Extent of Bollworm and Sucking Pest Damage on Modern and Traditional Cotton Species and Potential for Breeding in Organic Cotton

Resistance against cotton bollworm is one of the main arguments for the use of genetically modified (GM) Bt cotton around the globe. The use of GM is prohibited in organic systems and thus the remunerative value of organic cotton cultivation depends on effective bollworm control. In this study, we investigated the extent of bollworm and sucking pest damage in 68 different hybrid and varietal lines of Gossypium hirsutum and varietal lines of G. arboreum at two different locations with contrasting soil fertility and water dynamics. The damage potential of bollworms was assessed from open capsules at two time points. Sucking pests were assessed at three time points using a scoring method. G. arboreum varietal lines and G. hirsutum hybrids were on average significantly more tolerant than G. hirsutum varietal lines to bollworm under fertile and irrigated situations. For sucking pests, the G. arboreum varietal lines were clearly more tolerant than G. hirsutum hybrids and varietal lines. Since, recently, pink bollworm (Pectinophora gossypiella) became resistant against Bt cotton and pressure of sucking pests severely increased, screening of genetic resources and systems-based cotton breeding for bollworm and sucking pest tolerance will improve sustainability of organic and conventional cotton production

Influence of the Fast Spread of Bt Cotton on Organic Cotton Production: Examples from India and Burkina Faso

COTTON is grown in more than 120 countries by over 20 million cotton producers on 35 million ha in 2012 (Truscott, 2010, www.fas.usda.gov). In 2011, around 27 million tons of cotton were produced, mostly by smallholder producers in 'developing' countries which cultivate cotton as a cash crop on their own land averaging under 2 ha in size, or as contracted workers for bigger land owners. Cotton is usually grown as a monoculture. In industrialised countries, the level of mechanisation is high, thus cotton production does not provide a lot of work in rural communities. In contrast, in developing countries, the cultivation and harvest is mostly done by hand labour and thus provides a lot of work for the rural population. Cotton, particularly as a monoculture, uses significant amounts of pesticides, fertilisers, fossil fuels and water (Truscott, 2010). There are four commercially exploited cotton species: Gossypium hirsutum and G. barbadense, the 'New World Species', and G. arboreum and G. herbaceum, the Old World Species. Though Old World cottons are still grown in some areas of Africa and Asia, they have been almost totally replaced by New World cottons. Most dominant today are G. hirsutum cultivars, which are spread across 45 countries. About 90% of the annual global cotton harvest is derived from G. hirsutum. One negative outcome of the wide cultivation of G. hirsutum cultivars is the increased pest attacks, particularly by the American bollworm. Hence, cotton cultivation had a very bad reputation as the single largest user of pesticides in the world (Truscott, 2010). In the mid-1990s, conventional cotton production posed a serious threat to the environment, farmers' health and the economy. At one stage cotton accounted for the use of 15% of the world's pesticides and 25% of the world's insecticides.This resulted in two major responses. One response was the development of genetically modified (GM) insect-resistant cotton cultivars, which were rapidly adopted by many countries since its first commercial introduction in 1996. Approximately 82% of the world's cotton-growing area was grown under genetically modified cotton in 2011 (www.isaaa.org2). The other response was the adoption of organic methods of cotton production by farmers who believed that holistic, earth-friendly responses, optimised crop rotation and organic fertiliser could reverse the trend of the soaring use of chemical pesticides. The rapid spread of GM seeds in cotton has resulted in problems for the organic cotton sector, a few of which can be briefly examined, taking India and Burkina Faso as examples (Truscott, 2010)

Extent of Bollworm and Sucking Pest Damage on Modern and Traditional Cotton Species and Potential for Breeding in Organic Cotton

Resistance against cotton bollworm is one of the main arguments for the use of genetically modified (GM) Bt cotton around the globe. The use of GM is prohibited in organic systems and thus the remunerative value of organic cotton cultivation depends on effective bollworm control. In this study, we investigated the extent of bollworm and sucking pest damage in 68 different hybrid and varietal lines of Gossypium hirsutum and varietal lines of G. arboreum at two different locations with contrasting soil fertility and water dynamics. The damage potential of bollworms was assessed from open capsules at two time points. Sucking pests were assessed at three time points using a scoring method. G. arboreum varietal lines and G. hirsutum hybrids were on average significantly more tolerant than G. hirsutum varietal lines to bollworm under fertile and irrigated situations. For sucking pests, the G. arboreum varietal lines were clearly more tolerant than G. hirsutum hybrids and varietal lines. Since, recently, pink bollworm (Pectinophora gossypiella) became resistant against Bt cotton and pressure of sucking pests severely increased, screening of genetic resources and systems-based cotton breeding for bollworm and sucking pest tolerance will improve sustainability of organic and conventional cotton production