Analysis of genetic profiles of spring wheats from Russia.

S.P. Martynov and T.V. Dobrotvorskaya.
It is possible that the activities of plant breeders decrease the genetic diversity of wheat cultivars and, therefore, accelerate the extent of genetic erosion. There exists a tendency to grow a small number of highly productive and genetically closely related wheat cultivars on large areas of land. This can increase crop vulnerability and cause significant economic losses because of the uniform susceptibility to new pathogen genotypes. An examination of the genetic diversity can assist plant breeders in avoiding an undesirable narrowing of the genetic pool as a result of plant improvement. An analysis of genetic diversity is useful in planning crosses involving the hybridization of genetically divergent varieties.
This paper presents the results of a study of genetic diversity of spring wheats produced in the last 25 years performed with the aid of the genetic profile analyses of these wheats. Since 1970, 148 cultivars have been released in the former USSR (including cultivars from CIS). Four cultivars from the Trans-Caucasian Territory and Central Asia were excluded from this number. Also excluded were 36 cultivars with pedigrees that were impossible to analyse (in cases where a mixture of pollen from different cultivars was used as a male parent, if some parents pedigrees were unknown, or if cultivars were produced by means of open pollination). The full list of the 108 spring bread wheat cultivars from Belarus, Kazakhstan, Russia, and the Ukraine is as follows:
1971-1975: Biryusinka, Buryatskaya, Graecum-114, Kharkovskaya-93, Kinelskaya-30, Leningradka, Lutescens-44, Moskovskaya-21, Moskovskaya-35, Novosibirskaya-67, Pyrothrix-28, Saratovskaya-42, Shortandinskaya-25, Uralskaya-52, and Zarnitsa.
1976-1980: Belorusskaya-12, Bezenchukskaya-129, Karagandinskaya-2, Kutulukskaya, Lutescens-47, Mironovskaya yarovaya, Omskaya-9, Orenburgskaya-1, Primorskaya-14, Rannyaya-73, Salyut, Saratovskaya-44, Saratovskaya-45, Sibakovskaya-3, Sibiryachka-4, Saratovskaya-46, Shadrinskaya, Tselinnaya-20, Tselinnaya-21, and Uralskaya yubileinaya.
1981-1985: AS-29, Belorusskaya-80, Botanicheskaya-2, Buryatskaya-79, Dalnevostochnaya, Druzhina, Ershovskaya-32, Irtyshanka-10, Kharkovskaya-2, Kharkovskaya-6, Krasnoyarskaya, Kurganskaya-1, Michurinskaya rannyaya, Omskaya-12, Priobskaya, Rossiyanka, Saratovskaya-54, Taezhnaya, Tyumenskaya-80, Vega, Vera, Zhigulevskaya, and Zhuravka.
1986-1990: Albidum-28, Altaiskaya-81, Angara-86, Budimir, Diana-3, Enita, Kharkovskaya-10, Lutescens-25, Lyuba, Novosibirskaya-81, Omskaya-17, Omskaya-19, Saratovskaya-55, Simbirka, Spektr, Tselinnaya-26, Tselinnaya-60, Tselinnaya yubileinaya, Tulunskaya-10, Tulunskaya-12, Tyumenskaya rannyaya, Ulbinka-25, Uralochka, and Zyryanovka.
1991-1994: Albidum-29, Altaiskaya-50, Altaiskaya-88, Amurskaya-90, Dias-2, Erythrospermum-5, Erythrospermum-59, Ivolga, Kazakhstanskaya rannespelaya, Kharkovskaya-12, Komsomolskaya-29, Krestyanka, L-503, Leningradskaya-88, Lutescens-70, Lutescens-521, Novosibirskaya-22, Novosibirskaya-89, Omskaya-18, Omskaya-20, Prilenskaya-6, Primorskaya, Priokskaya, Samsar, Saratovskaya-58, and Tulaikovskaya-1.
With the aid of the Genetic Resources Information System for wheat (GRIS 1.5) package, the genetic profiles of cultivars were estimated. The genetic contributions of the different land race ancestors in the genome of the 108 cultivars were analysed with the aid of path coefficients. Cluster analysis was performed on the matrix of genetic profiles using a hierarchical agglomerative algorithm for the mean connection. The following equation was used to estimate the similarity between cultivar `k' and cultivar `l':
S (k,l) = SUM min {P (i,k); P (i,l)} ,
where S (k,l) is the measure of similarity between the cultivars `k' and `l'; min {P (i,k); P (i,l)} is the minimum of P (i,k) and P (i,l) where P (i,k) and P (i,l) are contributions of `i' ancestor to `k' and `l' cultivars.
The pedigrees of the 108 cultivars studied were traced to 106 land race ancestors from Russia; the Ukraine; and other countries of Europe, Asia, Africa, and America. Genetic profiles of spring wheats from the former USSR and CIS include, on average, 14 ancestors. A pedigree can include 1,000 and more parents, grandparents, great-grandparents, and so on. But all are produced from a smaller number of ancestors, land races and accessions with unknown pedigrees, which make the top of a pedigree tree. These are the components of the genetic profile.
An analysis of pedigrees indicates that the majority of cultivars from different regions are related because many of them have similar ancestors. For example, a land race from the Saratov province, Poltavka, is in the pedigree of 79 cultivars (73 %), including 53 cultivars (49 %) that are descendants of the spring wheat, Saratovskaya-29. Twenty-five cultivars (23 %) are descendants of the winter wheat, Bezostaya-1. Nevertheless, the pool of releasing cultivars is sufficiently diverse. The change of mean genetic contributions of 10 predominant ancestors is represented graphically in Figure 1 (1 - Poltavka, 2 - Selivanovskii Rusak, 3 - Crimean, 4 - Ostka Galicijska, 5 - Hard Red Calcutta, 6 - Iumillo, 7 - Rumkers Erli, 8 - K-34291 from Altai, 9 - a land race from the Ukraine, and 10 - a land race from the Irkutsk province). To study the genetic diversity of spring wheats produced in different regions, a cluster analysis was performed on the matrix of genetic profiles for given clusters. The 108 cultivars were divided into nine groups; every group included cultivars that were released in the corresponding region. In most cases the cluster analysis indicated more similarity between cultivars that were produced in one region than between cultivars from different regions (Table 1).
To study the time dynamics of genetic diversity, the 108 cultivars were divided into five groups. Every group included cultivars that were released in a 5-year period. Table 2 illustrates the similarity between and within these five periods using the similarity indices calculated as described above.
Within the groups (clusters), the indices of similarity indicate about the same intercluster index. This suggests a similar level of genetic diversity in the set of cultivars that were produced in the last five, 5-year periods.
Table 1. Matrix of mean indices of similarity within (diagonal) and between the nine groups from different regions.
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Regions*
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Cv. 1 2 3 4 5 6 7 8 9
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1 0.260 0.078 0.114 0.129 0.100 0.105 0.123 0.126 0.075
2 0.269 0.203 0.122 0.197 0.187 0.179 0.176 0.147
3 0.409 0.171 0.295 0.287 0.263 0.214 0.268
4 0.267 0.154 0.138 0.157 0.121 0.094
5 0.383 0.288 0.257 0.204 0.123
6 0.321 0.259 0.215 0.152
7 0.264 0.224 0.139
8 0.325 0.146
9 0.418
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* 1 - Belarus and Northwest of Russia, 2 - the Ukraine, 3 - South of Russia,
4 - Moscow province, 5 - Volga region, 6 - Kazakhstan, 7 - Ural and West Siberia,
8 - East Siberia, 9 - Far East region.
Some idea about the dynamics of the genetic diversity of cultivars is given by a mean number of land races that are included in the genetic profiles of cultivars. This index obviously increases from one 5-year period to the next: 1971-1975 = 6.4, 1976-1980 = 9.7, 1981-1985 = 13.8, 1986-1990 = 16.3, and 1991-1994 = 20.6. The analysis of variance of the genetic profiles indicates that the expansion of genetic profiles of released cultivars are significant (Table 3).
Table 2. Matrix of mean indices of similarity within (diagonal) and between the five groups from different 5-year periods.
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Period 1971-1975 1976-1980 1981-1985 1986-1990 1991-1994
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1971-1975 0.169 0.184 0.169 0.171 0.173
1976-1980 0.268 0.222 0.220 0.231
1981-1985 0.239 0.219 0.226
1986-1990 0.244 0.227
1991-1994 0.254
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Table 3. The analysis of variance for cultivar genetic profiles.
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Item SS df ms F-test
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Total 8742.9 107 - -
Periods 2505.7 4 626.4 10.7*
Error 6037.2 103 58.6 -
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* Significant at the 1 % level.

Consequently, the genetic base of modern spring wheat cultivars increases. For instance, the cultivars of Enita (1990), Ivolga (1992), and L-503 (1993), released in four regions of Russia, and Priokskaya (1993), released in five regions, have genetic profiles that include 33, 20, 34, and 40 land races, respectively.
Thus, there is no evidence of genetic erosion or narrow genetic diversity of spring bread wheats during the period of 25 years of wheat breeding in Russia. The results obtained show that, in the last five 5-year periods, a tendency has emerged toward an increase in the genetic base of new Russian spring bread wheats.
Vavilov Institute of Plant Industry (VIR)
Wheat Department, 44 Bolshaya Morskaya str., St.Petersburg 190000, Russia.
Fax: (7-812) 311-8762.
Development of the bread wheat near isogenic lines differing in Rht genes.
A. Merezhko, N. Loskutova, I. Zveynek, and E. Zuev.
Wheat breeders pay considerable attention to plant height as a character that has a significant influence on resistance to lodging. The development of semidwarf varieties is one of the highest achievements of 20th century in the world of wheat breeding and provided a breakthrough in grain production (Athwal 1971; Lupton 1980; Pugsley 1983). Twenty Rht genes (reduced height) are included in the "Catalogue of gene symbols for wheat" (McIntosh 1988). It is important to determine the best allelic combinations of these genes that provide the required resistance to lodging and high productivity in different regions.
The VIR wheat collection contains a rich diversity of forms with a gradual transition from very short (about 20-30 cm) to extremely tall, more than 160 cm (under favorable growing conditions). Although 20 Rht genes are identified, the plant height of the accessions in our experiments was controlled by 1-3 (more rarely 4) genes. This phenomenon can be explained by the fact that combining more than three major Rht genes in one genotype causes a low viability of the created forms and their elimination from genetic stocks.
We developed the near isogenic lines (NILs) using 15 sources of shortness and 2 sources of tallness and involving 2 to 7 backcrosses (BC). The results are in Table 1 below.
These sources cover almost all the intraspecies diversity of plant height in bread wheat. The lines Polukarlic and Kavkaz (EM1) and the varieties Miniluna, Rabamellekii, and Ostka Suska carry Rht genes that are still unidentified. The spring isogenic line (Vrn3) of the widely adapted winter variety, Mironovskaya 808 (M808S), was used as a recurrent parent. Such an approach also will permit the rapid creation of an NIL set with a winter growth habit.
A majority of Rht gene sources differ from M808S by one major gene and 1-2 minor genes that control plant height. For this reason, considerable attention was made to transfer to the NIL only the major genes. The genes rht8 and rht9 were selected from the variety Mara and their numbers were designated tentatively. It will be specified in further investigations. The cultivar Ai-bian 1 is known as the source of the dominant gene Rht10 (Izumi et al. 1981; Sasakuma and Izumi 1983). However, in addition to Rht10, it carries a second major recessive Rht gene. For development of the NILs, we transferred only Rht10. The preliminary study of the most advanced NILs in the Northwest of Russia in 1993-1994 has shown the following average plant height (cm): Rht RM - 151, Rht OS - 128; M808S (recurrent parent) - 119; rht1 - 93; rht2 - 99; Rht3 - 58; rht4 - 68; rht5 - 76; rht8 - 105; rht9 - 94; rht8, rht9 - 73; rht13 - 83; Rht PK - 76; rht Mn - 94.
The majority of Rht genes under consideration are recessive or intermediate and have mainly additive interactions. Some allelic combinations demonstrate the presence of weak epistatic effects. The existence of a complementary gene interaction between rht8 and rht9 can be proposed, because the sum of their individual effects on plant height reduction (39 cm) is smaller than joint effect of these genes combined in one line (46 cm).
The recurrent parent, M808S, tends to lodge, but all developed semidwarf NILs are resistant to this factor. The lines with genes rht8 and rht9 will lodge under wet conditions. The genetic background of very tall NILs (Rht RM, Rht OS) could be used for "elongation" of semidwarf lines; especially important for breeding in dry areas. Some Rht genes (e.g., rht5) have negative pleiotropic effects on spike productiveness. Therefore, their use in plant breeding is doubtful. According to the preliminary NIL evaluation mentioned above, the genes rht1, rht2, rht8, rht9, rht MN, and, probably, rht13, are more promising for transferring into adapted varieties.
Table 1. Near-isogenic lines developed using 15 different sources of Rht genes.
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Num. Source of Character Gene Number
Rht genes of BC
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1 Siete Cerros 66 Short Rht1 7
2 Bajio 67 " Rht2 5
3 Tom Pouce " Rht3 7
4 Burt ert 937 " Rht4 3
5 Marfed ert 1 " Rht5 5
6 Brevor " Rht6 2
7 Mara " Rht8 3
8 " " Rht9 3
9 " " Rht8, Rht9 3
10 Ai-bian 1 " Rht10 2
11 Karsagi 522 M7K " Rht12 2
12 Magnif 41M1 " Rht13 5
13 Durox " Rht15 2
14 Chris M1 " Rht17 2
15 Polukarlic " Rht PK 7
16 Miniluna " Rht MN 5
17 Kavkaz (EM1) " Rht KV 3
18 Rabamellekii Tall Rht RM 5
19 Ostka Suska " Rht OS 6
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References.
Athwal DS. 1971. Semidwarf rice and wheat in global food needs. Quart Rev Biol 46(1):1-34.
Izumi N, Sawada S, and Sasakuma T. 1981. A dominant gene of dwarfism located on chromosome 4D in Triticum aestivum cv. "Ai-bian 1". Wheat Inf Serv 53:21-23.

Lupton FGH. 1980. Breeding for higher yields. In: Physiological Aspects Crop Production, Werblaufen, Bern. Pp. 27-36.
McIntosh RA. 1988. Catalogue of gene symbols for wheat. Proc 7th Inter Wheat Genet Symp (Miller TE and Koebner RMD eds), Cambridge, England. Pp. 1225-1323.
Pugsley AT. 1983. The impact of plant physiology on Australian wheat breeding. Euphytica 32(3):743-748.
Sasakuma T and Izumi N. 1983. Genetical analysis of dwarfism in common wheat. Wheat Inf Serv 56:41-42.