Evaluation and characterisation of twenty-two Soyabean [Glycine max (L) MERRILL] lines under rust infested and non-infested conditions
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Soyabean [Glycine Max (L) Merril] is an important leguminous crop, mainly used for human nutrition and livestock feed, as well as improving soil. The major constraint or threat to soyabean production is soyabean rust, a devastating disease that can reduce yield by up to 100% in susceptible varieties. Soyabean rust resistant varieties could be a major component of an integrated soyabean rust management, if resistance can be identified in adapted and productive germplasm. An experiment was planted out at Rattray Arnold Research StationƒËlongitude 310131S,latitude 170161E, altitude 1360mƒÍ to characterize available sources of soyabean rust resistance by screening them under infested and non infested conditions.The experiment consisted of twenty-two soyabean lines that were planted in a split plot design with three replications. The main plot was the fungicide with 2 levels and sub-plot was variety with 22 levels. Punch Extra (Flusilazole/Carbendazim) was applied at a rate of 400 ml in 425 litres of water at 50, 70 and 90 days after planting. The gross plot was 21.6 m2 and net plot was 7.2 m2. Measurements taken included number of days from planting to 95% pod maturity, pod clearance scores, plant height in centimetres, lodged plants at maturity, mass of 100 seeds in grams, seed appearance scores, percentage crude protein content,green stem scores at first pod shattering and seed yield in kilograms per hectare. Significant differences were obtained for most variables measured (P<0.001). Thirteen varieties were identified as resistant to soyabean rust. These varieties were S731/6/57, SS722/6/28, S727/6/20, SS744/6/17, S717/6/17, S727/6/41, S748/6/96, S744/6/29, S727/6/55, S727/6/33, S726/6/9, S723/6/8 and S727/6/60. The study showed that seed mass; visual scores and seed yield in kilograms per hectare were indicators of rust resistance or susceptibility. For instance, the seed mass of a resistant variety under infested and non-infested conditions does not change much and therefore such a trait can be used to predict rust resistance and susceptibility. It is recommended that these varieties be used as sources of resistance in soyabean-breeding programmes.