* Osram, Evonik, RTL replace BayWa, Puma, SGL on MDAX * K+S retains spot on DAX after recent stock recovery * CompuGroup, Nemetschek replace Euromicron, Suess on TecDAX * BayWa, Puma, SGL, Kion, Deutsche Annington join SDAX FRANKFURT, Sept 4 (Reuters) - Germany's Osram Licht AG OSRn.DE , Evonik Industries EVKn.DE and RTL Group RRTL.DE will be added to Germany's mid-cap index MDAX .MDAXI following their flotation on the Frankfurt stock exchange earlier this year. Stock exchange operator Deutsche Boerse DB1Gn.DE said late on Wednesday that the three stocks would replace conglomerate BayWa BYWG.DE , sporting goods maker Puma PUMG.DE and carbon fibre specialist SGL SGCG.DE , which will move to the SDAX .SDAXI small-cap index. The index changes will become effective on Sept. 23. Osram was spun off of engineering conglomerate Siemens SIEGn.DE in July, and its shares have since gained almost 30 percent. RTL has gained about 38 percent since its April debut in Frankfurt, while Evonik has declined around 16 percent. Large-cap K+S SDFGn.DE , meanwhile, retained its place in Germany's blue-chip index, even though the salt miner had early last month looked set to drop out on expectations of a massive slump in the price of potash, its main product and a key fertiliser mineral. ID:nL6N0G3392 Russian miner Uralkali URKA.MM said on July 30 that potash prices could fall by more than 25 percent as it abandoned an export pact with Belarussian partner Belaruskali, one of the world's two big potash-exporting cartels. ID:nL6N0G013H Even though frictions between the two former Soviet neighbors have escalated, hopes that the cartel can eventually be mended have shored up the price of K+S stock in recent weeks. CompuGroup Medical COPMa.DE and Nemetschek NEKG.DE will join the TecDAX, while Euromicron EUCAn.DE and Suess MicroTec SMHNn.DE will leave it. Forklift truckmaker Kion KGX.DE and property firm Deutsche Annington ANNGn.DE , which also floated on the stock exchange recently, will join the SDAX. Along with BayWa, Puma and SGL, they will replace insolvent home improvement retail chain Praktiker PRAG.DE , RTL, SKW Stahl-Metallurgie SK1Gn.DE , Highlight Communications HLGZ.DE and SMT Scharf S4AG.DE . Deutsche Boerse said its next index review would take place on Dec. 4. (Reporting by Maria Sheahan, additional reporting by Ludwig Burger; editing by G Crosse) ((maria.sheahan@thomsonreuters.com)(+49-69-7565-1286)(Reuters Messaging: maria.sheahan.thomsonreuters.com@reuters.net)) Keywords: GERMANY STOCKS/DEBUTS