‘TAM Mild Jalapeno II’: A New, Multiple-virus-resistant, Mild Jalapeno Pepper

Kevin M. Crosby¹ and Benigno Villalon²

Texas Agricultural Experiment Station, 2415 E. Highway 83, Weslaco, TX 78596

Additional index words. Capsicum annuum potyviruses, resistance, germplasm, open pollinated

The Texas Agricultural Experiment Station (TAES) at Weslaco announces the release of ‘TAM Mild Jalapeno II’, a multiple-virus resistant, low-pungency pepper (Capsicum annuum L.). The project to breed virus-resistant peppers at the TAES began in 1971. Several cultivars of virus-resistant jalapenos have been released over the last 20 years (Villalon, 1983; Villalon et al., 1992, 1994). The production of hot and sweet peppers in Texas has fluctuated from 1200 to 7000 ha over the last 30 years. Currently, close to 1700 ha are cultivated statewide. One of the most persistent problems on peppers in south Texas has been virus infection. The two most serious virus pathogens are tobacco etch virus (TEV) and pepper mottle virus (PepMov), both transmitted by aphids primarily the cotton aphid (Aphis gossypii Glover) and the green peach aphid (Myzus persicae Sulzer). Traditionally, all common jalapeno cultivars grown in south Texas have been susceptible to local strains of TEV and PepMov. Yield reductions from infected plants may be as high as 45%, particularly when fruit is intended for the fresh market (Greenleaf, 1986). The best solution to the problem is the development of resistant cultivars with high quality fruit. Multiple sources of single resistance genes against these potyviruses have been documented in various germplasm lines (Cook, 1960; Greenleaf, 1956; Kyle and Palloix, 1997; Zitter and Cook, 1973).

Origin

‘TAM Mild Jalapeno II’ (TMJII) originated from an F¹² selection out of the cross of ‘Ferry Morse Jumbo Jalapeno’ and sweet jalapeno 76053, a line with resistance to Texas isolates of TEV, PVY, PepMov, and TMV (Fig. 1). This pedigree included three sources of potyvirus resistance, ‘Avelar’, ‘PI 264281’, and ‘AC 2207’ (Cook, 1960; Greenleaf, 1986; Zitter and Cook, 1973), as well as several jalapeno lines. Field selections were conducted for more than 12 generations. Progeny of the initial F3 single-plant selection were placed in isolation blocks for two consecutive seasons, bulking superior plants. This was followed by another single-plant selection. Selfed progeny of this plant were then grown in isolation blocks where superior plant selections were bulked to carry on the inbreeding. At each generation, seedlings were mechanically inoculated with Texas isolates of TEV and PepMov, prior to transplanting to the field, to verify resistance (Villalon, 1981). Susceptible control cultivars were included to ensure viral pathogenicity. The final selection was at the F12 generation and possessed uniform plant and fruit traits.

Description

‘TAM Mild Jalapeno II’ is adapted to the high temperatures and virus disease pressures of south Texas. The concentrated set of large, crack-free fruit on compact plants makes it ideally suited to once-over harvests and high density plantings. Comparisons for field performance, yield, fruit quality, and virus resistance were conducted at the TAES center at Weslaco during the period from 1996 to 2001. In addition, yield plots were established in a commercial field in Edinburg, Texas, during the Fall 2000 season. All plants were grown on a silty, clay loam soil (Weslaco) or sandy soil (Edinburg), under commercial practices: transplants, drip irrigation, and chemical pest control. Plants of both ‘TMJ II’ and ‘Mitla’, inoculated with TEV, PVY, and PepMov, were transplanted to 10-L pots in the greenhouse and into field plots to observe effects on plant growth and fruit quality.

In the fall season, ‘TMJ W had significantly larger fruit and thicker flesh than ‘Mitla’, and similar yield per plant. In the spring season, fruit size and flesh thickness were significantly greater than ‘Grande’, but yield was significantly lower at 350 g/plant compared to 372 g/plant (Table 1, Fig. 2). In both seasons, ‘TMJII’ matured 5 dbefore ‘Mitla,’ at Weslaco. In the Fall 2000 season, yields and fruit quality were compared among ‘TMJ 11’ and the commercial cultivars Mitla, Grande, and Tula, from a trial on sandy soils in Edinburg (Table 2). Yield of ‘TMJ II’ (435 g/plant) was not significantly different than the popular cultivar Grande (444 g/plant), but was significantly less than ‘Mitla’ (502 g/plant). However, the percentages of cull fruit for both ‘TMJ II’ (12%) and ‘Grande’ (13%) were significantly lower than the 19% level for ‘Mitla’. In addition, ‘TMJ II’ fruit produced very little anthocyanin compared to fruit of ‘Grande’ and ‘Mitla’. This purple-black pigment is undesirable for fresh-market peppers and reduces the value of the crop. Total capsaicin concentrations of mature fruits from ‘TMJ II’ plants grown in Uvalde and College Station,

Received for publication 30 Oct. 2001. Research conducted at the Texas Agricultural Experiment Station, Weslaco, Texas. Use of trade names does not imply endorsement of the products named nor criticism of similar ones not named. The authors thank Rick Hernandez, Cory Dombrowski, Kay Harding, and Alfredo Rodriguez for their valuable help in conducting greenhouse and field experiments. Thanks also to Dr. Richard Christie and Dr. John Kao for providing several different strains of TEV and Dr. Brad Reddick for providing a strain of PepMov.

¹Assistant Professor, corresponding author: k-crosby@tamu.edu.

²Professor Emeritus.

Texas, in Spring 2001, were measured by high-performance liquid chromatography (Hoffman et al., 1983). Fruits from a hot jalapeno cultivar, ‘Grande’, grown in College Station, were also analyzed for comparison. Total capsaicin, on a dry-weight basis, was converted to Scoville Heat Units (SHU) following the method of Collins et al. (1995). ‘TMJ II’ fruit from College Station had higher total capsaicin (108 mg.kg^-1, 1620 SHU) than fruit from Uvalde (72 mg.kg ^-1, 1080 SHU). By comparison, the hot jalapeno ‘Grande’ had a capsaicin concentration of 1332 mg.kg ^-1 (19980 SHU).

In both greenhouse and field plots, TEV inoculated plants of ‘Mitla’ had small, misshapen fruit, and chlorotic leaves, while inoculated plants of ‘TMJ II’ had normal fruit and no chlorosis (Fig. 3). None of the plants appeared to be reduced in height. PepMov inoculated plants of ‘Mitla’ exhibited severe leaf distortion, plant stunting, and reduced yield of misshapen fruit. ‘TMJ II’ plants inoculated with PepMov exhibited mild chlorosis on older leaves but no distortion or misshapen fruit. No symptoms were observed on ‘TMJ II’ or ‘Mitla’ after inoculation with PVY. ELISA tests were conducted on leaf samples from inoculated plants of ‘TMJ II’ and ‘Mitla’ to determine the presence of TEV, PepMov, and PVY. Leaves from ‘Mitla’ tested positive for TEV and PepMov with absorbance readings of 1.70 and 2.21, respectively, but negative for PVY (0.021). Leaves from ‘TMJ II’ tested negative for TEV (0.047) and PVY (0.019) and weakly positive for PepMov (0.49). Susceptible control bell pepper leaves tested positive for TEV (4.0) and PepMov (2.37).

The large, low-pungency fruit of ‘TMJ II’ will make it equally suited for fresh-market and processing uses. The multiple-virus resistance and adaptation to high temperatures will be valuable attributes in regions where these stresses exist.

Availability

Breeder’s seed will be maintained by the Texas Agricultural Experiment Station at Weslaco. Application for plant variety protection is being filed for ‘TMJ II’. This cultivar may be licensed through the Texas Agricultural Experiment Station, for commercial seed production.

Literature Cited

Collins, M.D., L.M. Wasmund, and P.W. Bosland. 1995. Improved method for quantifying capsaicinoids in Capsicum using high-performance liquid chromatography. HortScience 30:137-139.

Cook, A.A. 1960. Genetics of resistance in Capsicum annuum to two virus diseases. Phytopathology 50:364-367.

Greenleaf, W.H. 1956. Inheritance of resistance to tobacco etch virus in Capsicum frutescens and in Capsicum annuum. Phytopathology46:371-375. Greenleaf, W.H. 1986. Pepper breeding, p.67-134. In: M.J. Basset (ed.). Breeding vegetable crops. AVI, Westport, Conn.

Hoffman, P.G., M.C. Lego, and W.G. Galetto.1983. Separation and quantification of red pepper major heat principles by reverse-phase high-pressure liquid chromatography. J. Agr. Food Chem. 31:1326-1330.

Kyle, M.M. and A. Palloix.1997. Proposed revision of nomenclature for potyvirus resistance genes in Capsicum. Euphytica 88:231-239.

Villalon, B. 1981. Breeding peppers to resist virus diseases. Plant Dis. 65:557-562.

Villalon, B. 1983. TAM mild jalapeno pepper^-1 pepper. HortScience 18:492-493.

Villalon, B., F.J. Dainello, and D.A. Bender. 1992. ‘TAM Veracruz’ hot jalapeno pepper. Hort Science 27:184-185.

Villalon, B., F.J. Dainello, and D.A. Bender. 1994. ‘Jaloro’ hot yellow jalapeno pepper. HortScience 29:1092-1093.

Zitter, T.A. and A.A. Cook. 1973. Inheritance of tolerance to a pepper virus in Florida. Phytopathology 63:121-1212.

HORTSCIENCE, VOL. 37(6), OCTOBER 2002

CULTIVAR & GERMPLASM RELEASES

Fig. 2. Fruit of ‘Grande’ and ‘TAM Mild Jalapeno II’.