Soil pathogens such as Pythium ultimum kill or damage germinating seed and emerging arrowleaf clover seedlings, he said. Both Apache and Yuchi arrowleaf clover are susceptible to this seedling disease, and in laboratory trials, inoculation with the disease resulted in 100 and 73 percent dead or severely diseased seedlings, respectively.

“In contrast, Blackhawk is resistant to this disease, and only 33 percent of the seedlings showed any sign of damage due to fungal disease,” he said.

Smith is known nationally for the development of Apache arrowleaf clover, which he released in 2001, according to Dr. Charles Long, resident director of research at the Overton center. Clover can be an important part of forage production — and by association, beef production — in the southern U.S., Smith said.

Arrowleaf clover has long shown good production potential. If planted or overseeded into warm-season pastures in the fall, it promises grazing for cattle in early spring when warm-season grasses are dormant.

As early as the 1960s, from East Texas to Georgia, it was common practice to mix arrowleaf seed with crimson clover seed, according to Smith. By mixing the early- maturing crimson clover and late-maturing arrowleaf, ranchers and farmers could have forage from February through early June.

However, multiple disease problems, including plant viruses and fungal root diseases, effectively put a stop to the practice by the late 1980s and early 1990s, Smith said.

Of the diseases, bean yellow mosaic virus was one of the most prevalent and damaging problems. The virus didn’t affect crimson clover, but either killed or stunted arrowleaf clover.

It was in response to this problem that Smith developed and released Apache arrowleaf clover in 2001. Apache became one of the most widely used arrowleaf clovers in the U.S. South, according to Smith.

In terms of tonnage of forage produced per acre, Blackhawk and Apache are similar, Smith said. However, in addition to having natural resistance to soil pathogens that attack seedlings, the new clover has the additional advantage of going dormant about a week earlier.

This means it is less likely to compete with warm-season forages like Coastal or Tifton 85 Bermuda grass.

Despite the similarities, the histories of developing the two are “quite different,” he said. “On Apache, we started with a really broad germplasm base, and we selected for a number of generations for resistance to bean yellow mosaic virus. We stopped at that, and released Apache, and it’s been a great variety for us, and continues to be a great variety.

“With Blackhawk, we started at a different place. We used a large germplasm collection, but we selected initially for resistance to fungal seedling diseases. We want to get that fixed first, and then after we had resistance to those diseases, we selected for resistance to bean yellow mosaic virus.”

Essentially he continued, the new clover has multiple disease resistance.

The clover seed is black, hence its name, Smith said. Curiously, its resistance to seedling diseases is linked to seed pigmentation. This correlation between dark-pigmentation and fungal disease resistance in legumes has long been known, he said.

“Dark-seeded genotypes show increased tolerance to fungi such as Pythium ultimum and P. irregulare, when compared to light colored seeds,” he said. “The protective pigments are anthocyanins, which are also found throughout plants in flowers, leaves, seed, etc.”  FG

—From Texas A&M University news release