* Frosts damage crops in key exporters Russia and Ukraine

* Brazil foods continue to support soybean prices

* Traders await US corn, soy planting progress update

(Updates prices as of 1615 GMT, adds analysts' comments in paragraphs 4-6, changes byline/dateline from LONDON)

CHICAGO, May 20 (Reuters) - Chicago Board of Trade wheat futures posted their biggest one-day rally in about 10 months on Monday as concerns increased over crop losses in the important Black Sea region, analysts said.

Soybean and corn futures also advanced.

Russia was the wheat market's focus as the world's largest supplier of the grain suffered from damaging frosts.

The price of 12.5% protein Russian wheat scheduled for free-on-board (FOB) delivery in June climbed to $239 per metric ton last week from $221 per ton the previous week, the IKAR consultancy said.

In Ukraine, a major wheat and corn exporter, severe frosts across northern and eastern regions could reduce this year's grain and oilseed harvest, analyst APK-Inform said.

"Black sea weather continues to be bullish," said Don Roose, president of Iowa-based brokerage U.S. Commodities.

The most-active CBOT wheat contract was up 32 cents at $6.83-1/4 a bushel by 11:15 a.m. CDT (1615 GMT), near last week's 10-month high of $6.97. It was the market's biggest one-day rally since July.

Soybeans rose 15-3/4 cents to $12.43-3/4 a bushel, and corn jumped 8-1/2 cents to $4.61 a bushel.

Concerns over crop losses in Brazil's flood-devastated Rio Grande do Sul lifted soybean futures, traders said.

Excessive rains and heavy flooding have continued to constrain cargo movement at Rio Grande port, the country's fourth largest for soybean exports and third largest for fertilizer imports.

"The disruption of logistics has been severe, and the repair of damaged infrastructure would take up to a year, likely causing significant supply chain disruption," S&P Global Market Intelligence said.

In the U.S., the Department of Agriculture is slated to issue a weekly update on corn and soy plantings later on Monday. The pace of corn plantings fell behind average due to wet weather after being more active last week, analysts said. (Reporting by Tom Polansek in Chicago. Additional reporting by Nigel Hunt in London, Naveen Thukral in Singapore; Editing by Sherry Jacob-Phillips, Sohini Goswami, Vijay Kishore and Richard Chang)