For much of the past century, mutagenesis has gained popularity in plant genetics research as a means of inducing novel genetic variation. Induced mutations have been applied for the past 40 years to produce mutant cultivars in sunflower by changing plant characteristics that significantly increase plant yield and quality. The present study is focused on generating baseline data to elucidate the role of genotypic differences in the response of sunflower to induced mutagenesis with the aim of expanding the applicability of the use of induced mutant stocks in the genetic improvement of the crop and in its functional genomics. The strategy adopted was to estimate the optimal treatment conditions (doses of mutagens) through relating the extent of damage in seedling progeny to the exposure levels of the initiating propagates to mutagens. Seeds of fifteen elite sunflower genotypes of commonly used as breeding stocks and grown on commercial scales were treated with a range of mutagens: gamma rays (γ rays); fast neutrons and with ethyl-methane-sulphonate (EMS) at different treatment doses. The three mutagenic agents affected seedling height, reducing it with increasing dosage. Based on the mutagen damage on seedling height, the 50% and 30% damage indices (D50 and D30, respectively) were estimated for the 15 sunflower genotypes for the three mutagens. The D50 (D30) values for the sunflower lines ranged from 120 to 325 Gy (5 to 207 Gy) for gamma irradiation; 9 to 21 Gy (0.1 to 10 Gy) for fast neutrons and 0.69 to 1.55% (0.01 to 0.68%) concentration of EMS.
Sunflower is attacked by more than 40 different diseases of which only a certain number causes serious reduction of seed yield. One of the most damaging diseases is downy mildew, which is caused by the fungus Plasmopara halstedii (Farl.) Berl. et de Toni (syn. Plasmopara helianthi Novot.). Sunflower downy mildew has great economic importance in all countries where sunflower is grown. When the meteorological conditions during the vegetation period of sunflower become favourable for disease development, the damages produce considerable reducing of the seed yield and the oil content.
The best way of controlling the fungus is to grow resistant cultivars and because of that the major objective of this study was to develop sunflower genotypes genetically resistant to dominant races of downy mildew in Serbia. During this work two co-dominant CAPS markers for Pl6gene were developed which can also be used for Pl7gene. For introduction of these genes in breeding program marker assisted selection (MAS) was used. Developed commercial sunflower inbred lines exhibit resistance to all known races of downy mildew in Serbia indicated incorporation of resistance to downy mildew in well-known and widely produced hybrids. Besides that, Pl-genes were introduced to a large number of new inbred lines and new downy mildew resistant hybrids. These new hybrids reach higher seed and oil yields then hybrids widely produced.
The objective of the study was to provide new genetic variability in important agronomic traits that can be exploited for improvement of sunflower production. Seeds of eight sunflower inbred lines from gene collection of Institute of Field and Vegetables, Novi Sad were irradiated with gamma rays (γ) and fast neutrons (Nf) and treated in ethyle-methane-sulphonate (EMS) solution. The manifestation of mutations was mostly expressed in M2 and M3 generation. Seven mutants were developed; one early flowering, two short stature and one high, two with higher oil content and one branching. The stable progenies were evaluated in micro-plot tests in M6 generation for seed yield and other traits in comparison with respective original line. Further studies should be focused on testing new mutant lines in hybrid combinations, as well as the determination of inheritance of mutant traits.
Breeding for downy mildew resistance is one of the major goals in sunflower breeding programmes. In the last few decades new sources of resistance have been discovered and the position of 11 resistance genes was established on the genetic map of sunflower. For most of these resistance genes sequence specific markers have been developed, which facilitate their detection and make the selection process faster and more reliable. By combining the partial resistance provided by minor genes with specific resistance genes, durable resistance could be achieved.