One of the few changes made to the University of Georgia Peanut Disease Risk Index for this year was in the number of points assigned to certain varieties, a sure sign that the best hope growers have of battling diseases like tomato spotted wilt virus might be found in the development of new cultivars.
Older varieties such as Florunner and Southern Runner that no longer are planted have been removed from the index, says University of Georgia Extension entomologist Steve L. Brown, and the number of points assigned to some varieties in a disease category has been changed.
The number of points assigned to Georgia Green and other varieties in the spotted wilt category has been increased from 25 in 2005 to 30 in 2006. Brown says the change doesn't mean that Georgia Green and the other varieties are becoming less resistant to spotted wilt. Rather, it's an indication that the newer varieties that have been released in recent years have significantly greater resistance to the disease, and that the old point scheme has had to be adjusted to reflect the improved resistance.
No variety of peanut is immune to tomato spotted wilt virus, say researchers. However, a few varieties have consistently demonstrated moderate levels of resistance. In addition to reduced disease incidence, some varieties appear to have some degree of tolerance as well. Higher levels of resistance and tolerance are anticipated since peanut breeding programs are now evaluating potential new varieties for response to tomato spotted wilt virus.
Peanut varieties also can have a major impact on fungal disease. The variety Georgia Green is currently planted on the majority of the peanut acreage in the Southeast. However, new varieties from breeding programs at the University of Georgia and the University of Florida not only have improved resistance to spotted wilt but to fungal diseases as well.
But, just as none of the current varieties are immune to tomato spotted wilt virus, none are completely immune to fungal diseases either. However, improved resistance likely will lead to reductions in disease severity, according to plant breeders. It is important to remember that improved resistance to one disease does not mean that the variety also possesses superior resistance to other diseases, says Brown. For example, DP-1 and C99-R have greater resistance to leafspot than Georgia Green. However, Georgia Green has greater resistance to rhizoctonia limb rot.
The following varieties currently are available to growers and offer a wide range of characteristics that could be important in the selection process:
Andru II is an early maturity variety, but not as early as Andru 93 or ViruGard. It has high-oleic oil chemistry, excellent resistance to tomato spotted wilt virus (TSWV) and good white mold resistance. Anderson Peanut Company is the major supplier of Andru II seed.
ANorden is a medium maturity variety with good TSWV resistance and high oleic oil chemistry. ANorden has the same level of resistance to white mold, leafspot and rhizoctonia limb rot as Georgia Green.
This is a medium-maturity variety released by the University of Florida that has been licensed to Anderson Peanuts. It is a sister line to Carver. AP-3 has excellent resistance to TSWV and white mold, the highest available in a medium-maturity variety. Yields and grades were very good at Marianna and Gainesville.
This is a medium maturity variety with good resistance to TSWV and white mold. It has some resistance to CBR and rhizoctonia limb rot. Carver has good yield potential. A good leafspot spray is needed for this variety.
This has been one of the higher-yielding entries in tests at multiple locations and usually ranks as one of the best in resistance to TSWV. C-99R has resistance to leafspot, white mold, rust and has a small amount of resistance to CBR. It is a late-maturing variety with large seed and calcium needs that are similar to a Virginia type.
Ga 01R was released by the University of Georgia in 2001 and has shown resistance to TSWV, leafspot and CBR. It is similar to C-99R in seed size and maturity. It also has a spreading runner growth habit.
This high-oleic runner-type peanut was released in 2002 by the Georgia Agricultural Experiment Station. It has high-oleic and low-linoleic fatty acid content for improved oil quality. It has good resistance to both TSWV and cylindrocladium black rot (CBR).
This variety has a maturity range similar to Georgia Green. It has significantly larger pods and seed than Georgia Green. It has one of the highest levels of resistance to TSWV of all the runner-type varieties, but it lacks resistance to other diseases.
Due to high yields, good grades and resistance to TSWV and white mold, Georgia Green has become a very popular variety. Georgia Green has a small amount of resistance to late leafspot and CBR, but it does not take as long to mature as did Southern Runner, one of its parents.
Hull is a late maturity, jumbo runner seed size, high-oleic variety with good-to-excellent resistance to TSWV, late leafspot and white mold. It also has good resistance to CBR and some resistance to rootknot nematodes.
This variety matures 14 to 21 days earlier than other commonly grown varieties such as Georgia Green. It is a cross between NC-7 and Florunner, and it has a spreading bunch growth habit. ViruGard has good TSWV tolerance/resistance.
Gregory is a high-yielding variety that produces high percentages of jumbo pods and extra-large kernels with good TSWV resistance. Of the Virginia types, Gregory has been among the most resistant to TSWV.
This variety has larger seed than many others that are commercially available. It has an intermediate growth habit and normally matures in 150 to 155 days in Virginia. NC 7 is not as resistant to TSWV as Gregory.
This variety matures three to five days earlier than NC 7. It has a runner-type growth habit. It is somewhat resistant to CBR but is highly susceptible to sclerotinia blight and leafspot.
Except for CBR resistance and slightly earlier maturity, NC 12C is similar to NC 7. Under close plant spacing or conditions of high water availability, NC 12C produces excessive vine growth.
This 1989 joint release from North Carolina and Virginia is an early maturing variety that produces good yields. In Florida tests, the grade has tended to be lower than with other Virginia varieties. This variety has some resistance to TSWV and white mold under low pressure.
This variety is susceptible to all major diseases in the region. It has a runner growth habit and matures about five days earlier than NC 7.
This variety has good resistance to CBR, sclerotinia blight and web blotch. Perry tends to be highly susceptible to TSWV. It has a spreading runner growth habit.
Wilson matures five to seven days earlier than NC-7 and has excellent qualities for in-shell markets. It is moderately susceptible to TSWV, leafspot and other diseases in the Virginia-Carolina region.
This new high-yielding, high-oleic variety is intended for the same confectionary markets as other Spanish types. It has much better resistance to TSWV than other Spanish varieties. Seed supply will be limited for 2006.
Starr has an upright growth habit with plants typically producing flowers on the main stem. The maturity is similar to other Spanish cultivars. It has no resistance to common peanut diseases and insects.
This variety has plant characteristics very similar to Starr.
This variety is typical of Spanish-type peanut cultivars in vegetative growth, rate of growth, and mainstem height. It has some resistance to pythium pod rot and scletorinia blight compared to Florunner and Starr.
Pronto is a cross between two Spanish lines, Chico and Comet. Its plants exhibit more yellow-green color than other Spanish cultivars. Pronto matures three to four weeks earlier than Florunner and has yields and grades similar to Spanco.
Spanco is a sister line to Pronto but has greener foliage color when mature. It is similar to Pronto in yield and grade.
This is a Valencia-red cultivar that has outyielded and graded better than all other Valencia cultivars in Georgia. It is an excellent choice for the fresh-market boiling trade and home garden use.
This variety has a larger seed size compared to other Valencia varieties. It is an excellent choice for the fresh market boiling trade in the Southeast.