Phenetic and phylogenetic relationships in genus Helianthus were assessed by molecular markers. Forty taxa belonging to 36 species and 4 unclassified accessions of Helianthus were studied using the RAPD technology. Single ten mer primers were screened for those amplifying fragments common to species belonging to one section or common to all species of the genus. Sequence homology between RAPD fragments of the same size was confirmed by molecular hybridization. Most of the fragments were found to be of the same size in other species and to share the homology indicated by molecular hybridization. Out of 118 retained fragments, 33 were common to all Helianthus species, 56 were unique to perennial species of which 24 were unique to sect. Atrorubentes, 29 were unique to sect. Helianthus, whereas 0 were unique to sect. Ciliares. The presence/absence of RAPD (fragments or signal hybridizations) were used to determine all structures using correspondence analysis and to compute genetic distances. Correspondence analysis clearly separated the 3 sections and recognized some series. The Jaccard distance and the Sokal and Michener similarity were chosen with UPGMA and Neighbor Joining Method to construct phenetic trees which were very similar to those of the current taxonomy. The simple method used to characterize these fragments led to powerful tools to use RAPD for help in taxonomy.

Polymorphisms revealed by cDNA corresponding to genes involved in different agronomic traits were compared between a set of public lines and commercial hybrids. We expected that only few probes should reveal polymorphisms and that these polymorphisms should be more frequent in hybrids than in lines. In contrast, we found that all these probes revealed polymorphisms among lines and that the distribution of these polymorphisms were about the same between lines and hybrids. However for two of the probes we observed much more profiles in lines than in hybrids. Three hypotheses are discussed to explain these facts.

Moreover, two possible applications appeared: (1) lines identification and (2) to determine whether the environment, the genetic background or the genes involved in the fatty acid metabolism are responsible for variations in oleic and linoleic content.

The paper presents the marker gene collection and the possibilities to use them in sunflower breeding programs. There are two classes of markers: morphological and physiological. The marker genes are in connection with colors of ligulate flowers, anther and pollen grains, shape of ligulate flowers, branching of the stem, pigmentation, seed characteristics. Five different sunflower inbred lines with marker genes were crossed between them, in order to identify new linkages. Between F2 progenies, double and triple recessive genotypes were identified. A hundred of 10 mer primers were used to amplified DNA from three pairs of NILs differing in the recessive branching gene "b". Few RAPD markers were identified by polymorphisms analysis and three RAPD markers D7-1800 bp, C1-750 bp and C1-1450 bp, are presented, but none of them discriminated consistently between branched and unbranched inbred lines in all three NILs, as we expected. For practical breeding work it is desirable to identify only positive markers associated with branched genotype.

A study of diversity was performed on 81 wild Helianthus annuus populations sampled from North America. Morphological and development traits were evaluated for different organs. Principal component analysis of quantitative traits associated the first components 1) to precocity-related traits in agreement with the geographical origin of the populations and 2) to domestication traits. We did not find any structure of qualitative traits by correspondence analysis. A sub-sample of twenty-one contrasted populations was observed for RAPD in comparison with twelve cultivated sunflower inbred lines. One hundred and seventy four polymorph fragments were revealed using nine primers. Cultivated inbred lines were unambiguously separated from wild populations by any analysis. Using RAPDs, much more diversity of wild Helianthus annuus appears in comparison with cultivated sunflower inbred lines. Among these populations, no reliable structure or clusters were found. We inferred from these results that a great deal of polymorphisms among wild Helianthus annuus remains to be investigated for possible use in sunflower breeding. We inferred also that it was not possible to ascertain clear structures of any qualitative traits and RAPD for wild Helianthus annuus populations. This absence of structure could be related with the dispersal of these wild resources when used by nomadic early Americans.

The fungal pathogens Sclerotinia sclerotiorum and Phomopsis helianthi are two major diseases in sunflower. While the cultivated sunflower has a narrow genetic base, wild species have been used as a source of disease resistance. In this study. 41 different lines derived from interspecific crosses and inbred line HA89 have been infected with mycelium of Sclerotinia and Phomopsis in 1996 and 1997 and evaluated for resistance. Lines derived from H. argophyllus and H. tuberosus had the lowest Sclerotinia stem lesion. Several lines showing significantly lower Phomopsis stem lesions than the sunflower inbred line HA89 were detected from crosses between HA89 and H. argophyllus. H. tuberosus, H. deserticola and H. xlaetiflorus. BE94-186-02, TUB-5-3235, TUB-5-326 and TUB-1705-327. These inbred lines, derived from interspecific crosses, were resistant to both fungi, hence they are recommended for use in resistance breeding programs.

Mesophyll protoplasts isolated from four sunflower species: H. annuus. H. giganteus, H. maximiliani, H. nuttallii were subjected to cultivation in liquid media. Various factors were analyzed and their optimization resulted in a high and reproducible percentage of viable and dividing cells in liquid culture. Donor plant pre-cultivation in the dark for two days, usage of 8-12 day-old leaves, selection of undifferentiated protoplasts, a cultivation density of 6 x 104 protoplasts ml" and cultivation in day/night cycle were found to be essential for a high and synchronous division rate of more than 70% dividing cells. Cell division was obtained for all four species at different rates reflecting their cultivation potential.

In the past few years several attempts have been made to obtain sunflower genetic transformation using different tissues such as meristems, shoot axes, hypocotyls, cotyledons of young seedlings and immature embryos. Transgenic plants were obtained in some instances but the efficiency and reproducibility were low. The common problem was the difficulty to establish an efficient regeneration system strictly correlated with the transformation system. Several reports indicate sunflower cotyledons as one of the most effective explants for plant regeneration but unlike other sunflower tissues this material is not easily transformed by Agrobacterium. Particle bombardment is an important tool for monocot transformation and could be an interesting alternative also for sunflower cotyledons. Particle delivery system currently sold commercially has a limited focusing ability whereas cotyledons exhibited a confined regenerable area restricted to the embrionic axes. To overcome this problem a stainless steel focusing device that can be applied to the DuPont/BioRad PDS1000/He apparatus was constructed. This device was tested in a series of ß-glucuronidase expression carried out on sunflower cotyledons, cv. HA89 and experimental lines. Endogenous GUS-like activity was abolished by changing the sample buffer and by performing the reaction at 56℃ after having pre-equilibrated explants and buffer for 90 min. The device enabled to confine and concentrate more than 90% of the transformation events in a ring-shaped area at 5-6 mm from the target center. Without the device transformation was very low and scattered over a much wider surface. On the basis of these data an appropriate arrangement of the cotyledons could improve dramatically the probability to transform competent cell for regeneration; this could be even more evident if sunflower genotypes with a high frequency of shoot regeneration are used.

The objective of this study was to investigate the effect of different water availability on the main agronomic characteristics in several cultivated sunflower inbred lines and other inbred lines obtained by a divergent selection for physiological traits starting from a wild species (Helianthus argophyllus T&G). The trial was carried out at the Experimental Farm of the University of Udine, during 1996 under rain-out shelter conditions and during 1997 in the field. At incipient flowering of the crops, water stress was imposed and maintained until physiological maturity. Of the genotypes examined, L28, which was selected as the plus variant of the wild population for gas exchange and tissue hydration, had the highest water use efficiency. (WUE), the best drought susceptibility index. (S), and an increased harvest index, (HI) under drought conditions, Genotype differences in S were mostly attributed to adjustments in the number of filled seeds per head and not to individual seed weight, in a late drought period. The results obtained indicate that high HI values under drought, which are closely related to dryland yield under field conditions, in the presence of genotypic variability should be a selection criteria to breeding for drought resistance. The lack of correlation between S and seed yield potential indicated that a high level of drought resistance and high yield potential may be combined in improved sunflower cultivars.

During last 20 years, crops of sunflower have extended throughout the developing countries due to its capacity to adapt to dry environments. Although a plant moderately tolerant of drought, production from this oil crop is strongly influenced by the presence of water stress which Is found fairly regularly

In fact, drought is a permanent feature in many developing countries and may also periodically influence the economies of Europe and the USA.

The threat from the trends in the global climate render this property ever more important.

At a scientific level there is a mass of work on the relationship between water supply and plant yield, but most deal with crops under irrigation. In contrast, useful knowledge concerning the improvement of the species to environments with trophic, especially water. limitations are still scarce and fragmentary. In our paper we have attempted to establish the state of the art of research into the strategies to adopt for improving drought resistance in sunflower, whilst trying to identify which of the many agronomic factors and physiological parameters may be used to improve the efficiency of selection processes.

In the establishment of a genetic improvement program aimed at improving the resistance to water stress, the following points must be included:

1) define the types of drought environment encountered in the target environment for each plant breeding program. because different types of drought may require different approaches.

2) describe plant "ideotypes" once the target environment is accurately defined.

3) determine which traits are to be considered to assist the development of drought-resistant cultivars.

4) given the particularly difficult conditions and unusual nature of drought-prone environments, accuracy is required in the identification of the selection method and the conduction of the experiment, in an attempt to steer the choice (identification of better progeny) towards data with a high number of replicates and not just single values.

5) analysis of data which allow the interpretation of the G x E interaction, in particular, when we are in the situation of identifying a single genotype which is ideal for various environments with different types of stress,

Only after having obtained all these information and having analysed them in a combined and/or separate manner for each type of environment. will it be possible to supply a concrete contribution to those who work daily in these difficult environments and to accelerate the provision of material which is truly tolerant to water stress in each environment. Finally, help must also come from molecular marker technology, because difficulties in identifying and conducting reliable drought-resistance screens can be overcome by improving the efficiency of selection for drought resistance via the use of molecular markers.

Understanding mechanisms involved in the response of plants to environmental stress is a prequisite for chooising a suitable genotype for a given environment. Present study was carried out to identify morphological and physiological parameters that might be involved in adaptation of sunflower to salt conditions. Five sunflower genotypes (Oro 9, Mirasol, Flamme, Pinto and Ludo) were submitted, under greenhouse conditions, to four NaCl concentrations (0, 50, 75 and 100 mM). Results showed that increasing NaCl concentrations in the medium significantly reduced all morphological parameters of genotypes. Leaf area was more affected (-72% for Oro 9), followed by the plant height (-67% for Ludo). Root lenght and root volume were also affected. Sodium chloride depressed more root growth than shoot growth of all genotypes. Chlorophyll content declined drastically at 100 mM NaCl (-61,67%). Mirasol displayed the highest chlorophyll content. At the opposite, amino acids (AA) content of both leaves and roots of stressed plants increased as NaCl concentrations in the medium was increased. Oro 9 and Pinto accumulated less AA in their shoots whereas Ludo accumulated more. Under stress conditions, all genotypes accumulated soluble sugars in both shoots and roots. At 100 mM NaCl, Oro 9 showed the highest shoot soluble sugar content, whereas Mirasol alone showed the highest content in both shoots and roots. Proline was another solute that accumulates under stress conditions. Pinto displayed the lowest shoot proline content under saline conditions whereas Ludo had the highest. Proline content of root was also increased by NaCl. Flamme displayed the highest root proline content, whereas Oro 9 showed the lowest one. Root volume and shoot biomass were positively correlated (r=0.63) but total soluble sugars content and NaCl tolerance were negatively correlated (r =- 0.94).

It was concluded that soluble sugars could be a suitable criteria for screening plants for higher saline constraints (100 mM NaCl) with root volume and soluble sugars could be used for screening for lower salt conditions.

The experiment was carried out under greenhouse conditions. Three sunflower genotypes were tested: Oro 9 (a variety population) and two hybrids (Isostar and Flamme).

N and K deficiency affected significantly shoots and roots morphological parameters for all examined sunflower cultivars. Shoots appeared to be more sensitive than roots. Reduction were more pronounced for dry weight under N deficiency than under K deficiency.

Root volume play an essential role in water and mineral absorption. Under normal supply of N and K root volume vas highly correlated, to shoot dry weight (r=0.89), to root dry weight (r=0.84) and to total dry weight (r=0.86). Under No and Ko, reduction of root volume and root dry weight reflected growth inhibition caused by N and K deficiency. Root volume, under No and Ko, was highly correlated, to root dry weight (r=0.99 and r=0.97 respectively for No and Ko), to shoot dry weight (r=0.89 and r=0.96 respectively for No and Ko) and total biomass (r =- 0.93 and r=0.99 respectively for No and Ko).

Total soluble sugars accumulation under No and Ko was observed at two pairs of leaves for all genotypes. The accumulation was highly and negatively correlated to root biomass (r =- 0.98) under No. However. a weak and negative correlation (r =- 0.16) between these two parameters was found for Ko. Total soluble sugars were also strongly and negatively correlated, to root volume for No (r =- 0.98) and Ko (r =- 0.99). Cultivars with high root total soluble sugars content seems to be more sensitive to N and K deficiency like Isostar.

Response of cultivars to N and K deficiency resulted in an accumulation of amino acids.

Genotype Isostar, whose morphological characters (except leaf area) were severely affected, was the most sensitive. On the contrary Flamme was the least sensitive because of its capability to maintain an adequate growth rate causing a small reduction of morphological parameters. Oro9 had an intermediate behaviour.

Within the diallel crossing of sunflower inbred lines we have studied a heterosis level for major agronomic traits in F1. A genetic diversity of lines for 11 isoenzymic systems has been defined. Genetic relationships between lines were investigated by the cluster analysis, which was performed on the base of a matrix of genetic distances. Five groups of lines were singled out by the cluster analysis. Significant correlation between genetic distances and seed yield of F1 hybrids was shown. With the increase of genetic distances between lines, the heterosis level was also growing in F1 hybrids.

Superoxide dismutases (SODs) and abscisic acid (ABA) are implicated in the response to environmental stresses. We have evaluated the susceptibility of w-1, a mutant with ABA deficiency and a variant isoform of chloroplastic Cu/ZnSOD, to oxidative stress. The results indicate that w-1 leaves were less damaged by paraquat (MV) and H2O2 treatments in respect to the control. while no statistical differences were detected when water stress was imposed by leaf dehydration.

Spectrophotometric assays did not evidence a higher level of SOD activity in w-1 extracts than in the control, confirming that ABA concentration does not modify SOD actvity. The better response of w-1 leaves to MV treatment could be attributed to a higher efficiency of the chloroplastic isoform variant of SOD to induce the dismutation of superoxide anion radicals to hydrogen peroxide and oxygen, under oxidative stress.