Morphology,phylogeny and pathogenicity of Alternaria species,involved in leaf spot disease of sunflower in northern Iran

Leaf spot disease of sunflower is one of the most important foliar diseases on this crop worldwide. Several fungal groups are known to cause leaf spot disease on sunflower. Species of the genus Alternaria are the most common and serious leaf spot causing fungi on this crop. Leaf spot disease is the most destructive foliar diseases on sunflower in northern Iran; however, the identity of the causal agent remains unknown. The present study was aimed to characterise the identity of the causal agent of the disease by means of morphological and molecular data as well as to evaluate the pathogenicity of the responsible species. For this purpose, a total number of 97 fungal isolates were recovered from sunflower leaves with leaf spot disease symptoms from the sunflower fields in northwestern zone of Iran. All of the isolates were identified as Alternaria alternata based on cultural and morphological characteristics. A subset of isolates was subjected to phylogenetic analysis using sequence data from ITS-rDNA region, gpd and rpb2 genes. Sequence data from ITS-rDNA and gpd did not discriminate A. alternata from the other small-spored Alternaria species. A phylogeny inferred using sequence data from rpb2 gene clustered our isolates in several sub-clades within a single monophyletic clade. Sequence data for the type strain of the other small-spored Alternaria species has to be included in phylogenetic analysis, in order to make sure, whether the observed variations in rpb2 gene sequences are an indication for the population variation in sunflower isolates of A. alternata or define species boundaries among the small-spored Alternaria species. The results of pathogenicity assay on sunflower plants (cultivar Euroflor) under greenhouse condition revealed that A. alternata is pathogenic on sunflower.     

向日葵对向日葵螟抗虫性的研究进展

向日葵螟是取食向日葵花盘及籽粒最为猖獗的一种害虫,可造成严重的产量损失。本文综述了向日葵对两种向日葵螟(欧洲葵螟Homoeosoma nebulellum Denis et Schiffermüller和美洲葵螟Homoeosoma electellum Hulst)抗虫性的研究进展,从向日葵的花药腺毛、瘦果性状、次生化合物(黑色素、倍半萜类化合物和花粉萃取物)等方面概括了向日葵和向日葵螟的互作关系,阐述了向日葵的形态结构及化学组成对向日葵螟抗虫性的作用,初步说明了向日葵对向日葵螟抗虫性的物理生化机制,并对未来在抗虫育种工作的启示及可能的应用进行了展望。     

Genetic diversity and genomic distribution of homologs encoding NBS-LRR disease resistance proteins in sunflower

Three-fourths of the recognition-dependent disease resistance genes (R-genes) identified in plants encode nucleotide binding site (NBS) leucine-rich repeat (LRR) proteins. NBS-LRR homologs have only been isolated on a limited scale from sunflower (Helianthus annuus L.), and most of the previously identified homologs are members of two large NBS-LRR clusters harboring downy mildew R-genes. We mined the sunflower EST database and used comparative genomics approaches to develop a deeper understanding of the diversity and distribution of NBS-LRR homologs in the sunflower genome. Collectively, 630 NBS-LRR homologs were identified, 88 by mining a database of 284,241 sunflower ESTs and 542 by sequencing 1,248 genomic DNA amplicons isolated from common and wild sunflower species. DNA markers were developed from 196 unique NBS-LRR sequences and facilitated genetic mapping of 167 NBS-LRR loci. The latter were distributed throughout the sunflower genome in 44 clusters or singletons. Wild species ESTs were a particularly rich source of novel NBS-LRR homologs, many of which were tightly linked to previously mapped downy mildew, rust, and broomrape R-genes. The DNA sequence and mapping resources described here should facilitate the discovery and isolation of recognition-dependent R-genes guarding sunflower from a broad spectrum of economically important diseases.     

Analysis of transposons and repeat composition of the sunflower (Helianthus annuus L.) genome

A sample-sequencing strategy combined with slot–blot hybridization and FISH was used to study the composition of the repetitive component of the sunflower genome. One thousand six hundred thirty-eight sequences for a total of 954,517 bp were analyzed. The fraction of sequences that can be classified as repetitive using computational and hybridization approaches amounts to 62% in total. Almost two thirds remain as yet uncharacterized in nature. Of those characterized, most belong to the gypsy superfamily of LTR-retrotransposons. Unlike in other species, where single families can account for large fractions of the genome, it appears that no transposon family has been amplified to very high levels in sunflower. All other known classes of transposable elements were also found. One family of unknown nature (contig 61) was the most repeated in the sunflower genome. The evolution of the repetitive component in the Helianthus genus and in other Asteraceae was studied by comparative analysis of the hybridization of total genomic DNAs from these species to the sunflower small-insert library and compared to gene-based phylogeny. Very little similarity is observed between Helianthus species and two related Asteraceae species outside of the genus. Most repetitive elements are similar in annual and perennial Helianthus species indicating that sequence amplification largely predates such divergence. Gypsy-like elements are more represented in the annuals than in the perennials, while copia-like elements are similarly represented, attesting a different amplification history of the two superfamilies of LTR-retrotransposons in the Helianthus genus.     

The response of sorghum and sunflower to short-term waterlogging

Summary Sorghum and sunflower were waterlogged for nine days during the vegetative, floral initiation/buds-visible or anthesis stage of growth under glasshouse conditions to observe the effects on root growth and development. In addition, some plants were waterlogged at all three stages to observe any adaptations induced by waterlogging. The most marked effects occurred at the initiation/buds-visible stage where a 30% reduction in root length and a 40% reduction in root dry weight of sorghum occurred with comparable figures for sunflower being 50 and 60% respectively. Generally, sorghum roots had a higher porosity than sunflower which may contribute to its greater tolerance to waterlogging. The observed changes in root growth are discussed in relation to previously documented effects of waterlogging on growth of the two species and changes which occur in the soil environment.     

A functional analysis of large‐scale temporal shifts from 1970 to 2000 in weed assemblages of sunflower crops in France

Questions: What are the relationships between weed species traits and their change in distribution over a 30‐year period? What does it tell us about factors that have driven shifts in the composition of weed communities? Location: France. Methods: We analysed the links between change in the status of weed species in sunflower crops (decreasing or increasing) and a set of 17 traits using data sets collected in the 1970s and the 2000s, respectively. We analysed the contribution of traits to explain changes in the status of species both individually and in a multivariate way by mean of a clustering of species into functional groups. Results: 69% of the most widespread species had significantly changed their frequency rank status over the last 30 years. Nearly two thirds of the increasing species belonged to a single functional group, out of the five groups identified in this analysis. Overall, the weed flora occurring in sunflower crops has specialised since the 1970s in favour of ‘sunflower mimicking’ functional groups: increasing species were more nitrophilous, more heliophilous, less sensitive to sunflower herbicides and shared a rapid summer life cycle. Conclusions: The individual trait approach gave some indication as to the environmental factors likely to have caused the shift in sunflower weed communities. The functional group approach seemed to outperform direct trait comparisons as it accounted for major traits combinations i.e. cases where a species has a number of favourable traits, but is severely disadvantaged by the possession of one or a few deleterious traits.     

Sunflower stem weevil and its larval parasitoids in native sunflowers: is parasitoid abundance and diversity greater in the U.S. Southwest?

Classical biological control programs often target a pest's region of origin as a likely source for new biological control agents. Here, we use this approach to search for biological control agents of the sunflower stem weevil (Cylindrocopturus adspersus LeConte), an economically important pest of commercial sunflower. We conducted surveys of weevil natural enemy diversity and abundance across a transect running from the northern Great Plains to the southwestern U.S. (the presumed area of endemism of annual sunflower species in the genus Helianthus). Accordingly, natural enemy diversity and abundance were expected to be greater in the southwestern U.S. C. adspersus and their larval parasitoids were collected from stems of four native sunflower species (Helianthus annuus, H. nuttallii, H. pauciflorus, and H. petiolaris) from 147 sites across eight states. Native H. annuus constituted the majority of the sunflower populations. Mean weevil densities were significantly higher in sunflower stalks that were larger in diameter. Mean weevil densities within sites did not differ across the range of longitudes and latitudes sampled. After accounting for the effects of stalk diameter and location, weevil densities did not differ among the four sunflower species nor did they differ as a function of elevation. C. adspersus in H. annuus and H. petiolaris were attacked by seven species of parasitoids. No parasitoids were found attacking C. adspersus in H. nuttallii or H. pauciflorus stalks. C. adspersus were twice as likely to be attacked by a parasitoid when feeding on H. petiolaris than H. annuus. Furthermore, the likelihood that C. adspersus would be parasitized decreased with increasing elevation and increasing stem diameters. All parasitoid species have been previously reported attacking C. adspersus larvae in cultivated sunflower. Species richness was less diverse in these collections than from previous studies of cultivated sunflower. Our findings suggest that the species of larval parasitoids attacking C. adspersus in native sunflowers have successfully made the transition to cultivated sunflower.     

Inhibition of the phosphate transporter during isolation of intact chloroplasts from leaves of sunflower

Chloroplasts isolated from spinach leaves by the mechanical method were intact and exhibited high rates of CO₂-dependent oxygen evolution whereas chloroplasts isolated from sunflower leaves by the same technique were also intact but showed only low rates of oxygen evolution. The rate of uptake of orthophosphate (Pi) from the suspending medium with sunflower chloroplasts was less than 20% of that in spinach chloroplasts. The apparent Km for Pi transport was lower in sunflower chloroplasts but uptake was competitively inhibited by 3-phosphoglycerate in chloroplasts from both species. Uptake of malate (via the dicarboxylate transporter) and of ATP (via the adenine nucleotide transporter) was also reduced in sunflower chloroplasts compared to spinach chloroplasts. The endogenous Pi content and total exchangeable phosphate pool of sunflower chloroplasts were less than half that in spinach chloroplasts.Addition of a number of possible protective agents to the grinding medium failed to prevent the loss of photosynthetic activity during mechanical isolation of sunflower chloroplasts. Grinding mixtures of spinach and sunflower leaves together indicated that spinach chloroplasts were not inhibited by the sunflower leaf extract. Chloroplasts isolated from sunflower leaves via protoplasts had high rates of CO₂-dependent oxygen evolution. The Vmax and Km for Pi uptake, endogenous Pi content and total exchangeable phosphate pool of chloroplasts isolated from sunflower protoplasts were all similar to spinach chloroplasts. It is concluded that inner envelope membrane proteins are damaged during mechanical isolation of sunflower chloroplasts. The decrease in activity of the phosphate transporter and loss of endogenous phosphate may contribute to the low rates of photosynthesis observed in chloroplasts isolated by the mechanical method from leaves of sunflower and possibly other species.Abbreviations PGA 3-phosphoglyceric acid     

Effects of 2,4-D butyl vapour on the growth of six crop species

Six species of crop plants (tomato, lettuce, clover, cabbage, sunflower and field bean) were exposed to concentrations of 2,4-D butyl in the range 3–50 ng/litre, for 3.5 h, using an air-flow system. Symptoms of phytotoxicity were recorded during the following 4 wk, after which the plants were harvested. Sunflower and field bean were found to be most sensitive, with tomato, lettuce and cabbage less affected and clover least sensitive, on the basis of weight. Small tomato plants were more sensitive than ones approximately twice the weight. A 50% reduction in dry weight was caused by a 3.5h exposure to less than 3 ng/litre 2,4-D butyl for sunflower, compared with over 50 ng/litre for clover. The ranking of sensitivities did not agree with reports based on liquid doses of 2,4-D, especially for field bean, which was found to be more sensitive than previously thought.     

The effect of different host plants on the reproduction and longevity of Nysius natalensis

Nysius natalensis Evans (Hemiptera: Orsillidae) is a pest of sunflower in South Africa. Adults invade sunflower fields from their weedy hosts which occur inside crop fields and on surrounding headlands. The host plant suitability for survival and reproduction as well as the effect of within‐generation host switching was studied on different wild host plants and sunflower. Life history parameters used to assess host plant suitability were F₁ adult survival, pre‐oviposition period, fecundity, and longevity. Nymphs and adults were provided with stems and seeds of five host plants, viz., Amaranthus hybridus L. (Amaranthaceae), Portulaca oleracea L. (Portulacaceae), Chenopodium album L. (Chenopodiaceae), Conyza albida Spreng. (Asteraceae), and sunflower, Helianthus annuus L. (Asteraceae). Nymphs were reared on crushed seed of the five plant species. After completion of the nymphal stage, emerging adults of each host plant group were provided with seed of a different host plant species for food. Adults did not survive long on stems only and very few eggs were laid. Seeds of the host plant species were shown to be an essential source of nutrients for N. natalensis reproduction, whereas the vegetative plant parts were unsuitable. Nymphal food and host‐plant switching between the nymphal and adult stages significantly affected the pre‐oviposition period. Nymphal and adult food source also affected female longevity. The number of eggs laid was not influenced by nymphal food, but was influenced by adult food and the switch between nymphal and adult food. The comparative attractiveness of sunflower and wild host plants for oviposition was also investigated and showed that females preferred to lay eggs on wild host plants, compared with sunflower. These results may explain why N. natalensis will lay their eggs on sunflower after weeds in the vicinity are controlled, or senesce toward the end of the growing season.     

Effect of field limestone applications on cadmium content of sunflower (Helianthus annuus L.) leaves and kernels

Nonoilseed sunflower (Helianthus annuus L.) is naturally higher in cadmium (Cd) than many other grain crops. Because raising soil pH usually depresses Cd uptake by most species, a study was designed to determine if application of agricultural limestone to neutralize soil acidity would decrease Cd uptake by sunflower plants grown on different soils in the production area of North Dakota. The field experiments were conducted at 3 locations in 1991 and 2 locations in 1992. At each site, limestone was applied to bring soil pH to 6.5–7.0, or an additional 45 Mg ha^-1 more limestone was applied, and these two treatments were compared to no-lime control. Commercial nonoilseed hybrid 954 was planted in these experiments. The rapid short-term lime-soil reaction occurred in first 12 weeks following limestone application. Mean kernel Cd concentration for each treatment varied from 0.35 to 1.45 mg kg^-1 DW in the first year of the experiments, and from 0.37 to 1.23 mg kg^-1 DW in the experiments of 1992 across all locations. Large variations in kernel Cd levels between locations were obtained. There were no significant differences among control and limestone treatments for kernel Cd, seedling leaf Cd and diagnostic leaf Cd within each location, respectively. In regression analysis, we found that kernel Cd level correlated with diagnostic leaf Cd concentration in each treatment, but poor correlations were obtained among other variables. These results indicated that limestone application did not reduce Cd uptake and transfer to kernels of sunflower, in contrast with most species studied.     

Septoria Leaf Speck, a New Disease of Sunflower, Caused by Septoria helianthina sp. nov.

Many strains of a pathogenic fungus were isolated from diseased sunflower leaf tissue. According to their characteristics they belonged to the genus Septoria . Leaf speck symptoms, characteristic for spontaneous infection, were also reproduced by artificial inoculation of sunflower plants in the greenhouse.
Comparing the morphological, cultural and pathogenic properties of the isolated fungus with other sunflower pathogens, it was indicated that the strains, originating from diseased sunflower leaves represented a new, so far not described species. Therefore, for the causal agent of this disease, the name Septoria helianthina Petrov & Arsenijevic was suggested.     

The Responses of Field-grown Sunflower and Maize to Mechanical Support

The effects of mechanical support on two contrasting speciesof herbaceous annual, the dicot sunflower (Helianthus annuusL.) and the monocot maize (Zea mays L.), were investigated bycomparing the growth and mechanical properties of supportedplants and those which were left to sway freely in the wind. Providing support had its greatest effect on the more highly-stressedbasal areas of the plants, such as the lower stem and the baseof the lateral roots. The diameter of the stem bases of bothspecies was approx. 10% lower in supported plants, but therewas no difference between treatments in the diameter of thestem above 50 cm. Roots of both species also showed a reductionin rigidity and bending strength of 40–50% in the supportedplants compared with freely swaying plants. There was a significantreduction in the partitioning of biomass to the root systemsof supported plants of both species. There were differences in the way in which sunflower and maizeresponded to the provision of support; in sunflower, the reductionin lateral diameter was about twice that in maize, whereas inmaize the decrease in the number of first-order laterals wastwice that of sunflower. This study suggests that thigmomorphogenesismay be a localized response, but that different species canrespond in different ways to mechanical stimulation. Wind; support; anchorage; thigmomorphogenesis; Helianthus annuus L.; sunflower; Zea mays L.; maize     

Inhibitory effect of leachate from Helianthus annuus on germination and growth of Kharif crops and weeds

Allelopathic potential of sunflower (Helianthus annuus L.) fresh plant tissues aqueous extraction in bioassay, rhizosphere soil in pot experiment and phytotoxicity of decomposed sunflower plant biomass in bioassay against Vigna radiata, Pennisetum glaucum, Trianthema portulacastrum and Parthenium hysterophorum was investigated. In bioassay aqueous extracts of fresh sunflower plant tissue inhibited the germination, seedling growth (shoot and root) and dry matter accumulation of test plant species. In pot study sunflower rhizosphere soil inhibited growth attributes (plant height, population, number of branches) and yield attributes (grain yield, biomass yield) of selected crops and weeds. Phytotoxicity of decomposed sunflower biomass showed inhibitory effect on selected plant species. The fresh plant tissues was greatest inhibitory to test plants and followed by that of the decomposed biomass extracts in all bioassays. Significant reductions in the root and shoot growth were observed as the extract concentration was increased. The concentrations of extract fraction of fresh sunflower was determined, since nine compounds i.e. ferulic, p-coumaric, syringic, chlorogenic acid, isochlorogenic acid, neochlorogenic acid, vanillic acid, p-hydroxybenzoic acid, caffeoylquinic acid, found to be main growth inhibitors in sunflower plant tissue. These results suggested that sunflower plants may possess allelopathic potential, and the plant tissues may be potentially useful for weed management.     

No-tillage system applied to the sunflower (hybrid pioneer PR64E83) resistant to the tribenuron-methyl in the conditions from Romania

In the year 2006, the first experience with the NO-TILLAGE system for sunflower crops was organized in Romania, using the Pioneer PR64E83 sunflower hybrid resistant to the tribenuron-methyl herbicide. The experience took place in the Danube river flood plain, on an alluvial soil with a content between 3.1-4.5% and a content of clay of 34-40%. In the conventional system, in the fall of the year 2005, autumn ploughing was carried out, along with harrowing, and in spring the land was tilled two more times, using both the disk and the harrow. Before sowing, the land was prepared by using the combiner-machine. After the sunflower sprouted, three-time mechanical hoeing between the rows, as well as three-time manual hoeing on the sunflower row were performed. In the no-tillage system, no autumn ploughing, nor any other soil work were performed, and the sunflower was sowed directly, by using the Gaspardo seeder. Before sowing, the soil was covered in proportion of 70% by species of weeds of the Cirsum, Sonchus and Polygonum amphibium type. To destroy these species of weeds, 3 days before sowing, the soil was treated with the Roundup herbicide in a dose of 7 litres/ha. After the sunflower sprouted, when the plants had 4-5 leaves, the following sulphonylurea herbicides were applied post-emergently. (1) Express 50SG--which contains tribenuron-methyl (2) Granstar 75DF--which contains 75% tribenuron-methyl (3) Titus 25DF--which contains 25% rimsulfuron (4) Mistral--which contains 40 g/L nicosulfuron (5) Lintur 70WG--which contains 4.1% triasulfuron + 65.9% dicamba (6) Peak 75WG--which contains 75% prosulfuron The Express 50SG and Granstar 75DF herbicides were selective for the sunflower hybrid PR64E83, and the other herbicides although belonging o the same sulphonylurea group, they proved to have a very phytotoxic effect upon the sunflower crop. In the report, selectivity is presented depending on the dose of herbicide, weed control and sunflower production.     

Host range and risk assessment of Zygogramma bicolorata,a defoliating agent released in South Africa for the biological control of Parthenium hysterophorus

Parthenium hysterophorus (parthenium) is a weed of international importance and is spreading rapidly in sub-Saharan Africa. Consequently, it has been targeted for biocontrol in South Africa since 2003. Based on precedents elsewhere in the world, the defoliating beetle Zygogramma bicolorata was prioritised as a candidate agent. Although no-choice tests, involving some 48 test plant species, indicated a significant preference for parthenium, significantly reduced feeding and oviposition was recorded on some species. Multiple-choice tests resolved many of these non-target results; however, Helianthus annuus (sunflower) was still selected for oviposition and feeding. Of the 12 sunflower cultivars tested, four were selected for oviposition, while two were selected for oviposition and feeding. These six cultivars were then subjected to larval development trials, together with three native and two weed species (in the Asteraceae). These trials showed high levels of complete development on parthenium, significantly reduced development on sunflower cultivars, and partial development on only one of the weed species. Finally, a risk assessment was conducted on the six sunflower cultivars to quantify Z. bicolorata feeding and reproductive performance. Feeding risk calculations revealed these cultivars to have an extremely low risk (<0.2%) of supporting Z. bicolorata feeding and development. Similarly, reproductive risk calculations showed a very low risk (<0.16%) of supporting viable Z. bicolorata populations. These data are supported by findings from both the native (Mexico) and introduced ranges (Australia, India) of Z. bicolorata, where it has never been recorded as a pest of sunflower. These considerations were accepted by the regulatory authorities and in August 2013, Z. bicolorata became the second insect agent to be released in South Africa for the biocontrol of parthenium.     

Effects of nitrogen supply on growth, yield and yield components of safflower and sunflower

Safflower (Carthamus tinctorius L.) represents an important oil crop internationally and may have a certain production potential under low input conditions, particularly in organic farming systems, where the putatively low nutrient requirement would be an advantage. However, little is known about the nutrient requirements of safflower. This study was undertaken to determine the growth and yield response of safflower as compared to sunflower (Helianthus annuus L.) under different N supplies. Safflower and sunflower plants were grown in Mitscherlich pots containing equal volumes of sand, nutrient-poor limed soil, and perlite. Nitrogen supply was the same for both species (0.25, 0.5, 1.0, 1.5, and 2.0 g per pot) in the first year, but was raised for sunflower (0.5, 1.0, 2.0, 3.0, and 4.0 g per pot) in the second. Increased N supply enhanced plant growth and yield for both species. Growth and yield of safflower increased up to 1.0 g pot⁻¹, while the optimum for sunflower was 2.0 g pot⁻¹. Safflower out-yielded sunflower at low N supply, while at high N level the opposite occurred. Functional analysis according to Michaelis–Menten revealed that – in terms of yield formation – safflower is superior to sunflower under N-limited conditions. Safflower is generally more efficient than sunflower in concentrating N in their shoots. N concentration in the photosynthetically active youngest mature blade of both species exhibited the same functional relationship with the N supply, but safflower required a much lower leaf N concentration to produce optimal yield as compared to sunflower, indicating the higher efficiency of the former in terms of NUE. Yield components analysis revealed that in safflower, yield is tightly correlated with the number of capitula per plant and the mass per achene, both being strongly correlated, too. On the contrary, sunflower yield was merely determined by the number of achenes per capitulum, followed by the mass per achene. Path coefficient analysis showed that in safflower, the direct effects of the achene and leaf N content as well as the leaf dry matter on oil yield are small, and mediated principally via indirect effects on the number of achenes per capitulum, while for sunflower the number of achenes per capitulum exerts a strong direct effect. Dedicated to the late Prof. Dr. Burkhard Sattelmacher, who passed away on November 21, 2005.     

The response of sorghum and sunflower to short-term waterlogging

Summary The effect of waterlogging on water use and nutrient uptake in sunflower and sorghum was investigated in relation to stage of development of the crops and the timing and duration of waterlogging. Waterlogging at the vegetative and floral initiation stages of plant growth induced a reduction in water use of sunflower, with corresponding declines in leaf expansion and leaf water potential; in sorghum, the transpiration rates were much lower than for sunflower and relatively unaffected by waterlogging. Waterlogging at anthesis, however, caused an immediate reduction in water use in sunflower with a similar but delayed effect in sorghum. The differences in response of these two species are discussed in relation to the relative importance of water stress and nutrient uptake. Plant analysis at maturity indicated that waterlogging at any growth stage reduced both total and seed phosphorus in sunflower; similar effects were recorded with sorghum, with the exception of anthesis waterlogging which did not reduce nutrient uptake. Waterlogging effects on plant potassium levels were variable.     

The chemical control of Sorghum halepense species in sunflower culture, in the Danube meadow

In the latest years, sunflower was cultivated in Romania on an area of 800-900 thousand hectares. On 100 or 150 thousand hectares we find it cultivated also in agricultural farms in the Danube Meadow, because sunflower has favorable conditions on these soils, productions exceeding sometimes over 4000 kg/ha, of course, in irrigation conditions. In the Danube Meadow, the first experiments on Sorghum halepense (Johnson grass) species were performed by Fane Popa and colleagues (1986), at the agricultural station of Braila, using the herbicide Fusilade. In our experiments, the herbicide fusillade was compared with different more recently synthesized herbicides: Super, Pantera, Agil, Select, with the specific purpose of identifying the most favorable dose.     

Fungal populations on sunflower ( Helianthus annuus ) anthosphere and their relation to susceptibility or tolerance to Sclerotinia sclerotiorum attack

Analysis of the fungal flora from different floret parts of various sunflower (Helianthus annuus) varieties showed that there are differences in both fungal species and frequency, depending on whether the sunflower variety is susceptible (SV) or tolerant (TV) to attack of the flower heads by the ascomycete pathogen Sclerotinia sclerotiorum. The sunflower varieties analyzed were SV: HA 300 and Z 20028, and TV: HA 302, Z AV 8410 and Z 30629. The isolates showed different “in vitro” behavior as biocontrol agents. The most common types of interaction with Sclerotinia sclerotiorum were D2 and D2+ (hyphal contact) for isolates from SV and TV, while some of the isolates from TV displayed antibiosis. The microorganisms that colonize TV florets play a part in an indirect mechanism that protects flowers from ascospore germination and pathogen growth. This revised version was published online in June 2006 with corrections to the Cover Date.