Volume 35, Issue 57

SUMMARY Overview and scope of the presentation: Efficient exploitation of heterosis is central for successful hybrid breeding in sunflower. Here we discussed important genetic hypotheses of the phenomenon of heterosis including dominance, overdominance, and epistasis. Moreover, we presented different approaches suggested for prediction of hybrid performance. Outline of recent major discoveries: Several experimental designs have been proposed to study the causes of heterosis. Among them, QTL analyses based on triple test cross in combination with the immortalized F2 design or the use of triple test cross designs based on near-isogenic lines are of particular interest. Several approaches have been used to predict hybrid performance using phenotypic, genomic, transcriptomic, and metabolomic data. Prediction accuracies have been studied using experimental data of maize, which clearly points towards the large potential for knowledge-based hybrid breeding. Perceived significant gaps in research, current debates, and perspectives for future directions of research: Experimental design and quantitative genetic theory is ready to be applied in sunflower to study the genetic basis of heterosis. Furthermore, we speculate that genomic selection possesses great potential to revolutionize hybrid prediction in sunflower.

SUMMARY Interspecific hybridization is frequently restricted by genetic cross incompatibilities, genetic distances and different ploidy levels. To overcome this incompatibility a direct organogenesis method has been used successfully. Different molecular methods have been used for verification of success interspecific and intergeneric crosses. It could be demonstrated by results of RAPD fingerprinting that interspecific hybridization is also a valuable tool for broadening genetic variability in sunflower. The successful hybridization between ( H. annuus (cv. Albena) × H. salisifolius ) was achieved. In total 21 RAPD primers (10 bp) length were used for the characterization of interspecific progenies. We were able to demonstrate that RAPD could be used for characterization of interspecific progenies in sunflower at a late stage of selection (F9). It was possible to discriminate between the H. annuus parents and their progenies, where an increased genetic variability was detected. Results of UPGMA cluster analysis confirmed the hybrid nature of the interspecific lines and showed that hybrid progenies which originate in the same cross combination formed specific cluster each, i.e., distinct genetic pools.

SUMMARY High oleic trait has been rarely studied in reciprocal crosses and in most of these cases the maternal effect on the content of unsaturated fatty acids has not been identified. The aims of this study are: i) to check if any maternal effect on oleic acid content is present in high oleic mutants and (ii) if maternal effect and environment conditions could modify the 90% threshold for oleic acid content. Two high oleic inbred lines with different origins were evaluated: 342mt, a selection derived by Ha 342 USDA (maintainer) and line R978 (male fertility restorer, branched) selected by University of Udine and their reciprocal crosses (R978 × 342mt and 342mt × R978). The two inbred lines respond differently to the same environmental conditions. Reciprocal hybrids showed a different accumulation pattern on the first sowing date, and they showed the same response as their female parent. There is a maternal effect in the early stages of the seed filling phase. Low temperature increased linoleic acid and decreased oleic acid at 13 DAF only in 342mt inbred line and in the 342mt × R978 hybrid. High oleic inbred lines with different genetic backgrounds respond differently to the same environmental conditions. It was determined that there was the importance of female parental line choices in breeding to obtain hybrids insensitive to environmental conditions and with a stable oleic acid content over 90%. For the first time a maternal effect on temperature response was found in high oleic sunflower.

SUMMARY As in several regions where sunflower production has moved to areas with limiting water availability, the search for water-stress tolerant genotypes has been intensified. Helianthus annuus ssp. annuus L. constitutes a potential genetic resource because it has naturalized in the semi-arid zone of central Argentina. The assessment of these genetic materials for water deficit tolerance is of interest because they may represent a source of genes for drought tolerance, useful to sunflower breeding. Drought resistant genotypes should be achieved using easily identified phenotypic traits. Parameters like leaf area are widely used to characterize the performance under stress. Leaf temperature is an easily measured physiological parameter that allows an indirect estimate of plant transpiration and is well correlated with water availability. Relative water content indicates the ability to retain water from the soil and expresses plant osmotic adjustment ability. Specific leaf area is a morphological parameter related to leaf thickness. The objectives of this study were to evaluate the drought tolerance of Argentine wild sunflower biotypes and identify morphological and physiological traits expressing differences between stressed biotypes. Wild biotypes were evaluated during three years in the experimental field of the Agronomy Department, Universidad Nacional del Sur, Argentina. Groups of 10-15 plants of each biotype were evaluated under two water conditions, drought (deficit supply) with drip irrigation to cover a half of the potential evapotranspiration during flowering, or with optimal water supply. Soil surface was covered with black polyethylene to exclude rainwater. Wild sunflower comprised five biotypes collected from different habitats in the semiarid region of Argentina. Crosses between the wild biotypes and inbred lines were also included every year. Inbred lines and a commercial hybrid (DK4000) were used as controls. Recorded traits were: plant height, stem diameter, petiole length, leaf area, leaf number, head number and reproductive surface. Leaf parameters were: relative water content (RWC), specific leaf area (SLA), canopy temperature (CT), and chlorophyll content (SPAD). A susceptibility index (SI) was obtained to compare the performance under water stress with that obtained in optimal conditions. Biotype evaluation and parameter characterization were performed separately for each year because water stress levels were different. Wild sunflower responses to water stress were different for all parameters among biotypes, except for plant height and petiole length. Wild biotypes had better RWC and lower SLA than cultivated biotypes. Under water stress wild biotypes showed higher values and greater range of RWC and SPAD than cultivated sunflower. Susceptibility index showed that leaf area of wild sunflower biotypes had lower stress susceptibility than cultivated sunflowers. Nevertheless, wild biotypes showed increased susceptibility to the remaining plant morpho-physiological parameters. RWC and CT had a significant relationship in wild sunflower biotypes under water stress. Drought tolerant type identification was complex because of the complex responses among parameters. Wild biotypes might have a physiological mechanism which allows higher RCA than cultivated sunflower under drought stress. The lower SLA under water deficit could be attributed to a greater leaf thickness and could be related with RCA. Lower leaf area reduction under stress in wild sunflower is an interesting trait that might be used to improve cultivated sunflower. As the RWC is related with CT under stress in wild biotypes, this trait evaluation allows the fast examination of a high number of plants. The assessment of Argentina wild sunflower biotypes for traits associated with drought tolerance has not yet been done. Their identification could increase sunflower crop yield under drought in semiarid regions.

SUMMARY This investigation is directed at improving sunflower using hybrid forms resulted from interspecific hybridization. The aim is to create new B/A and R lines from interspecific hybrid forms that are resistant to diseases, the parasite broomrape, herbicides, and other stress factors and are characterized with high combining ability and to obtain on this basis highly productive oilseed sunflower hybrids with varied fatty acid composition of oil. The investigation was carried out during the period 1983-2010. It involved 16 cultivars and 18 B lines with their analogues as well hybrid material originated from 38 Helianthus species - 9 annuals and 29 perennials. Intraspecific hybridization and purposeful selection were the methods used. Crossing between interspecific hybrids and crossing of interspecific hybrids with sunflower cultivars or lines were applied. Self-pollination, sib-pollination, backcross with pollen from cultivated sunflower and pollination with pollen from different interspecific hybrids were carried out. Phytopathological and biochemical evaluation of seeds and plants and morphological characterization of sunflower forms, lines and hybrids were performed. New sunflower forms and lines were created as a result of this investigation. A greater part of them possess resistance to downy mildew, phomopsis, phoma and alternaria, tolerance to sclerotinia and full resistance to the different races of the parasite broomrape. The new forms were distinguished by new plant architecture, different vegetation period and seeds with different size and coloration. New B/A and R lines having high combining ability and seed oil and fatty acid contents were obtained. Fifteen sources of cytoplasmic male sterility ( cms) were obtained from interspecific hybrid forms, as were 251 sources of genes for restoration of fertility ( Rf genes). Five new hybrid cultivars of the oilseed type that were obtained on the basis of these lines were created and registered. The obtained results from the investigations showed that by interspecific hybridization new genetic material was transferred to the cultivated sunflower. These results have augmented the contribution of interspecific hybridization to sunflower breeding.

SUMMARY Sunflower broomrape ( Orobanche cumana Wallr.) is a parasitic angiosperm regarded as one of the most serious production constraints in many sunflower-producing countries. Historically, sunflower breeders have been successful in developing cultivars resistant to this parasite, but the introduction of new resistance sources has been frequently followed by the appearance of new pathogenic races overcoming the resistance. The present review sets out to examine the principal achievements in this field that took place during the last decades, focusing on the most recent advances in the research. In recent years, several research groups have made relevant contributions in breeding for the resistance and the development of control strategies. Following the identification and characterization of new virulent races, new sources and mechanisms of resistance have been developed and characterized at the genetic and molecular level. There have been also important contributions to the knowledge of the biology and genetics of the parasite that will contribute to the understanding of the dynamics of broomrape populations and race evolution. Important advances have also been made in the use of imidazolinone (IMI)-resistant hybrids as an alternative method of control. Most of the studies on sunflower breeding for resistance to O. cumana have been concentrated so far on the host plant, but in spite of the recent advances little is known about the important aspects of the parasite side of the equation such as the breeding system and genetics of virulence. An unsolved problem is the existing uncertainty in the designation of races and resistance genes identified in different countries. There is a need for international cooperation in this area using common differentials and molecular tools. Emphasis is given to the need for a multidisciplinary approach ranging from studying the mechanisms underlying resistance in the host plant to the reproductive biology and genetics of traits related to parasitism in O. cumana . The combination of long term strategies involving the complete host-parasite system and the integration of classical and molecular approaches is expected to contribute to the development of more durable sources of resistance and to improve sunflower performance in areas infested by broomrape.

SUMMARY Although there are some examples of gene discovery for non-target site mechanisms of tolerance in sunflower, the main focus of research and development during the last decade was directed to the discovery of altered acetohydroxyacid synthase (AHAS) genes and enzymes. In this way, several natural or induced mutant alleles of the sunflower Ahasl1 locus were reported and characterized. Four of these alleles were utilized to develop different non-GMO traits and technologies of weed control: Clearfield®, Clearfield Plus®, Sures, and ExpressSun®. Each one of these technologies has their own characteristics, cross-tolerance pattern, benefits and drawbacks, which are briefly reviewed. Some methods to speed up the introgression of these traits into the breeding program are described, as well as the dominance relationships between some members of the multiallelic Ahasl1 locus. Proper utilization of these technologies allowed, and will continue to allow, an excellent weed control for the sunflower crop. However, some of these genes and their allelic interactions remain to be tested and developed in the years to come in order to create novel technologies. Additionally, it is clear that only one mode of action - the inhibition of the AHAS enzyme - is being exploited so far in sunflower. This will prompt the rapid selection of tolerant weeds that may jeopardize the sustainability of all these technologies. Selection over cultivated germplasm, wild Helianthus species and mutagenized libraries will allow the discovery of new sources of HT, especially to other modes of action apart from the inhibition of AHAS, in order to complement the current technologies.

RESUMEN El significativo incremento de la siembra directa en Argentina y la anticipación de las fechas de siembra en suelos más fríos y húmedos, generó condiciones favorables para la difusión del downy mildew, una de las enfermedades potencialmente más destructivas del girasol causada por el hongo Plasmopara halstedii. Si bien existen cultivares de buen comportamiento frente al patógeno, la obtención de nuevas fuentes de resistencia reduce el riesgo de vulnerabilidad asociado al origen común del germoplasma. El objetivo del estudio fue detectar nuevas fuentes de resistencia a downy mildew en el germoplasma de INTA Pergamino tanto en materiales locales como exóticos. Se analizó la reacción de 1062 entradas de germoplasma de girasol de la EEA Pergamino frente downy mildew. Los análisis se realizaron en el laboratorio de Fitopatología EEA Pergamino desde el año 2001 al 2008 a través del método de inoculación de radícula (Gulya et al ., 1991b). Solo el 1,7% del total de líneas evaluadas fue resistente a downy mildew. En el grupo exótico se obtuvo 1,99% de líneas resistentes, en el Local 0,34% y en Local × Exótico 2,29%. En el grupo exótico la resistencia provino de HA 335/HA 412(con resistencia a razas 700, 730 y 770) y de ND (North Dakota con resistencia a imidazolinonas). En el local la resistencia provino del compuesto P1 de la EEA Pergamino y en el grupo Local × Exótico de EstanzuelaxMP 557/ Negro Bellocq/KLM/HA 300, HA 341/ PEREDOVIK/P1 y P1/KLM/HA 300. Se obtuvo un buen “screening” de líneas de INTA para identificar nuevas fuentes de resistencia a la raza 770 de Plasmopara halstedii. La combinación de los grupos Local × Exótico fue la que permitió obtener el mayor número de materiales resistentes. Debería aumentarse el número de selecciones a partir EstanzuelaxMP 557/ Negro Bellocq/KLM/HA 300 por su buena performance y diferente origen. Los resultados son provechosos para el programa de mejoramiento de INTA. Se continuará con estudios para identificar los genes involucrados en la nueva fuente de resistencia. La detección de nuevas fuentes de resistencia permitirá incorporar el carácter a otros materiales, reduciendo la vulnerabilidad del germoplasma frente a la enfermedad

SUMMARY In tests of sunflower hybrids' susceptibility to broomrape under artificial inoculation conditions, a high germination rate of broomrape seed used for infestation is prerequisite. On the other hand, one of the ways to reduce the great potential of broomrape seeds is biological control. Seed germination was evaluated on three different media. The first medium was water agar with giberellic acid (GA3) and presence of roots of the susceptible sunflower hybrid NS-H-111. The medium for the evaluation of influence of the biological agent on seed germination was the same with bioagent Trifender added in concentration of 1%. The check was a medium with GA3 only. Seeds of Orobanche cumana were collected in sunflower fields in Vojvodina at five different localities. The seeds were placed in Petri dishes with nutritive media and incubated at 25°C in the dark. Germination rate, germ length and distance of germinated broomrape seed from sunflower root were determined at 7 day intervals under the dissecting microscope. After 28 days on the GA3 medium with sunflower roots broomrape seeds germinated at the rate of 44-68%, while on media with Trifender they had significantly lower germination (4-41%). There was no broomrape seed germination on water agar with GA3 only in any sample. Germ lengths of seeds on the GA3+sunflower roots media were significantly longer than those on the medium with Trifender. Orobanche seed which were closer to the sunflower root had better germination on both media.

SUMMARY In order to determine the race composition and distribution of broomrape in Bulgaria during the period 2007 - 2011, samples (seeds) of the parasite were collected in 116 different locations from the main sunflower production regions. The collected seeds were used to infect differential sets of genotypes by a standard methodology. According to the results obtained from this investigation, the broomrape population in Bulgaria includes 4 races: E, F, G and H. Races E and G were most widely distributed. During the years of investigation race E gradually decreased its percentage in the population but was still predominant in the region of north-east Bulgaria while becoming almost equal with race G in the region of central north Bulgaria. In south-east Bulgaria, the population included only race G, which will probably increase its percentage in other regions as well in the upcoming years. Race F was of sporadic occurrence. It was isolated in single years, its distribution was limited and there is no danger of its mass occurrence. The population identified as race H was isolated only in 2007. This population may be considered a “primary” source of infection that will be expanding from now on; for the time being, however, it is localized on a very small area.

SUMMARY The physical properties and compressive loading of six domestic sunflower hybrids were studied. The mean values of length, width, thickness, geometric diameter, surface area, porosity, single kernel mass, sphericity, bulk and true density, 1000-kernel weight and coefficient of friction were measured at a single level of moisture content. The results for the sunflower seeds showed that the length, width, thickness and geometric diameter dimensions ranged from 9.31-11.52 mm, 4.71-5.92 mm, 2.95-4.87 mm and 5.12-6.31 mm, respectively. The mean sphericity, porosity, static coefficient of friction, bulk and true density ranged from 0.313-0.550, 0.313-0.363, 0.211-0.237, 330.10-449.86 and 502.74-701.21 kg m -3 , respectively. The objective of this study was to evaluate and compare the behavior of six domestic sunflower hybrids (Perun, Bačvanin, Krajišnik, NS-H-111, Pobednik and Šumadinac hybrids) during compressive loading considering the seed moisture content. The seeds of NS-H-111, Šumadinac, Pobednik and Krajišnik demonstrated low values of bio yield force ranging from 29.3 N to 45.2 N when seeds had a low moisture content (between 3.7 and 5.9% w.b.). The opposite occurred for the Bačvanin and Perun hybrids (60.6 N and 76.2 N, respectively) within the same seed moisture content. For all the hybrids, the machine head displacement (deformation) increased as the seed moisture content increased. The linear model shows a decreasing trend of bio yield modulus for all hybrids as the moisture content of seeds increased.

SUMMARY Sunflower ( Helianthus annuus L.) breeding programs typically target heterogeneous regions, where large genotype × environment interactions (GEI) complicate genetic progress. Some understanding of the underlying factors, nature and repeatability of GEIs can help to accommodate their effects. This review summarizes the findings of a series of studies conducted in Argentina with the goals of understanding the effect of GEIs on sunflower yield progress and design breeding strategies aimed at impacting on future rates of genetic advance. Pattern analyses revealed that the central and northern subregions are different mega-environments (ME), which suggests that yield gains in the northern ME would have been reduced if selection had been done in central environments and vice versa. Photoperiod and minimum temperature during the reproductive phases are the main environmental factors underlying the observed GEIs. Genetic gain analyses indicated clear and continuous improvements in oil yield due to plant breeding during 25 years and confirmed the prediction about lack of yield gains under the northern ME from selection done in central environments. The central ME showed the highest and most consistent genetic progress, probably because it concentrates most breeding programs and shows the highest repeatability. Breeding progressed to merge the best combinations of two original hybrid groups, reducing the original maturity range within MEs and concentrating on different maturity types among MEs. The model of correlated response to selection indicated that dividing the central- north region of Argentina in central and northern MEs and exploiting specific adaptation would result in faster genetic progress. In the central ME, there is scope to replace years with locations at no costs in heritability. In the northern subregion, trials should be conducted over at least four years. Late planting dates in a central location associated positively with the northern environments in terms of genotypic discrimination; which constitutes an opportunity for indirect selection for the northern ME. Physiological models served to establish the importance of attributes and processes affecting crop performance in the post-anthesis phase in determining the observed genotypeby- planting time interaction. The diameter of the empty center and canopy stay green were found to be efficient secondary indicators related to seed set and duration of grain filling, respectively - indicators that can be used to improve the efficiency of selection for specific adaptation to late plantings and to the northern ME.

SUMMARY Seed quality is a complex character that is determined by a large number of parameters. Because of this, knowing the interrelationships among these parameters is of utmost importance, not only from the point of view of plant selection but also from the standpoint of crop production itself. The objective of this study was to investigate the influence of production season and production region ( i.e., environmental conditions) on quality parameters and yield of sunflower hybrid seed. The study was conducted on the seed of the hybrids NS-H-111 and Rimi that had been produced at sites located in Serbia and Ukraine. The following traits were studied: germinability, 1000-seed weight, husk content, protein content, and seed yield per hectare. All of the studied parameters were affected the most by the genotype itself. Germinability ranged from 87.75% in NS-H-111 produced in Serbia to 95.50% in Rimi produced in Ukraine. The 1000-seed weight was greatly influenced by the production area. All of the studied factors individually produced highly significant differences in husk content, which ranged from 20.35% in NS-H-111 to 31.40% in Rimi. Seed protein content was highly significantly affected by all the factors studied. On average, genotype had the greatest effect on seed yield as well, with the difference in yield between the hybrids (833.0 kg) being highly significant. On the average, looking at the production season and area, differences were observed with regard to seed yield, but those were not statistically significant.