GRAINS-Wheat gains as dryness hits US winter crops; corn firms on plating delay

• Chicago wheat firms as U.S. winter crop rating slides
• Corn, soybeans rise on concerns over planting delays

SINGAPORE, April 22 (Reuters) - Chicago wheat futures gained some ground on Tuesday, underpinned by worries over dry weather threatening to reduce U.S. winter crop yields.

Corn rose on support from wet weather delaying field work in the U.S. Midwest. Soybeans also inched higher.

"The condition of the winter wheat crop deteriorated over the last week, which is supporting prices," said one grains trader in Singapore.

The most-active wheat contract on the Chicago Board of Trade (CBOT) Wv1 rose 0.2% to $5.53-1/4 a bushel as of 0331 GMT, having dropped nearly 2% on Monday. Corn Cv1 added 0.2% to $4.90-3/4 a bushel and soybeans Sv1 rose 0.4% to $10.45-3/4 a bushel.

The U.S. Department of Agriculture (USDA) rated 45% of the winter wheat crops to be in good or excellent condition, down from half of the crop in that condition a year ago, with dryness hitting the U.S. Plains.

Analysts on average expected a 47% rating, unchanged from a week earlier.

Wet weather forecast in parts of the U.S. Midwest is likely to slow corn planting even as farmers seeded their crops faster than normal last week, data showed.

Farmers planted 12% of the nation's corn crop by April 20, topping the five-year average of 10%, the USDA said in a weekly crop progress report on Monday. Growers planted 8% of the soybean crop, above the five-year average of 5%.

Russian wheat export prices dropped last week, partly in response to general market optimism about a potential settlement of the Ukraine conflict, analysts said.

The Sovecon consultancy estimated prices for Russian wheat with 12.5% protein content at $250-$252 a ton free-on-board (FOB), compared with $250-$253 last week.