Aleksandra Dimitrijević

Mapping of a new gene for resistance to broomrape races higher than F

Broomrape (Orobanche cumana) is one of the most important parasitic plants that can drastically reduce sunflower yield. Breeding for resistance is regarded as the most effective and environmentally friendly control measure. Due to the constant changes in broomrape race composition, i.e. the emergence of races F and higher, the majority of the existing resistance genes have become insufficient for crop protection. In this paper we report the genetic analysis and mapping of a new resistance gene for broomrape races higher than F. Broomrape resistance was evaluated using F1 plants and F2:3 families derived from a cross between the resistant sunflower inbred line AB-VL-8 and the susceptible line L-OS-1. The results showed that F1 plants were susceptible, indicating a recessive resistance. In the derived F2 population and F3 families, the resistance segregation deviated significantly from the one-gene Mendelian ratio. However, marker analysis revealed polymorphism only on LG3, indicating that presumably single gene in this region conferred the resistance. The closest marker to the gene, tentatively designated as orab-vl-8, was ORS683 with the genetic distance of 1.5 centimorgans. The discovery of orab-vl-8 will provide a much needed new sunflower resistance gene for new broomrape races, and the associated markers will facilitate the introgression of the gene into different sunflower lines.

Sunflower Hybrid Breeding: From Markers to Genomic Selection

In sunflower, molecular markers for simple traits as, e.g., fertility restoration, high oleic acid content, herbicide tolerance or resistances to Plasmopara halstedii, Puccinia helianthi, or Orobanche cumana have been successfully used in marker-assisted breeding programs for years. However, agronomically important complex quantitative traits like yield, heterosis, drought tolerance, oil content or selection for disease resistance, e.g., against Sclerotinia sclerotiorum have been challenging and will require genome-wide approaches. Plant genetic resources for sunflower are being collected and conserved worldwide that represent valuable resources to study complex traits. Sunflower association panels provide the basis for genome-wide association studies, overcoming disadvantages of biparental populations. Advances in technologies and the availability of the sunflower genome sequence made novel approaches on the whole genome level possible. Genotype-by-sequencing, and whole genome sequencing based on next generation sequencing technologies facilitated the production of large amounts of SNP markers for high density maps as well as SNP arrays and allowed genome-wide association studies and genomic selection in sunflower. Genome wide or candidate gene based association studies have been performed for traits like branching, flowering time, resistance to Sclerotinia head and stalk rot. First steps in genomic selection with regard to hybrid performance and hybrid oil content have shown that genomic selection can successfully address complex quantitative traits in sunflower and will help to speed up sunflower breeding programs in the future. To make sunflower more competitive toward other oil crops higher levels of resistance against pathogens and better yield performance are required. In addition, optimizing plant architecture toward a more complex growth type for higher plant densities has the potential to considerably increase yields per hectare. Integrative approaches combining omic technologies (genomics, transcriptomics, proteomics, metabolomics and phenomics) using bioinformatic tools will facilitate the identification of target genes and markers for complex traits and will give a better insight into the mechanisms behind the traits.

Potential of Legume–Brassica Intercrops for Forage Production and Green Manure: Encouragements from a Temperate Southeast European Environment

Legumes and brassicas have much in common: importance in agricultural history, rich biodiversity, numerous forms of use, high adaptability to diverse farming designs, and various non-food applications. Rare available resources demonstrate intercropping legumes and brassicas as beneficial to both, especially for the latter, profiting from better nitrogen nutrition. Our team aimed at designing a scheme of the intercrops of autumn- and spring-sown annual legumes with brassicas for ruminant feeding and green manure, and has carried out a set of field trials in a temperate Southeast European environment and during the past decade, aimed at assessing their potential for yields of forage dry matter and aboveground biomass nitrogen and their economic reliability via land equivalent ratio. This review provides a cross-view of the most important deliverables of our applied research, including eight annual legume crops and six brassica species, demonstrating that nearly all the intercrops were economically reliable, as well as that those involving hairy vetch, Hungarian vetch, Narbonne vetch and pea on one side, and fodder kale and rapeseed on the other, were most productive in both manners. Feeling encouraged that this pioneering study may stimulate similar analyses in other environments and that intercropping annual legume and brassicas may play a large-scale role in diverse cropping systems, our team is heading a detailed examination of various extended research.

Identification and validation of breeder-friendly DNA markers for Pl arg gene in sunflower

Abstract Downy mildew is a fungal disease of sunflower that can lead to severe yield losses. The damage caused by the pathogen can be controlled by growing resistant sunflower varieties. Gene Plarg was introgressed into cultivated sunflower from the wild species Helianthus argophyllus and provides resistance against all known downy mildew races. In this study, we used a mapping population from the cross-RHA 419/RHA-N-49. We identified a new co-segregating simple sequence repeat marker ORS675 and confirmed the co-segregation of markers ORS716 and ORS662 with Plarg gene. The markers were validated on two registered resistant inbred lines RHA 443 and RHA 464, as well as on twenty inbred lines RH 1–20 obtained through methods of classical breeding. Molecular marker ORS716 was assessed for usefulness in selecting resistant progeny in 12 BC populations. Markers were found to be valuable for molecular breeding in diverse genetic backgrounds and enabled transfer of the resistance gene in different sunflower genotypes.