Abstract:

The high incidence of leaf disease in Ammopiptanthus mongolicus is a serious threat to the normal growth of plants. In order to identify the pathogenic bacteria causing leaf diseases of A. mongolicus and develop disease control scheme, morphological characteristics and rDNA-ITS sequence analysis were used to identify the pathogenic bacteria, and field spraying agents were used to determine the control effect of fungicides on the diseases. The results showed that the diseases on the leaves of A. mongolicus were caused by pathogenic fungi. The mycelia in vitro were villous and dense, gray and white, and the back of the mycelia was gray and black. Under microscope, the mycelia were straight and flexible, with septum, and produced dark conidia stalks, which extended in axial form, with single conidia at the top. ITS sequence identification was 100% similar to Alternaria destruens ATCC 204363 (NR_13714 3.1), and it was preliminary identified as Deuteromycotina, Hyphomycetes, Hyphomycetales, Altemaria. Field control experiments with different agents showed that 75% chlorothalonil wettable powder sprayed twice had a control effect of 87%, and the control effect of Bordeaux solution 2000 times was 57.9%. The control effect of 75% chlorothalonil wettable powder was better than that of Bordeaux solution 2000 times. The morphological characteristics and identification results of the pathogenic fungi are reported for the first time, and the field control scheme of the diseases is formulated, which can provide a theoretical basis and effective technical measures for the disease control.

Key words: Ammopiptanthus mongolicus, leaf disease, Alternaria destruens