GrainGenes

Laboratory of Plant Physiology

Agricultural Research Institute for South-East Regions, Tulaikov St. 7, Saratov 410020 Russia.

Drought resistance and grain yield of spring bread wheat - is there a contradiction?

A.P. Igoshin.

The present view on drought resistance in spring bread wheats is very clear, once it is coupled to the absence of reliable criteria for evaluating this trait. The comparison of cultivars for grain yield under drought conditions or detecting yield decreases by comparing yield under optimum conditions is very difficult, because different cultivars have different potential productivities and many mature early. Attempts at the early diagnosis of drought resistance were made in the past and continue, but at present, no methods are available to evaluate drought resistance in the early stages. We think this situation is not by accident.

After more than 20 years of investigation, we can conclude that the main criterion reflecting the status and productivity of a plant during any vegetation period is biomass accumulation. Furthermore, the differences for some physiologic processes (e.g., photosynthesis, respiration, and transpiration) that we observed between productivity and drought resistance level off because of compensating effects. Biomass accumulation by the main stem during the period from plantlet to anthesis under optimum vegetation conditions and drought conditions depends on the length of the period. The shorter, high-yielding cultivars differ from the taller cultivars only by differences in the distribution of biomass accumulation in the main stem between straw and spike, and in the reaction of the vegetative organs (leaves and straw) and spikes to drought. This reaction is more prevalent in the vegetative organs.

The marked regularity in biomass accumulation during the period from plantlet to anthesis is induced by protracted evolutionary development of such fundamental processes as growth and photosynthesis, which are under the general regulative and collective influence of meristems. The failure of such strong chloroplasts in bread wheat and other species with C3 photosynthesis may serve to confirm our hypothesis. In the latter part of the vegetative period, this situation essentially changes.

Optimum conditions. The high-yielding, short cultivars have an advantage over older, taller cultivars (under equally early maturity) for biomass accumulation by the main stem. According to our studies, it is correlated with aging and the decrease in the rate of photosynthesis in short cultivars. This decrease in photosynthetic rate provides an increase in photosynthesis potential during the period of grain formation and grain filling. The duration of the photosynthetic apparatus is correlated closely with the quantity of grain produced in the spikelet. The distal grains definitely lag behind the most proximal grains in development until the milky-ripe stage. The lag in the development of the distal grains, which are physiologically young and active, probably influences the hormonal status of the whole plant. Luckily, in this case, the young growing points serve as regulators of the process and dynamics in the plants.

Drought conditions. In drought conditions, the advantage of biomass accumulation in drought-resistant cultivars is independent from the level of potential productivity. Nevertheless, the high-yielding cultivars, which have multiflorous spikes, under conditions of stress produce a greater number of ovaries, so the total number of grains in the spike is equal to that of the taller cultivars.

We propose a new method of drought-resistance evaluation, which allows for comparison of the cultivars differing for productivity and early maturity. This method is based on the results of only one drought year. The basis of this method is the relative increase in the weight of the main stem compared to its weight at anthesis, i.e., from grain filling to the waxy-mature phase.

In drought conditions, the drought-resistant cultivars have a higher relative increase and (if these cultivars are equally early maturing) an absolute increase in the weight of the main stem for the period from grain-filling to waxy maturity.

Our data show that differences in cultivars for drought tolerance did not correlate with the amount of photosynthesis, the possibility of temporary storage of assimilates in vegetative organs, or the ability to reuse structural matter. The difference likely is induced by resistance in active generative meristems and by their regulatory influence. The first, or generative, meristems are influenced by evolutionary organization. Likely, they are less adaptive in comparison to the vegetation meristems. Second, some genotypes are regulated because they are more-or-less adapted to environmental conditions. Thus, when breeding in any environmental condition, the fundamental processes of photosynthesis, growth, and the accumulation of storage products do not limit productivity. The grain production of spring bread wheat, in optimum and drought conditions, is based on the formation of reproductive meristems and their regulatory influence on activity in the whole plant. This fact explains genotypes with high productivity and high drought tolerance.

THE RUSSIAN ACADEMY OF AGRICULTURAL SCIENCES

Information and Computation Centre, P.O. Emmaus, 171330, Tver, Russia.

Genetic profiles of new winter wheat cultivars from Russia.

S.P. Martynov and T.V. Dobrotvorskaya.

In the 4 years since the formation of independent countries from the former USSR, 33 winter bread wheat cultivars were released in Russia (Table 1).

With the aid of the Genetic Resources Information System (GRIS 2) which contains more than 90,000 cultivars, including synonyms, the pedigrees of 32 cultivars were traced to 80 landraces from Russia, Ukraine, other countries of Europe, Asia, the United States, and Africa. Genetic profiles or sets of landraces including the traced pedigrees were constructed. The genetic contributions of landrace components of the profiles were estimated by the calculation of parentage coefficients.

The genetic profiles of the 32 winter wheats produced during 1992-95 and put on the National list of breeding achievements contained 17 original ancestors on average and varied from 2 to 37 landraces.

The predominant ancestors that are present in not less than 10 % of the realized cultivars are shown in Table 2. The frequencies of presence of same ancestors in the cultivars produced in the preceding 10 years are shown in the same table for comparison.

Table 1. New winter wheat cultivars released in Russia from 1992-95.

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Name Pedigree* Region

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1992

Donshchina Line-560-78/Don polukarlikovaya Rostov

Tarasovskaya-87 Dneprovskaya-41/Donetskaya-5 Rostov

Kazanskaya-84 (M)Velutinum-97/Albidum-114 Tatarstan

Kuibyshevka Milturum-253-h-63/Ep.139//Lut 560-h-23 Samara

Sibirskaya-niva (M)PPG-186 Omsk

Skifyanka (S)Spartanka Krasnodar

Yuna Obrii/Lut 2338 Krasnodar

Zernogradka-6 Line-560-76/Don polukarlikovaya Rostov

Zvezda Kharkovskaya-46/AG.GL//Mir 808/Lut 329 Moscow

1993

Bazalt Donetskaya-79/Albidum-114 Voronezh

Chernozemka-212 Belgorodskaya-5/Dneprovskaya-782 Voronezh

Dakha Zernogradka-2/Rubin Krasnodar

Sfera Lut 166-h-111/Rubin Krasnodar

Soratnitsa Odesskaya-66/Partizanka Krasnodar

Lutescens-9 Mir 808/N-52/Albidum-114 Bashkiriya

Meshinskaya-2 (S)Meshinskaya Tatarstan

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Table 1 (continued). New winter wheat cultivars released in Russia from 1992-95.

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Name Pedigree* Region

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1993 (continued)

Pamyati-Fedina Mir 808/Krasnodar karlik-1//Zarya/Yantarnaya-50 Moscow

Kolos-Dona Yrozhainaya/Line-904-76 Rostov

Zernogradka-8 Don bezostaya/Don polukarlikovaya Rostov

1994

Bagrationovskaya (P)Mir yubileinaya Novosibirsk

Kulundinka ? Novosibirsk

Bezenchukskaya-380 Mir 808/Severokubanka//Mir 808 Samara

Donskaya-yubileinaya Don bezostaya/Don polukarlikovaya Rostov

Eika Don polukarlikovaya/Er 2300-g 11313 Krasnodar

Rufa Obrii/Mir 808 Krasnodar

Yugtina Zagorka/Don polukarlikovaya//Krasnodar 57/ Krasnodar

Er 2300-g-11313

1995

Ershovskaya-10 Ershovskaya-8/Albidum-114 Saratov

Saratovskaya-90 Lut 36/Mir 10//Mir 10 Saratov

Imeni-Rapoporta PPG-186(M)/Mir 808 Moscow

Krasnodarskaya-90 Obrii/Don.bezostaya//Lut 2574-h-352 Krasnodar

Leda Obrii/Lut 3161-a-29 Krasnodar

Nika-Kubani Obrii/Krinitsa Krasnodar

Stavropolskaya- kormovaya (M)PPG-186 Stavropol

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* Don = Donskaya; Er = Erythrospermum; Lut = Lutescens; Krasnodar = Krasnodarskaya; Mir = Mironovskaya.

In the preceding 10 years, 32 winter wheat cultivars were produced in Russia. The analysis of pedigrees showed that the germplasm of the wheat cultivars developed during 1982-91 included 64 landraces. The set of predominant ancestors for cultivars produced during 1982-91 fully coincides with that for cultivars produced during 1992-95, but in the latter case, it is broader by about one third. The genetic diversity of new cultivars from Krasnodar Breeding Centre Yuna, Eika, Rufa, Leda, Yugtina, Krasnodarskaya-90, and Nika-Kubani increased significantly because of the crosses with spring wheats `Red-River 68' and `Siete-Cerros 66'.

The analysis of variance of the frequency of presence of predo- minant ancestors for wheats produced in the last 4 years and in the preceeding 10 year period (Table 3) showed a significant increase of the average frequency of presence: 1982 to 91ó27.6 %, 1992 to 95ó37.5 %. Hence, the genetic diversity of new Russian winter wheat cultivars has increased somewhat.

Table 2. The frequency of presence of predominant ancestors in winter wheat cultivars released in 1992-95 and the preceding 10 years.

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Frequency of presence*

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Ancestors Country 1992-1995 1982-1991

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Akakomugi Japan 81.3 90.3

Banatka Hungary 81.3 90.3

Barleta Argentina 81.3 90.3

Crimean Ukraine 81.3 93.5

Local variety Ukrain 81.3 87.1

Local variety Uruguay 81.3 90.3

Mediterranean Mediterranean 81.3 90.3

Rieti Italy 81.3 90.3

Zeeuwse-witte Netherlands 81.3 90.3

Kharkovskaya Ukraine 65.6 41.9

Local variety from Kremenchug Ukraine 65.6 71.0

Local variety from Odessa Ukraine 43.8 16.1

Petkus (Rye Germany 31.3 19.4

Uckermarkischer-Dummel Germany 31.3 19.4

Local variety from Kharkov (T. durum) Ukraine 28.1 9.7

Hard-red-Calcutta India 28.1 12.9

Ostka-Galicyjska Poland 28.1 12.9

Yaroslav-emmer Russia 25.0 9.7

Agropyron glaucum derivative ? 21.9 16.1

Daruma Japan 21.9 ó

Eliseevskaya (Rye) Russia 21.9 35.5

Etawah India 21.9 ó

Goldendrop Great Britain 21.9 ó

Indian-G India 21.9 ó

Iumillo (T. durum) Italy 21.9 ó

Redchaff USA 21.9 ó

Red-straw Great Britain 21.9 ó

Richelle-Blanche-de-Napoles Italy 21.9 ó

T. timopheevii derivative ? 21.9 ó

Turco Brazil 21.9 ó

Polyssu Brazil 18.8 3.2

Sandomierka Poland 18.8 6.5

Sterling-B ? 18.8 3.2

Wase-Nibay Japan 18.8 3.2

Chinese-spring China 15.6 ó

Kenya-C-9906 Kenya 15.6 ó

Marroqui Morocco 15.6 ó

Grushevskaya Russia 12.5 3.2

Kaliforniiskaya USA 12.5 3.2

Local variety from Dagestan (T. durum) Russia 12.5 3.2

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* Frequency is the percent of winter wheat cultivars that are related to each respective ancestral.

Table 3. Analysis of variance of frequencies of presence of predominant ancestors (%) in

production periods.

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Variable ss df ms F

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Total 81,939.750 79

Ancestors 76,784.312 39 1,968.828 24.2*

Periods 1,979.062 1 1,979.062 24.3*

Error 3,176.375 39 81.446

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The latest winter wheat cultivars and the cultivars produced in the preceeding 10 years, in most cases, are descendants of the winter wheats `Bezostaya-1' and `Mironovskaya-808'. Twenty-six cultivars (81 %) among the last releases and 27 cultivars (87 %) in the preceding period are the descendants of Bezostaya-1. The number of descendants of Mironovskaya-808 remained constant, at 22 cultivars (71 %) in 1982-91 and 21 cultivars (66 %) in 1992-95.

The increase in the number of ancestors from 64 for wheat produced during 1982-91 to 80 for wheat produced during 1992-95 and the increase in the average frequency of presence of predominant ancestors in the newest cultivars showed a tendency to widen the genetic base of modern winter bread wheats. However, this broadening of the genetic base relies on the existence of a stable set of predominant ancestors.