Hope Part of Watermelon Variety Trial

By Ryan McGeeney U of A System Division of Agriculture , 08/2/20 5:03 PM


HOPE — Among the many things that can quickly devolve into “fighting words” in Arkansas, perhaps two of the more surprising are “seedless watermelon.” But when Matt Bertucci, assistant professor of horticulture for the University of Arkansas System Division of Agriculture, decided to pit a number of older, popular seeded varieties against more recently developed hybrids, he knew he was stepping onto contested ground.

AS SWEET AS IT GETS — A recent watermelon variety trial, conducted by researchers at the University of Arkansas System Division of Agriculture, involved six varieties of watermelon grown on two quarter-acre test plots at the Southwest Research and Extension Center in Hope, Arkansas and at the Vegetable Research Station in Alma, Arkansas, respectively, took place over the summer of 2019. (Division of Agriculture photo.)

“People have told me the idea of growing seedless watermelon in their county is practically sacrilege,” he said with a laugh.

The trial, which involved six varieties of watermelon grown on two quarter-acre test plots at the Southwest Research and Extension Center in Hope and at the Vegetable Research Station in Alma, Arkansas, respectively, took place over the summer of 2019. Bertucci said the small trial, which produced roughly 1,000-1,500 melons, was intended as a small-scale “proof of concept” that could later be scaled up if the fruit-growing community in Arkansas and elsewhere expressed interest.

Bertucci’s research was jointly funded by the Cooperative Extension Service and the Arkansas Agricultural Experiment Station, the research arm of the Division of Agriculture.

The intent was to evaluate both older varieties of watermelon, which have been grown in Arkansas for decades, and newer, hybrid varieties for sweetness, nutrients, yield potential and marketability.

“There has been a lot of progress in the last 15-30 years, in terms of fruit improvements,” Bertucci said. “We have watermelon plants now that are disease resistant, potentially capture more nutrients from the soil, have sweeter taste profiles or sturdier rinds for shipping purposes. There are all sorts of improvements that plant breeders have been able to make.

“I think that sometimes growers may not be aware of that if there isn’t somebody to put it right under their nose,” he said. “They might say, ‘I’ve grown Jubilee for 40 years, it’s always produced a good melon for me, and I’m going to stay with it.’ And that’s their prerogative — they’re more than welcome to grow it.

“But this is an opportunity to say, if you’ve been growing Jubilee or Charleston Gray for three decades, you might want to try some of these newer varieties,” he said. “Or you might not.”

Bertucci’s trial included two seeded watermelon varieties — Jubilee and Charleston Gray — and four seedless varieties: Exclamation, Excursion, Fascination and WDL4410. The melons were germinated in a greenhouse, then transplanted to field conditions once seedlings had sprouted three to five leaves, and were then grown under black plastic with drip irrigation.

Stacking up

A few of the trial’s findings surprised Bertucci, notably how well the fruiting productivity of the older varieties stacked up against the newer hybrids.

“The Jubilee and the Charleston Gray yielded pretty impressively,” he said. “I was expecting them to have a yield penalty because they’re ‘old material’ — they’re not advanced germplasm or advanced breeding lines.”

The trial found that all varieties yielded between 30,000 and 38,000 pounds per acre. Bertucci also considered “marketable yield,” setting the minimum threshold weight at 9 pounds per melon. Jubilee, one of the two older, seeded varieties, led the pack in both categories.

In terms of marketable fruit, however — the number of individual melons over 9 pounds, rather than simply the overall weight of the crop — all six varieties were very similar, with hybrids Excursion and WDL4441 at the top.

The cultivars also were all similar in sweetness, with each measuring between 14 and 15 on the Brix scale (expressed as “degrees Brix”), although the hybrid Fascination did take the lead.

Bertucci said that one flaw in the study, which he might address in a larger trial, was that it didn’t address physical appearance in the marketability of the melons.

“One shortcoming in our study is that we didn’t discard melons with blemishes or marks on the fruit rinds,” he said. “Charleston Gray and Jubilee had a propensity for rot on the rinds. You wouldn’t be able to sell it. The fruit grew and reached a good size, but there’s no way you could sell it at a farmers’ market.”

Bertucci said that growing modern hybrids does tend to incur higher input costs — both because the seed itself is more expensive (although most producers growing “seeded” varieties tend to purchase new seed each season anyway), and because the hybrid varieties usually require greenhouse conditions for seedlings to germinate, as opposed to the older varieties, which will germinate well in open field conditions.