Study On Safflower Rust Caused By Puccinia Carthami(Hutz)Corda

Safflower was a important medicinal plant caused by Puccinia carthami (Hutz)Corda.The safflower rust was the most destructive foliar disease of safflower. The biological characteristics and the infection of the pathogen were studied first and systematically.The results wrer as follows:1.The biological characteristics of the P.carthami(Hutz) CordaThe biological characteristics of three kinds of spores were studied mainly, including Teliospore,Urediniospore and Aeciospore.The temperature range for Yeliospore germination was 5 to 30℃,the optimum temperature was at 25℃.The most suitable pH value was 7-8.The lowest relative humidity of germination was 90%.The minimum rate of Teliospore germination was in water,and host juice stimulated Teliospore germination of the Teliospore markedly.The lethal temperature of Teliospore was 45℃.(10min)or 44℃.(20min).The optimum temperature of Uredospore germination was 25℃in the range from 5℃to 30℃.The optimum pH value for Uredospore germination was 7.The lowest relative humidity of germination was 90%and the maximum rate of Uredospore germination was in water.The percentage of Uredospore germination in water drop is higher than that in other nutrition.Germination of Uredospore started within 2 hours and the percentage of germination reached above 80%at 12 hours.The light hadn't evident effect on Uredospore germination.The lethal temperature of Uredospore was 42℃(15min) or 43℃(10min).Aeciospore germinated at 10 to 32℃,with optimum temperature of 25℃,and the percentage of germination reached 95.5%at 12 hours.The Teliospore can germinate without dormancy.Teliospore,Urediniospore and Aeciospore may live as long as320d,140d and 120d.2.The infection process of P.carthami(Hutz)CordaInfection process to safflower by Puccinia carthami(Hutz)Corda was studied. Results showed that Uredospore germinated on the leaves surface,then formed the branched hypha,when hypha reached stomata,The appressorium was not formed clearly.The pathogen was able to penetrate host through two paths such as stomata and epidermis after inoculation.The direct penetration into stomata was considered as a major way.The mycelium spread in the leaf cells gap.The cells that were infected became empty.After a certain period,Mycelium formed a colony.The colony assembly under the epidermis formed Uredinium,which break through epidermis and spilled out uredospore after maturity.3.The infection conditions of P.carthami(Hutz)CordaThe infection of safflower by Teliospore,Urediniospore and Aeciospore could be occured at 10 to 28℃,the incubation period was the shortest and the optimum temperature of infection was about 23℃.The shortest incubation period of Teliospore was 12d.The incubation period of Urediniospore was the shortest(8d) at 23℃and the optimum temperature of infection was 20 to 23℃.The incubation period of Aeciospore was 7d at 23℃.The Urediniospore infected the basal leaves firstly,the spreaded to the upper leaves.Old leaves had more conducive to the infection.The optimum wetness period was 36-48hours and the incubation period was the shortest(8d).4.The infection sources and diesease dynamics of safflower in fieldSafflower rust can be caused by the teliospore which on the seed and the disease leaves and in the soil.Under Ya'an in Sichuan ecological conditions,the Teliospore which on the seed plants and the disease leaves in the field infected safflower seedlings directly without overwinter.The primary diseased plants could be observed one month later.The Teliospore infected cotyledon firstly,where appeared chlorosis spot and Aeciospore.From November to February of the following year,the disease developed slowly with chilliness.From February to April,the development of the disease accelerated gradually with the temperature rise.The Urediniospore on leaves spreaded by air and infected leaves as reinfection sources.The expansion of the disease from the lower leaves to upper leaves and nearby plant.At the end of April, the index of disease up to the highest,then the disease degree began to slow down gradually.With the cessation of safflower growth and the development of the disease stopped at the end of April.Urediniospore was replaced by Teliospore,which would infect host next season on the feasible condition.5.Resistance evaluation for safflower rustThe result shown that there were obvious difference among eleven tested varieties.Two varieties were immune to the disease;one variety was HS;others were MR or MS.The result is useful in breeding for disease resistance.