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Powdery mildew is a widespread disease of common wheat in Europe and in other regions with cool and temperate climate and significantly reduces grain yield. Only a few major resistance genes are currently in use at present in commercial wheat cultivars. Thus, new sources of disease resistance are needed.

We investigated the resistance to powdery mildew in introgresed wheat lines produced at the Institute of Plant Industry, St.Petersburg, Russia. These lines were selected in the progeny of intraspecific hybrids and characterized by disease resistance (Zarubailo 1984). The genetical control of powdery mildew resistance and inheritance of the resistance genes were determined in the Department of Genetics of the Institute of Plant Industry (Lebedeva 1984, 1987). This study aimed to identify the mildew resistance genes in introgressed wheat lines. The seeds of these lines were kindly provided to us by Prof. B. Rigin (Institute of Plant Industry, St. Petersburg, Russia).

The tests for mildew resistance were made on segments of primary leaves of host-plants grown in a phytotron. The leaf segments were placed in petridishes on 6 g/l agar with 35 mg/l benzimidazole (Lutz et al. 1992). The mildew isolates used for the elucidation of resistance genes were collected from several European countries and selected from single spore progenies by E. Limpert, Zurich, Switzerland. Near-isogenic lines of the cultivar Chancellor with known mildew resistance genes and TP114, backcrossed to the cultivar Starke and possessing the resistance gene Pm6, were kindly provided by Prof. R. McIntosh, Australia. The remaining differential cultivars were obtained from Profs. F. Zeller and F. Felsenstein, Institut für Pflanzenbau und Pflanzenzüchtung, Weihenstephan, Germany.

Table 1 presents the different types of interactions between cultivars and lines of common wheat carrying known major genes for resistance to powdery mildew and 11 pathogen isolates. Host-plant reaction was classified as follows: r = resistant, s = susceptible, i = intermediate. Compound ratings r,i and i,s indicate both reaction types. The rating s/i means that both susceptible and intermediate responces were observed in the plant population.

Table 1. Reaction of cultivars and differentiating lines carrying genes for resistance to powdery mildew inoculated with 11 isolates of Erysiphe graminis f. sp. tritici. Host-plant reaction was classified as follows: r = resistant, s = susceptible, i = intermediate; compound ratings r,i and i,s indicate both reaction types; the rating s/i means that both susceptible and intermediate responces were observed in the plant population.

Cutlivar/line Pm resistance gene Erysiphe graminis tritici isolate no.

2 5 6 9 10 12 13 14 15 16 17

Axminister / 8*Cc 1 r s r i,s r s s s r s s

Ulka / 8*Cc 2 s r r s r s s s r s s

Asosan / 8*Cc 3a r s r r r s r r s s i

Chul / 8*Cc 3b r s s r r r r r s r i,s

Sonora / 8*Cc 3c r s s i r s r i,s s s s

Kolibri 3d s s s r s r s r r s r

Khapli / 8*Cc 4a s r s r i r s s i s i

Armada 4b s r s r r r s s s s s

Hope 5 s s s s r s s r s s s

TP 114 / 2*St 6 s r,i r,i r r,i s r,i r,i r,i i s

Disponent 8 r s s r s r s s s s r

Normandie 1+2+9 r r r r r s s s r s s

BRG 3N 16 r r r r r r r r r r r

XX 186 19 s s r r r r i,s r s r,i r

Table 1. Reaction of cultivars and differentiating lines carrying genes for resistance to powdery mildew inoculated with 11 isolates of *Erysiphe graminis* f. sp. *tritici*. Host-plant reaction was classified as follows: r = resistant, s = susceptible, i = intermediate; compound ratings r,i and i,s indicate both reaction types; the rating s/i means that both susceptible and intermediate responces were observed in the plant population.
Cutlivar/line	Pm resistance gene	Erysiphe graminis tritici isolate no.
2	5	6	9	10	12	13	14	15	16	17
Axminister / 8*Cc	1	r	s	r	i,s	r	s	s	s	r	s	s
Ulka / 8*Cc	2	s	r	r	s	r	s	s	s	r	s	s
Asosan / 8*Cc	3a	r	s	r	r	r	s	r	r	s	s	i
Chul / 8*Cc	3b	r	s	s	r	r	r	r	r	s	r	i,s
Sonora / 8*Cc	3c	r	s	s	i	r	s	r	i,s	s	s	s
Kolibri	3d	s	s	s	r	s	r	s	r	r	s	r
Khapli / 8*Cc	4a	s	r	s	r	i	r	s	s	i	s	i
Armada	4b	s	r	s	r	r	r	s	s	s	s	s
Hope	5	s	s	s	s	r	s	s	r	s	s	s
TP 114 / 2*St	6	s	r,i	r,i	r	r,i	s	r,i	r,i	r,i	i	s
Disponent	8	r	s	s	r	s	r	s	s	s	s	r
Normandie	1+2+9	r	r	r	r	r	s	s	s	r	s	s
BRG 3N	16	r	r	r	r	r	r	r	r	r	r	r
XX 186	19	s	s	r	r	r	r	i,s	r	s	r,i	r

Table 2 summarizes our data on the reaction of wheat lines inoculated with 11 different isolates of powdery mildew. All lines in this study were divided into four groups. The first group includes lines developed on the basis of Triticale : IL-1, IL-2, IL-3, and IL-4. These spring types have one gene conferring resistance to powdery mildew, which is located on the 2B chromosome (Lebedeva 1987). The 2B chromosome is known to carry the highly effective resistance gene Pm6 (Jorgensen and Jensen 1973). The reaction of plants to inoculation with test isolates leads us to assume that lines IL-1, IL-2, IL-3, and IL-4 have the resistance gene combination Pm2 + Pm6. Resistance of the second group of lines, developed from the hybrid progeny (Jalta / Timvera // Gabo /3/ Dunde 48), was established earlier by Lebedeva (1987), who assumed that these lines have one resistance gene and, very likely, a gene(s) modifier.

Table 2. Disease response of 13 wheat lines inoculated with 11 isolates of Erysiphe graminis f. sp. tritici. Host-plant reaction was classified as follows: r = resistant, s = susceptible, i = intermediate; compound ratings r,i and i,s indicate both reaction types; the rating s/i means that both susceptible and intermediate responces were observed in the plant population.

Line Resistance gene Isolates of E. graminis tritici Pedigree

2 5 6 9 10 12 13 14 15 16 17

I group

IL-1 Pm2+Pm6 s r r r r s r r r r s Triticale / T. aestivum // T. aestivum

IL-2 Pm2+Pm6 s r r r r s r r r r,i s

IL-3 Pm2+Pm6 s r r r r s r r,i r,i r s

IL-4 Pm2+Pm6 s r r r r s r r r,i r,i s

II group

248-1 Pm2+Pm6 s r r r r,i s r r r r,i s Jalta / Timvera // Gabo /3/ Dunde 48

248-2 Pm2+Pm3a r,i r,i r,i r r s r r,i r,i s s

248-3 Pm2+Pm6? r,i r r r r r,i r r,i r r r,i

249-1 Pm2+Pm3a r r r r r i,s r r r s s

249-2 Pm2+Pm6+ Pm4b s r r r r r,i r r r r s

III group

250-4 Pm2+Pm6 s r r r r,i s r,i r r r s Mengavi /3/ Gabo // Koda / Spica

251-1 Pm2+Pm3a r r r r r s,i r r r s s

IV group

250-3 ? s r r r s r,i r,i r s s r,i Koda / Gabo / Eureca / CI12632

252-2 --- s i r,i s s s i/r s s s i Gabo / Kapstein

Table 2. Disease response of 13 wheat lines inoculated with 11 isolates of *Erysiphe graminis* f. sp. *tritici*. Host-plant reaction was classified as follows: r = resistant, s = susceptible, i = intermediate; compound ratings r,i and i,s indicate both reaction types; the rating s/i means that both susceptible and intermediate responces were observed in the plant population.
Line	Resistance gene	Isolates of E. graminis tritici	Pedigree
2	5	6	9	10	12	13	14	15	16	17
I group
IL-1	Pm2+Pm6	s	r	r	r	r	s	r	r	r	r	s	Triticale / T. aestivum // T. aestivum
IL-2	Pm2+Pm6	s	r	r	r	r	s	r	r	r	r,i	s
IL-3	Pm2+Pm6	s	r	r	r	r	s	r	r,i	r,i	r	s
IL-4	Pm2+Pm6	s	r	r	r	r	s	r	r	r,i	r,i	s
II group
248-1	Pm2+Pm6	s	r	r	r	r,i	s	r	r	r	r,i	s	Jalta / Timvera // Gabo /3/ Dunde 48
248-2	Pm2+Pm3a	r,i	r,i	r,i	r	r	s	r	r,i	r,i	s	s
248-3	Pm2+Pm6?	r,i	r	r	r	r	r,i	r	r,i	r	r	r,i
249-1	Pm2+Pm3a	r	r	r	r	r	i,s	r	r	r	s	s
249-2	Pm2+Pm6+ Pm4b	s	r	r	r	r	r,i	r	r	r	r	s
III group
250-4	Pm2+Pm6	s	r	r	r	r,i	s	r,i	r	r	r	s	Mengavi /3/ Gabo // Koda / Spica
251-1	Pm2+Pm3a	r	r	r	r	r	s,i	r	r	r	s	s
IV group
250-3	?	s	r	r	r	s	r,i	r,i	r	s	s	r,i	Koda / Gabo / Eureca / CI12632
252-2	---	s	i	r,i	s	s	s	i/r	s	s	s	i	Gabo / Kapstein

The responses of lines 248-1, 248-2, 248-3, 249-1, and 249-2 after inoculation with a set of 11 powdery mildew isolates appears to correspond with resistance genes Pm2 and Pm6. Two lines of this group, 248-2 and 249-1, exibit a similar type of resistance with protection by the gene combination Pm2 + Pm3a. The resistance of line 249-2 is thought to be controlled by the gene combination Pm2-+ Pm6 + Pm4b. Results of earlier genetic analysis showed that lines of the third group, 250-4 and 251-1, evidently possess two unlinked resistance genes (Lebedeva 1984). The present study establishes that line 250-4 has the gene combination Pm2 + Pm6, and line 251-1 has the gene combination Pm2 + Pm3a.

We did not succed in identifing the genes using the available isolates that control resistance in line 250-3. The response of line 252-2 following inoculation with powdery mildew isolates showed that this line did not possess any effective resistance genes. The obtained results showed that the most of introgressed lines included in the I, II, and III groups have the resistance genes Pm2 and Pm6. The pedigrees of resistant lines have derivatives of T. timopheevii (Timvera, Mengavi, C.I. 12632) and T. durum (Gabo, Koda). The genes Pm2 and Pm6 were introduced to T. aestivum from T. timopheevii (Allard and Shands 1954; Nyquist 1963; Jorgensen and Jensen 1972, 1973). Our earlier data also support the assumption that the genes Pm2 and Pm6 can be transferred successfully to the common wheat genome from T. timopheevii (Peusha et al. 1995). The resistance genes from T. timopheevii and from other wheat relatives may be valuable additions to wheat germplasm.

Allard R and Shands RG. 1954. Inheritance of resistance to stem rust and powdery mildew in cytologically stable spring wheats derived from Triticum timopheevii. Phytopathology 44:266-274.

Jorgensen JH and Jensen CJ. 1972. Genes for resistance to wheat powdery mildew in derivatives of Triticum timopheevii and T. carthlicum. Euphytica 21:121-128.

Jorgensen JH and Jensen CJ. 1973. Gene Pm6 for resistance to powdery mildew in wheat. Euphytica 22:423-425.

Lebedeva TV. 1984. A genetic characteristic of age resistance to powdery mildew in introgressive lines of soft wheat. Bull Appl Bot, Genet and Plant Breed 85:19-23.

Lebedeva TV. 1987. Genetic analysis on powdery mildew resistance in introgressive soft wheat lines-rye derivatives. Res Bull N. Vavilov Inst of Plant Industry 174:32-35.

Lutz J, Limpert E, Bartos P, and Zeller FJ. 1992. Identification of powdery mildew resistance genes in common wheat (Triticum aestivum L.): I. Czechoslovakian cultivars Plant Breed 108:33-39.

Nyquist WE. 1963. Inheritance of powdery mildew resistance in hybrids involving a common wheat strain derived from Triticum timopheevii. Crop Sci 3:40-43.

Peusha HO, Stephan U, Hsam SLK, Felsenstein FG, Enno TM, and Zeller FJ. 1995. Identification of genes for resistance to powdery mildew in common wheat (Triticum aestivum L.): IV. Breeding lines derived from wide crosses of Russian cultivars with species T. timopheevii Zhuk., T. militinae Zhuk. et Migush., T. dicoccum (Schrank) Schuebl., Aegilops speltoides Taush. Rus J Genet 31:1-7.

Zarubailo TYa. 1984. Some results of genetic studies. Bull Appl Bot, Genet and Plant Breed 85:3-5.