| Henan province,one of the main peanut production areas,has large planting area and high yield,and accounts for 25 % of the total production in China.As the main cash crop in Henan Province,peanut has been paid more attention lately.Peanut collar rot is one of the serious diseases in the main planting areas,where it results in economic losses up to 30 % ~ 50 %.Peanut collar rot can occur at all stages during peanut growth period,especially at seedling stage,which is the most susceptible stage in that the whole plant will be shortly died once infected.In order to study the causes of peanut collar rot,we isolated the pathogenic strains of peanut collar rot,and studied its growth in different conditions.Then the control efficiency of different agents on the pathogenic strains were screened,and the disease resistance in 33 peanut strains were identified using toothpick inoculation method.We also carried the bioinformatics analysis of the AP2/ERF gene family,and characterized the expression of one AhERF gene in resistant and susceptible lines.The main results are as follows:1.During growing year in 2015 and 2016,peanut plants infected with peanut collar rot were collected for evaluation from six counties in Henan province.As a result,seven strains were isolated after indoor identification,and six of them could cause peanut collar rot after inoculation.The isolated pathogen strains showed the same features as inoculated bacteria.The conidia of the strain were oval,oblong or oval with truncated base and blunt end.The unit cell with double wall was sized as(22.75 ~ 30.25)μm ×(12.5 ~ 15.1)μm.By analyzing the ITS sequences of different strains,six of the seven strains were identified as Diplodia gossypinaae,synonymous with B.theobromae and L.theobromae,and the remaining one was Aspergillus.2.The pathogen strain,Diplodia gossypina,was cultured in different culture medium and different p H value to measure its growth rate.Its lethal temperature was measured by treating mycelium with ten minutes at different temperature.The result showed that the pathogen strain growed faster on the MEA medium than others,and mycelium growed more compact on peanut stalk medium.The mycelium failed to grow when p H value ≥ 12,and the optimum p H value was 4 ~ 8.The lethal temperature of mycelium was above 56 °C for ten minutes.3.The effects of different reagents on controlling D.gossypina were determined in laboratory using growth rate method.The results showed that nanometer zinc oxide has no obvious inhibitory effect on D.gossypina.However,the colony growth of pathogenic bacteria was the slowest with 25 % tebuconazole wettable powder treatment,which was significantly different from CK in view of the higher bacteriostatic rate.The treatment with 60% pyraclostrobin metiram water dispersible granules performed secondly.However,compared with CK,70% wettable powder,80% carbendazim imported products and 50% kresoxim methyl WDG had no significant difference,had poor inhibitory effect.4.The resistances to D.gossypina were identified in 33 peanut varieties(lines)by toothpick inoculation,and the resistance of each variety(line)was valued based on diseased plant rate.The results showed that different peanut strains were generally resistant to D.gossypina.There were no high-resistant varieties among the 33 varieties(lines).Most of them showed high susceptibility,except one line,PX19,showed resistance,and another line,PX27,showed moderate resistance.5.AP2/ERF transcription factor family plays an important role in the expression of biotic and abiotic stress-related genes in plants.In this paper,the bioinformatics analysis of the AP2/ERF transcription factor family showed that the gene family consisted of 70 members,which were divided into four types.There were 33,24,12 and one genes in the AP2 subfamily,the ERF subfamily,the DREB subfamily,and the RAV subfamily,respectively.6.The relative expression level of AhERF gene in pathogen-resistant strain,PX.19,and highly susceptible line,PX.15,was determined by qPCR after infection with pathogenic bacteria.The results showed that AhERF gene was expressed in the roots of both cultivars.The relative expression of AhERF gene in PX.15 was significantly lower than that in CK on the 0 day and the 2nd day after inoculation,and it reached the maximum on the 4th day,then decreased rapidly on the 6th day.The relative expression of AhERF gene in PX.19 reached the highest level after inoculation,and then decreased rapidly,which showed no significant difference between the treatment and CK on the 6th day.It can be seen that the expression level of AhERF gene in PX.19 roots after inoculation with pathogenic bacteria increased rapidly,while in PX.15 the response was slower and only increased rapidly on the 4th day. |
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