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a ARC-Small Grain Institute, Private Bag X29, Bethlehem, South Africa, 9700;
b PANNAR Research Department, P.O. Box 17164, Bainsvlei, South Africa, 9338
c Department of Entomology, Kansas State University, Manhattan, KS, 66506, USA
* Corresponding author (TolmayV{at}arc.agric.za)
Betta-Dn1 (Reg. no. GP-785, PI 634768), Betta-Dn2 (Reg. no. GP-786, PI 634769), Betta-Dn9 (Reg. no. GP-787, PI 634770), Tugela-Dn1 (syn: ‘Tugela-DN’, Reg. no. GP-784, PI 591932), Tugela-Dn2 (Reg. no. GP-788, PI 634772), Karee-Dn2 (Reg. no. GP-789, PI 634774), and Karee-Dn8 (Reg. no. GP-790, PI 634775) Russian wheat aphid (RWA), Diuraphis noxia, resistant near isogenic lines (NILs) were developed and released by ARC-Small Grain Institute, Bethlehem, South Africa during the past 15 yr.
The first crosses in an extensive backcross breeding program to transfer resistance from PI 137739, PI 262660 (du Toit, 1987) and PI 294994 (du Toit, 1988b) to well-adapted commercial cultivars including ‘Betta’ (PI 591916) and ‘Tugela’ (PI 634771) were made in 1986. Homozygous lines, produced by selfing BC3F1 plants twice, were tested for resistance to RWA and agronomic traits under field conditions in the Free State Province in 1989 (du Toit, 1993). Initial crosses between the recurrent parent ‘Karee’ (PI 634773) and the resistance donors mentioned above were made in 1993. By 1997, BC5F1 of the combination with PI 294994 and BC3F1 of the combination with PI 262660 were completed. Resistant homozygous lines were derived through selfing by the end of 1998. RWA screening of seedlings in the greenhouse was undertaken between each generation using the method of du Toit (1988a) where seedlings were infested with about 5 RWA per plant and damage was rated 3 wk after infestation on a scale of 1 to 10 (Tolmay et al., 1999) with 1 highly resistant and 10 dead. Rust evaluations were conducted in the greenhouse on seedlings using single races prevalent in production regions at the time of screening and/or under field conditions (adult plants) using a composite of races. Rust races used in the evaluations included the following for: leaf rust (Puccinia triticina Eriks.) 3SA122, 3SA132, 3SA133, 3SA140; stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. and E. Henn) 2SA4, 2SA32, 2SA36, 2SA55, 2SA88, 2SA99, 2SA100, 2SA101, 2SA102, 2SA103; and stripe rust (P. striiformis Westend. f. sp. tritici Eriks.) 6E16, 6E22, 7E22A. Reactions to other disease were noted from field infestations if they occurred.
Betta (syn: ‘Klein Impacto’) (PI 591916) is a hard red intermediate (facultative) wheat with a medium growth period, released in South Africa in 1970 (Van Niekerk, 2001). It is especially well adapted to the medium yield potential areas of the Free State Province in South Africa. Karee (Betta//‘Triumph’/‘Agent’), a hard red intermediate (facultative) wheat with a shorter growth period than Betta, adapted to low to medium potential areas of the Free State Province, was released in 1983 (Van Deventer et al., 1984; Van Niekerk, 2001). Tugela (‘Kavkaz’/‘Jaral’) is a high-yielding hard red intermediate wheat with a medium growth period. It was released in South Africa in 1985 (Van Niekerk, 2001) especially for medium to high potential areas of the Free State Province.
PI 137739 (‘Gandum I Fasai’) a hard white winter wheat from Iran containing Dn1 (du Toit, 1987), PI 262660 (‘Turtsikum’) a white winter wheat from Azerbaijan containing Dn2 (du Toit, 1987), and PI 294994 (‘Strelinskaya Mestnaya’) a hard red winter wheat from Bulgaria initially considered to confer only Dn5 (du Toit, 1988b; Marais and du Toit, 1993), were used as RWA resistance donor parents. In subsequent work with PI 294994, Elsidaig and Zwer (1993) indicated two resistant genes, one dominant and one recessive, in this line. Zhang et al. (1998) thereafter determined that genetic variation within the accession PI 294994 was responsible for the conflicting results found in various studies and regrouped the original PI 294994 into four subaccessions based on their resistance to RWA. All three resistance donor accessions were confirmed resistant to South African RWA in both the greenhouse (du Toit, 1987, 1988b) and under field conditions (du Toit, 1990).
All NILs reported here have resistance to South African RWA in both seedling and adult plant stages. Betta-Dn1 has the pedigree Betta*4/PI 137739 and is also known as Betta-DN, a commercial cultivar well adapted to low to medium potential areas of the Free State Province, South Africa. Like Betta, Betta-Dn1 has excellent preharvest sprouting resistance, good straw strength but poor tolerance to aluminum in the soil. Betta-Dn1 has a mean test weight of 78 kg hL–1, coleoptile length of 94 mm, plant height of 1040 to 1050 mm and growth period of 122 to 144 d. This compares well with Betta that also has a mean test weight of 78 kg hL–1, coleoptile length of 92 mm, plant height of 950 to 1120 mm and growth period of 120 to 140 d. Betta-Dn1 is moderately resistant to stem rust, and glume blotch [caused by Septoria nodorum (Berk.) Berk. in Berk. & Broome], moderately susceptible to leaf rust and susceptible to stripe rust and crown rot (caused by Fusarium spp.).
Betta-Dn2 (tested as line T93/14) with the pedigree Betta*4/PI 262660 is very susceptible to aluminum in the soil, stem rust, and leaf rust. Betta-Dn2 has good resistance to preharvest sprouting, a similar growth period to that of Betta, a mean coleoptile length of 86 mm, plant height of 700 to 800 mm and test weight of 75 kg hL–1.
Betta-Dn9 is a selection by Lui et al. (2001) from the line tested as T96/5. T96/5 with the pedigree Betta*4/PI 294994, is very susceptible to aluminum in the soil and leaf rust but has resistance to preharvest sprouting and stem rust. It has a mean coleoptile length of 85 mm, test weight of 75 kg hL–1, a mean plant height of 1190 mm and a growth period of 130 to 140 d. It is not known from which subaccession of PI 294994, as identified by Zhang et al. (1998), Betta-Dn9 is derived.
Tugela-Dn1, with the pedigree Tugela*4/PI 137739, is also known as Tugela-DN (PI 591932), a commercial cultivar that was released in 1992 (Van Niekerk, 2001). It has a limited vernalization requirement, is well adapted on low to high potential areas in the Free State Province, and similar to Tugela has a very good straw strength and good tolerance to aluminum in the soil but poor preharvest sprouting tolerance. The mean test weight of Tugela-Dn1 is 76 kg hL–1; mean coleoptile, 67 mm; plant height, 800 to 850 mm; and growth period, 130 to 140 d. Recurrent parent Tugela has a mean test weight of 75 kg hL–1, mean coleoptile of 65 mm, plant height of 750 to 820 mm, and a growth period of 135 to 140 d. Tugela-DN is resistant to both stem rust and stripe rust but susceptible to crown rot and glume blotch, while Tugela is resistant to stem rust, moderately susceptible to leaf rust and crown rot, and susceptible to scab (caused by Fusarium spp.) and glume blotch.
Tugela-Dn2 (tested as line T93/12), with the pedigree Tugela*4/PI 262660, is tolerant to aluminum in the soil and resistant to stem rust but susceptible to preharvest sprouting and leaf rust. Tugela-Dn2 has a mean test weight of 76 kg hL–1, mean coleoptile length of 62 mm, mean plant height of 700 to 850 mm, and growth period similar to that of Tugela.
Karee-Dn2, with the pedigree Karee*4/PI 262660, and Karee-Dn8, with the pedigree Karee*6/PI 294994, are un numbered backcross breeding lines for which no agronomic data are available. The recurrent parent Karee has fair straw strength, good resistance to preharvest sprouting, and poor tolerance to aluminum in the soil. It has a mean test weight of 80 kg hL–1, mean coleoptile of 74 mm, mean plant height of 950 to 1100 mm, and mean growth period of 125 to 130 d. Karee is resistant to stem rust and moderately resistant to leaf rust and glume blotch but susceptible to scab and crown rot. It is not known from which subaccession of PI 294994, as identified by Zhang et al. (1998), Karee-Dn8 is derived.
Seed of all lines has been deposited in the U.S. National Plant Germplasm System where these materials will be available for research purposes. Small quantities of seed (5 g) are also available to researchers on written request to the Research and Technology Manager, ARC-Small Grain Institute, Private Bag X29, Bethlehem, South Africa, 9700. It is requested that the source of this material be appropriately acknowledged in future usage by wheat breeding and genetics programs.
NOTES
Accepted for publication June 30, 2005.
REFERENCES
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