A study was conducted in Mococa, State of Sâo Paulo, Brazil, from l98l to 1989, to evaluate sunflower as a dry season optton, mahly after short-sea son soybean and maize and to study the effects of crop rotatlonal management systdns on soil chemical conditions and the yields and agronomic parameters of sunflower, soybean and maize. The treatments were: (a) Continuous sunflower grown in the wet and dry seasons (Cont. SFw/SFd); (b) Contlnuous succession soybean/dry season sunflower (Cont. S/SFd); (c) Continuous malze (Cont. M); (d) Rotation malze followed by soybean/dry season sunflower (M-S/ SFd); (e) Rotation maize followed by wet season sunflower/green manure (M-SFw/GM); (f) Rotation maize followed by wet season sunflower/dry season sunflower (M-SFw/SFd). The results show that sunflower lmproves phospho rus avatlability in the upper soll layers and lncreases soil acidification; continuous S/SFd accumulates more K at all soil depths; there is a positive lnfluence of the leguminous crop on sunflower grain and dry matter yield; for the Sâo Paulo State condltlons, maize grain yield in rotational treatments performs 30% higher than continuous maize, soybean grain and dry matter yield of the succession soybean/sunflower, even in continuous cropping, maintain the same productivity Ievels than in rotational treatments; rotational treatments has no influence ln sunflower head diameter.

Microscopic studies on single-spore-infected sunflower seedlings were carried out in order to study the homothallic or heterothallic nature of sexual reproduction in sunflower downy mildew, Plasmopara halstedit. The formation of oospores was found in the host tissue of all plants infected with single zoospores of three different pathotypes and originating from different geographic areas. This documents the homothallic nature of sunflower downy mildew and is of epidemiological importance. since a single infection in a field can lead to the contamination of the soil with oospores. Initiation of sexual reproduction started two to three weeks after inoculation of two-day-old seedlings with single, micromechanically selected zoospores. Oogonia and antheridia developed in close proximity to each other at the same hypha. The cytoplasm of the gametangia was separated from that of the adjacent hypha through the formation of a septum which consists of callose-like material according to histochemical staining with resorcin.

During the past six years the occurrence of Plasmopara halstedit and the regional distribution of its pathotypes in the southern parts of Germany was investigated. More than 50 isolates, representing fields of all regions relevant for sunflower production in the State of Baden-Württemberg, two areas in Bayern and one locality in Hessen were collected. Pathotype characterization, based on sunflower differential lines and evaluated according to a triplet code system, indicated the existence of at least five pathotypes. Among them, pathotype 730 (former race 4) dominated by far, frequently accompanied by 710 (former race 8), while pathotypes 330 (former race 7 or 9). 310 (former race 6) and 300 (former race 2) were only sporadically present. Studies on single spore isolates selected from certain field samples mostly documented the existence of more than one pathotype per field.

Secondary infection of Plasmopara halstedit was studied at several growth stages under controlled conditions or under netting cages in the field. Infection was conducted by placing fresh zoosporangia of race 100 on flower bud or on top of shoot with a micropipette. Percent of successful infection, symptom development and agronomic characters of seeds were observed macroscopically. Progression of fungus in organs of infected plants after inoculation was observed microscopically.

Sunflower plants naturally infected by downy mildew were observed at flowering and classified into four categories according to the intensity of symptoms. Capitula of infected plants were harvested for agronomic character analysis. These results were compared with those obtained with artificial infections.

Secondary infection can occur on leaf tissues or on the flower bud; and symptoms after artificial infection on 28- and 42- day-old plants correspond with symptoms observed in naturally infested sunflower at flowering.

The economic risks of secondary infection of P. halstedit can be divided into three categories: 1) loss of plants infected at the age of 7 and 14 days, 2) plants infected at the age of 28 days may produce no seed, 3) plants infected at the age of 35 or 42 days may produce a reduced quantity of contamined seeds.

Morphological variability of two Heltanthus species, H.giganteus and H.maximillani (section Divaricatt), was assessed at the Institute for Field and Vegetable Crops, Novi Sad. Fifteen populations of each species, with five plants per population, and thirty characters for each plant were analyzed. Three H.giganteus populations were found to differ morphologically in relation to the typical populations. Population 78 differed in the number of leaves per stem, length of involucral bracts and the length of ray flowers: population 2014 differed in leaf color and width and the angle between lateral veins and the midrib: population 2018 differed in stem color and the dentation of leaf margin. These populations originated from the western boundary of the distributional range of H.giganteus where species variability is high, representing specific adaptations that play an important role in the evolution of the species.

Behavior of some morphological traits in F1 hybrids between perennial wild species was studied in sunflower. The dark green coloring of leaves dominated over green one. The dark green coloring from H.divaricatus also dominated over grey-green coloring of H.mollis. The grey-green coloring of H.mollis, as well as dark green, dominated over green one, especially in the cases when H.mollis was represented in crossing as a female parent. While crossing species with green leaves the hybrids had only green color of leaves. Sessile leaf of H.mollis was found in all hybrids with this species. Hybrids, which included H.divaricatus, except hybrids between H.divaricatus and H.mollis, had the same petiole (0.3-0.4 cm) as H.divaricatus. An intermediate inheritance of petiole length was observed in combinations where H.eggertti was present, which was characterized by completely sessile leaf.

Studies were made on thirty crosses (Fo) involving three CMS lines and 10 restorer parents. The influence of different pollen sources on the female parents was positive and significant for all the characters studied. Five pollen parents R 6D-1, R X-13. R 857. RLC 2Br and R IV 83 were found to influence all seed characters when pollinated on three CMS lines. The percent increase of Fo seed values over mean sibbed values of females ranged from 5.67 to 21.51 for 1000 seed weight, 0.79 to 9.04 for oil content, 2.72 to 20.39 for seed density. 0.18 to 13.61 for volume weight. - 0.45 to 13.00 for K/H ratio and -0.99 to 7.39 for hull content. These results indicated the stimulating effect of foreign pollen on resulting seed characters at the Fo level.

Twenty perennial and annual wild species from Hellanthus genus were Included in the research. Thirteen of them were diploid, three were tetraplold and four were hexaploid. Among the diploid species, four were annuals and

Four types of nutrient media with different NAA and BAP concentrations were used for callus Induction. In the diploid species, callus formation varied from 0.6 to 48.9%, in the tetraploid from 16.7 to 38.3%, and in the hexaploid nine were perennials. from 0.1 to 33.3%.

The variation in the perennial diploid species was from 0.6 to 48.9%, and in the annual from 17.2 to 26.7%.

Two variants of nutrient medla were used for regeneration from the obtained embriogenic calli - a medium with growth regulators and a medium without hormones. For primary regeneration. the medium with growth regulators gave a better response, while for the secondary regeneration reaction was positive on the hormone-free medium.

Regeneration was obtained in four of the studied species - H.mollts (M-020), H.mollis (M-034), H.salicifoltus (M-045) and H.smithit (M-008). The initial reaction in the species M-020 has begun from 3 embryogenic calli, In M-034 from 2 calli, in M-045 from 3 calli, and in M-008 from 5 calli, the numbers of obtained plants being 28. 38, 49 and 51, respectively.

The ploidy level of the obtained regenerants was determined floweytometrically.

Studied in this paper was the effect of PETI and ANN5 cytoplasms on plant height, hectoliter mass, seed kernel content, and seed husk content of four inbred sunflower lines as well as of the crosses of the lines' sterile forms with three restorers. In the crosses, heterosis relative to the parental mean (H1) and heterosis relative to the better parent (H2) were calculated. PETI cytoplasm affected plant height in lines L-1, L-10, and L-14, hectoliter mass in all of the lines, and on seed husk content in lines L-11 and L-10. ANN5 cytoplasm, for its part, influenced plant height in lines L-10. L-14, and L-19 and on hecto- liter mass in lines L-1, L-10, and L-14. PET1 cytoplasm caused no significant increase in the seed kernel content of the lines, and ANN5 cytoplasm did not significantly increase the lines' kernel and husk contents, either. The said cytoplasms' effects on the expression of the quantitative traits under study were not equally significant in all of the crosses. The incorporation of PET1 cytoplasm proved the most useful in the L-10P x RHA-1 cross, where it caused highly significant increases of plant height, hectoliter mass, and seed kernel content as well as a decrease of seed husk content. ANN5 cytoplasm, on the other hand, was most effective in the cross L-14A x RHA-2, in which it produced a highly significant increase in hectoliter mass, a significant increase in seed kernel content, and a highly significant decrease of seed husk content as well as a certain decline in plant height.

The inheritance of increased (mid) oleic acid content about 62% of an inbred line, LG27, was studied in the crosses with high oleic HA89OL (89%). high oleic LG26OL (86%) and low oleic LG28 (22%).

Fatty acid composition of single seeds was determined by gas chromatography of methyl esters.

The crosses of high x increased oleic and high x low oleic genotypes revealed the genetic control on oleic acid content with multiple allelism. Three alleles of one gene - dominant Ol, recessive ol1 and recessive ol lead in homozygote to the high, increased and low oleic phenotypes, respectively.

Genetic segregations in F2 and BC of the cross of increased x low oleic lines did not show clear-cut phenotypic classes. No maternal inheritance was observed.

A study was conducted to determine the extent of genetic divergence with respect to 16 quantitative characters in 144 sunflower genotypes consisting of 66 germplasm accessions, 75 inbred lines and three checks at the University of Agricultural Sciences (UAS), Bangalore, India. Univariate and multivariate analyses of variance confirmed the presence of significant differences among the genotypes. Mahalanobis' D2 statistics indicated the presence of substantial genetic diversity. Higher D2 values were observed among the inbred lines than in the germplasm accessions. Clustering of the genotypes resulted in the formation of seven and 14 clusters in the germplasm accessions and inbred lines, respectively. Some clusters were unique having only a single genotype, while clusters with up to 55 genotypes were also formed. Factors other than geographic origin appeared to be a potent source of genetic diversity. The intercluster distance showed that clusters II and V among the germplasm accessions and clusters XI and XIII among the inbred lines were most divergent. Clusters were also demarcated with respect to characters they excel and/or for which they were inferior.

The interrelationships of 12 physio-morphological traits of 144 sunflower genotypes including 66 germplasm accessions, 75 inbred lines and three checks were investigated using a 12 x 12 simple lattice design at the University of Agricultural Sciences, Bangalore, India. The study revealed that there were significant positive correlations between seed yield per plant and plant height, number of filled seeds, head diameter, stem girth. 100 seed weight, and harvest index on one side and oil yield per plant on the other. Percent autogamy was negatively correlated with seed yield per plant and other yield-contributing traits. Days to maturity and oil content were significantly associated with seed yield per plant only in the inbred lines. The breeding method followed in developing the genotypes has less influence in altering the magnitude and direction of correlation. Genotypic path analysis revealed that number of filled seeds and 100 seed weight had significant positive direct effects on seed yield per plant. Seed yield per plant followed by oil content had the highest direct positive influence on oil yield per plant. These traits were also the main channels to direct other components to influence the seed and oil yields per plant accordingly.

Sunflower hybrids which were under FAO varietal experimentation during 1996-97 were tested for resistance to broomrape in Turkey. Results are discussed in this report.

Cet article présente une méthode simple de conservation des zoosporanges de Plasmopara halstedti à -30°C. Si cette technique ne permet pas de conserver avec fiabilité l'inoculum plus de 5 mois, elle a l'avantage de ne pas nécessiter d'azote liquide ni de matériel sophistiqué.

Dans cette courte communication, nous proposons une technique simple qui permet d'isoler Plasmopara halstedit, parasite blotrophe du mildiou du tournesol, à partir des feuilles chlorosées soit sans fructification ou avec une fructification séchée.