Riis Lisbeth, Bellotti Anthony Charles, Castaño Oscar
Centro International de Agricultural Tropical, Pest and Disease Management Unit, A.A. 6713 Cali, Colombia SA.
J Econ Entomol. 2003 Dec;96(6):1915-21.
The hypothesis that cyanogenic potential in cassava roots deters polyphagous insects in the field is relevant to current efforts to reduce or eliminate the cyanogenic potential in cassava. To test this hypothesis, experiments were conducted in the field under natural selection pressure of the polyphagous root feeder Cyrtomenus bergi Froeschner (Hemiptera: Cydnidae). A number of cassava varieties (33) as well as 13 cassava siblings and their parental clone, each representing a determined level of cyanogenic potential (CNP), were scored for damage caused by C. bergi and related to CNP and nonglycosidic cyanogens, measured as hydrogen cyanide. Additionally, 161 low-CNP varieties (< 50 ppm hydrogen cyanide, fresh weight) from the cassava germplasm core collection at Centro Internacional de Agricultura Tropical (CIAT) were screened for resistance/tolerance to C. bergi. Low root damage scores were registered at all levels of CNP. Nevertheless, CNP and yield (or root size) partly explained the damage in cassava siblings (r2 = 0.82) and different cassava varieties (r2 = 0.42), but only when mean values of damage scores were used. This relation was only significant in one of two crop cycles. A logistic model describes the underlying negative relation between CNP and damage. An exponential model describes the underlying negative relation between root size and damage. Damage, caused by C. bergi feeding, released nonglycosidic cyanogens, and an exponential model fits the underlying positive relation. Fifteen low-CNP clones were selected for potential resistance/tolerance against C. bergi.
木薯根中的生氰潜力可在田间阻止多食性昆虫这一假说，与当前降低或消除木薯生氰潜力的努力相关。为验证这一假说，在多食性根食性昆虫伯格圆盾蝽（半翅目：土蝽科）的自然选择压力下于田间开展了实验。对多个木薯品种（33个）以及13个木薯同胞植株及其亲本无性系进行了评分，每个品种都代表了一定水平的生氰潜力（CNP），评估伯格圆盾蝽造成的损害，并将其与以氰化氢衡量的CNP和非糖苷类氰化物相关联。此外，对国际热带农业中心（CIAT）木薯种质核心库中的161个低CNP品种（鲜重中氰化氢含量<50 ppm）进行了伯格圆盾蝽抗性/耐受性筛选。在所有CNP水平下均记录到较低的根部损害评分。然而，CNP和产量（或根大小）在一定程度上解释了木薯同胞植株（r2 = 0.82）和不同木薯品种（r2 = 0.42）中的损害情况，但前提是使用损害评分的平均值。这种关系仅在两个作物周期中的一个中显著。一个逻辑模型描述了CNP与损害之间潜在的负相关关系。一个指数模型描述了根大小与损害之间潜在的负相关关系。伯格圆盾蝽取食造成的损害会释放非糖苷类氰化物，一个指数模型符合潜在的正相关关系。挑选了15个低CNP无性系用于对伯格圆盾蝽的潜在抗性/耐受性研究。
