| Potato is one of the staple food crops in China,and is becoming increasingly important with the implementation of staple food strategy.Late blight caused by Phytophthora infestans is the most devastating disease of potato,which occurs in all major growing areas all over the world.In 1840 s,more than one million people died of starvation in Ireland and about two millions people migrated to other countries as a result of the famine caused by the spread of late blight pathogen.The occurrence and epidemic of potato late blight are closely related to the composition and adaptation of P.infestans.In recent years,ozone depletion caused by air pollution,increased the intensity of ultraviolet irradiation on the earth.Effect of altitude on the UV adaptation of P.infestans was explored the 150 distinct genotypes(30 from each altitude)were selected from 350 isolates collected from different five altitudes in Yunnan Province in 2016.This project tried to analyses the effects of ultraviolet(UV)irradiation on the genetic diversity and spatial distribution of P.infestans populations at different altitudes to clarify the composition and evolutionary mechanism of P.infestans populations,and try to find the theoretical basis for the control of potato late blight.The main results are as follows:1.The 150 strains of P.infestans were exposed to different UV irradiation times of(40 s,120 s,360 s,and 1080 s)and then inoculated on rye culture medium to investigate the effect of different UV irradiation on P.infestans sampled from different altitudes.The results showed that the growth rate of P.infestans was negatively correlated with the UV irradiation time.The 40 s UV irradiation had little effect on the growth of P.infestans at different altitudes in Yunnan Province,120 s UV irradiation had the greatest effect on the growth rate of Phytophthora infestans in Yunnan province.Phytophthora infestans at different altitudes had different adaptability to different UV irradiation treatments.P.infestans sampled from A,B,and D altitudes had the lowest grow-th rates under 120 s UV irradiation(followed by 0.640,0.608,and 0.616)and had significant difference with other treatments(P<0.05).The growth rate of P.infestans in the altitude of 120 s showed the lowest(0.642)under UV irradiation for 120 s,but was significantly lower than that under 360 s and 1080 s UV irradiation,the difference of growth rate was not significant.The rate of growth of P.infestans at the altitude of C was the lowest(0.615)at 1080 s UV treatment.P.infestans from A altitude had stronger resistance to UV irradiation and Phytophthora infestans on C altitude was sensitive to UV treatment.The QST value(0.221)for five altitudes was greater than the FST value(0.164).The maximum QST value between two altitudes of A and D was 0.444,and the minimum QST value between two altitudes of B and D was 0.The maximum Fst value between two altitudes of A and E was 0.232 and the minimum Fst between two altitudes of C and D was 0.016.There was a significant positive correlation between the QST value of the two altitudes and the relative difference between the altitudes of the two altitudes(r=0.662,P=0.037<0.05).2.150 isolates of P.infestans were treated with UV irradiation(40 s,120 s,360 s,and 1080 s)at different times and then inoculated on detached leaves to investigate the effect of different UV.The results showed that the pathogen area of P.infestans at different altitudes increased first and then decreased with the increase of UV dose.The average diseased area of P.infestansat different altitudes under different UV irradiation times was significant at the level of 0.05.The maximum average lesion area of the potato after 40 s UV irradiation was 2.835 cm2 and 360 TV irradiation with the minimum lesions area of 0.817 cm2.Compared with the control,the pathogenicity of P.infestans at all altitudes decreased after UV irradiation.UV irradiation delayed the incubation period of P.infestans populations. |
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