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Striga is a parasitic weed causing remarkable yield lose in Sorghum bicolor. In this study, phytotoxicity of leaf and flower extracts of Striga hermonthica were investigated on three sorghum varieties under laboratory conditions. Before allelopathic bioassay, total phenolics, alkaloids and terpenoids were quantified in the extracts. For allelopathic bioassay, 5 and 10% (w/v) aqueous extracts were prepared by reconstituting dried crude extracts of leaf and flower of S. hermonthica in distilled water. Varieties of sorghum named Muyra 1 (M1), Muyra 2 (M2) and Fendishe (Fe) were treated with equal amounts of 5 and 10% (w/v) extracts in Petri dishes lined with Whatman no.1 filter paper. The control treatment received distilled water and treatments were laid out in a completely randomized design with three replications. Germination parameters were monitored for 15 days and General linear model was used to analyze data. Results showed that both leaf and flower of S. hermonthica produce phenolics, alkaloids and terpenoids. Values of total phenolics and total alkaloids did not show significant variation, whereas total terpenoid was significantly higher in flower than leaf. Percent germination, shoot and root lengths as well as their dry weights were significantly affected by extract concentration, sorghum variety and their interactions. Compared to control, percent germination and seedling growth were highly reduced at 5% w/v extract concentration and completely inhibited at 10% w/v extract concentration. Varieties were not differentially affected by leaf extracts, but M1 and M2 appeared to be more affected than Fe by flower extract. The result also showed that root growth was more affected by extracts than shoot growth. Overall, this study for the first time revealed that S. hermonthica reduces yield of S. bicolor not only due to parasitism, but also through its negative allelopathic effect on seed germination and early seedling growth.

In breeding for drought tolerance, availability of precise, cheap and easy to apply selection tool is critical. The aim of the present study was to identify potential screening tools that are useful for selection of drought tolerant genotypes in potato and select drought resistant potato genotypes. The study assessed sixty clones arranged in a 10×6 alpha lattice design with two replicates in a managed stress experiment. Two irrigation treatments were applied: fully watered non-stress and terminal drought, where the irrigation water supply to the crop was withheld after 50 % flowering to induce post-flowering stress. Stress indices were calculated based on tuber yield of genotypes in both stressed and non-stressed conditions. Identification of drought tolerant genotypes based on a single index was less informative as different indices identified different genotypes as drought tolerant. Hence, to determine the most desirable drought tolerant clones rank sum of indices, correlation, and bi-plot display of the principal component analysis was employed. The indices modified stress tolerance index based on non-stressed yield, Men productivity, Geometric mean productivity, Stress tolerance index, Harmonic mean, modified stress tolerance index based on stressed yield and Yield index exhibited strong association with both yield under stressed and non-stressed yield. These indices discriminated drought tolerant genotypes with higher tuber yielding potential both under stress and non-stress conditions. Genotypes CIP-398180.612, CIP-397069.5, and CIP-304371.67 were identified as drought tolerant. These genotypes could be potentially grown both under drought prone and potential environments and these selection attributes could help to develop climate resilient potato varieties.