Materials and methods Two experiments were carried out to assess the potential yields and screen the germplasm for resistance/tolerance to Napier grass stunting disease. Experiment 1 was carried out at KARI Kitale, Trans Nzoia District which lies in the Upper Midland 4 (UM4) agro-ecological zone. Fifty two accessions/varieties were planted in a Randomized Complete Block Design replicated three times in 2 mX3 m plots. The spacing was 1m between rows and 50cm between plants in a row. Phosphate fertilizer was applied at the rate of 20kg P205 ha-1 at planting. The plots were cut back to a basal height of 5 cm, 4 months after planting and top-dressed with 60 kg N ha-1. This was followed by 3 harvests at intervals of 8 weeks to determine herbage dry matter yields. Analysis of variance was carried using SAS (2001).
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Experiment 2 evaluated Napier grass accessions for resistance/tolerance to stunting disease. This study was carried out at the Farmers Training Centre (FTC) in Busia District. A plot was selected in the middle of a stunting diseased Napier grass field. The old Napier grass stools were uprooted and the field thoroughly cleared to ensure that there were no remnants of plantlets that could regrow. Fifty three clean planting materials of local accessions and those introduced from IARCs and maintained at KARI Kitale were used with 50 being those that were in experiment 1. They were planted in an unreplicated plot measuring 2 mX1m giving a plant density of 6 plants spaced at 1m x 0.5m. The experimental plot was surrounded with infected Napier grass to enhance transmissibility of disease to the experimental plot. Recommended cultural practices for managing Napier grass were followed. In this experiment the Principal of Busia FTC was allowed to harvest (cut) the foliage 3 months after planting followed by a harvest after every 6 weeks. Scoring for resistance/tolerance to stunting disease was done after the first, second and fourth harvest but not after the third harvest due to logistical problems. The scoring was based on visual observations on disease incidence per plot, 6 weeks after re-growth (i.e. just before the next harvest) using a scale of 1 to 5 where 1 = no symptoms, 2 = very mild symptoms, 3 = medium mild symptoms, 4 = severe symptoms and 5 = very severe symptoms.