GrainGenes

Complex-step hybridization in spring bread wheat breeding for drought resistance and high grain quality.

A.I. Kusmenko, L.G. Ilyina, A.N. Galkin, K.F. Guryanova, V.A. Danilova, and T.K. Sotova.

The main trend in the bread wheat breeding program in the southeast region of Russia from the earliest breeding work of Saratov in 1911 is for drought resistance coupled with high grain quality. The main breeding method is complex-step hybridization, as worked out by A.P. Shekhurdin. At the present time, the screening nurseries include some advanced lines that combine these important agronomic characteristics. These advanced lines originated from the cultivars Tselinnaya 20, Tselinnaya yubileinaya, and L-503 from Russia and Allex and ND-600 from the U.S.A. The best line, S-2052, originated from the cross `Saratovskaya 58/Saratovskaya 60//Saratovskaya 58/Tselinnaya 20'. Yield performance and grain quality of this advanced line are presented in Table 4.

Table 4. Yield performance and grain quality of the advanced line S-2052 (1993-95 average).

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Grain yield Flour baking quality

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Loaf Texture Valorimeter

% of check* volume score number

Varieties t/ha S. 42 S. 58 (cub. sm.) (1-5) (u.v.)

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S-2052 2.27 146 122 657 4.9 60

S.58 1.86 120 100 709 4.7 65

S.42 1.55 100 80 644 4.4 60

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* S. 42 = Saratovskaya 42; S. 58 = Saratovskaya 58.

The new line had a much greater grain yield compared with the check cultivars Saratovskaya 58 and Saratovskaya 42 in the very dry 1995 season (33 and 74 %, respectively) and in the more favorable years 1993-94 (19 and 40 %, respectively). In addition, S-2052 has a more stable yield over a wide range of environments. The highest grain yield from this line was in 1993 at 3.05 t/ha (0.25 t/ha better than Saratovskaya 58 and 0.6 t/ha better than Saratovskaya 42). In all years, S-2052 had strong gluten. In conclusion, complex-step hybridization allows the development of wheat varieties that combine such important characteristics as drought resistance, response to environmental improvement, stable yields, and high grain quality.

Response of different wheat species in anther culture.

T.I. Dyatchouk and S.W. Stoljarova.

Anthers from different wheat species and interspecific hybrids were cultured on Chinese potato medium. Among the species studied, the range of the frequency of callus induction was T. aestivum > T. persicum > T. durum > T. timopheevi > T. dicoccum. In general, a higher frequency of responding anthers was observed in bread wheat than in other species. Under favorable conditions, the frequency of embryo formation was 5.64 %, the regeneration rate was 1.94 %, and green plant formation was 1.02 %. About 70 % of spring bread wheat genotypes (including cultivars from the southeast region of Russia and F2 and F3 generation crosses) produced plants. Very little is known about the anther culture ability of tetraploid species. In our data, T. persicum was the best-responding species among the tetraploids. Callus induction frequency was 1.2-7. 4 % according to seasonal influences, with a relatively high number of regenerated plants compared to hexaploid wheat. Triticum timopheevi and T. durum responded with 0.16-7.83 % embryogenic structures. In durum wheat, plant regeneration was very low and most of the plants were albino. From T. timopheevii calli, plants could not be regenerated. Triticum dicoccum did not respond to anther culture. Interspecific hybrids of bread wheat and tetraploid species were tested for their in vitro androgenesis capacity. The microspore-derived calli values were intermediate between or somewhat higher than those of both parents. In backcross generations, the callus induction frequency was approximately equal to that of the reccurent parents. Single plants were regenerated from interspecific hybrids of bread wheat with T. durum and T. timopheevii. In general, more than 300 DH lines from interspecific crosses were developed, with most of the lines from `T. aestivum x T. persicum' crosses.

Subunit composition of storage proteins and breadmaking quality of wheat.

Yu.V. Italianskaya.

The breadmaking quality of wheat is known to be associated with seed storage protein properties. To understand the role of protein quality for breadmaking, the endosperm proteins have been characterized by gel electrophoresis, and their controlling genes subjected to genetical analysis. However, most researchers studied either the positive or negative influence of individual, allelic gliadin or glutenin proteins on quality. The results obtained are contradictory.

In our work, differences in breadmaking quality that occur between wheat varieties were shown to be caused by the accumulation in a maturing seed of different HMW polypeptides (60-95 kD) and especially the protein subunits with middle molecular weight (MMW) in the range 45-55 kD, rather than by the presence of any individual components. After single seed SDS-PAGE of whole storage proteins, the biochemical quality index (Q) was evaluated as a ratio of protein amount in the HMW zone to that of the MMW zone. This technique, a modification of the method of Bogdanov and coworkers (1987), showed a strong Q-index association with the technological parameters of quality. The correlation coefficients were highest for the most important quality factors, i.e., flour strength and volume of baked bread (r = -0.88 and -0.85, respectively). The advantages of this method include the small sample required and independence of the environment in which the material was grown. This test is the most useful for screening large numbers of newly developed wheat lines for potential breadmaking quality.

The plastid apparatus of different organs spring wheat.

Luda O. Mozayskaya.

Under field conditions at the start of grain filling, the flag leaf contains the highest amount of chloroplasts per leaf area, which is positively correlated with high leaf photosynthetic activity. Genotypical differences are related to different amounts of assimilative cells per leaf area. The amount of chloroplasts in the surfaces of stems and glumes does not exceed 20 % of the amount in the leaf. Regardless, these organs have a high photosynthetic activity, 45-50 % per leaf unit area. Such high activity in nonleaf organs is the reason for the high photosynthetic activity of a leaf's chloroplasts (Table 5).

Table 5. Some structural and functional findings of chloroplast activity in different assimilating organs of wheat.

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Index Flag leaf Stem Glume

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Photosynthetic

action, MgCO2*10-9 9.0 ± 0.6 28.5 ± 2.9 30.4 ± 3.7

chloroplasts/hour

Chlorophyll content,

mg*10-9 chloroplasts 5.2 ± 0.2 29.7 ± 3.5 36.0 ± 4.7

Volume in cubic meters 27.0 ± 1.6 21.3 ± 1.0 22.2 ± 0.5

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Chloroplasts of the stem and glume have a high chlorophyll content for their volume. The high chloroplast activity in nonleaf organs and the high rate of CO2 diffusion through the external membrane of the chloroplast may be consequences of its small volume, which is determined by the optimal surface to volume ratio. Note that glumes are situated in close proximity to a powerful acceptor, the filling grain. The ultrastructure of leaf and glume chloroplasts differs. The chloroplast ultrastructure of the glume looks like that of accessory cells of an aspartate-type C4 plant. These results indicate essential differences between CO2 metabolism of the glume and C3 metabolism of the leaf.

Growth succession on the main shoot of bread wheat.

Nataly A. Zakcharchenko and Vadim A. Kumakov.

The linear growth (including `hidden' growth in the leaf sheath) of all nodes and their parts (leaf blade, sheath, and internode) of the main shoot of a bread wheat were controlled in an experiment during 1993-95. The following succession was observed. As the first leaf finishes growth (or the day previous), the third leaf begins to grow; and the same happens with the second and fourth leafs.

Leaf development then accelerates. The sixth leaf starts developing 2-3 days before the fourth leaf finishes growth. The seventh leaf then starts to develop. Finally, the eighth leaf begins to grow when the fifth leaf ceases development.

The leaf sheaths of the second and third nodes initiate growth when those of the first and second sheaths stop development. However, the leaf sheaths of nodes 5, 6, 7, and 8 start as the sheaths at nodes 3, 4, 5, and 6 stop.

As the fourth internode stops development, the sixth internode starts growth. This sequence also occurs in the fifth and seventh and sixth and eighth internodes.

Thus, the development of the wheat plant is according to the following formulae: `plus 2' for the lower leaf blades (leaves 1-5) and `plus 3' for the upper leaves (6-8); `plus 1' for the lower leaf sheaths and `plus 2' for the middle and upper sheaths; and `plus 2' for all internodes.

This synchronization of the wheat stem is not changed or influenced by weather. These growth rates need to be assessed when evaluating plants for environmental or pest stress.