QTL mapping of partial resistance to basal stem rot in sunflower using recombinant inbred lines

Basal stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is an important cause of yield loss in sunflower (Helianthus annuus L.). Quantitative trait loci (QTLs) implicated in partial resistance to basal stem rot disease was identified using the 116 recombinant inbred lines (RILs) from the cross between the sunflower parental lines PAC2 and RHA266. RILs and their parents were arranged in a completely randomized design with six replications and inoculated with a moderately aggressive isolate (SSU107) of S. sclerotiorum under controlled conditions. QTLs were mapped using a recently developed high-density single sequence repeat/ amplified fragment length polymorphism (SSR/AFLP) sunflower linkage map. Analysis of variance showed highly significant differences among the sunflower genotypes for susceptibility to basal stem rot. The frequency distribution of genotypes for susceptibility to disease showed continuous patterns, suggesting that resistance is controlled by a polygenic system. Transgressive segregation for resistance occurred in this cross. Composite interval mapping analysis revealed 7 QTLs for percentage necrotic area, localized on 7 linkage groups. The effects of QTLs were small to moderate indicating a polygenic control of the studied character. However, like any other quantitative trait, it is necessary to confirm the position of the QTLs and carry out fine-scale mapping before marker assisted selection (MAS). LG8 and LG16 are good candidates for further analysis to develop molecular markers for resistance to Sclerotinia disease

Composition, Antifungal, Phytotoxic, and Insecticidal Activities of Thymus kotschyanus Essential Oil

Essential oils (EOs) are some of the outstanding compounds found in Thymus that can exert antifungal, phytotoxic, and insecticidal activities, which encourage their exploration and potential use for agricultural and food purposes. The essential oils (EO) obtained from Thymus kotschyanus collected in the East Azerbaijan Province (Iran) were characterized using a gas chromatography-mass spectrometry (GC-MS) analysis. Thymol was the most important compound (60.48%), although 35 other active compounds were identified in the EO. Significant amounts of carvacrol (3.08%), p-cymene (5.56%), and γ-terpinene (6.67%) were found in the EO. The T. kotschyanus EO was tested against important phytopathogenic fungi (Botrytis cinerea, Aspergillus niger, and Penicillium expansum). The antifungal assay showed that the use of ≥500 ppm of EO resulted in a fungicidal effect against all funguses tested. In a similar way, the use of ≥500 ppm of EO inhibited the germination of all crop weed seeds (Amaranthus retroflexus L. and Panicum miliaceum L.) and their subsequent growth, which demonstrated its herbicidal effect. Finally, the insecticidal capacity of T. kotschyanus EO was also observed against selected insects (Oryzaephilus surinamensis and Sitophilus oryzae). O. surinamensis was more susceptible to the effect of EO (LC50 = 4.78 µL/L air) than S. oryzae (LC50 = 13.20 µL/L air). The obtained results of the present study can provide new safe resources to the development of new products for the food, agriculture, and pharmaceutical industries