The relationship between powdery mildew (Sphaerotheca fuliginea) resistance and leaf chlorosis sensitivity in cucumber (Cucumis sativus) studied in single seed descent lines

Summary The genetic relation between powdery mildew resistance and sensitivity for leaf chlorosis of glasshouse cucumber was investigated. The powdery mildew resistant, leaf chlorosis sensitive hybrid variety Profito was crossed with the powdery mildew susceptible, non chlorosis sensitive hybrid variety Corona. Forty four F₆ inbred lines of this cross, produced by single seed descent, were tested for powdery mildew resistance (PMR) and leaf chlorosis sensitivity (LCS). PMR and LCS were positively correlated (r=0.59). One or more of the PMR genes probably causes LCS as a pleiotropic effect or is closely linked to LCS, but also other factors, not genetically linked to PMR can cause LCS. Five F₆ lines combined a significantly higher level of PMR than Corona with a significantly lower LCS than Profito. Three of these lines could hardly be distinguished from Corona for the level of LCS.Abbreviations LCS leaf chlorosis sensitivity - PMR powdery mildew resistance - SSD Single Seed Descent