Resistance of winter wheat in the eastern forest-steppes of the Ukraine to Septoria tritici.

Olena M. Dolhova, Iryna M. Chernyaeva, Olha P. Man'ko, and Olena Yu. Afons'ka.

Considerable spread of S. tritici in the eastern forest-steppe of the Ukraine has been observed since the 1980s. Plant infection reaches 50-60 % every year and has been as high as 80-100 % in 1991 and 1996. We hoped that artificial inoculation would assist us in searching for resistant wheats. Twenty-five isolates of the fungus were obtained from infected wheat leaves and grown in vitro on different nutrient media. We noted differences in growth rate, color, sporulation intensity, and morphology in the isolates. The data confirm the heterogeneity of the S. tritici population in the Ukraine. We used the most pathogenic isolates to artificially inoculate plants in the field by spraying them with a spore suspension in water. The infectious load was 10⁶ spores/ml. The most efficient way to raise mass inoculum was by culture on potato-glucose medium for 4 days. The greatest growth and pycnidial formation in vitro were achieved by alternating light and dark periods with a 3-fold ultraviolet irradiation.

Resistance in nearly 800 foreign and domestic wheat cultivars to S. tritici has been studied. None of the lines was completely resistant to the fungus. Disease dynamics distinguished a number of moderately susceptible lines with prolonged latent periods. These lines were 141-18-32, 316-92, and 4140-3 (Bulgaria); Auburn and Century (USA); 363 k-2-121 and F 494 j-6-11 (Romania); Hdm 13349/85 (Germany); and Rovenska 31, Odesska 130, Odesska ostysta, and Odesska zernokormova (Ukraine).

Resistance to local populations of S. tritici in the European cultivars Ikarus (Austria); Arina (Switzerland); K-4711, Granada, and Niclas (Germany); KOC 583, CHD 283, and Panda (Poland); V-22-21-1 (Bulgaria); Nemchinovskaya 25 (Russia); and the U.S. cultivar Mit remained stable for 4 years (infection of 5-10 %). The most resistant (infection up to 10 %) modern Ukrainian wheats were Luna 3, Krymska 12, Myronivska 33, Myronivska 65, and Myrych. The data for several of these lines in comparison with susceptible cultivars are given in Table 3. The resistance inheritance to S. tritici is known to be polygenic and high (Bronniman 1975). The above-mentioned cultivars should prove to be adequate sources of S. tritici resistance for breeding programs.

Table 3. Resistance of selected winter wheats to infection by Septoria tritici in 1996. Data are on the middle leaves (evaluated on 17 June) and flag leaves (evaluated on 1 July) and expressed as a percent of leaf area infected.

Accelerated aging of seed of six wheat species.

O.A. Zadorozhna.

The aging of seed of different wheat species is interesting as a theoretical and applied problem. We investigated seed aging in the following wheats: the diploid T. monococcum; tetraploids T. timopheevii, T. dicoccum, and T. durum cultivars IR-7115 and Svetlana; and hexaploids T. spelta and T. aestivum cultivars Kutulukskaya and Tselinnaya 20. Seed was stored for 5 months in the laboratory without any special drying treatment after harvest in 1995. The moisture content of the seed at the start of the experiment was 12-13 %. Aging was accelerated by the method of Lihachev (1978). Briefly, the seed was placed in hermetically covered glass bottles at 37 °C for 20 days. Control seed was stored for 20 days in the laboratory. After this time, the experimental and control samples were germinated and evaluated for quantity of chromosomal aberrations.

Accelerated aging lowers seed germination in T. timopheevii and T. dicoccum (Table 4). These species possibly do not tolerate long seed storage. Seed of the experimental samples of both T. durum cultivars had higher germination than the controls (Table 4). This phenomenon has been reported previously (Lihachev 1980; Palanisamy and Balakrishnan 1994). Consequently, this effect is negated as active vital processes dry the seed embryo tissues. This process possibly may cause a quicker loss of seed viability than in cases when no positive effects occur. These regimes to accelerate aging resulted in no difference in seed viability in T. monococcum, T. spelta, or T. aestivum. The species can be ranked in order of resistance to aging: T. timopheevii, T. dicoccum, T. durum, T. monococcum, T. spelta, and T. aestivum.

Table 4. Germination rates in wheat seed stored under normal laboratory (control) and at experimental (37 °C) conditions.

Chromosome damage occurs during long-term storage of seed (Navashin 1933; Roberts 1972). We have analyzed the number of seedlings with aberrations and numbers of aberrations in seedlings. Seed of most wheat species have a tendency for an increase in the common number of aberrations (Table 5). An analysis of this component shows an increase in the number of seedlings with chromosome aberrations (number of seed in which there are aberrations). We noted that 30 % of the T. durum seedlings had aberrations. Consequently, early types of seed aging may increase the number of plants with chromosome aberrations (number of seeds with aberrations). However, the level of aberrations in the seedlings (seeds) is not higher than in nature.

In T. timopheevii, chromosome aberrations may be a function of viability (Roberts 1972). Triticum timopheevii seed are much less viable, but do not exhibit chromosome aberrations in the first mitosis. Possibly, T. timopheevii seeds with aberrations lose viability.

These data show that accelerated aging has occurred to a different extent in seed of six wheat species. Aging increases the normal number of chromosome aberrations by increasing the quantity of seedlings with chromosome aberrations. However, the level of chromosome aberration in these seedlings is not higher than natural.

References.

Navashin MS. 1933. Origin of spontaneous mutations. Nature 131:436.

Lihachev BS and Musorina LI. 1978. Using of extreme seed storage conditions in modeling aging process. Bulletin VIR. 77:57-62 (in Russian).

Lihachev BS. 1980. Some methodological questions of seed biology aging studying. Selskohozyajstvennaya biologia. 15 (6):842-844 (in Russian).

Palanisamy V, Balakrishnan K, and Karavaratharaju TV. 1994. Accelerated aging for evaluating onion, watermelon and cosmos seeds. South Indian Horticulture. 42 (4):219-223.

Roberts EH ed. 1972. Viability of seeds. London, UK.

Table 5. Quantity of cells, quantity of seedlings, and number of chromosome aberrations observed in germinated seed of different wheat species under different storage regimes.

Useful traits of wheat amphidiploids and their hybridization with bread and durum wheat cultivars.

Oleg V. Golik.

The availability of artificial amphidiploids and their valuable attributes, including alien addition and substitution stocks, enhances their practical use in wheat breeding. In 1993, the Yurjev Institute for Plant Production (Kharkov, Ukraine) received a collection of 46 spring-type amphidiploids from the N.I. Vavilov Institute of Plant Industry, made using Aegilops and Haynaldia species. These lines were parents in hybridizations with bread and durum wheat cultivars. We assayed the level of immunity of these amphidiploids under field conditions and using artificial inoculation with powdery mildew, leaf rust, leaf blotch, dusty smut, and common bunt fungal pathogens.

To transfer resistance to the above-mentioned fungal pathogens to wheat, reciprocal crosses were made between the spring-type cultivars Kharkovskaya 2 and Kharkovskaya 93 and amphidiploids from the wheat species T. monococcum, T. sinskaya, T. timopheevii, T. militinae, T. dicoccum, and T. persicum with genomes of their wild relatives Ae. tauschii, Ae. umbellulata, Ae. speltoides, Ae. ventricosa, and H. villosum. We also used the spring durum wheat cultivars Kharkovskaya 15 and Kharkovskaya 19 in crosses. A total of 18 cross combinations was made in 1994.

Analyzing the crossability of the amphidiploids with bread wheat, in crosses where wheat was the maternal parent, showed seed set was from 2-39 % and the kernels were plump. In the reciprocal crosses, crossability was higher (from 57 to 85 %), but the kernels were shrivelled. One exception was in the hybrid combination Haynatricum (H. villosum x T. dicoccum; k-38259, TSKHA), where with both bread wheat cultivars, seed set was from 14-22 %. One probable explanation is the presence of the Haynatricum cytoplasm in a genus phylogenetically far from wheat, rather than other crossing components.

When wheat was the maternal parent, seed set was high (28-44 %) in the majority of cases. In the reciprocal combination, seed set was low (10-16 %). Some exceptions were the reciprocal crosses `Kharkovskaya 19 x PAG-31' (all amphidiploids named PAG from the VIR were made by the crossing of various forms of T. turgidum with T. monococcum, genome structure A<sup>u</sup>A<sup>u</sup>A<sup>b</sup>A<sup>b</sup>BB), where seed sets were 44 and 80 %, respectively, and `Kharkovskaya 19 x AD (T. dicoccum-Ae. speltoides amphidiploid)', where seed sets were 3.1 and 2.4 %, respectively. In these crosses, and also in the `PAG-12 x Kharkovskaya 19' combination, the kernels were nonviable. Low homology and homoeology between the parental genomes in these crosses probably explains the differences observed in seed set.

We studied the pollen fertility and seed set of the F₁ hybrid plants from these crosses after natural and artificial selfing in 1995. The hybrids F₁ also were backcrossed with the paternal wheat cultivars. High pollen fertility was found in the cross combinations `PAG-31 x Kharkovskaya 19', `PAG-12 x Kharkovskaya 15', and the reciprocal hybrids `PEAG x Kharkovskaya 93', `PEAG x Kharkovskaya 2', and `Kharkovskaya 93 x AD (Ae. ventricosa-T. dicoccum amphidiploid)'. In comparison, low pollen fertility was observed in hybrids between `Kharkovskaya 93 x AD-217 (T. timopheevii-Ae. umbellulata amphidiploid)' and `T. migushovae x Kharkovskaya 2'. The pollen was sterile in other cases. A visual evaluation of male fertility using the degree dehiscence of the anthers during flowering confirmed these data. However, in two hybrids with sterile pollen, dehiscence of some anthers was noted. These crosses were between `AD (Ae.ventricosa-T.dicoccum amphidiploid) x Kharkovskaya 93' and `AD (T. dicoccum-Ae. speltoides amphidiploid) x Kharkovskaya 93'.

The hybrid F₁s were mainly sterile, even when artificially pollinated. Exceptions were in three hybrid combinations `PEAG x Kharkovskaya 2' (seed set 2.9 %), `PEAG x Kharkovskaya 93' (46.6 %), and `Kharkovskaya 93 x AD (Ae. ventricosa-T. dicoccum amphidiploid)' (2.5 %). Hybrid combinations of PEAG with bread wheat cultivars appeared to be the most productive (seed set in backcrosses was 43.8-50.9 % and with open pollination was 40-61.1 %). The high fertility of hybrids is explained by the homology between the genomes that were crossed.

Reciprocal hybrids `AD (T. timopheevii-Ae. umbellulata amphidiploid) x Kharkovskaya 93' were completely sterile. There was no seed set from backcrosses, open pollinations, or artificial selfings. The hybrids of amphidiploids with durum wheat were generally less viable and produced less seed than crosses with bread wheat. Seed was set in five hybrids `PAG-31 x Kharkovskaya 19' (15.6 % in backcrosses, 22.3 % in open pollination), `PAG-12 x Kharkovskaya 15' (15.0 % and 14.1 %) and the reciprocal (5.6 % and 25.7 %); `AD (Ae. ventricosa-T. dicoccum amphidiploid) x Kharkovskaya 15' (1.9 % and 2.2 %) and the reciprocal (32.8 % and 7.3 %). Selfing these hybrids has not produced any grain. The different fertilities of hybrids between amphidiploids and durum wheat cultivars is impossible to explain by genome homology, because each amphidiploid contained the AB genome from T. dicoccum or T. persicum. Both genomes are homologous to the genome of T. durum. These differences are likely explained by genotype characters of the crossed lines.

Conditions in 1995 allowed us to evaluate the field resistance of F₁ hybrids to leaf rust. Hybrids of both bread wheat cultivars with PEAG, PAG-31, AD (T. dicoccum-Ae. speltoides amphidiploid), T. kiharae, T. migushovae, and AD Zhirov (T. militinae-Ae. tauschii) are completely immune in the amphidiploid. In the reciprocal cross of the hybrid `AD-217 x Kharkovskaya 93', we noted an intermediate level of resistance. Hybrids of Haynatricum and AD (Ae. ventricosa-T. dicoccum amphidiploid) with bread and durum wheat and also hybrids of PAG-12 with both durum wheat cultivars were more susceptible than the parental form.

Inheritance of 17 morphological traits was investigated in four reciprocal hybrid combinations: AD(Ae.ventricosa-T. dicoccum amphidiploid), AD-217, PEAG, and T. kiharae with Kharkovskaya 93, PAG-12, and Kharkovskaya 15. In all four combinations, the reciprocal effect was shown for the traits of ear axis length and glume length but was absent for ear width, glume tooth length, and the length of first and second awns of spikelet.

In reciprocal crosses of `PAG-12 x T. durum Kharkovskaya 15', the majority of traits had reciprocal effects, because of the comparative genetic affinity of parental plasmons. More often, whole domination or superdomination (hybrid depression) by the parent with smaller expression of a trait (as a rule wheat) was observed. The exceptions were for glume width and length of the first and second awns (both parents are awned), where the absence of the reciprocal effect dominated (awn length) or superdominated (glume length) by the parent with the higher trait expression.

Awnlessness dominated in hybrids with Kharkovskaya 93. In crosses with AD (Ae. ventricosa -T. dicoccum amphidiploid), the reciprocal effect was observed for 12 of 17 traits. The parent with the higher level of expression of the trait commonly dominated, or positive heterosis was observed in direct crosses. Dominance by the parent with less significant traits or hybrid depression was observed in the reciprocal hybrids. Distinctions between direct and return hybrids on the height of plants and peduncle length were especially sharp. The reciprocal effect of three other hybrids AD-217, PEAG, and T. kiharae with Kharkovskaya 93 was observed for 6-9 of the 17 traits, i.e., less compared with previous amphidiploids. Whole dominance usually was inherited from the parent with a lower expression of a trait.

The difference in the quantity of reciprocal effects in hybrids of amphiploids with bread wheat can be explained by the degree of distance of the cytoplasms (i.e., plasmons) from the parental forms. The AD (Ae. ventricosa-T. dicoccum amphidiploid) cytoplasm is from Ae. ventricosa, which inherited the cytoplasm from Ae. tauschii. The cytoplasms of the other four amphiploids were from wheat: PEAG from T. dicoccum, and AD-217 and T. kiharae from T. timopheevii. The reciprocal effect probably expressed more strongly in hybrids of the first amphiploid than in the other four hybrids. Although AD-217 and T. kiharae have cytoplasms from the same source, the reciprocal effect of their hybrids with bread wheat is not always for the same attributes. The plasmons of these amphiploids are under the influence of nuclear genomes from the moment of their creation. Comprehensive research using amphiploids with different genomic structures as a resource for selection can have scientific and practical significance.
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