Tobacco variety doing ‘very well in our testing’ for black shank control
Virginia flue-cured tobacco growers will soon choose varieties for next year’s growing season. One that has shown impressive yields and excellent black shank resistance in variety tests is NC 1226.
“NC 1226 has done very well in our testing and represents a step forward in terms of black shank resistance in flue-cured tobacco,” said David Reed, an Extension tobacco specialist at Virginia Tech’s Southern Piedmont Agricultural Research Center in Blackstone, Va. “Growers that planted NC 1226 in 2020 were generally very pleased with both the yield and quality of the tobacco, and the survival in problem black shank infested fields is far superior to any other released variety.
“The only significant problem encountered last season was the performance of the seed in the greenhouse and the number of usable transplants produced,” Reed continued. “I expect this issue to be corrected for the upcoming season, and this was not completely unexpected with seed of a new hybrid that may have been rushed to market.”
Stephen Barts, unit coordinator and Extension agent in Pittsylvania County, Va., says his observation of NC 1226 is it “stood up well to black shank, had a good frame and leaf count [not overly bulky or hard to handle], colored well — especially in the upper stalk — and was on the later end of the maturity spectrum.”
He hasn’t compiled all 2020 harvest data, but Barts said 2019 data of NC 1226 revealed excellent black shank resistance compared with other varieties planted.
Barts said disease tables by Virginia Tech Plant Pathologist Charles Johnson showed that NC 1226 exhibited strong yielding ability when black shank was present and had a 98-percent survival rate, better than some other varieties such as NC 196 at 36 percent, K 326 at 34 percent and GF 318 at 54 percent.
“In the 2019 [Official Variety Test], it showed a higher than average yield,” Barts says, “but suffered some in its quality index, which is to be expected given its high level of resistance.”
North Carolina State University Plant Breeder Ramsey Lewis developed NC 1226, and it was available to growers on a limited basis in 2020. He says NC 1226 doesn’t carry the partial resistance level as that of K 346, but it holds the necessary attributes that a single variety should have such as black shank resistance and high yields. In fact, in N.C. State University tests, NC 1226 yielded better than the standard high yielder of K 326 and exhibited black shank resistance equal to K 346.
NC 1226 yielded high because it reduced the incidence of the black shank disease. For instance, an OVT conducted by N.C. State showed that crop loss due to black shank was nearly 0 or right at 0, Lewis indicates, “and the yield ability was about higher than K 326 and about the same as NC 196.”
Data from across three multiple locations in a regional farm test showed NC 1226 had the highest level of black shank resistance, and yield was relative to K 326.
However, Lewis warns that NC 1226 is not the savior for black shank resistance, at least not yet. “I shouldn’t receive phone calls saying, ‘We observed plants that have died of black shank,’ because NC 1226 is not immune to black shank,” he says. “There is no variety to the best of my knowledge anywhere in the world that’s immune to black shank, and I’m not sure that will ever happen in my lifetime.”
Lewis says just because NC 1226 records high levels of black shank resistance doesn’t mean growers can stop good production practices to lessen the disease. On the contrary, they must continue to rotate tobacco with other crops in their rotation plan. Along the same thought, they should apply chemical inputs on a timely schedule.
“It also does not mean that the high resistance that we currently observe in NC 1226 will be that way for years to come,” Lewis says.
He explains that past research has shown that disease populations can adapt to resistance. So not only does he advise growers to rotate the variety in different fields but also rotate varieties within fields. Following these practices will help improve quality and yield, if weather conditions are conducive to a beneficial growing season.
Reed has two important suggestions in 2021. “First, growers that do not have significant black shank do not need to plant NC 1226, as there are other varieties with less resistance that have equal or higher yield potential that would be a better choice. Second, for growers with problem black shank fields, we should not rely solely on the high-resistance level of the variety but incorporate the variety in an overall management program that utilizes rotational out of tobacco and incorporates the use of soil-applied fungicides.”
Barts cautions growers when selecting a black shank variety.
“I see this variety being used in places that have historical instances of black shank. We have varieties with significantly less resistance that perform better in both yield and quality, so it wouldn’t be among my first choices for areas with no significant disease history. It’s performance in fields that have significant disease history was strong, especially when coupled with an appropriate fungicide regiment. NC 1226 has strong black shank resistance, and its placement on the farm should reflect that strong point.”
When breeding for disease resistance, Lewis measures a variety’s yielding ability because higher yields are what most growers are looking for each season. With that said, growers don’t expect a variety to always out yield everything on the market, “but it has to be high-enough yielding, combining other traits to make it a viable variety for their production operation,” he says.
His objective is to develop a variety that has black shank resistance equal to K 346, and a variety that has yielding ability comparable to K 326.
These two are the standards for resistance and yields.
He evaluates how a variety’s leaf performs in the curing barn, and if tobacco manufacturers and growers in all flue-cured growing regions will accept how it cures.
Acceptable levels of disease resistance are so important when breeding for new varieties. That includes resistance not only to black shank but also to the diseases bacterial wilt and Granville wilt.
In his plant breeding career, Lewis continues to learn and understand black shank resistance and identify new sources of resistance while maintaining high yields, something very difficult to do for plant breeders.
“It’s not difficult to stack the genetic elements to develop a variety for high levels of black shank resistance,” he says, “but what’s not so easy to do is keep yields where they want to be, or growers want them to be.
“There’s generally an unfavorable relationship between the genetics of black shank resistance and genes that affect yield,” Lewis adds. “In general, as resistance goes up, there’s a tendency for the yield of that material to go down. That doesn’t mean it’s impossible to produce high-yielding black shank varieties. It just means it’s more difficult to do.”
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