Bt cotton plants, with bollworm resistant trait, have been widely adopted since introduced in India in 2002. As a proactive measure to prevent evolution of resistance to Bt protein(s), it was approved for commercial cultivation with a stipulation of structured refuge of minimum 20% of the Bt area, constituted by plants that do not produce Bt toxins and thus allow growth and development of population of Bt susceptible pests. Though the refuge cotton seeds are provided in a separate pouch within each Bt cotton seed packet, Indian farmers have been reluctant to sow refuge. To find out a method for ensured refuge planting, we experimented with ‘built-in-refuge’ (BIR) in which non-Bt cotton seeds were blended with Bt cotton seeds in various proportions ie 5,10, 50% along with 20% recommended structured refuge and each treatment was evaluated in terms of fruiting body damage by major cotton lepidopterans, relative to the regulator stipulated 20% non-Bt structured refuge at five locations during cotton growing season of 2012–13. A major outcome from this study was that treatments with 5 and 10% non-Bt blends with bollga0rd-II were as effective as the 20% structured refuge, based on fruiting body damage due to bollworms, a key factor in managing Bt resistance without any compromise to the seed cotton yield. It can be concluded that the seed blend technology is a good option to impose refugia compliance to delay resistance in Bt cotton to bollworms in a country having lesser alternate hosts available for the target bollworms during the season and voluntary compliance of refuge is absent.

中文翻译：

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评估 Bollgard-II 与相应的非 Bt 杂交种子混合物中棉铃虫损伤和产量损失，作为棉花中的“内置避难所”

具有抗棉铃虫性状的 Bt 棉花植物自 2002 年引入印度以来已被广泛采用。作为防止对 Bt 蛋白抗性进化的积极措施，它被批准用于商业种植，规定了最低限度的结构化避难所Bt 区域的 20%，由不产生 Bt 毒素的植物构成，因此允许 Bt 易感害虫种群的生长和发育。尽管每个 Bt 棉花种子包内的单独袋子中都提供了避难棉种子，但印度农民一直不愿意播种避难所。为了找到一种确保避难所种植的方法，我们试验了“内置避难所”（BIR），其中非 Bt 棉花种子与 Bt 棉花种子以不同比例混合，即 5,10，50% 和 20% 推荐的结构化避难所，每个处理都根据主要棉花鳞翅目昆虫对子实体的损害进行评估，相对于监管机构规定的 2012-13 棉花生长季节期间五个地点的 20% 非 Bt 结构化避难所。这项研究的一个主要结果是，根据棉铃虫引起的子实体损伤，用 5% 和 10% 的非 Bt 混合物与 bollga0rd-II 处理与 20% 结构化避难所一样有效，这是管理 Bt 抗性的关键因素，没有任何影响籽棉产量。可以得出结论，种子混合技术是一个很好的选择，在一个国家，在一个季节内可用于目标棉铃虫的替代宿主较少且没有自愿遵守避难所的国家，可以强制遵守避难所以延迟 Bt 棉花对棉铃虫的抗性。