Seed-borne fungi in 69 sunflower cultivars were evaluated which comprised 52 confectionery and 17 oilseed types. Seed coats were placed on both NP-10 (Nonylphenol Ethoxylate based surfacant −10) and potato dextrose agar (PDA) media to culture fungi. The rate of contamination among the different varieties was calculated by counting seed coats with fungal colonies. The rate of contamination in the confectionary group (88%) was significantly (p ≤ 0.05) higher than in the oilseed group (71%). Of the 52 confectionery varieties, the dominant fungi recovered were Verticillium dahliae along with Alternaria spp., Fusarium spp., and Rhizopus spp., whereas the oilseed type varieties were contaminated with only V. dahliae. Molecular identification of fungal species via BLAST (Basic Alignment Search Tool) was performed on fungal sequences obtained from PCR (Polymerase Chain Reaction) analysis. The results included five Alternaria spp. that included Alternaria tenuissima, Alternaria alternata, Alternaria helianthiinficiens, Alternaria longipes, and Alternaria tamaricis, three Fusarium spp. such as Fusarium oxysporum, Fusarium incarnatum, and Fusarium proliferatum, and V. dahliae and Cladosporium cladosporioides. These were identified from pure fungal cultures recovered from seed coats. To efficiently control seed-borne fungi, four broad spectrum fungicides (carbendazim, triadimefon, caprio F-500, and flusilazole) were screened against V. dahliae isolate Gn3, which was isolated from a diseased LD 5009 sunflower plant. Flusilazole was selected based on its low half-maximal effective concentration value (EC₅₀), 78.7 µg/mL. Seeds of diseased LD 5009 plants obtained from two different locations treated with formulated flusilazole fungicide at optimum parameters showed a significant (p ≤ 0.05) increase in seed germination and a decrease in contamination rate from 98% to less than 10%. The results affirmed that confectionery cultivars are much more susceptible to fungal contamination than oilseeds, and also that seed pretreatment is a suitable way to prevent the spread of soil- and seed-borne fungi in sunflower production.

Broomrape (Orobanche cumana Wallr.) is a holoparasitic plant which parasites sunflower roots. The infected sunflower plants are smaller, have a reduced kernel/husk ratio and yield decreases dramatically. It has become a severe problem for sunflower production all over the world. In recent years, due to importation of sunflower hybrid seeds, frequent local seed transportation and insufficient plant quarantine, broomrape widely occurs in sunflower production areas of China. This review addresses recent research progress on sunflower broomrape in China, focusing on occurrence, potential damage, seed germination mechanisms, physiological race identification, integrated control and breeding of resistant sunflowers. This review should provide useful reference information for future research and also integrated control of sunflower broomrape.

Sunflower Verticillium wilt is a widespread and destructive disease caused by the soilborne pathogen Verticillium dahliae. To better understand the process of infection and seed transmission of the fungus, sunflower roots were inoculated with a V. dahliae strain (VdBM9-6) labeled with green fluorescent protein (GFP) and monitored microscopically. After 24 to 96 h postinoculation (hpi), conidia germinated and developed into mycelium on root hairs, elongation zones, and caps of lateral roots. Mycelium colonized vascular bundles of lateral roots and taproots at 7 days postinoculation (dpi). At 10 weeks postinoculation (wpi), the epidermal cells, cortical tissues, and vascular elements of stem, petiole, and leaf veins were colonized by mycelium. By 12 wpi, strong GFP signals were detected not only on different tissues of inflorescence but also on testa of seed and a small fraction of pollen grains. A GFP signal was not observed on cotyledon tissues in the seed. Additionally, the colonization of V. dahliae on testa was also confirmed with MNP-10 selection medium, indicating that the testa of seed is the main carrier for the long distance transmission of sunflower yellow wilt.