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Hung-Chang Huang
Agriculture & Agri-Food Canada,
Research Centre, Lethbridge, Alberta, Canada (Emeritus);
30-8051 Ash Street, Richmond, B.C.
Canada V6Y 3X6
e-mail: hchuang39@gmail.com

ABSTRACT

Agriculture is fundamental to the economy of the Asian and Pacific (ASPAC) region. Farmers in this region are facing challenges of feeding a large population with limited arable land and dwindling water resources. Developing agri-biotechnology, conventional or non-conventional, is of paramount importance in resolving problems associated with agricultural production. The application of agri-biotechnology could help countries of the ASPAC region in coping with poverty and hunger. However, in the present age of environmental sensitivity, all technologies developed for application in agriculture must be economically feasible, ecologically sound, environmentally safe and socially acceptable. Therefore, commercialization of agri-biotechnologies may only be possible if they are effective, safe, affordable and easy to use. Risk assessment is essential for application and adoption of eco-friendly agri-biotechnologies. Since farmers in developing countries of the ASPAC region are largely poor, research support by government and industry is crucial to ensure successful development and adoption of technologies that are beneficial to producers, agri-business people and the general public in the countries of this region.

Key words: Agriculture biotechnology, sustainable agriculture, risk assessment

INTRODUCTION

The world population has increased from 2.5 billion in 1950 to 6.8 billion today and is expected to reach 9 billion by 2050(62). Most of the population increase will be in developing countries, from 2.3 billion in 2009 to 5.6 billion in 2050. Fifty percent of the world's poorest people are small and resource-poor farmers(42) and a large proportion of poor people are in the Asia-Pacific (ASPAC) region. Population increase, poverty, and hunger are the major problems facing most of the countries in this region. For example, China(58) and India(60) are the largest countries in Asia, yet they are not self-sufficient in food supply.

Agricultural biotechnology, conventional or modern, plays a key role in counteracting problems associated with crop production. In the past, the global agriculture industry was focused on introducing yield-increasing technologies such as high-yield cultivars, crop protection products, fertilizers, improved irrigation systems, and introducing more land to agriculture(52). More importantly, use of chemical pesticides to control crop pests (diseases, insects and weeds) in conventional agriculture has impacted significantly on the environment. Zadoks(65) defined two distinct periods in recent history of crop protection: `chemism' for the period of 1940-1990 and `environmentalism' for the period of 1990 to present. In the era of `chemism', agricultural production relied heavily on the use of chemical pesticides and chemical fertilizers. Nevertheless, numerous chemical pesticides killed not only the targeted pest species but also destroyed numerous non-target species. The `one chemical kills all' approach for managing crop pests is detrimental to microbial biodiversity in agroecosystems. Therefore, heavy reliance on chemical pesticides and chemical fertilizers for crop production is no longer a viable option in the current era of `environmentalism'.

During the past two decades, dramatic progress has been made in the development of genetically modified organism (GMO) technologies for agriculture. The global area of GM crops increased from 1.7 million hectares in 1996 to 114.3 million hectares in 2007(42). In 2007, the number of countries planting GM crops increased to 23, and comprised 12 developing countries and 11 industrial countries(42). The area of GM cotton in 2007 reached 6.2 million hectares in Indiaand 3.8 million hectares in China(42). Despite rapid growth and spread of transgenic crops over the past decade, the potential environmental and social impact of GM crops remains controversial in many cases.

The impact of GMO and conventional non-GMO technologies may be positive or negative, depending upon the nature of individual technologies. This review discusses prospects and constraints of conventional and modern biotechnologies for the agricultural industry in the countries of the ASPAC region.

DEVELOPMENT AND APPLICATION OF AGRI-BIOTECHNOLOGY

Both conventional and biotechnological techniques have benefited agriculture immensely by making food, animal feed and clothing more plentiful and affordable. The prospects of developing conventional and modern biotechnologies for agriculture are discussed below.

Conventional agri-biotechnology

Prior to the introduction of modern biotechnology, agricuture has relied on conventional technologies to increase crop production and food supply. There are numerous examples of success on the development and applications of these technologies such as conventional breeding to increase crop yield and improve crop resistance to diseases and cultural practices to control crop pests (pathogens, insects and weeds) and improve soil fertility.

Conventional crop breeding

Conventional breeding methods were used to alter the genetic components of domesticated crops and new cultivars were usually generated from the same species or same genus. These techniques have been successfully used in breeding in many cases. Wheat breeding during the Green Revolution in Mexico(10) and in Asia(60) in 1950s and 1960s is a good example of successful application of this technology. Through cross-breeding of wheat varieties developed by Dr. Norman Borlaug in Mexico and local species in India, new wheat varieties with high yield were developed. The use of high yield varieties resulted in increase of wheat production from 12 million tons a year in the early 1960s to 70 million tons a year in late 1990s in India(60).

Breeding is considered the most economical means of control of crop diseases because it eliminates the need for pesticides. In Canada, three alfalfa cultivars (Barrier, AC Blue J and AC Longview) with resistance to Verticillium wilt (the most important disease of alfalfa caused by Verticillium albo-atrum) and high yield were developed through conventional breeding(1, 28). The economic benefits of growing these disease-resistant cultivars in western Canada were estimated at $26.6 million (Canadian dollars) per year(59). Developing effective and efficient screening techniques are essential to the success of crop breeding for pest resistance(30).

Biological control of crop diseases

Biological control is recognized as a sound strategy for the management of crop diseases and is considered a viable alternative to chemical control. There are two different approaches to achieve biological control of plant diseases: 1) direct approach (or inundative approach) by deliberate use of specific biological control agents such as antagonistic microorganisms or hyperparasites, and 2) indirect approaches which involve cultivation strategies, such as field sanitation, crop rotation(20, 27) and organic soil amendment(31).

Numerous reports indicate that application of antagonistic or hyperparasitic microorganisms are effective in the control of crop diseases. For example, application of Coniothyrium minitans, a mycoparasite of the fungal pathogen Sclerotinia sclerotiorum, was effective in the control of Sclerotinia diseases (caused by S. sclerotiorum) on sunflower(11, 26), lettuce(13), bean(35) and rapeseed(45). In 1997, C. minitans was released as a commercial product Contans® by Prophyta in Germany(47) and Koni® by Bioved Ltd. in Hungary (www.bioved.hu) for controlling Sclerotinia diseases in crops. Other reports showed that rhizobacteria such as Erwinia rhapontici and Rhizobium leguminosarum bv. viceae were effective agents for controlling damping-off of safflower, canola, field pea, and sugar beet caused by Pythium spp.(6, 7, 33). These examples and many others suggest the possibility of using beneficial microorganisms (fungi, bacteria etc) for the management of crop pests.

Crop rotation

Crop rotation is a cultivation strategy which has long been regarded as an effective method for control of plant diseases. A long-term crop rotation study (1959-2000) in Hokkaido, Japan, showed that, during the period of 1989-2000, the average annual seed yield of bean was 2380 kg/ha in the treatment of 6-year rotation (with a rotation sequence of potato, sugar beet, oat, kidney bean, winter wheat, and red clover), compared to the annual seed yield of 970 kg/ha in the treatment of bean monoculture, representing a 59% yield loss in bean monoculture(37). The build-up of soilborne pathogens such as Pythium spp.(37, 43) is responsible for the severe loss of bean in monoculture. Other studies in Canada show that a rotation of legume crops with cereals is superior to cereal monoculture because: 1) the legume-based rotation system improves the yield of cereal crops(14, 64), 2) improves fertility and quality of soils(8, 25), and 3) increases soil microbial populations including fungi, bacteria and actinomycetes(9). Research on the sequence of crops is of paramount importance in determining success of a crop rotation system. However, crop rotation research is of long-term nature and it needs long-term commitments from government to support this type of research.

Function and integration of agri-biotechnology

Development of agricultural biotechnologies must consider their environmental, ecological, social, and economic consequences. For example, methyl bromide is an effective chemical for controlling plant pathogens and insect pests, but it has consequential environmental effects like its contribution to the depletion of the ozone layer. According to the UN Montreal Protocol signed by 160 countries, governments agreed to phase out the use of methyl bromide by 2005 for developed countries and by 2015 for developing countries (http://www.pan-uk.org/pestnews/Issue/pn38/pn38p9.htm).This suggests the need to develop environmentally friendly methods for controlling crop pests. Studies showed that certain agricultural wastes contain allelopathic chemicals that are harmful to soilborne pathogens(31, 51) and, therefore, can be used to control plant diseases. For example, crucifers (Brassica juncea; B. napus etc.) are rich in Glucosinolates (1'-Thio-B-D-glucopyranosyl-alkyl-Z-N-hydroximin sulphate esters) (GSL). Enzymatic degradation of GSL in crucifers results in the production of isothiocyanates (ITC) which are toxic to plant pathogens. This presents the possibility of developing biofumigants using ITC-containing crucifers for use as an alternative to methyl bromide for control of crop pests(18, 19), http://www.pi.csiro.au/biofumigation2008/links/1stBiofumigationSym_Italy2004_Abstracts.pdf).

In the past, most agri-biotechnologies have focused on products developed for a singular purpose such as a microbial agent specifically designed to control plant disease or to improve soil fertility. Future development of technologies should shift their focus from singular to multi-purpose technologies to increase their market potential. One example of multi-purpose technologies is the treatment of pea seeds with the nitrogen fixing bacterium R. leguminosarum bv. viceae for pea production(7, 33). This microbial seed treatment technique is effective in controlling Pythium damping-off of peas, enhancing growth of pea plants, and increasing population of this beneficial bacterium in the soil. Thus, R. leguminosarum bv. viceae is an agent with multitasking properties because it is a biopesticide, a biofertilizer and a symbiotic bacterium for nitrogen-fixing legume crops such as Pisum, Lens, Vicia and Lathyrus(12, 33). In addition to developing biotechnologies with multifunctional properties, integration of diverse methods such as cultural method (crop rotation), physical method (organic amendments, microorganisms) and breeding method (disease resistant cultivars) are important aspects to consider in the practice of sustainable agriculture(29).

Modern agri-biotechnology

DNA-based technology has created a significant impact on many aspects of agriculture in the world. It is used in the development of GMOs and in diagnostics. Molecular technology has potential to fill the gaps found in conventional research methods and has become a strong driving force to change agricultural practices in the Asia-Pacific region, and in the world.

GMO for crop production

GMO technology can be used to accelerate or enhance breeding process for development of crops that are more adaptive to the effects of climate change(42). The use of this technology in crop production and crop protection has increased in the number of crops and number of countries over the past two decades. GMO potentially reduces negative environmental impacts caused by the conventional technologies in crop production such as the use of synthetic pesticides to control crop pests. For example, since the release of Bt (Bacillus thuringiensis) cotton in China in 1996/1997, cultivation of this crop reached 3.8 million hectares (or 69% of the 5.5 million hectares of cotton) by 2007(42). In India, Bt cotton was introduced in 2002 and the area of this crop reached 6.2 million hectares by 2007(42). This indicates a successful integration of this transgenic crop by small farmers in these two largest countries in Asia. In Taiwan, transgenic lines of papaya with resistanceto Papaya Ring Spot Virus virus (PRSV) were developed(4, 17). These PRSV resistant lines also showed a high degree of broad-spectrum resistance against PRSV strains from Hawaii, Thailand, and Mexico under greenhouse conditions(4) and in the field(5).

Rice is the most important food crop in the ASPAC region. Research on transgenic rice is an important focus for the countries of this region to develop new lines with resistance to pests and diseases. Studies in China indicate that insect and disease resistant GM rice increased yields by 2 to 6% and reduced pesticide use by 17 kg/ha (or nearly 80%)(41).

Other instances in the development and application of transgenic technologies include the generation of GM crops with tolerance to environmental stress. Drought, flood, and temperature change is predicted to become more prevalent and severe, indicating a need to develop crops that are well adapted to changing climatic conditions(42). Identification and use of stress tolerance genes to improve crop production and reduce post-harvest losses are some of the important future priorities(67). A recent drought in Northern China brought a shift in focus to developing drought-resistant transgenic crops due to growing concerns over water shortages in that region(41). Crop loss at post-harvest stage is another serious problem in many countries. Studies in Taiwan showed that transgenic expression of isopentenyltransferase (ipt) in broccoli (Brassica oleracea var. italica) enhanced shelf-life and reduced post-harvest losses(16). Thus, DNA marker technology and molecular marker-assisted selection (MAS) will likely be the driving force for crop improvement both in developed and developing countries.

DNA-based technology for diagnostics

DNA-based molecular techiniques have been used in the identification of plants and microorganisms. Many countries have established strict quarantine regulations for import and export of plant germplasms. There is a need for rapid, specific, and highly sensitive diagnostic methods for detection of quarantine pests in pedigreed seeds or plant materials. For example, the conventional procedures for testing common blight (Xanthomonas campestris pv. phaseoli) (XCP) and halo blight (Pseudomonas syringae pv. phaseolicola) (PSP) pathogens in bean seed consist of plant inoculation techniques and plating seed-soak extracts on differential and semiselective media. This method is time-consuming and labor intensive. A quick PCR-based procedure was developed for concurrent detection of these two bacterial pathogens (common blight and halo blight) in bean seed(3). In combination, X4 (common blight) and HB (halo blight) primers successfully detected individual and mixed infections of bean common and halo blights and yielded distinctive DNA fragments from batches containing as few as 1 infected seed in 10,000 seeds(3).

Real time PCR assays were developed to detect and quantify the transgene DNA of a commercially released Bt-corn hybrid (DKC42-23)(66). The real time PCR assays are proven useful for investigating the persistence of transgene DNA derived from the MON863 event in soil environments(66). Other studies showed that real-time PCR assay is more sensitive than conventional PCR for detection of Colletotrichum lagenarium, an anthracnose pathogen of curcurbits, in diseased plant tissues (C. P. Kuan, personal communication).

RISK ASSESSMENT AND REGULATION OF AGRI-BIOTECHNOLOGY

All agri-biotechnologies developed by traditional or frontier technologies must be properly assessed for their environmental and social impact. The impact of GMO and conventional non-GMO technologies may be positive or negative, depending on the nature of the organisms involved and their effects on target and non-target organisms.

GMO biotechnology

DNA derived from plants is an important source for soil DNA(15,24,63), and thus, any new genetic material carried by plants can contribute to the diversity of the soil DNA pool(66). Genetically modified (GM) crops have been used commercially for more than 10 years. Available impact studies of insect-resistant and herbicide-tolerant crops show that these technologies are beneficial to farmers and consumers, with economic, environmental, and nutritional benefits(53). However, widespread public concern has led to a complex regulatory system governing the use of GM crops. Overregulation has become a real threat for the further development and use of GM crops(53).

Bt cotton was among the first genetically modified (GM) crops to be used in commercial agriculture for control of certain lepidopteran insects. Qaim and de Janvry(54) analyzed effects of insect-resistant Bt cotton on pesticide use and agricultural productivity in Argentina and found that the technology reduced application rates of toxic chemical pesticides by 50%, while significantly increasing yields. Rapid resistance buildup and associated pest outbreaks appear to be unlikelyif minimum non-Bt refuge areas are maintained. Qaim and de Janvry(54) concluded that Bt cotton could cause significant economic and ecological benefits, provided that pest populations would not rapidly overcome this resistance. However, conclusive statements about the technology's sustainability require longer-term monitoring of possible secondary effects and farming practices in maintaining refuges(54). In China, debate on the impact of Bt cotton is growing as a result of rapid adoption of this transgenic crop in that country(22). Use of Bt cotton has seen a significant 10% increase in cotton yield and a 60% (or 35 kg/ha) reduction in pesticide use(41). However, major concerns with Bt cotton in China remain, including problems such as gene flow, insect resistance, effects on non-target insects, soil ecosystem and food safety(22).

Bt corn provides another example of biosafety concerns such as horizontal gene transfer over the current use of transgenic crops. In a three-year field trial of the Bt hybrid corn DKC42-23 (derived from MON863 and commercially released in Canada in 2003), Zhu et al.(66) found that under continuous cultivation of DKC42-23, its transgenic DNA signature was detectable in the field plots all-year around. The study also found that the neomycin phosphotransferase (nptII) gene carried by DKC42-23 could be taken up and integrated into naturally competent Pseudomonas stutzeri pMR7 cells, leading to the restoration of the antibiotic resistance of P. stutzeri pMR7. However, after the cultivation of a soybean line in the same plots for the subsequent growing season, the presence of transgenic DKC42-23 DNA was reduced to undetectable levels at the end of that growing season. Zhu et al.(66) conclude that existing corn-soybean crop rotation practices reduce the availability of transgene DNA in soil, and thus minimize the risks that might be attributable to horizontal gene transfer. Even though some microcosm experiments using marker-rescue systems demonstrated that naturally competent bacterial cells were able to take up transgene DNA through homologous recombination in the laboratory(23, 49, 50, 61), there has been no evidence showing the occurrence of gene transfer from transgenic plants to indigenous bacteria in fields(66).

The possibility of gene transfer from Roundup Ready® (RR) canola (Brassica napus event RT73) to the fungal pathogen, Sclerotinia sclerotiorum, was investigated in a two-year field trial(40). This study reveals that the complete cp4-enolpyruvylshikimate-3-phosphate synthase (cp4epsps) gene confers glyphosate resistance in RR canola® is undetectable in any of the sclerotia of S. sclerotiorum collected from diseased stems of RR canola®(40). However, a transgene fragment was detected in a single sclerotium tissue recovered from a RR canola plant. This fragment was not stably integrated as the transgene fragment could not be detected in mycelia produced from germination of this sclerotium(40). This finding(40) confirms other reports of animal feeding trials that the complete transgene cp4epsps (1363 bp) of RR canola® is rapidly degraded upon release(2,56,57).

Non-GMO biotechnology

Like GMO technologies, the potential risks of conventional or non-GMO biotechnologies should also be properly assessed for potential detrimental outcome. Take biological control of plant disease for example, E. rhapontici(6,46) and R. leguminosarum bv. viceae (7,33) are both effective agents for control of damping-off of pulse crops caused by Pythium spp. but their effects on non-target microorganisms are drastically different. The environmental risk is low for R. leguminosarum bv. viceae because it controls crop diseases and improves soil fertility through its symbiotic relationships with some legume crops(32). In contrast, the environmental risk of E. rhapontici is high because it is a pathogen causing pink seed disease of pea(34), bean(36), lentil, chickpea(38) and wheat(48,55) as well as crown rot of other plants(39). Therefore, R. leguminosarum bv. viceae is more eco-friendly than E. rhapontici(32).

Regulation of agri-biotechnology

All agricultural activities constitute human intervention into natural systems and processes, and all efforts to improve crops involve a degree of genetic manipulation(53). Positive and negative impacts of every biotechnology should be carefully considered to provide scientific information for policymakers to establish regulations to safely implement new technologies. However, different regulation process may also affect the efficiency by which agri-biotechnology can be applied to existing farms. For example, the number of biological control products registered in Japan varied under different regulations, 11 biopesticides registered under the regulations of Chemical Pesticides in the period of 1954-1993 and 32 biopesticides registered under the new Guideline for Microbial Pest Control which was approved in 1998(44). Over-regulation may become one of the major constraints for implementing biotechnological applications(53). Cook(21) suggested that the same protocols to assess the effect in the environment of genetically modified plants should apply to plants derived through conventional breeding.

CONCLUSIONS AND RECOMMENDATIONS

The continuing increase in population will lead to further increased demand for food and reduced per capita availability of arable land and irrigation water in the Asia-Pacific region. To cope with population pressure and climate change in this region, the goal of agriculture should emphasize the need to develop crops with improved yield, improved resistance to pests and increased tolerance to environmental stresses such as drought and salt injuries. Agricultural biotechnologies (conventional and frontier technologies) could provide farmers with tools to achieve the goal of increasing crop yield to maintain sustainable food production and alleviate problems of poverty and hunger in the countries of this region.

In the present era of `environmentalism'(65), public demands from the agriculture industry will emphasize the need to produce low cost food with minimum impact on the environment. Heavy reliance on chemical pesticides and chemical fertilizers for crop production is no longer acceptable because of their potential harmful effects to agro-ecosystems and the environment. Therefore, farmers must adopt more eco-friendly technologies for sustainable agriculture and sustainable intensification of agricultural systems(52,60).

Adoption of new agri-biotechnology often comes with apprehension due to uncertainty of its impact. Risk assessment of traditional and GMO biotechnologies is critical in gaining public confidence and broad acceptance of the technology. Thus, developing a biotechnology for commercial application must be based on: 1) foundational research to collect baseline data such as efficacy and efficiency; 2) impact research such as effects of the technology on food safety, biodiversity, soil and water quality, gene flow and its consequences; and 3) risk reduction research such as development of risk assessment methods and containment practices to restrict unwanted effects of the technology. Farmers will apply biotechnology in crop production only if the technology is effective, affordable and safe. Since farmers in the Asia-Pacific region are largely resource-poor, they lack the capacity in dealing with risk problems associated with agri-biotechnologies. Government agencies and private industries should bear the high investment costs of research on benefits and risks of agri-biotechnology in the areas of financial needs, scientific supports, and policy making. Effective and safe biotechnology would contribute to a more sustainable agriculture and better food security in developed and developing countries. Development and application of effective and safe agri-biotechnologies tailored to the specific needs of farmers in the countries of the ASPAC region may lead to creation of another Green Revolution in this region.

ACKNOWLEDGEMENTS

Dr. Hung-Chang Huang (Emeritus Principal Research Scientist of Agriculture and Agri-Food Canada) is a visiting Chair Professor at the Taiwan Agricultural Research Institute, Wufeng, Taichung, Taiwan, sponsored by the National Science Council, Taiwan.

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