QTL Analysis Of Field Resistance To Brown Leaf Spot (Cercosporidium Henningsii) In An F₁ Population Of Non-inbred Parents In Cassava

Cassava Brown Leaf Spot (BLS) is a major leaf disease of cassava caused by Cercosporidium henningsii, the disease mainly destroyed cassava leaves. The fully formed lesions are large, necrotic spots, circular or irregular in shape and dark brown on both surfaces of the leaf. The development of these lesions in affected leaves generally results in leaf drop, leading to a direct loss in tuber yield. The disease has a wide distribution and has been reported that brown leaf spot of cassava is found wherever the crop is grown. Cassava brown leaf spot is often happened in our country too.People have attached importance to the resistant heredity of cassava brown leaf spot and breeding for disease resistance, and plant's disease resistance is the most effective method of controlling diseases. The heterozygous character of cassava genome is available to choose better clones but it diffuse the hybrid breeding. Because heterozygosity make severe separation of F1 population and it's not easy to foresee selected genetic advantage. Traditional breeding for resistant variety has three disadvantage, long cycles for breeding, low efficiency and weak in foreseeability. In most cases, levels of efficiency in selection at early generations and characterization in later generations are the tangible deliverables from MASSo One segregated population with 184 lines hybridized between non-inbred Wenchang red resistant to brown leaf spot and susceptive SC6 was used to SSR analysis and screening of QTL for resistance. This was a good method to estimate the gene's location, the style and size of the gene's effect, and the mode of effect, etc. This work can provide research basis for Molecular Marker-assisted Selection, new genes finding and resource improvement.Disease response has been investigated in field condition with artificial inoculation. Disease index (DI) of individuals were acquired in 3 environments including shooting stage and rooting stage during 2004-2005. It is shown that: distribution of DI of individuals in 3 environments all is biased-normal shown double peak state, indicate there may be main effective genes resistant to brown leaf spot.17 polymorphism SSR primers were discovered from more than 400 SSR primers by amplified to resistance and susceptive gene pool and double parents. And 50 diversity...