susceptible potato varieties grown at that time were eliminated as the blight spread across Ireland, Europe and North America.
Devastating losses in the 1970s caused by the southern corn blight outbreak in the US maize crop further highlighted the risk of relying on a few high-yielding varieties. Genetic vulnerability has also caused large-scale rice losses in the Philippines and Indonesia. crop wild relatives are important for maintaining genetic diversity and preventing such losses, which can have serious consequences for food security.
The natural populations of many species of crop wild relatives are increasingly at risk. They are threatened primarily by habitat loss, degradation and fragmentation. Climate change is having significant impacts on species distributions through reducing suitable habitat and increasing the rate of habitat fragmentation. It is likely that within fifty years, climate will cause many important species of crop wild relatives to be threatened with extinction. There is an urgent need to identify priority species and areas for conservation and to develop integrated in situ and ex situ conservation strategies to ensure that the rich genetic diversity of crop wild relatives is protected for the benefit of future generations.
Source: Bioversity International