Studies On Stem Rot Occurrence Regulation And Resistance Of Sclerotinia Sclerotiorum Isolates To Carbendazim In Shaanxi Province

It was well known that the Sclerotinia sclerotiorum of oilseed rape was one of occurring commonly widespread diseases of oilseedrape in the world. It is much severe in China. It caused large-scale rape reduction in many rape-producing areas, which led to huge economic losses. So, this paper want to understand stem rot occurrence regulation and resistance of sclerotinia sclerotiorum isolates to Carbendazim in Shaanxi province at present so that it can provide a theoretical guidance for prevention and treatment of disease,we observed the main rape producing areas in Shaanxi Province from 2008 to 2009 and carried out sensitivity of Sclerotinia sclerotiorum isolates to carbendazim in doors. The main results were as follows:1. The number of wintering sclerotia survey results showed that wintering sclerotia distribution was inhomogeneous in the field and bund, the sclerotium can survive on corn crops,but it was all zero on rice crops. The average of every sample point of the sclerotium on corn crops and on bund in Guanzhong area was more than in Hanzhong area.2. The number of apothecium survey results showed that there was more apothecium in the bund drainage (river) side, rape bar stacking land and rape residue nearby. The average of per square meter of the apothecium on corn crops was 14.20, but that on rice crops was zero.3. The occurrence of stem rot on different previous crops showed that the occurrence of stem rot on different previous crops had significant difference. The incidence of this disease on corn crops was higher than that on rice crops.The occurrence of stem rot in different areas showed that the incidence of this disease had significant difference in different areas and on the same variety in the different areas.The occurrence of stem rot on different varieties showed that no significant difference in occurrence of the disease was observed among the main three cultivars.4. The occurrence of stem rot on different lesion location showed that the third leaf position had the highest disease incidence in Guanzhong and Hanzhong areas, and there was no significant differenc in occurrence of stem rot of the third leaf position; The lesion center distance below 5cm from the ground hah the highest disease incidence in two area, and no significant differenc in occurrence of stem rot was observed. 5. The dynamic changes of Sclerotinia sclerotiorum apothecium showed that the apothecium of the pathogen in Hanzhong area appeared in the early of February, from February toMarch, there were two peaks of the apothecium occurrence, February 27 and March 19; there was the apothecium of the pathogen in Guanzhong area in the middle of March, the peak of the apothecium occurred in March 31.The result of correlation analysis showed the temprature and the rain precipitation in the five days were the key factors affecting the apothecium number and showed positive correlation.6. The dynamic changes of rape stem disease incidence showed that the stens were infected directively by Sclerotinia sclerotiorum in Hanzhong area in the middle of April and in Hanzhong area in the last of April; it increased very fast in the early of May until the rape was reaped. The result of correlation Analysis showed the key factors were the temprature and the rain precipitation in the five days.7. The resistance of S. sclerotiorum collected from some regions of Shaanxi province to carbendazi m (MBC) was monitored.Out of the total 363 tested isolates, 112 iso lates were MBC resistant with the proportion of 32.51%, and the ratio of resistant isolates had significant differenc in different area. The ratio of resistant isolates reached 33.68% inHanzhong area, but this was 22.22% in Guanzhong atea. Moreover, there was significant differenc for the ratio of resistant isolates in different districts and counties of the same region.Besides, pathogenicity to detached rape leaves was not different between MBC resistant and sensitive isolates of S. sclerotiorum; MBC resistant and sensitive isolates of S. sclerotiorum were sensitive to osmotic pressure; the resistance to MBC of these isolates was stable through two sexual propagations.