A Burley Tobacco Resistant to TVMV, TEV, and PVY
R. D. Miller
Department of Plant and Soil Science
Tobacco Experiment Station, Greeneville, Tennessee
The University of Tennessee Agricultural Experiment Station
The author expresses deep appreciation to the following individuals and companies who participated or assisted in the development of TN 86:
Dr. Phil Hunter, Superintendent of
the Tobacco Experiment Station, Greeneville, Tennessee, and
Lawson Safley and Dr. Dennis Onks, former and present
Superintendent of the Highland Rim Experiment Station,
Springfield, Tennessee, for supervision and assistance in the
production of breeding line trials and nurseries at the research
Tobacco vein mottling virus (TVMV) and tobacco etch virus (TEV) have become widespread throughout the burley-producing regions of Tennessee, Kentucky, Virginia, and North Carolina in recent years (Gooding and Sun 1972; Gooding et al. 1980; Pirone et al. 1973; Sievert 1974). TVMV and TEV are transmitted to tobacco from horse nettle (Solanum caolinense ), dock (Rumex sp.), ground cherry (Physalis sp.), and possibly other weed hosts by the green peach aphid, Myzus persicae (Sulzer) (Pirone et al. 1973; Sun et al. 1974). Because symptoms of TVMV, TEV, and potato virus Y (PVY) are very similar (Gooding and Lapp 1980), it is usually impossible to distinguish these diseases without doing serological assays (Gooding and Sun 1972). Initial symptoms of these diseases, which are often referred to as the PVY complex, may be limited to a slight mottling, yellowing, or other discoloration of the tissue around the veins of the leaves (Pirone et al. 1973). As the diseases progress, leaf specking and necrosis may occur, which can result in leaf deterioration (Figure 1). This often causes infested tobacco to be harvested prematurely, thus resulting in reduced yield and quality (Sievert 1978)>
Although several tobacco cultivars have some tolerance to TVMV and TEV, studies have indicated that all commercial cultivars are susceptible to both diseases (Gooding and Ross 1970; Pirone 1974; Pirone and Gooding 1973). In general, cultivars having resistance to the black shank fungus, Phytophthora parasitica Dast., are very sensitive to TVMV and TEV (Gupton et al. 1981). In a study conducted by the University of Tennessee and North Carolina State University, yield reductions due to TVMV or TEV infection averaged approximately 200-500 pounds per acre, depending on the tobacco cultivar grown (Rufty et al., North Carolina State University, unpublished data). In addition, virus-infected tobacco was unsound and thin-bodied with undesirable color, resulting in a significant reduction in quality. Although considerable variation was found among the commercial varieties for leaf damage and yield reduction due to virus infection, all black shank-resistant varieties were moderately to severely damaged.
'Tobacco Introduction' (TI) 1406, a breeding line developed in West Germany, has good resistance to TVMV, TEV, and PVY (Koelle 1961). This line, sometimes referred to as 'Virgin A Mutant,' has been the primary source used to incorporate resistance to the PVY complex into tobacco breeding lines (Chaplin et al. 1980; Gupton 1980; Nielson et al. 1982; Smeeton 1976). However, breeding lines having PVY resistance derived from TI 1406 have been reported to be unusually susceptible to tobacco budworms, Heliothis armigera (H¸bner) (Smeeton 1976); tobacco flea beetles, Epitrix hirtipennis (Melshimer) (Nielsen et al. 1982); grasshoppers, Melanoplus spp, and Japanese beetles, Popillia japonica Newman (Gupton 1980); and tarnished plant bugs, Lygus lineolaris (Pless and Miller 1986). The high degree of insect susceptibility found in TI 1406 and PVY-resistant breeding lines derived from it has been associated with the lack of trichome exudates that are normally produced in tobacco (Nielsen et al. 1982).
'Tennessee 86' (TN 86) was released by the Tennessee Agricultural Experiment Station as a commercial variety in February 1986 (Miller 1987). It is the first burley tobacco variety having resistance to TVMV, TEV and PVY (Figure 2). Although resistance to the PVY complex is derived from TI 1406, TN 86 produces normal trichome secretions and does not exhibit the insect susceptibility normally seen in PVY-resistant breeding lines (Miller and Pless, the University of Tennessee, unpublished data). TN 86, which is also resistant to black shank; black root rot, Theilaviopsis basicola (Berk. & BR.) Ferr; and wildfire, Pseudomonas tabaci (Wolf and Foster) Stevens, was developed at the Tobacco Experiment Station in Greeneville, Tennessee.
Origin and Development
TN 86, which was tested as Greeneville (GR) 136, was developed from a cross between 'Burley 49' (Hoffbeck et al. 1965) and the breeding line 'PVY-202.' PVY-202, which was derived from a cross between Burley 49 and TI 1406, is a sister line to 'GR 107.' GR 107 is a TVMV, TEV, and PVY-resistant breeding line released cooperatively by the Tennessee Agricultural Experiment Station and USDA-ARS in 1979 (Gupton 1980). A single plant selection from the F2 generation of the Burley 49 x PVY-202 population was crossed to 'Burley 21' (Heggestad et al. 1960). In the F2 generation of the new population, a backcross was made to Burley 21. The original cross and subsequent backcross were made by Dr. Creighton Gupton, former USDA-ARS burley tobacco breeder at the Tobacco Experiment Station in Greeneville.
Selections were made in black shank, TVMV, TEV nurseries and progeny tested in greenhouse disease screenings. In 1982 a single plant having superior agronomic characteristics and black shank resistance was selected from the F4 generation following the Burley 21 backcross. All F5 selections that were determined to be homozygous for resistance to TEV, TVMV, wildfire, and black root rot were bulked and designated as breeding line GR 136 in 1983.
PVY-202 provided the resistance to TVMV, TEV, and PVY, which originated from TI 1406. Burley 49 was the source of resistance to black root rot, wildfire, and black shank. Burley 49 derived its resistance to these diseases from Nicotiana debneyi, Nicotiana longiflora, and 'Fla 301,' respectively. GR 136 was in the F8 generation at the time of its release as TN 86.
A comparison of the agronomic characteristics of TN 86 and selected commercial burley varieties is presented in Table 1. TN 86 has a more erect leaf habit, a higher leaf number, and a shorter leaf internode than most other burley varieties (Figure 3). The growth habit and plant size of TN 86 are similar to Burley 21. Under normal growing conditions TN 86 has 4 to 7 more leaves than 'MS KY 14 x L8,' but 2 to 4 fewer leaves than 'Burley 64.' The leaf size and shape of TN 86 are similar to those of 'VA 509' and 'KY 14.' TN 86 has a medium stalk diameter that is larger than MS KY 14 x L8 but is significantly smaller than VA 509.
Because of the upright growth habit of TN 86, breakage and loss of leaves during harvesting is minimized. TN 86 should be topped at about 22 to 26 leaves; higher topping will result in overly large plants that are difficult to manage and harvest. TN 86 is usually ready for harvest approximately 10 days to 2 weeks later than is MS KY 14 x L8; however, it matures about 7 to 10 days earlier than Burley 64. The yield potential of TN 86 is significantly reduced by early harvest.
In comparison to other commercial varieties, TN 86 is lighter green while growing in the field. The cured leaf is generally reddish-tan and has consistently sold for prices comparable to or higher than those for other varieties.
TN 86 appears to be widely adapted. When grown under disease-free conditions, TN 86 is competitive with the highest yielding commercial varieties and is substantially higher yielding than varieties having resistance to Race 1 black shank (Table 2). It has also performed well in yield and quality in advanced breeding line trials and on-farm trials throughout Tennessee (Tables 3 and 4). TN 86 performs particularly well in areas where heavy outbreaks of TVMV and TEV usually occur each year.
In the 1984 and 1985 Regional Variety Test programs (Tables 5 and 6), TN 86 was the highest yielding line among 22 entries in 1984 and was the second highest yielding line among 19 entries in 1985. It also received the highest ratings in industry evaluations for leaf color, leaf quality, and overall industry usability.
TN 86 has high resistance to TVMV, black root rot, and wildfire; medium high resistance to TEV; medium resistance to Race 0 and Race 1 black shank; and is resistant to most strains of PVY (Table 7).TN 86 yields were 800 to 2500 pounds per acre higher than those of virus susceptible varieties when grown in tests artificially inoculated with TVMV or TEV (Table 8). Yields of TN 86 exceeded those of all other black shank-resistant varieties by more than 1000 pounds per acre in these studies. Under moderate to heavy natural infestations of TVMV and/or TEV, yields of TN 86 were 200 to 2000 pounds per acre higher than yields of susceptible varieties (Tables 4 and 8).
Several strains of PVY with different levels of virulence have been identified. Although the level of resistance to these strains varies in TN 86, the resistance is similar to that of TI 1406 and is significantly higher than that of other burley varieties (Table 9).
Recent studies conducted in Mexico and Puerto Rico have indicated that TN 86 is more sensitive to blue mold than are other burley tobacco varieties (E.A. Wernsman, 1987, personal communication). Also, TN 86 is susceptible to tobacco mosaic virus. The reaction of TN 86 to alfalfa mosaic virus, tobacco ringspot virus, and tobacco streak virus is similar to that of other burley varieties (Table 10).
The level of black shank resistance in TN 86 is similar to that of VA 509, which is the variety most commonly used for the control of black shank in Tennessee and Virginia (Figure 4). TN 86 is not as resistant to black shank as is 'KY 17,' (the most popular black-shank resistant variety in Kentucky) and some other hybrid burley varieties. However, TN 86 has out-yielded other black shank-resistant varieties in test grown in black shank-infested soils (Table 11).Limited losses due to black shank may occur when TN 86 is grown in heavily infested fields under normal growing conditions. Under extreme drought and black shank pressure, survival of TN 86 may be significantly lower than that of some other black shank-resistant varieties. However, TN 86 has performed as well as or better than VA 509 in test plots, regardless of the severity of black shank conditions.
The chemical composition of TN 86 has been well within the specifications established for burley tobacco by the Burley Tobacco Quality Committee--Varieties (Tables 13 and 14). The quality of smoke produced from cured leaf of TN 86 has consistently been judged to be acceptable by industry smoke panels (Table 15).
TN 86, the first burley tobacco variety having resistance to TVMV and TEV diseases, was released by the University of Tennessee as a commercial cultivar in 1986. The new cultivar, which is also resistant to black shank, black root rot, wildfire, and most strains of potato virus Y, was developed at the Tobacco Experiment Station in Greeneville, Tennessee. Unlike earlier breeding lines having TVMV and PVY resistance derived from TI 1406, TN 86 has normal levels of leaf trichome secretions and is not unusually susceptible to tobacco insect pests. TN 86 is a medium-to-late-maturing cultivar that has more leaves and a more upright growth habit than other burley cultivars. Extensive testing throughout Tennessee and surrounding states has demonstrated that TN 86 is widely adapted. TN 86 has substantially out-yielded other burley cultivars in areas that have heavy infestations of TVMV or TEV diseases. The cured leaf is generally reddish-tan in color and has consistently sold for prices comparable to or higher than those for other cultivars. Because other black shank-resistant cultivars are highly susceptible to TVMV and TEV, burley producers who must grow their crop in black shank-infested ground should benefit from using TN 86.
Chaplin, J.F., L.G. Burk, G.V. Gooding, and N.T. Powell. 1980. Registration of NC 744 tobacco germplasm. Crop Sci. 20:677.
Gooding, G.V., Jr., and N.A. Lapp. 1980. Distribution, incidence and strains of potato virus Y in North Carolina. Tob. Sci. 24:89-92.
Gooding, G.V., Jr., and Harold Ross. 1970. Effect of tobacco etch virus disease on yield and market value of commercial cultivars of burley tobacco in North Carolina. Tob. Sci. 14:55-57.
Gooding, G.V., Jr., and M. Sun. 1972. A newly recognized virus disease of burley tobacco in North Carolina. Phytopathology 62:803.
Gooding, G.V., Jr., J.B. Young, and T.W. DuVall. 1980. Distribution and incidence of tobacco vein mottling virus in Madison County, North Carolina. Tob. Sci. 24:89-92.
Gupton, C.L. 1980. Registration of Greeneville 107 burley tobacco germplasm. Crop Sci. 20:116.
Gupton, C.L., G.V. Gooding, Jr., and T.C. Corbin. 1981. Tolerance to potato virus Y and tobacco vein mottling virus in black shank resistant burley tobacco (Nicotiana tabacum L.). Tob. Sci. 26:89-93
Heggestad, H.E., E.E. Clayton, M.O. Neas, and H.A. Skoog. 1960. Development of Burley 21, the first wildfire-resistant variety, including results of variety trials. Bulletin 321, Tennessee Agricultural Experiment Station.
Hoffbeck, L.J., M.O. Neas, H.E. Heggestad, and H.A. Skoog. 1965. Burley 49--a new disease resistant burley tobacco. Bulletin 395, Tennessee Agricultural Experiment Station.
Koelle, G. 1961. Genetic analyse einer Y-virus (Rippenbraune) resistenten mutante der tabaksorte Virgin A. Zuchter 31:71-71.
Miller, R.D. 1987. Registration of TN 86 burley tobacco. Crop Sci. 27:365-366.
Nielsen, M.T., G.A. Jones, and G.B. Collins. 1982. Inheritance pattern for secreting glandular trichomes in tobacco. Crop Sci. 22:1051-1053.
Pirone, T.P. 1974. Effect of tobacco vein mottling virus on yield of burley tobacco cultivars. Tob. Sci. 18:110-111.
Pirone, T.P., and G.V.Gooding, Jr. 1973. Effect of tobacco vein mottling virus on field-grown burley tobacco varieties. Plant Dis. Reptr. 57:845-847.
Pirone, T.P., G.V. Gooding, Jr., and J.H. Smiley. 1973. Tobacco vein mottling virus on burley tobacco in Kentucky. Plant Dis. Reptr. 57:841-844.
Pless, C.D., and R.D. Miller. 1986. Injury by the tarnished plant bug to selected potyvirus-resistant burley tobacco lines. Tob. Sci. 30:127-129.
Sievert, R.C. 1974. Tobacco vein mottling virus found in Tennessee. Plant Dis. Reptr. 58:1073-1074.
________. 1978. Effect of early harvest of burley tobacco infected with potato virus Y on yield, quality, and chemical constituents. Tob. Sci. 22:51-53.
Smeeton, B.W. 1976. Budworm susceptibility of PVY resistant cultivars. Tob. Sci. 20:156.
Sun, M.K.C., G.V. Gooding, Jr., T.P. Pirone, and Sue A Tolin. 1974. A virus disease of tobacco caused by tobacco vein mottling virus. Phytopathology 64:1133-1136.