Sunflower In Argentina Research Articles

Phomopsis Head Rot caused by Diaporthe helianthi: A New Disease on Sunflower in Argentina

ABSTRACTDuring a survey conducted in the 2021, 2022 and 2023 seasons, sunflower heads showing symptoms of dry rot were collected from 80 fields in the semi‐arid Pampa region of Argentina. A total of 72% of the fields examined in 2021, 71% in 2022 and 63% in 2023 showed the presence of the disease. The highest incidence was recorded as 70% in 2021. Phomopsis head rot began as dry, brown spots on the back of the head, progressing to necrosis and twisting of adjacent leaves. Infected head tissue samples were surface sterilised, cultured on potato dextrose agar (PDA) and incubated at 25°C for 14 days. Diaporthe helianthi was identified based on cultural and morphological characteristics as well as molecular data. A phylogenetic analysis was performed. Internal transcribed spacer (ITS), translation elongation factor 1‐α (ef1‐α) and β‐tubulin sequences were deposited in GenBank, showing the identity with the ex‐type D. helianthi strain CBS 592.81. Pathogenicity experiments confirmed the presence of similar disease symptoms in inoculated sunflower heads, and D. helianthi was consistently reisolated from these organs. Our Koch's postulates testing results on heads constitute the first confirmed report that D. helianthi is the cause of Phomopsis head rot on sunflower in Argentina.

First report of Diaporthe ambigua causing Phomopsis stem canker on sunflower in Argentina

First report of <i>Diaporthe ambigua</i> causing Phomopsis stem canker on sunflower in Argentina

Oil-con hybrids as a potential tool to prevent eared dove damage to sunflower crops

Abstract Eared doves (Zenaida auriculata) cause significant economic damage to mature sunflower in Argentina. Empirical evidences indicate that some sunflower hybrids (e.g. confectionary and stripped oilseed) might be less susceptible to bird damage than others (e.g. black oilseed). However, these less susceptible hybrids could imply a trade-off between damage reduction and oil content on the seeds. In this work, we investigated the potential of a new oil-con hybrid types (OC: oilseed × confectionary cross) as a tool to prevent eared dove damage to sunflower crops. We compared the performance (damage values), morphological characteristics and nutritive quality of this hybrid compared to other three standard sunflower hybrids (BO: black oilseed, SO: striped oilseed, and CON: confectionary), both in the field and in cages. In both tests, doves significantly selected BO and SO hybrids over CON and OC hybrids. The OC hybrid was not selected, despite its high nutritional value. Results suggest that achene size could be an important morphological trait influenced eared dove selection of hybrids, independently of other seed characteristics. Based on these results, the OC hybrid tested in this study seems to be a promising tool for preventing eared dove damage to sunflower in Argentina.

Six Species of Diaporthe Associated with Phomopsis Stem Canker of Sunflower in Southern Pampean Region of Argentina

A survey of 67 commercial fields in 19 locations was conducted in the southern Pampean region of Argentina for Phomopsis stem canker of sunflower (Helianthus annuus L.) between 2014 and 2019. A total of 210 plants having typical symptoms of Phomopsis stem canker were randomly sampled, and fungal isolation was performed. Of the 187 isolates of Diaporthe that were recovered, 94% of the isolates showed morphological characteristics similar to D. helianthi, 3% to D. gulyae, 1% to D. caulivora, 1% to D. sojae, 0.5% to D. kongii, and 0.5% to D. longicolla. Following morphological characterization, the identity of the six morpho-species was confirmed by phylogenetic analyses of β-tubulin, translation elongation factor 1-α, and internal transcribed spacer gene regions. Koch’s postulates were completed for the six fungi by inoculating one susceptible sunflower hybrid with one isolate each of the six species of Diaporthe using the stem-wound inoculation method. Seven days postinoculation, significant differences in disease severity were observed between the six isolates (P &lt; 0.0001), with D. helianthi and D. gulyae isolates causing significantly greater disease severity. To our knowledge, this is the first report of D. kongii, D. longicolla, D. caulivora, and D. sojae associated with Phomopsis stem canker of sunflower in Argentina.

First Report of Tobacco Streak Virus Infecting Sunflower in Argentina

Fil: Cabrera Mederos, Dariel. Instituto Nacional de Tecnologia Agropecuaria; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Fitopatologia y Modelizacion Agricola. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Unidad de Fitopatologia y Modelizacion Agricola.; Argentina

Genetic Diversity and Population Structure of Wild Sunflower (Helianthus annuus L.) in Argentina: Reconstructing Its Invasion History.

Studying the levels and patterns of genetic diversity of invasive populations is important to understand the evolutionary and ecological factors promoting invasions and for better designing preventive and control strategies. Wild sunflower (Helianthus annuus L.) is native to North America and was introduced, and has become invasive, in several countries, including Argentina (ARG). Here, using classical population genetic analyses and approximate Bayesian computation (ABC) modeling, we studied the invasion history of wild sunflower in ARG. We analyzed 115 individuals belonging to 15 populations from ARG (invasive range) and United States (US, native range) at 14 nuclear and 3 chloroplast simple sequence repeat markers along with 23 phenotypic variables. Populations from ARG showed similar levels of nuclear genetic diversity to US populations and higher genetic diversity in the chloroplast genome, indicating no severe genetic bottlenecks during the invasion process. Bayesian clustering analysis, based on nuclear markers, suggests the presence of 3 genetic clusters, all present in both US and ARG. Discriminant analysis of principal components (DAPC) detected an overall low population structure between central US and ARG populations but separated 2 invasive populations from the rest. ABC modeling supports multiple introductions but also a southward dispersal within ARG. Genetic and phenotypic data support the central US as a source of introduction while the source of secondary introductions could not be resolved. Finally, using genetic markers from the chloroplast genome, we found lower population structure in ARG when compared with US populations, suggesting a role for seed-mediated gene flow in Argentina.

Impact of Imazamox and Imazapyr Carryover on Wheat, Barley, and Oat

Imazapyr and imazamox are frequently applied postemergence to control grass and broadleaf weeds in imidazolinone-resistant sunflower in Argentina. Herbicide carryover to rotational crops represents a disadvantage of these herbicides, particularly in regions with low rainfall during the months prior to rotational crop sowing. Between 2009 and 2012, field and greenhouse studies were conducted on four important sunflower-cropped areas of Argentina. The objective was to quantify the effects of imazapyr alone and imazamox plus imazapyr applied in sunflower crops on the subsequent establishment, growth, and yield of barley, oat, and wheat. In all field experiments, imazapyr alone and imazamox plus imazapyr were applied at recommended rates (80 gha–1and 66 plus 30 gha–1, respectively), and also, in some experiments, at double the recommended rates. Soil bioassays were also conducted in the greenhouse to study the effect of these herbicides on barley, oat, and wheat seedlings. The mixture of imazamox plus imazapyr was safer for rotational crops than imazapyr applied alone, because of the reduced rate of imazapyr in the mixture treatments. Barley was more sensitive to imidazolinones, particularly imazapyr, than the other winter cereals. Imazapyr at double rate (160 gha–1) reduced barley yield by 45% when seeds were sown 165 d after herbicide application and with 240 mm rainfall after herbicide application.

Increases in the source to sink ratio related to a higher carbohydrate concentration reduce phoma black stem in sunflower

Fil: Nunez Bordoy, Iris Evangelina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

NEW VARIANTS OF VERTICILLIUM DAHLIAE CAUSING SUNFLOWER LEAF MOTTLE AND WILT IN ARGENTINA

The sunflower leaf mottle and wilt caused by Verticillium dahlie Kleb. is a major disease of the crop. The populations of V. dahliae are variable and physiological races of the pathogen have been reported in lettuce, pepper, spinach, sunflower and tomato. The classification of V. dahliae isolates based on their pathogenicity in differential sunflower genotypes to determine races of the pathogen gives useful information for growers and breeding programmes. Two new Verticillium dahliae races causing sunflower leaf mottle and wilt in sunflower hybrids previously known as resistant were recognized. The sunflower inbred lines ADV29 and ADV53 allowed to differentiate specific pathogenicity patterns. One isolate that affected both genotypes was postulated as race VArg3, and another group that did not cause disease on either genotypes was described as race VArg4. Sunflower genotypes showing inverse differential reactions to races VArg3 and VArg4 were not found. However, the observed pathogenicity patterns could be considered a phenotypic marker useful to identify the V. dahliae races VArg3 and VArg4 in monitoring studies. The current presence of four races of V. dahliae affecting sunflower in Argentina is discussed.

Complete genome sequence of sunflower ring blotch virus, a new potyvirus infecting sunflower in Argentina.

The complete genome sequence of sunflower ring blotch virus (SuRBV), a previously undescribed potyvirus infecting sunflower in Argentina, is reported. The SuRBV genome comprises 9555 nucleotides (nt) and encodes a polyprotein of 3061 amino acids, flanked by 5' and 3' untranslated regions of 117 and 255 nt, respectively. Phylogenetic analysis showed that SuRBV belongs to the potato virus Y (PVY) subgroup and clusters together with sunflower chlorotic mottle virus and bidens mosaic virus. Percentage nucleotide identity between the whole genomes of SuRBV and BiMV was 70.6%, suggesting SuRBV should be considered a distinct species in the genus Potyvirus.

Identification and molecular characterization of a phytoplasma associated with sunflower in Argentina

Sunflower (Helianthus annuus L.) plants showing capitulum with virescence, phyllody and flower malformation, shortened internodes and abnormal branches were found in a field in Pedro Luro (Buenos Aires province, Argentina). Pleomorphic bodies resembling phytoplasmas were observed in sieve tube elements of symptomatic plants but not in healthy ones. DNA from all symptomatic sunflower plants analysed yielded, in direct PCR with phytoplasma universal primers P1/P7 and R16F2n/R2, fragments of expected size 1.8 kb and 1.2 kb, respectively. The phytoplasma associated with the disease, was named Sunflower Phyllody (SunPhy). Real and putative RFLP of the 16S rDNA showed the affiliation of SunPhy to 16SrIII (X-disease group), subgroup J. The 16S rDNA sequence from SunPhy showed the highest identity (99 %) with 16SrIII members and the phylogenetic tree confirmed a closer relationship to subgroup J of the 16SIII ribosomal group. This is the first report of a phytoplasma related to the 16SrIII group affecting sunflower.

Sequencing of two Sunflower chlorotic mottle virus isolates obtained from different natural hosts shed light on its evolutionary history

Sunflower chlorotic mottle virus (SuCMoV), the most prevalent virus of sunflower in Argentina, was reported naturally infecting not only sunflower but also weeds. To understand SuCMoV evolution and improve the knowledge on its variability, the complete genomic sequences of two SuCMoV isolates collected from Dipsacus fullonum (-dip) and Ibicella lutea (-ibi) were determined from three overlapping cDNA clones and subjected to phylogenetic and recombination analyses. SuCMoV-dip and -ibi genomes were 9,953-nucleotides (nt) long; their sequences contained an open reading frame of 9,561 nucleotides, which encoded a polyprotein of 3,187 amino acids flanked by a 5'-noncoding region (NCR) of 135 nt and a 3'-NCR of 257 nt. SuCMoV-dip and -ibi genome nucleotide sequences were 90.9 identical and displayed 90 and 94.6% identity to that of SuCMoV-C, and 90.8 and 91.4% identity to that of SuCMoV-CRS, respectively. P1 of SuCMoV-dip and -ibi was 3-nt longer than that of SuCMoV-CRS, but 12-nt shorter than that of SuCMoV-C. Two recombination events were detected in SuCMoV genome and the analysis of d(N)/d(S) ratio among SuCMoV complete sequences showed that the genomic regions are under different evolutionary constraints, suggesting that SuCMoV evolution would be conservative. Our findings provide evidence that mutation and recombination would have played important roles in the evolutionary history of SuCMoV.

The foraging preferences of two species of Melissodes Latreille (Hymenoptera, Apidae, Eucerini) in farmed sunflower in Argentina

The present study addresses the pollen preferences of two species of wild bees of the genus Melissodes in the intensively farmed temperate Pampean region of Argentina. The resources used by M. (Ecplectica) tintinnans and M. (Ecplectica) rufithorax were studied in a commercial plot of sunflower and its field margins in the locality of Carlos Casares, province of Buenos Aires. Surveys before, during and after the bloom of sunflower were carried out. The bees emerged synchronously with the beginning of the bloom, but continued foraging for over a month after maturation of the crop. Pollen analyses of scopal loads indicated that sunflower was a major component of the diet. Bees also collected pollen from other Asteraceae during and after the blooming of the sunflowers. Pollen from Ligustrum sp. and Eucalyptus sp., two trees common in the hedgerows, was also collected in significant amounts. The vegetation on the field margins facilitated maintenance of the populations after the blooming of the sunflower. The two species of native Melissodes used pollen of plant taxa that are frequent and widespread in the Pampean agricultural ecosystems. This fact, together with their habit of nesting in aggregations, indicates that these bees represent a valuable resource as crop pollinators.

Exploring environmental determinants of the geographic distribution of broomrape (Orobanche cumana Wallr.)

Broomrape is one of the most critical biotic constraints to sunflower crop production. In the most extended sunflower crop area of the world, distributed across Black sea region, this parasitic weed shows a high occurrence. The weed, originally from the Caucasus region, has progressively migrated to the South of the Eurasia continent. The actual invaded area reaches Spain, Israel, Kazakhstan, China, Mongolia and Iran. Due to the usual seed exchange between macro-regions it is not clear why this weed is absent in other extended sunflower crop area located in South America. It is possible that the invasive process could be limited by abiotic restrictions. With the aim to estimate the influence of environmental factors on the actual broomrape geographic distribution, we evaluated 14 sunflower habitats of Serbia with different levels of natural infection and nine natural habitats of wild sunflower in Argentina. The altitude, latitude, longitude, mean hottest month temperature, mean coolest month temperature, and average rainfall of 10 habitats from Serbia showed no differences between infected and non-infected soils. The natural initial infection of four soils from Serbia did not influence the Orobanche attack intensity in a greenhouse experiment with artificial inoculation. Soil texture, total N, humus and calcareous content, as well as pH, had no effect on Orobanche attack intensity. In the greenhouse experiment, Principal Components Analysis showed that Orobanche attack intensity (expressed as parasite plant number per sunflower plant) was inversely associated only with P availability (ALP2O5), but the linear relationship between both variables was not significant. When Argentinean habitats were included in the database, strong differences between invaded and not invaded areas were found regarding geographic localization, as expected. The invaded habitats differed by the coolest month mean temperature, but no significant differences were found for the remaining climatic parameters. Soil fertility and the texture of 13 soils with different natural Orobanche infection showed no differences between invaded and non-invaded habitats. A better understanding of the abiotic determinants of Orobanche geographic distribution could help to design management tools to prevent the continuous increase of the invaded area and to limit damage to sunflower in the regions presently affected by the weed. [Projekat Ministarstva nauke Republike Srbije, br. TR 31025]

Spatial and seasonal effects confounding interpretation of sunflower yields in Argentina

Sunflower in Argentina is grown in subtropical (northern) and temperate (central and southern) environments. These environments can substantially complicate hybrid selection due to large genotype×environment (G×E) interactions. The spatial and seasonal differences between and within central and northern regions were investigated through two complementary approaches: (i) pattern analysis was applied to a long-term environmental data record, in order to group environments based on the mean value of each variable for the different crop stages in a range of years and locations; (ii) a trial dataset, comprising 68 trials, covering 8 years (Y) and 18 locations (L), was analyzed to quantify G, E, and G×E variance components for grain yield, oil concentration and oil yield. Pattern analysis of environmental data separates northern and central environments over both years and locations. Northern environments had shorter photoperiods, less rainfall and lower temperatures during vegetative phases; shorter photoperiods during flowering, and higher temperatures during grain filling. Seasonal differences in trial yield were highly associated with rainfall during reproductive phases. Residual maximum likelihood analyses detected that 86% (central region) and 83% (northern region) of the total G×E interaction for oil yield was attributable to G×L×Y. The relatively low G×L interaction compared with G×L×Y implies that broad adaptation within regions is required. To achieve repeatabilities of more than 80%, trials would need to be conducted over at least 6 years with 15 locations per year. Environmental differences between regions showed a strong degree of repeatability, and were consistent with differences in magnitude of G×E interactions for oil yield components.

Genetic improvement of sunflower in Argentina between 1930 and 1995: Part III. Dry matter partitioning and grain composition

We compared the partitioning of dry matter and the oil and protein content in the grain of sunflower ( Helianthus annuus L.) cultivars released in Argentina between 1930 and 1995. At anthesis, the fraction of plant dry matter partitioned to leaf and head increased, whereas the fraction in the stem decreased with year of cultivar release. Improved oil yield was related to the increase in: (i) harvest index (grain mass/shoot mass) from about 0.3 to 0.5; (ii) kernel-to-grain ratio from 0.6 to 0.8; and (iii) kernel oil concentration from 58 to 70%. The duration of the period of grain growth as a fraction of season length accounted for half of the variation in harvest index. Kernel oil concentration was negatively associated with protein concentration which dropped from 23 to 13%. Further improvement in partitioning may be possible, including increase in harvest index resulting from enhanced contribution of stored assimilate to grain growth. Owing to the dramatic improvement in partitioning achieved in the last seven decades, however, further increase in yield may need to focus on increasing biomass production.

Genetic improvement of sunflower in Argentina between 1930 and 1995: II. Phenological development, growth and source–sink relationship

Historic sets of sunflower ( Helianthus annuus L.) cultivars released in Argentina between 1930 and 1995 were compared in two field experiments. Breeding and selection shortened cycle length: most of the reduction came from a reduction in time to anthesis, which together with a stable time from anthesis to maturity increased the proportion of the growing cycle given to grain growth. Shoot biomass at maturity was unrelated to year of cultivar release but a greater portion was produced after anthesis. The ratio between leaf area index duration from anthesis to maturity and grain number was taken as a measure of source-to-sink ratio; this ratio was smaller in hybrids than in open-pollinated cultivars. Variation in both the amount of oil per grain and grain mass were small in comparison with the variation in source-to-sink ratio indicating that additional carbon may have attenuated the effects of less leaf area duration per grain. Owing to the relative stability of the amount of oil per grain and the reduction in grain mass, the grain oil concentration increased despite the drop in source relative to sink. Further yield improvement will mostly depend upon the increase in the supply of substrates to fill the grain provided grain size is not restricted by events occurring before anthesis.

Genetic improvement of sunflower in Argentina between 1930 and 1995. I. Yield and its components

Historic sets of sunflower cultivars released in Argentina between 1930 and 1995 were compared in two field experiments to identify contributions of breeding to the improvement of yield potential. Three yield components were considered: grain number; grain weight; and grain oil concentration. Both grain and oil yield were positively associated with year of cultivar release. There was a clear discontinuity in yield trends, however, with a marked step around 1970, when the first hybrids were released. No improvement in yield potential was apparent during long periods before and after this turning point. On average, hybrids outyielded open-pollinated cultivars by 23% for grain and 36% for oil. More grains that are slightly lighter and of greater oil concentration accounted for most of the variation in grain and oil yield between open-pollinated cultivars and hybrids. Increased grain number resulted from greater floret production, rather than enhanced floret fertility; variation in grain weight was associated with variation in rate rather than duration of grain filling. Further increase in yield potential could be achieved by maintenance of grain number ca. 7500 m −2 and increasing grain weight and oil concentration. The trade-off between grain weight and oil concentration deserves special attention. Targeting yield components in this way may accelerate the rate of improvement in grain and oil yield potential.

Characterization of a Potyvirus Infecting Sunflower in Argentina.

A virus causing chlorotic mottling symptoms on sunflower was found in various locations in Argentina. Symptoms were small chlorotic spots, yellow blotches on leaves, and plant stunting. Virus transmission efficiency by mechanical inoculation was 73 to 100%, and by Myzus persicae was 31 to 49%. The host range included members of the Amaranthaceae, Asteraceae, Chenopodiaceae, and Solanaceae families. Electron microscopy of leaf dips from infected plants revealed flexuous particles 17 nm wide and 770 nm long. Cytoplasmic laminar aggregates and pinwheel inclusions were observed in ultrathin sections. Purified virus preparations analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved a capsid protein of 33 kDa. A monoclonal antibody to aphid-transmitted potyviruses reacted with the capsid protein of this virus. In dot blot immunoassays, a polyclonal antiserum (early bleeding) reacted with infected sunflowers and weakly with Bidens mottle potyvirus, but not with either maize dwarf mosaic potyvirus or potato virus Y. The evidence suggests that a potyvirus is infecting sunflower, and a partial characterization of the causal agent is reported.