[Genetic potential of local endemic forms of the pea (Pisum sativum L.) on the basis of nitrogen fixation and productivity].

Morphological and symbiotic traits were studied in local endemic forms of the pea originating from Egypt, Syria, Afghanistan, and Palestine. A number of endemic forms exceeded the zoned Druzhnaya variety of the fodder pea in productivity of the seeds in field and greenhouse experiments. In order to improve nodulation and nitrogen fixation, endemic forms were crossed with the supernodulating K301 mutant marked by the nod4 gene. Recurrent selection of lines up to F5,6 generations was conducted with an estimation of productivity, nodulation, and nitrogen fixation. The most promising recurrent lines with a high productivity, active nodulation, and high nitrogen fixation were obtained during the crossing of endemic forms with the recurrent line marked by the nod4 gene. The line was previously created during the crossing between the Druzhnaya variety and the supernodulating K301 mutant marked by the nod4 gene.

[Study of dominant symbiotic mutants of pea Pisum sativum L].

Phenogenetic studies of four symbiotic hypernodulating mutants of pea (Pisum sativum L.) induced from seeds of cultivar Rodno by chemical mutagen EMS were conducted. All mutants have improved symbiotic traits, i.e., an increased number of root nitrogen fixating nodules and high activity of nitrogenase. Symbiotic traits were shown to be inherited dominantly. Mutants grown in the field or in a greenhouse showed superiority over the original cultivar in productivity. An important feature of hypernodulating mutants was found that is responsible for the appearance of high-height productive plants in F2 after crossing mutants and the original cultivar. Constant lines retaining the ability for high-level production up to the F5 generation were created based on individual plants.

[Physiological and agrochemical properties of different symbiotic genotypes of pea (Pisum sativum L.)].

Physiological characters of symbiotic mutants of pea were studied: nodulation, activities of nitrogenase and nitrate reductase, chlorophyll content in leaves and their water-holding capacity, biomass accumulation, and nitrogen forms. The parameters reflecting the genotype state of the macrosymbiont under soil conditions considerably varied. Supernodulation mutants stood out against symbiotic pea genotypes by high contents of chlorophyll and nonprotein nitrogen compounds, high nitrogenase activity, and low nitrate reductase activity. The efficiency of the legume-rhizobium symbiosis was largely mediated by the macrosymbiont genotype. The highest atmospheric nitrogen fixation (50-80%) was observed in the parental pea varieties. Despite the highest nitrogenase activity in the nodules, the supernodulation mutants were inferior to the parental varieties by the nitrogen fixation capacity (40-60%), which was due to their low productivity.

[Study of morphological and symbiotic traits during the ontogeny of supernodular and hypernodular pea mutants].

Morphological (plant height and vegetative biomass amount) and symbiotic (number of nodules and nitrogenase activity) traits of six symbiotic pea mutants and the original cultivar Rondo were studied at different vegetation periods. Of the mutants studied, one (K10a) was supemodular and the remaining five (K1a, K2a, K5a, K7a, and K27a) were hypemodular. Essential distinctions in the absolute values and time course of the changes in individual morphological and symbiotic traits of different pea mutants were demonstrated. The supemodular type is inferior to the original cultivar in plant height and production of vegetative biomass, but exceeds it in nodulation and nitrogen fixation. The hypemodular mutants either surpass the original cultivar with respect to the production capacity or display similar results. The symbiotic traits-number of nodules and nitrogen fixation activity--of these mutants are higher compared with the Rondo cultivar. The mutants K1a, K2a, and K27a were demonstrated to be useful in breeding pea for an increase in nitrogen fixation.

[Expression of the symbiotic nod4 pea gene against various genotypic backgrounds].

Experiments on the effect of genotypic environment on the expression of the nod4 gene, responsible for supernodulation in pea, were performed. The genotypic background was found to affect the manifestation of both major symbiosis-related traits (number of nitrogen-fixing bacterial nodules and nitrogenase activity) and productivity-related traits (stem height, seed number, and seed weight), which form the pleiotropic complex of the mutant gene. Using recurrent selection, we developed supernodulating lines significantly exceeding the original mutant line and studied them up to generations F5-F6. Of special importance is the fact that these lines showed high levels of nodulation and nitrogen fixation. The results are discussed from the viewpoint of breeding.

[Creation and genetic study of a collection of symbiotic mutants of the pea (Pisum sativum L.)]. / Sozdanie i geneticheskoe izuchenie kollektsii simbioticheskikh mutantov gorokha (Pisum sativum L.).

A collection of symbiotic pea mutants consisting of 34 lines was created. The morphobiological and symbiotic description of different types of pea mutants is presented. The mode of inheritance of symbiotic characters is analyzed. For the first time in pea, hypernodulation mutations with dominant inheritance were isolated. Differences in the structure of bacteroid tissues of root nodules were revealed between mutants with effective and ineffective nodules. Using reciprocal root/stem and stem/root grafts, the plant organ producing nodulation-controlling factors was established. New hypernodulation-controlling genes--nod4 and nod6--were identified. For the first time in pea, using pure lines derived from cultivars with contrasting nodulation, the new gene Nod5--nod5 was found. The dominant allele of this gene controls abundant nodulation, high nitrogen fixation, and nitrate resistance. Pea cultivars carrying the Nod5 gene that can be used in selection for improved symbiotic properties were identified.

[Level of phytohormones in various types of symbiotic pea mutants]. / Izuchenie urovnia fitogormonov u raznykh tipov simbioticheskikh mutantov gorokha.

The levels of the phytohormones auxin and gibberellin were studied in the original pea (Pisum sativum L.) cultivars Rondo and Ramonskii 77 and in different types of symbiotic mutants (non-nodulating, with single nodules, and supernodulating) induced from them. The results obtained indicated that the levels of the phytohormones in the symbiotic mutants depend on the plant's genotype, developmental phase, and infection with rhizobia. Two mutants were isolated whose phytohormonal statuses markedly differed from the original forms. These mutants may be used for identification of the genes that determine the auxin and gibberellin statuses.

[Ultrastructure of bacteroid-containing tissue of Pisum sativum L. peas having various regulatory mechanisms of nodulation]. / Ul'struktura bakteroidsoderzhashchei tkani linii gorokha Pisum sativum L., imeiushchikh raznye reguliatornye mekhanizmy kluben'koobrazovaniia.

The infected root nodule cells of Pisum sativum cvs. Torsdag, Rondo and its supernodulating mutant nod3 have been investigated by transmission electron microscopy and morphometrically. Torsdag and nod3 developed effective nodules, when grown with or without nitrates in the growth medium. The nodules developed by Rondo were ineffective in the presence of nitrates, and otherwise effective. An obvious similarity in the fine structure of bacteroid tissue of root nodules has been observed in Torgsdag (Nod5) and the supernodulating mutant nod3, both forms being nitrate-tolerant, but nodulation being controlled by different genetic systems. The statistical processing results showed significant differences in the respective morphometric parameters of nodule cells between the plants grown according to either scheme: with and without nitrates. Combined nitrogen is likely to affect the ratio of symbionts in the infected nodule cells of cultivars with nitrate-tolerant nodulation.

Growth, activity of phytohormones and inhibitors, and photosynthesis of dwarf pea mutants under different conditions of illumination.

A clear correlation was found between the growth of mutant forms of pea plants and the light intensity: With an increase in the latter the growth of the plants was inhibited and the rate of photosynthesis increased. The inhibitory action of light on stem growth affected not only tall pea plants, but also dwarf forms. A definite link was observed between the genetic apparatus and the balance of endogenous phytohormones and inhibitors. The content of bound forms of gibberellins was directly related to the growth intensity--the content of these substances was highest in the tall Torsdag pea plant, it was lower in the semidwarf K-29, and it was very low in the dwarf K-202. The content of quercetin glucosylcoumarate was lowest in Torsdag pea plants, in dwarf mutants the greater the amount of this compound the shorter the stem. The genetically determined ratio of phytohormones and inhibitors in the original tall and dwarf forms of pea plants is retained under all illumination conditions at various intensities.