Study On Identification Of Pathogens Causing Hyacinth Soft Rot And Rust Symptoms And Disease Control

Hyacinthus orientalis is a famous bulb plant with high ornamental value, currently cultivated in many parts of China, but the bulbs still import from the Netherlands. Due to the geographical, climatic and other factors, hyacinth is vulnerable to soft rot and rust disease, which causes a direct impact on the domestic production work of hyacinth bulbs.Bacterial soft rot occures worldwide and is one of the most destructive diseases for hyacinth, especially for hyacinth bulbs and leaves. In this study, two strains of EQ and EP were isolated and purified from hyacinth cultivars'Blue Giant'and'Carnegie'infected bulbs. Based on pathogenicity tests, culture characteristics, flagella and gram staining,potato tuber decay test, physiological and biochemical tests and 16S rDNA gene sequencing and comparison, the pathogen was identified as Erwinia carotovora subsp. carotovora. This was the first specific study report that associates Erwinia carotovora subsp. Carotovora with hyacinth soft-rot disease. In addition, the results of biological characterizations of typical strain EQ demonstrated that the two isolates could propagate fastest at 37℃and in pH neutral conditions.Rust disease is a common fungal infection that affects a wide range of floricultural crops. It mainly infects plant leaves. In this study, one strain was isolated and purified from hyacinth'Anna Marie'leaves. An extensive characterisation involving pathogenicity tests, colony and spore morphology, 18S rDNA sequence amplification was made of the isolate. Uromyces muscari was identified as the main pathogen which was consistent with previous foreign studies. This was the first specific study which combined with molecular methods to identify hyacinth rust pathogens. Different temperatures were tested to control the strain propagation, and the results showed that it grew fastest at 28℃and stopped propagation at 4℃or 45℃. Compared with healthy hyacinth leaves, the chlorophyll content of infected leaves reduced significantly. CAT, POD, SOD activity increased significantly after disease symptoms appeared for five days, which revealed that enzyme protection system was working. But after ten days, CAT and POD activity decreased, SOD activity was still higher than that of healthy leaves, which showed that the balance of intracellular reactive oxygen production and scavenging was destroyed. Different chemical agents with different concentrations were used to control soft rot and rust disease. The results showed that Carmazine had the best effect to control soft rot and pathogenic bacteria stopped propagating on the medium with Carmazine 0.56×10^-6 g·mL^-1, the second is Agricultural Streptomycin with 5.76×10^-3 g·mL^-1。For rust disease, triadimefon had the best effect, followed by Topstn-methyl and carbendazim. In contrast, Carmazine had the weakest fungistasis. Carmazine and Agricultural Streptomycin can make as preferred potion for soft rot control while Triadimefon for rust disease.