Abstract
Sunflower White Mold caused by Sclerotinia sclerotiorum and Sclerotinia minor is a devastating disease worldwide. To investigate the effect of low temperature (4 °C) on biological characteristics and aggressiveness of isolates of the two species, which were collected from the same field in Baiyinchagan, Inner Mongolia, their mycelial growth rate, oxalic acid secretion level and polygalacturonase activity were compared under normal culture temperature (23 °C) and low temperature (4 °C). Aggressiveness was also evaluated on detached leaves by inoculating the isolates produced in both temperatures. The results suggested that culture of isolates at 4 °C not only promoted mycelial growth, but also enhanced secretion of oxalic acid and polygalacturonase activity of both S. sclerotiorum and S. minor isolates compared to that cultured at 23 °C. Additionally, the corresponding aggressiveness of tested isolates of the two species also increased after culture at 4 °C. However, S. sclerotiorum always showed faster mycelial growth, higher oxalic acid levels and greater polygalacturonase activity than S. minor at both 23 °C and 4 °C, indicating that S. sclerotiorum is generally the more aggressive species than S. minor.
Highlights
4 Conclusion and discussion In Inner Mongolia, both S. sclerotiorum and S. minor were isolated from diseased plants with Sunflower White Mold (SWM) symptoms, but, S. minor isolates were only collected from sunflower fields which were located in the northern piedmont region of Yin mountain with high altitudes and low temperatures in summer
SWM infected plants caused by S. sclerotiorum were observed in fields in which SWM was dominantly caused by S. minor, but co-infection by both S. sclerotiorum and S. minor was never encountered
Previous studies showed that mycelial growth of both S. sclerotiorum and S. minor occurred at temperatures ranging from 12 °C to 27 °C, and sclerotia of S. minor germinated and exhibited mycelial growth at temperatures ranging from 6 °C to 30 °C, but S. minor shows much more sensitivity to low temperature (Domingues et al, 2016)
Summary
Oxalic acid (OA) was thought to be a necessary virulence factor for S. sclerotiorum infection, reducing the pH of host cells and enhancing the activity of CWDE, and inhibiting the oxygen burst and selfphagocytosis, facilitating cell apoptosis in host plants (Godoy et al, 1990; Guimarães and Stotz 2004; Williams et al, 2011; Kabbage et al, 2013). Apart from the pathogenicity theories mentioned above some effectors have been identified based on genomic sequence analysis, and these have been verified as functional virulence factors if the host does not contain corresponding resistance proteins (Liu et al, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
