Sunflower is usually affected by white rot (WR) a disease produced by Sclerotinia sclerotiorum . Thus breeders select WR resistant hybrids by means of field experiments replicated in different environments. The WR selection will be effective when the correlation between the phenotype and the set of genes controlling the trait is high. This study aimed to estimate the relationship between the genotype and phenotype for components of WR partial resistance in hybrids. Also the genotypic merit of these hybrids is estimated to determine their value in breeding programs. To this end 37 cultivars were used during three years in Balcarce (southeast of Buenos Aires Province AR). Plants were inoculated with S. sclerotiorum in their capitula. The WR variables evaluated were the relative incubation period (RIP) the daily lesion growth (DLG) and the relative DLG. By using transformed data the degree of genetic determination (DGD) reached values of 0.78 (RIP) 0.63 (relative DLG) and 0.35 (DLG). Although all error variances and their relative contributions to the total variance had the highest values the DGD values for RIP and relative DLG were higher than those reported in the bibliography. The best linear unbiased predictors (BLUPs) detected six hybrids with most suitable genetic merit for RIP and relative DLG. The BLUP correlation coefficient suggested that resistance genes involved in RIP and relative DLG were not the same. Thus these genes could be used simultaneously to develop new sunflower hybrids with more complex WR resistance.

Helianthus annuus subsp. annuus and H. petiolaris are wild North American species that have been naturalized in central Argentina. They have a sporophytic self-incompatibility genetic system that prevent self-fertilization but the occurrence of self-compatible plants in Argentina was observed in both species and could in part explain their highly invasive ability. Their geographical distribution coincides with the major crop area. The domestic sunflower is self-compatible can hybridize with both species and presents a considerable amount of gene flow. The aim of this study is to understand the self-incompatibility mechanism in both wild Helianthus species. Reciprocal crossing and seed production were used to identify self-compatible genotypes the number and distribution of self-incompatibility alleles within populations and the type and extent of allelic interactions in the pollen and pistil. The behaviour of S alleles within each population was explained by five functional S alleles and one non-functional allele in each species differing in their presence and frequency within accessions. In both species the allelic interactions were of dominance/recessiveness and codominance in pollen whereas it was only codominance in the pistil. Inbreeding effects in wild materials appeared in the third generation of self-pollination with lethal effects in most plants. The number of S alleles is low and they behave in a similar way of other Asteraceae species. The self-compatibility was addressed to non-functional S alleles introgressed in wild Helianthus plants through gene flow from self-compatible sunflower.

Simultaneously identify superior performing in terms of seed yield and seed oil content and broad adaptation across a wide range of different environments is an important target for sunflower breeder. So 10 sunflower genotypes were evaluated across the eight various environments created by sowing at four locations i. e. Kafr El Hamam/ Sharkia Shandaweel /Sohag Tag El Ezz/ Dakahlia and Al Arish/ North Sinai Agricultural Research Stations Agricultural Research Center (ARC) Egypt during the two successive summer seasons 2018 and 2019 using randomized complete block designs with four replications in each environment. Results showed that mean squares due to environments genotypes and their interaction were highly significant for seed yield and seed oil content. Most stability approaches revealed that high performing stable genotypes were L240 for seed yield and Sakha 53 L110 and L235 for seed oil content under divergent environments. Hence these four stable sunflower genotypes could be behaved as good breeding materials stock for sunflower improvement.

The development of automated precision technologies for the phenotyping test of seeds by a complex of functional features in the selection process of sunflower is relevant and promising. The task of developing a device for the automatic phenotyping test of seeds and the algorithm for finding and isolating seeds based on color information was set. Research was conducted on a stand which consisted of the following elements: Video Microscope Camera 1080 P 16MP HDMI USB manufactured by Eakins a set of LEDs of three types (red green blue) and a personal computer. The results of experimental studies of the process of automatic phenotyping test of seeds of different sunflower varieties allowed us to establish an average error of determining the geometric dimensions of sunflower seeds (length L and width B) – 0.06 mm. The histograms of the color distribution of sunflower seeds in the RGB color space with different illumination are established. As a result of the analysis of the obtained histograms of the color distribution of sunflower seeds in the RGB color space it is established that in the case of color homogeneity the discreteness of the channels with red illumination is most clearly seen. A device for automatic phenotyping test of seeds has been developed which preserves the accuracy of individual measurement of the geometric dimensions of sunflower seeds determining their shape and color which corresponds to modern measuring tools and provides low complexity and high technological implementation of the phenotyping test procedure (determination ascertaining and identification) material according to its morphological and marker features.

In order to identifying of high yielding compatible sunflower hybrids for different regions of Iran a set of 10 exotic hybrids from Serbia Turkey and Italy and four Iranian hybrids were evaluated for agronomic traits; days to flowering and maturity plant height head and stem diameter 1000-achenes weight achene number per head oil content and achene and oil yield. The experiments were conducted as completely randomized block design with four replications in Alborz Mazandaran Khuzestan and West Azerbaijan Provinces for two years (2017–2018). According to the results growing period of the hybrids were variable from 86 days for Dukat to 98 days for Fantaziya. The hybrids Slatki and Dukat had the highest (70 g) and lowest (56 g) 1000-achenes weight. The highest oil content was observed in 08TR003 (45.6%). Among the locations Miandoab had the highest achene yield (3110 kg/ha). In Sari; the hybrids Barzegar Fantaziya and Slatki (3080 2893 and 2853 kg/ha respectively) In Dezful; Barzegar Cartago and Oscar (3234 3409 and 3226 kg/ha respectively) in Karaj; Oscar Shams and Fantaziya (3138 3081 and 3050 kg/ha respectively) and in Miandob Shams Fantaziya and Slatki (4093 4038 and 3895 kg/ha respectively) had the highest achene yield. Considering overall mean Fantaziya Shams and Oskar had the highest achene yield (3286 3145 and 3087 kg/ha respectively) as well as Fantaziya followed by Barzegar and Shams had the highest oil yield (1396 1335 and 1330 kg/ha respectively). Considering phenotypic variability among the exotic hybrids Fantaziya Oskar Slatki Novak 08TR003 and Meteor with lower coefficient of variation and higher achene yield considered as the stable higher yielding hybrids in four test locations of Iran. Through identifying high-yielding and compatible hybrids the results of this study can assists in increasing of sunflower yield and production in Iran.

Carduus acanthoides L (spiny plumeless thistle) a biannual wild species with 2 n = 22 chromosomes was crossed with Helianthus annuus L. When crossing pollen from C . acanthoides germinated and pollinated the stigmas of sunflower lines HA 89A after 48 h. The crossability rate was low but seeds and hybrid plants were obtained. The F 1 plants strongly resembled the cultivated sunflower with the most important bio-morphological characters even though they had an intermediate type of heritability. The hybrid nature was confirmed by RAPD markers. The polymorphism between H . annuus C . acanthoides and their F 1 hybrids was studied using RAPD. The result showed introgression of C . acanthoides in the hybrid progeny. It was established that the wild species carried Rf genes for the CMS PET-1. After self-pollination and sib-pollination of the F 1 plants and back-crossing with cultivated sunflower F 2 BC 1 and next generation hybrid progenies were obtained. The investigation encompassed the period 2000–2007 and 2014–2018. Some of the new lines have been included in a heterosis breeding program for developing hybrids for the sunflower market.

Field studies conducted in 2018–2019 in the northern Steppe of Ukraine with sunflower hybrids of different maturity groups (LG 50300 LG 5580 LG 5478 LG 5638 LG 5662) showed that the crop density of early-crop hybrid LG 50300 from 55000 plants/hectare to 70000 plants/hectare led to a decrease in productivity by 0.11 t ha −1 and a decrease in oil content by 0.9%. The density of middle-early hybrid LG 5580 resulted in a decrease in sowing productivity of 0.21 t ha −1 while oil content remained nearly the same. Another middle-early hybrid LG 5478 showed slight variations in productivity and oil content with an increase of crop density. The study of the mid-season hybrid LG 5038 showed a decrease in sowing productivity by 0.2 t ha −1 with the density up to 70000 plants/hectare. Mid-season hybrid LG 5662 with density of 70000 plants/hectare showed productivity increase by 0.14 t ha −1 .