Loaded with citrus from the orange groves of central Florida and assorted other fruits and vegetables, the modern version of the Orange Blossom Special rumbled through an orange grove north of Orlando on a warm spring night.

Suddenly, the scent of orange flowers filled the freight train--a few seconds' fragrant testimony to the aptness of the name.

At 9:34 on a Tuesday night, the train had pulled out of a freight yard in Orlando, Fla., headed for major East Coast produce markets carrying celery bound for Jessup, Md., oranges bound for the Hunt's Point Terminal Market in New York, and grapefruit, lettuce, bananas, tomatoes, tangerines and potatoes bound for other markets.

Through the moonlit night, the Orange Blossom sailed through north Florida and Georgia, past lonely farm road crossings, backyards and small-town train stations, sometimes pulling aside briefly for a southbound train. "Your train looks good," engineer W. H. Dixon radioed passing engineers.

By dawn, the Orange Blossom was in South Carolina, tunneling through pale mists that rose from swamps and floated above clumps of palmettos and fields of rust-red sour weed. On through the day, the Orange Blossom continued north.

By Wednesday evening at 8:30--22 hours and 50 minutes after departure from Orlando, the freight train pulled into Wilmington, Del., the end of the line for this produce-carrying train that started making its East Coast run last November.

The old Orange Blossom Special that inspired the fiddle tune was a passenger train that ferried frozen Northerners to winter vacations in Florida. The new Orange Blossom Special is theSeaboard System Railroad's attempt to win back a market in which it once competed successfully, but which the rails conceded to truckers approximately a decade ago.

"The fact is that we are seeing across the country that the railroads are starting to get involved in this business more than they have been in the last several years," said Martin Fitzpatrick, director of the U.S. Agriculture Department's office of transportation. The increase so far is small, he noted, but produce shipments by rail in the first two months of 1983 were up 12 percent from the same period the previous year, helped in part by the truckers' strike.

"I don't know why the railroads ever got out of the business," said Harold Arost of Emerald Packing Co. Before the railroads did, Arost said he shipped about 50 percent of his produce by rail. Arost ships less produce now than then, but about 70 percent of it travels by rail.

Seaboard Systems (the result of a merger of the Seaboard Coast Line and Louisville and Nashville rail systems) loads produce onto 45-foot refrigerated piggyback trailers at packing houses, trailers that can hold 1,100 boxes of 80 to 100 oranges each.

Cranes lift the trailers onto the train in the Orlando freight yard and pluck them off in Wilmington. From the rail yard in Wilmington, Chessie Motor Express trucks haul the trailers to produce terminals. (Seaboard Systems is a unit of the CSX Corp., as is Chessie Motor Express.)

What the Orange Blossom peddles to packers is speed and reliability. According to Dave Vernon, manager of perishable sales for Seaboard, the Orange Blossom is the fastest scheduled freight train in the United States, with top speeds of 70 miles per hour and an average speed of 49.

The fastest run for the train so far was 19 hours; the slowest, the 26 hours scheduled for the trip. The average from Nov. 15 to the end of March was 21 hours and 35 minutes, according to the railroad.

"It's very good," USDA's Fitzpatrick said of the Orange Blossom's speed. "That is important to the shipper in their efforts. I think that's what makes it a success."

Even so, Fitzpatrick said he doesn't expect to see wholesale replacement of produce trucking by the railroads. "I don't see piggybacks becoming a major carrier for produce because there are still advantages to carrying produce in trucks that many shippers like, such as the fact that they are more mobile, they can go directly from point to point, and in some cases trucks are faster," he said.

"Railroad service is inherently slow because of the physical problems of breaking up trains and making up trains," said Edward V. Kiley of the American Trucking Associations. The train time is "railroad yard to railroad yard" time rather than packing plant to produce market time, he pointed out.

White Rose celery was picked up at 4:30 p.m. on the afternoon the train left. Having arrived in Wilmington at 8:30 p.m. on the following evening, Wednesday, it was loaded on a truck and left Wilmington at 1:08 a.m. Thursday. By 5 a.m. Thursday, less than 48 hours after it was picked, the celery was delivered to a wholesaler in Jessup.

"It will be interesting to see what they can do," said Kiley, who conceded the delivery time for the celery was comparable to truck time. But he added, "Historically, it's been difficult for the rails to match truck service."

The train is scheduled to run regularly until June when hot weather ends the Florida produce shipping season. At that point the 400 trailers that the railroad has leased for three years will be returned to California and put to other uses there until next fall.

Seaboard officials claim that the train's first season has been a success. "We're right on target despite the rainy weather," said Seaboard spokesman Owen Pride. "If it were not for the weather problems, we'd be well ahead of projections. We're well satisfied with it."

What made the resumption of service possible, according to Seaboard officials, is the freedom that the railroads acquired through the 1980 Staggers Rail Act, which deregulated the railroads in large measure. The changes brought about by that act allow the rails to offer "on-the spot" rates to compete with truckers, Seaboard president Richard D. Sanborn said.

Sitting in a tiny office in the freight yard, sales manager Vernon coaxed a would-be customer on the telephone. "Don't pull no stuff on me. What's the truck rate?" Vernon asked. "Will you give it to me for the same rate? Okay."