Infection Sources And Fungicides Screening Of Apple Bitter Rot

Apple bitter rot is the most important fruit rot disease of apples in China. It caused by the fungus Glomerella cingulata (Stonem.) Spauld. And Schrenk, anamorph Colletotrichum gloeosporioides (Penz.) Sacc.and Colletotrichum acutatum. The fact that the fungus is responsible for both the fruit rot and canker forms of the disease has been fully established , but is not known to occur on the leaves. In this paper,we research the pathogenicity of Colletotrichum acutatum from the other host to apple, investigate the ability of Colletotrichum spp. to infect apple leaves under laboratory and field condition, and sceeen the fungicides to the two pathogens. The results were as follows:(1) The differentiation of colony morphology and growth rate of among C. acutatum isolates isolated from the other hostis as follows: the color of isolates 9300158, HG-150, CD-153 is a little dark (the host are grap, calabash gourd and bean respectivly), the color of isolates PT-173-1, PT-173-2 and PT-173-h are light, only present light pink or white, and there hosts are also grap. There are great difference between isolates WLH and W-2, both of them are isolated from apple fruit. The growth rate is different from the different isolates, but the difference is not great, although these isolates from the some host. Every isolate can cause typical bitter rot symptoms on apples and the pathogenic is different between different isolates. This result indicated C. acutatum from different host may be important infection source of apple bitter rot in the field.(2) Infection structrues of C. gloeosporioides and C. acutatum on living and isolated apple leaves were observed based on microscope and electron microscope, we found that the conidia of the two pathogens can generate germ tubes, appressoria and penetration pores, but there are some different in the period time. C. acutatum generate germ tubes and appressoria are earier than C. gloeosporioides. The germ tube formatted many branches and become to a long mycelial occur easier on C. acutatum.There are no difference between two pathogens, both of them could penerate the cell membrane of cuticular, the hyphae shriking when they penerate the cell wall, and then enlargement. At last, acervulus generated in the cuticular .The results shows that the two pathogens could generate germ tubes, appressoria and penetration pores on living and isolated apple leaves, but there are no symptoms on the living leaves. Host cells are dead around infection court, the pathogen expand rapidly and generate the infection hypae and acervulus, the defoliation may be an important infection source(3) Difenocoleonaz and Carbendazim inhibited conidia germination of the two pathogens. Difenocoleonaz, Carbendazim and Propineb inhibited hypha growth of the two pathogens. The effect of Carbendazim, Propineb, Difenocoleonaz, Polyram to C. gloeosporioides are better than C. acutatum, but the effect of Iprodion is better to C. acutatum. The effect of Difenoconazole and Polyram on C. gloeosporioides are better, and the Carbendazim Iprodione and Propineb are better on C. acutatum. This research suggest that Difenocoleonaz and Iprodion are appled to control apple bitter rot in field.