Onion is one of the most important vegetable crops in the world including Ethiopia. The field experiment was conducted in Arsi zone at Kulumsa Agriculture Research Center and Ziway Dugda districts under irrigation condition. A total of five improved onion varieties were evaluated in Randomized Complete Block Design with three replications with the objectives of studying the performance and adaptability of improved onion varieties for bulb yield and yield related traits in 2017 during off season. The combined Analysis of variance (variety by location) revealed that significant difference between improved onion varieties for maturity date, marketable and unmarketable bulb yield tons per hectare, bulb length in centimeter, and bulb weight in gram was observed. But non-significant difference for plant height in centimeter, total bulb yield tons per hectare and average bulb diameter in centimeter were observed between improved onion varieties. Except variety Adama Red all the tested improved onion varieties (Melkam, Nafis, Nasik Red and Bombay Red) was well performed and adapted. These varieties were gave more than 40 marketable bulb yield t ha -1 . So those improved onion varieties were recommended for the study area and areas of similar agro-ecological zones under off season growing condition.

Potato is a high potential food security crop in Ethiopia. Genetic variability is the basis of all crop improvement programs. The study was conducted at Adet in 2018 with the objective of assessing the extent and pattern of genetic variability of potato genotypes for yield and yield related traits. A total of 36 potato genotypes were evaluated for 18 quantitative traits in simple lattice design. The analysis of variance revealed that highly significant difference among the tested potato genotypes for all quantitative traits except stem number per hill. The phenotypic coefficient of variation was ranged from 4.56 to 56.01% (for specific gravity and unmarketable tuber yield ha-1 respectively) and the genotypic coefficient of variation was ranged from 2.32 to 40.66% (specific gravity and late blight severity percentage respectively). Days to attain 50% emergence, leaf area index, number of marketable and total tubers per plant, marketable and total tuber yield ha-1, and late blight severity percentage showed high heritability and high genetic advance as percent of mean. Most of the traits had high phenotypic coefficient of variation and genotypic coefficient of variation; and coupled high heritability with high genetic advance as percent of mean. Traits having high heritability and high genetic advance as percent of means is effective for simple selection.

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Potato is one of the most important crops in the farming system of Bekoji and Kofele in the cool highlands of Arsi where potato is usually grown biennially during the main and 'bulg' seasons. 'Belete' has been the dominant potato variety in these areas for the last ten years now and farmers prefer to grow this variety for its high productivity and resistance to late blight disease. Nevertheless, farmers have complaints on its big sized tubers, considered as unmarketable, which costs them more seed to cover a given area of land and less suitable for cooking. Besides, farmers often use random population density and time of harvesting, which also contribute to this problem. The present study was therefore intended to manage the tubers' size distribution of this variety without negatively affecting the yield of the crop through modifying plant spacing and time of harvesting from previously recommended practices. Twelve combinations of four plant spacing and three time of harvesting were studied on variety "Belete' at Bekoji and Kofele in the main seasons of 2018 and 2019. The experiment was laid out in a completely randomized block design with 4x3 factorial arrangement in three replications. The analysis of variance revealed that the interaction effect of spacing and time of harvesting significantly (p<0.001) affected the marketable tuber yields. The narrow spacing (60cmx20cm) or high population treatment (83,333 plants/ha) with 120 days after planting resulted in the highest marketable and total tuber yield compared to the rest. While the least yields were recorded from the wider spacing of 75cmx30cm (44,444plants/ha) and early harvesting (90 days). The spacing 60cmx20cm did 17.2% increment in marketable yield over the previously recommended spacing of potato (75cmx30cm, 44,444plants/ha). From this study, therefore, it can be recommended for Belete that the narrow spacing of 60cmx20cm and harvesting at 120 days after planting could be the optimum spacing and time of harvesting to produce marketable tubers.