Today we face many critical issues in agriculture: (a) an exponentially growing human population; (b) recurrent famine; (c) the destruction of natural landscapes such as tropical rain forests to extend agriculture to previously unused lands; (d) the exodus of human civilization from rural communities to cities; (e) the destruction of environmental quality resulting from exposure to agrochemicals, erosion of soils and salinization of soils as well as exhaustion and contamination of fresh water resources; (f) the loss of biodiversity through monocropping and the destruction of natural habitats; (g) the reliance of agricultural production, transport, and storage systems on fossil fuel; (h) the acquisition and concentration of agricultural wealth by multinational corporations; and (i) an issuant lack of knowledge by a growing proportion of human civilization on how to cultivate, prepare, and preserve food. The United Nations Food and Agriculture Organization predicts that agricultural productivity in the world will be able to sustain the growing human population by 2030 but hundreds of millions of people in developing countries will remain hungry and environmental problems caused by agriculture will remain serious (FAO 2002). By 2025,83% of the expected global population of 8.5.2 billion will be in the developing world (United Nations 2002). The social consequences are obvious. Food is a basic human need and right. How can we sustain the food needs of the earth's biotic community in the 21st century and beyond while preserving environmental quality and the diversity and quality of life on earth (Time, August 26, 2002)? What solutions can biotechnology provide to address these problems (Khush and Bar 2001)?
In the last century, the Green Revolution addressed the food needs of the human population through the development of high yielding and early maturing varieties that performed under favorable conditions of nutrition and moisture (Khush 2001). Prior to this time, increased production was dependent on expansion of land area for crop production. In recent years, yield gain through breeding has not kept pace with population growth (Serageldin 1999). Furthermore, genotype is not the only factor limiting productivity. Abiotic and biotic stress factors also contribute to losses in yield both pre and postharvest. For example, in Asia these technical constraints on rice production may reduce production by 23% (Evanson et al. 1996). Socioeconomic constraints also contribute to practices that affect yield. Ninety percent of the world's rice is grown in Asia on small farms with limited resources. Thus, decisions are made based on economics rather than achieving technically optimum yields. Despite much research on the application of biotechnology to solve these technical production constraints, biotechnology has had limited impact to date on rice production in Asia (Houssain 1997). This has been due in part to the reluctance to adopt the use of genetically modified organisms (GMOs) in most countries of Asia. China is the only Asian country that has embraced biotechnology on any notable scale as a solution to technical production constraints in agriculture (Huang et al. 2002; Pray et al. 2002). For example, over four million smallholders have been able to increase yield and reduce pesticide costs and adverse health effects of applying pesticides by using transgenic Bt-cotton (Pray et al. 2002). Another constraint relates to the complexities of ownership rights that can delay and discourage the scientific application of biotechnology discoveries and their transfer to the market place (Kowalski et al. 2002). Finally, public concern about the safety of consuming GMOs has left tons of food aid containing transgenic corn untouched in
Zimbabwe and Zambia despite the prediction that 13 million people are now at risk of famine due to severe drought in Southern Africa (Paarlberg 2002). Organic growers worldwide have rejected GMOs as an allied technology to disease and pest management. Late blight in potato is still very difficult to control in these farming systems (Mader et al. 2002).
Biotechnology as applied to plant protection against fungal pathogens has seen three phases of development over the last 20 years: (a) the application of molecular markers to marker-assisted breeding and the map-based cloning of genes associated with disease resistance and the plant defense response as well as to study fungal pathogenesis and host recognition; (b) the development of routine methods for stable and transient transformation of plants and fungi with foreign genes; and (c) the application of New Biology approaches to study plant growth and development and mechanisms of plant response to abiotic and biotic stresses and fungal pathogen-esis. The purpose of this short review is to provide a critical analysis of these recent biotechnological approaches to plant protection with emphasis on fungal pathogens.
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