A training guide for in situ conservation on-farm: version 1.

On-farm varietal biodiversity was studied through household surveys in two high potential production systems in Chitwan and Nawalparasi districts of the Nepal Terai and in Lunawada sub-district, Gujarat, India. Diversity was extremely low in Chaite rice in the Nepal study area (weighted diversity 0.04) and low in main season rice in the India study area (weighted diversity 0.34). In both areas, one cultivar dominated, CH 45 in Nepal and GR11 in India. In the India study area, biodiversity varied with the socio-economic group and better-off farmers had a greater varietal diversity. Participatory varietal selection (PVS) identified new varieties that farmers preferred. Their adoption by farmers increased on-farm varietal biodiversity within the three cropping seasons studied. Despite the commonly assumed uniformity of high potential production systems, the new varieties occupied specific niches in the farming system. Farmers' preferences for different varieties – there were large differences in quality traits and maturity period among the new varieties – should help to maintain biodiversity. Overall production is expected to increase as each niche becomes occupied increasingly by the best-adapted variety. PVS is a simple and powerful method of increasing food production in the high potential production systems that produce most of the developing world's grain.

Increasing genetic diversity by participatory varietal selection in high potential production systems in Nepal and India

Genetically modified plants are widely grown predominantly in North America and to a lesser extent in Australia, Argentina and China but their regions of production are expected to spread soon beyond these limited areas also reaching Europe where great controversy over the application of gene technology in agriculture persists. Currently, several cultivars of eight major crop plants are commercially available including canola, corn, cotton, potato, soybean, sugar beet, tobacco and tomato, but many more plants with new and combined multiple traits are close to registration. While currently agronomic traits (herbicide resistance, insect resistance) dominate, traits conferring “quality” traits (altered oil compositions, protein and starch contents) will begin to dominate within the next years. However, economically the most promising future lies in the development and marketing of crop plants expressing pharmaceutical or “nutraceuticals” (functional foods), and plants that express a number of different genes. From this it is clear that future agricultural and, ultimately, also natural ecosystems will be challenged by the large-scale introduction of entirely novel genes and gene products in new combinations at high frequencies all of which will have unknown impacts on their associated complex of non-target organisms, i.e. all organisms that are not targeted by the insecticidal protein. In times of severe global decline of biodiversity, pro-active precaution is necessary and careful consideration of the likely expected effects of transgenic plants on biodiversity of plants and insects is mandatory. In this paper possible implications of non-target effects for insect and plant biodiversity are discussed and a case example of such non-target effects is presented. In a multiple year research project, tritrophic and bitrophic effects of transgenic corn, expressing the gene from Bacillus thuringiensis (Bt-corn) that codes for the high expression of an insecticidal toxin (Cry1Ab), on the natural enemy species, Chrysoperla carnea (the green lacewing), was investigated. In these laboratory trials, we found prey-mediated effects of transgenic Bt-corn causing significantly higher mortality of C. carnea larvae. In further laboratory trials, we confirmed that the route of exposure (fed directly or via a herbivorous prey) and the origin of the Bt (from transgenic plants or incorporated into artificial diet) strongly influenced the degree of mortality. In choice feeding trials where C. carnea could choose between Spodoptera littoralis fed transgenic Bt-corn and S. littoralis fed non-transgenic corn, larger instars showed a significant preference for S. littoralis fed non-transgenic corn while this was not the case when the choice was between Bt- and isogenic corn fed aphids. Field implications of these findings could be multifold but will be difficult to assess because they interfere in very intricate ways with complex ecosystem processes that we still know only very little about. The future challenge in pest management will be to explore how transgenic plants can be incorporated as safe and effective components of IPM systems and what gene technology can contribute to the needs of a modern sustainable agriculture that avoids or reduces adverse impacts on biodiversity? For mainly economically motivated resistance management purposes, constitutive high expression of Bt-toxins in transgenic plants is promoted seeking to kill almost 100% of all susceptible (and if possible heterozygote resistant) target pest insects. However, for pest management this is usually not necessary. Control at or below an established economic injury level is sufficient for most pests and cropping systems. It is proposed that partially or moderately resistant plants expressing quantitative rather than single gene traits and affecting the target pest sub-lethally may provide a more meaningful contribution of agricultural biotechnology to modern sustainable agriculture. Some examples of such plants produced through conventional breeding are presented. Non-target effects may be less severe allowing for better incorporation of these plants into IPM or biological control programs using multiple control strategies, thereby, also reducing selection pressure for pest resistance development.

Implications of transgenic, insecticidal plants for insect and plant biodiversity

Conservation of agrobiodiversity is an important component of sustainable agriculture and is important internationally. Ex situ conservation in genebanks has been the dominant strategy. Recently, in situ conservation has been advocated as a complementary strategy. This review (1) defines the context of agrobiodiversity conservation, (2) discusses its value and measurement, (3) explores the advantages and disadvantages of ex situ and in situ conservation approaches, and (4) outlines the importance of seed exchange and ethical concerns.

http://azueroearthproject.org/wp-content/uploads/2012/11/A.C1002_Love_2007_eng.pdf

Agrobiodiversity: Its Value, Measurement, and Conservation in the Context of Sustainable Agriculture

There is a long-standing concern that modern plant breeding reduces crop genetic diversity, which may have consequences for the vulnerability of crops to changes in pests, diseases, climate and agricultural practices. Recent molecular assessments of genetic diversity changes in existing genepools of major agricultural crops may shed some light on the impact of plant breeding on crop genetic diversity. Reviewing published assessments revealed different impacts of plant breeding on improved genepools, not only narrowing or widening their genetic base, but also shifting their genetic background. In general, the genome-wide reduction of crop genetic diversity accompanying genetic improvement over time is minor, but allelic reduction at individual chromosomal segments is substantial. More efforts are needed to assess what proportion of lost alleles is associated with undesirable traits.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1479262106000104

D. Wood

Papers

Does plant breeding lead to a loss of genetic diversity