No abstract

The molecular genetic diversity of the broomrape (O. cumana) populations, parasitizing on sun flower in Russia, Romania and Kazakhstan, was studied with codominant microsatellite markers. By means of cluster analysis, the populations of broomrape were divided into two clusters, regardless of their racial com position. In the first cluster, 19 samples from Russia and Kazakhstan, representing one gene pool are grouped; the second cluster consisted of five populations from Romania, united in another pool. According to Nei, the genetic distance between the clusters was 0.137. The analysis of molecular variance revealed that 22% of total variance were caused by differences between the genetic pools and 78% appeared due to differences between the samples within the each gene pool. The pairwise comparisons performed by Wright's statistics showed that the differences between these two gene pools are sufficient (F st = 21.9%) in order to make the conclusion about the existence of small genetic differentiation between the pools. The descriptive population genetic sta tistics for each pool indicate that the broomrape populations from Russia and Kazakhstan are characterized by a higher level of intrapopulation diversity than the populations from Romania.

Broomrape (Orobanche cumana Wallr.) is an obligate parasite of higher plants, which affects sunflower in many countries, cultivating this crop. For the past decades, it is noted the formation of new highly virulent biotypes of broomrape and their spreading to other areas. In our work we studied the molecular genetic diversity of broomrape populations of O.cumana, parasitizing on sunflower in Russia, Romania, and Kazakhstan, by using codominant microsatellite markers. During cluster analysis, the broomrape populations are divided into two clusters, regardless of their racial composition. One cluster grouped 19 samples from Russia and Kazakhstan, and the other -5 populations from Romania. The genetic distance between clusters according to Nei was 0.137. The analysis of molecular variance (AMOVA) revealed that 22% of genetic variability was due to differences among the gene pools and 78% was due to differences within the gene pools. Pairwise comparisons made using Wright's statistics showed that the differences between these two gene pools are sufficient (Fst ¼ 0.219) to state the existence of a small genetic differentiation between them. Descriptive population genetic statistics for each of the two pools showed that the broomrape populations from the former Soviet Union countries are characterized by a higher level of intrapopulation diversity than the populations from Romania. Molecular genetic differences between broomrape populations parasitizing on sunflower on the post-Soviet territory and in *Corresponding author: Saida Guchetl, Laboratory of Immunity and Electrophoresis, All-Russia Research Institute of Oil Crops by the name of V.S. Pustovoit, 17 Filatova str.,

An analysis of DNA microsatellite sequences of 17 sunflower inbred lines and hybrid combinations developed at VNIIMK has been conducted. Nine of the10 studied microsatellite loci were polymorphic, with the average number of alleles per locus of 2.2. One locus was monomorphic. Dominant type of inheritance was found in two loci, codominant in seven. At the level of similarity between lines from 0.19 to 0.97, individuality of each line and hybrid combination is revealed. Their molecular genetic passports were made on the basis of the nine loci. Suitability of the 9 loci for genetic purity tests of sunflower seeds in commercial lots has been shown. The seven codominant loci are suitable for definition of hybrid vigor.

One of the most dangerous diseases on sunflower is downy mildew caused by oomycete Plasmopara halstedii. Introduction of dominant genes of resistance to this pathogen into a host-plant is the most effective economic and ecologically safe method of this pathogen control. The current DNA-technologies allow controlling these genes presence at the any stage of breeding. Currently, the genes Pl6, Pl13 and Plarg are the most effective ones controlling resistance to the most races of P. halstedii. We approbated known from the literary sources two STS and two SSR-markers of these genes on the lines and breeding samples. Three studied molecular markers – HаP3 (locus Pl6), ORS1008 (locus Pl13) and ORS509 (locus Plarg) – allowed us identifying the mentions genes in lines and breeding samples of VNIIMK. The studied DNA-markers can be interested in marker-associated sunflower breeding on resistance to a downy mildew pathogen.

During the last years in Rostov region of Russian Federation highly virulent biotypes of broomrape have propagated, affecting both hybrids of foreign breeding, and the native sunflower assortment, which used to be resistant earlier. Apart from that, the resistance of some known European sunflower types to broomrape races had disappeared, which testifies about the presence of the races F, G, H in the region at least. Consequently, the search of the sources of resistance is urgent.14 samples of annual and 27 of perennial wild sunflower from the collection of Kuban experimental station VIR were tested for resistance to the most virulent broomrape population. From the annual species only H. petiolaris had weak degree of affection (1-3 tubercles/plant), while the other were affected to a high degree. The majority of perennial sunflower samples have shown the immunity.Perennial wild species of the sunflower of the same name that were used earlier in the research of Ruso et al. (1996) as resistant species against the Spanish populations of broomrape, show resistance also to high virulent O. cumana, which had propagated in the Rostov region of the Russian Federation.The immunity to broomrape of the studied wild perennial sunflower samples is not related to the absence of stimulating effect of root exudations on the seeds of the parasite. The immunity is more likely connected to physiologicalbiochemical features of cortex root cells.

After a long period (about 30 years) without broomrape problems in sunflower fields, intensive infestations were observed in some parts districts of Northern Caucasus. Virulence of the pathogen populations from some regions of Northern Caucasus was compared with those of race F from Spain and a mixture of races F, G, H from the European part of Turkey. It was shown that the broomrape populations from Northern Caucasus have heterogeneous structure. The populations Svetlogradskaya, collected in 2005, and Morozovskaya, collected in 2006, were most virulent. The first has the virulence comparable to one from Turkey and it is a mixture of nonvirulent and virulent races for the studied sunflower genotypes. Race F predominates in the mixture and has a there is an admixture (although insignificant) of more virulent individuals. The population Privolnenskaya from 2003 collection, is a mixture of different races also, but it is less virulent, containing race E and some insignificant admixture of more virulent individuals (most likely race F).

In the tubercle of O. cumana of high-virulent populations from Rostov region of Russian Federation some changes were found, which helped to improve the seed productivity and to decrease the development period of fruiting shoots. The maintenance of high level of seed productivity can be realized by setting multiple meristematic zones in a tubercle and simultaneous development of several adventive shoots from them. The maintenance of viability of tubercle and the formation of new shoot apexes after the seed ripening on one or several stems, grown out of it and finished in the vegetation period, also go in the favour of the improvement of seed productivity. The development of the apexes of tubercle rudimentary roots into adventive shoots was observed in this paper.The polymorphism of inflorescence in the quantity of the setting flowers and their distribution along the stem and even below the soil level was observed. The flowering ability of flowers, hidden in the soil, and the seed formation in them, was defined. All that leads to the improvement of seed productivity of individual plant. On the whole, the described peculiarities of the development of O. cumana show that there is an accumulation of traits, which goes in the favour of the high potential of reproductive function in parasite's ontogenesis.