PCR-based molecular markers were used to map the recessive branching gene (b1) and the fertility restoration gene (Rf1) in sunflower. Sixty-one dominant RAPD markers, generated by 31 random primers, as well as 14 STS markers, were analyzed among an F2 population (C3) of 230 plants derived from cross RPG01 x AEHC1. Fourteen STS markers were analyzed in a second population (C4) of 211 plants from the cross RPG01 x R300V. Ten STS markers were analyzed in both populations. A linkage map of 64.6 cM containing the bl locus, 9 RAPD markers and 2 codominant STS markers was identified using JOINMAP based on segregation data. An RAPD marker, UBC105_740. was mapped at 5 cM from the gene bl. Another linkage group of 34 cM, containing the male fertility restoration locus Rfl as well as one RAPD and one STS marker, was also identified. The STS markers could be easily integrated into the previously established sunflower RFLP maps and should permit to verify the identity of branching and fertility restoration genes of different origins.

PCR with random primers was used for inter- and intraspecies differentiation in the genus Helianthus. Species-specific primers as well as polymorphic ones between lines were observed. A phenogram, reflecting the genetic relation between wild and cultivated Helianthus accessions, was constructed. PCR analysis could effectively classify and identify species most related to H. annuus which will be used for the improvement of cultivated sunflower.

Sclerotinia spp. can attack most parts of the sunflower plant, including capitula and leaves. The different levels of partial resistance shown by a range of hybrids were determined by the rate of growth of Sclerotinia mycelium on plant parts. Even though Sclerotinia isolates varied greatly in agressivity, a similar ranking of the sunflower genotypes according to their resistance to mycelial growth was obtained with all isolates. HPLC analysis of soluble phenolic compounds present in healthy or infected capitula and leaves showed the presence of 25 different compounds in capitula and 19 in leaves. Total phenol content in leaves was much greater than that in capitula; both varied considerably between genotypes. In the two tissues, Sclerotinia infection stimulated the accumulation of existing phenolic compounds to different extents according to genotype. Relations between resistance level and phenol accumulation were tissue specific. In capitula, total phenol content was correlated with resistance, whereas in leaves, the best marker of resistance was the amount of compound 9. It is suggested that phenolic compounds in healthy sunflower plants could be used as markers of Sclerotinia resistance.

The aim of the work was to study the relationships between different pathological characters and some yield components reduction in sunflower hybrids artificially inoculated at the base of the stem with the fungus Sclerotinia sclerotiorum. Eight commercial hybrids were inoculated at the closed flower-bud stage at three planting dates. They were evaluated for their suscept- ability by recording: the lesion lenght (LL), the percentage of dead plants (PD) and a disease severity index (DSI) based on the wilting degree at three different moments. At physiological maturity both non-inoculated and inoculated plants from all the hybrids were harvested to determine the number of fertile capitula. number of seeds per capitulum and 1000-cypselae weight. The percentages of yield reduction in the diseased plants were calculated with respect to each hybrid check.

Correlation studies showed highly significant and positive coefficients between all the pathological characters and yield reduction at two evaluation moments (10 and 13 days after inoculation) at first planting date. At second planting date the same type of correlation was observed for LL (7 and 13 days). and for DSI (13 days). At third planting date (most severe environment), yield reduction was not correlated with the pathological characters.

Positive and significant correlation coefficients were found between the lesion lenght measured 7 days after the inoculation with all planting dates. It was concluded that lesion lenght measured few days after the inoculation seems to be a simple and direct evaluation method that also related with yield reduction in moderate-attack conditions.

A wild Helianthus annuus L. population collected in Kansas, U.S.A., showed about 25% of its plants fully resistant to the herbicide imazethapyr applied in post-emergence at doses between 26.6 and 53.2 g.a.i./ha. Some plants survived treatments of 851.2 g.a.i./ha, i.e., 32 times the normal doses used in soybean. Artificially infected plants of this population with the parasitic weed species Orobanche cernua Loefl. (including O. cumana Wallr.) showed 100% of the plants susceptible. Artificially infected plants treated with imazethapyr in post-emergence on 40-day old plants killed most of the parasite nodules growing on the sunflower roots. The control of broomrape was 100% if the count only included the number of emerged broomrape shoots per plant. These results open the possibility of a new method for the control of Orobanche cernua in sunflower based on the use of resistance to this natural herbicide and the post-emergence treatment with imazethapyr.

The research was carried out at the Institute of Wheat and Sunflower "Dobroudja" near General Toshevo with the aim to ascertain the effect of broomrape intensity of attack on some morphological and biochemical indices that determine sunflower yield and quality. The objects of the study were the cultivar Peredovik and the hybrids Albena, Super start and NS-H-26, each attacked by the parasite to a different degree. Morphological measurements indicated that with the increase in the intensity of attack, the growth and development of sunflower plants were heavily suppressed - the plants were shorter, with smaller head diameter and lower yield per head. The broomrape attack caused considerable changes in some morphological and biochemical indices of sunflower seeds; the values for the mass of 1000 kernels, oil and protein content in 1000 kernels and net oil and protein in 1000 kernels were lower. The research was carried out at the Institute of Wheat and Sunflower "Dobroudja" near General Toshevo with the aim to ascertain the effect of broomrape intensity of attack on some morphological and biochemical indices that determine sunflower yield and quality. The objects of the study were the cultivar Peredovik and the hybrids Albena, Super start and NS-H-26, each attacked by the parasite to a different degree. Morphological measurements indicated that with the increase in the intensity of attack, the growth and development of sunflower plants were heavily suppressed - the plants were shorter, with smaller head diameter and lower yield per head. The broomrape attack caused considerable changes in some morphological and biochemical indices of sunflower seeds; the values for the mass of 1000 kernels, oil and protein content in 1000 kernels and net oil and protein in 1000 kernels were lower.

A field experiment with 12 sowing dates, ranging from February 2, 1989 to January 19, 1990, in monthly intervals, was carried out in a randomized block design, with four replications, with the objective to evaluate the development of Alternaria disease in three sunflower genotypes. The disease level was evaluated at 10-day intervals, up to physiological maturity. The interaction between sowing dates and genotypes was statistically significant; furthermore. the genotype Conti 621 showed less disease severity than VNIIMK 8931 and IAC-Anhandy. August sowing date showed, on the average, the lower area under disease progress curve (AUDPC) and disease index (DI), which should be a consequence of the low rainfall during this period.

Downy mildew disease caused by Plasmopara halstedii is emerging as one of the major diseases of sunflower in the Indian sub-continent. The yield loss due to this pathogenic fungus is accounting for more than 50% in the susceptible sunflower genotypes. The results of the present study clearly indicated that downy mildew causes extensive cellular changes, leading to hypertrophism and leakage of the cellular contents. A reduction in the total soluble protein was recorded in the infected leaves with no reduction in the percent of heat-stable proteins. Further, characterization of the PR proteins in the downy mildew infected leaves resulted in the isolation of two 100 kD proteins which appear to be specific to downy mildew infection.

A field study was conducted in Córdoba, Spain, to assess the effect of N fertilizer on the N content, N accumulation, N partitioning, N remobilization and their relationship with seed yield. Two sunflower hybrids, early (AB-E353) and late (Sungro 380) season types, were grown in sandy loam soil (Typic xerofluvent). Nitrogen at rates of 150 kg ha'1 (1987) and 300 kg ha"1 (1988) was applied before planting. In both years, the N content (%) and N accumulation (g m'2) in the organs of sunflower increased with N fertilization. The highest N concentrations were observed during early growth stages; N concentrations subsequentially decreased until physiological maturity. Nitrogen uptake ceased earlier in N-fertilized sunflower than in unfertilized sunflower and this was reflected in a lower nitrogen harvest index (NHI). In N+ a greater percentage of N accumulated in the seeds was supplied by the vegetative organs. This redistribution increased in relation to the N and genotype growth cycle. The leaf was the organ which accumulated most N and which made the greatest contribution to the seeds. The amount of N supplied by the shoot to the seeds and N accumulation in the leaf (g m'2) 66 days after emergence showed a higher correlation with the seed yield.

Achenes of seven different genotypes of Helianthus annuus L. were tested for germination at four concentrations of sodium chloride solutions and their germination behaviour was compared. Seedling growth exhibited similar sensitivity as germination, under high salt levels. The varieties Morden and CO-4 were found to be more sensitive than others. Newly germinated seedlings exhibited a decrease in size with increase in salt levels.

Influence of heating a heterogeneous pollen population on some quantitative characters of the resulting sporophytic generation was studied in sunflower. Pollen of interspecific hybrids H. annuus cv. Lider x H. argophyllus and H. annuus cv. Yubileiny x H. bolanderi was treated with the temperature of 40-60℃ during 1-3 hours, then used for backcrossing. Heating pollen at 60ºC for 3 hours was most effective. This treatment significantly increased the frequency of taller plants as well as the portion of genotypes with longer emergence-flowering stage and minimum number of branches. Taking into consideration that the parental forms of the used hybrids differed in these traits, the conclusion can be drawn that heat treatment selectively affected pollen grains favoring gametes of a cultivated genotype.

The observations in this paper indicate that a new chlorophyll-deficient mutation has been found in sunflower. The mutant is characterized by having a lutescens-like phenotype during the early stages. However, in later stages, the plants have a light green color and they not only reach the reproductive stage, but also give a normal seed set. The objective of this paper was to determine the mode of inheritance of this new chlorophyll-deficient mutation.

Different crosses were made between normal and mutant plants to obtain the F1, F2 and BC F1 generations. The ratio of the observed phenotypes in the different segregating progenies investigated were chi-square tested for goodness of fit and heterogeneity.

All these results suggest that this new chlorophyll-deficient mutation is controlled by a recessive nuclear gene. The symbol lgr-1 (light green-1) is proposed to designate this recessive allele.

Research carried out by the Forage Research Institute Iregszemcse in 1995 revealed diversity in dynamic of achene dry matter accumulation (DMA) of sunflower hybrids by growth analysis. Twelve different hybrid genotypes (produced by factorial mating of 3 cms lines and 4 restorers) were planted in a randomized complete block design. During the period of maturity achene samples (six times at 7-day intervals, 5 heads per hybrid) were collected. Growth curves, equations and bRGR were computed on the basis of a special formula, InY = Po + P1X + P2X2. In this case, relative growth rate (RGR) is a linear curve (RGRy = P1 + 2P2X). Consequently, the curve of RGR is possible to be characterized by the coefficient of the variate X. 2P2 = bRGR. Coefficient bRGR defines the speed of the growth process. Achene dry matter accumulation can be described precisely by this model, because the cubic component was not significant. There were clear differences among DMA, absolute growth rate (AGR) and RGR of genotypes. The effect of parental lines on bRGR was computed by the analysis of variance in M x N table (M = cms lines, N = restorer lines) without replications. Significant effect of cms lines on bRGR was detected. Results indicate that the speed of DMA, which is measured by bRGR, is an important heritable character of sunflower.

This study was conducted in 1995 in Erzurum, Turkey, to determine changes in some quality characteristics in relation to the position of kernels on the head of five sunflower lines.

According to the results of the study, when progressing from the periphery to the center of the head, seed number, kernel percentage. 1000-seed weight, crude protein and oil content of hulled seeds decreased but crude protein and oil content of dehulled seeds did not differ.

Fifty-two germplasm accessions of sunflower were evaluated for use as confectionery types. Analysis of variance revealed significant differences among the genotypes for all the characters. The estimates of genotypic and phenotypic coefficients of variability were high for seed yield per plant, percent husk, head diameter and number of filled seeds per plant. High heritability estimates were observed for days to 50 percent flowering, number of leaves per plant, percent husk and seed oil content. Genetic advance was high for number of filled seeds per plant, seed filling percent and percent husk. The accessions SG-1142, SG-1262, SG-1266, SG-1419. SG-1501, SG-1505, SG-1601, SG-433, SG-354 and SG-914 have been identified as promising confectionery type sunflower based on the attributes such as low seed oil content, low husk percent, high 100-seed weight, high 100-kernel weight and high seed yield.

The Venezuela areas with soils classified as Inceptisols, Vertisols and Alfisols, present in Barinas and Portuguesa States, are most suitable for sunflower crop. Soil pH is more than 5.8, with moderate to high moisture retention, and textures varying from loam, sandy loam to clay loam. The climate is tropical with a 12-12.5 h day/dark photoperiod. The average experimental yield is 1,500 kg ha"1. Sunflower is sown after a main crop (corn, rice) usually in October-November in high areas, and November and December in low areas. Harvest occurs at the beginning of year, in the absence of rainfall. The main problems are: selection and soil preparation, planting dates, hybrids not adapted to tropical conditions, and the high price of seed, which is imported.