* U.S. cold, Brazil drought raises doubts about corn harvests * Big, timely crops needed after China imports eroded supply * Soybeans hit new 7-year high above $15 in oilseed surge * Wheat also extends gains on weather worries, corn spillover (Updates with European trading, changes byline/dateline) By Gus Trompiz and Naveen Thukral PARIS/SINGAPORE, April 22 (Reuters) - Chicago corn futures gained more ground on Thursday, with prices holding around eight-year highs, as cold weather in the United States and dryness in Brazil raised doubts about whether next harvests will replenish declining stocks. Soybeans breached the $15 a bushel threshold to set another near seven-year high, as concern over U.S. planting added to tensions across oilseed markets. Wheat also extended gains to approach a near seven-year peak, supported by unfavourable weather in North America and the prospect of high corn prices boosting demand for wheat in livestock feed. The Chicago Board of Trade (CBOT) May corn contract was up 1.0% at $6.32 a bushel by 1146 GMT, having earlier climbed to $6.37-1/2, the highest front-month price since mid-2013. "This (rally) is because corn is in short supply and is likely to remain so in 2021/22," Commerzbank said in a note. "There seems to be no end to the news to this effect." Cold weather this week in the United States could slow the germination of newly seeded corn, while showers in the Midwest forecast for next week could slow ongoing planting. In Brazil, developing drought in southern Brazil was adding to question marks over the country"s heavily exported second corn crop, after earlier planting delays. On the demand side, a report issued by the U.S. Department of Agriculture"s attache in Beijing estimated China"s corn imports for 2020/21 at 28 million tonnes, above the USDA"s official estimate of 24 million. China, which has been grappling with high prices and falling inventories of corn, issued guidelines on Wednesday recommending a cut to corn and soymeal in pig and poultry feed. Chinese buyers are thought to have purchased at least half a million tonnes of new-crop French wheat for shipment over July-September, which may at least partly be used in feed, traders said. The most active CBOT wheat futures added 1.2% to $6.82-3/4 a bushel. CBOT soybeans were up 1.2% at $14.96-3/4 a bushel, after earlier reaching another highest since June 2014 at $15.04-1/2. Support from low U.S. soybean inventories was being amplified by tensions in related oilseed and vegetable oil markets. The CBOT front-month soybean oil contract extended a rally to a near 13-year high of 61.79 cents per lb, while palm oil reached a one-month peak. Prices at 1139 GMT Last Change Pct End Ytd Pct Move 2020 Move CBOT wheat 682.75 7.75 1.15 640.50 6.60 CBOT corn 612.25 5.75 0.95 484.00 26.50 CBOT soy 1496.75 17.25 1.17 1311.00 14.17 Paris wheat May 236.50 5.00 2.16 210.50 12.35 Paris maize Jun 231.50 2.50 1.09 198.75 16.48 Paris rape May 587.75 26.00 4.63 412.00 42.66 WTI crude oil 60.99 -0.36 -0.59 48.52 25.70 Euro/dlr 1.21 0.00 0.16 1.2100 -0.40 Most active contracts - Wheat, corn and soy US cents/bushel, Paris futures in euros per tonne