The pathogen of M. sextelata is classified in Pestalotiopsis spp.. This genus, is characterized by five cells and the middle three by dark color, which is a fungi imperfecti and was established and named by Steyaert in 1949 (Steyaert RL, 1949). It is very difficult to classify and identify (Maharachchikumbura SSN et al., 2011). At present, the morphology of conidia is the most widely used taxonomic feature of Pestalotiopsis spp., which is classified by the length, width, cell color, number and length of attached filaments of conidia(Jeewon R et al., 2004).However, because of the morphological similarity between species, only observing the morphology of conidia is not enough to accurately identify the species. Therefore, the molecular data are also gradually used in the classification of this genus, and the classification and identification system of this genus is gradually improved from single analysis of conserved ITS sequence to joint analysis of multiple genes(Liu AR et al., 2010). Now, the most commonly used multi-gene joint analysis is through the combination of three sequences: ITS sequence, tub2 and tef1, which shows better differences among different species(Maharachchikumbura SSN et al., 2012). In this study, the pathogen of M. sextelata was identified as Pestalotiopsis trachicarpicola by the method described above.
Pestalotiopsis spp. is an important plant pathogen, which causes diseases all over the world. It can not only cause diseases of seeds and seedlings, but also cause leaf spot, branch and trunk blight and fruit rot. Among them, leaf spot is the most common, and the main host includes Camellia sinensis(Maharachchikumbura SSN et al., 2016, Wang YC et al., 2019, Chen YJ et al., 2017), Photinia × fraseri(Zhu YH et al., 2021, Xu XL et al., 2021), Paris polyphylla(He X et al., 2020),Vitis davidii(Tang XB et al., 2020), Banana(Bhuiyan MAB et al., 2021), Strawberry(Morales-Mora LA et al., 2019), Eucommia ulmoides(Li SJ et al., 2018), Mango(Shu J et al., 2019)and so on. Its typical disease symptoms on the leaf consisted of circular, semicircular or irregular shape of the disease spot, brown at early stage and grayish brown to grayish white at middle stage and eventually lead to leaf abscission. Branch and trunk blight often occurs on Blueberry Bushes(Borrero C et al., 2017), Chinese Hickory(Liu YJ et al., 2014), Loquat(Fang L et al., 2013), Pinus bungeana(Qi M et al., 2021) and grapevine(Jayawardena RS et al., 2015). Initially, the necrotic lesions appeared on the branch and trunk, which led to the discoloration and cracking of the bark with the development of the disease, branch and trunk with the lesion were wilt at the end. Fruit rot mainly occurs in the harvest and storage period of Grape(Ghuffar S et al., 2018, Jayawardena RS et al., 2015), kiwifruit(Li L et al., 2016), rambutan(Keith LM, 2008), Guava(Keith LM et al., 2006), Persimmon (Palou L et al., 2015)etc. Dark brown to black spots appears in the disease spot at early stage and white hyphae grow in the later stage, whole fruit rots at the end. If the fruit is damaged, it is more likely to be infected. The infection phenomenon of each species will be different. In addition, it also causes the problems of Cunninghamia lanceolata (Zeng SH, 1998, Huang TZ, 1983), strawberry(Hua XF et al., 2021) rotten seed, rotten root and seedling growth decline. However, so far, the pathogenic effect of this genus on macrofungi has not been found.
It has been reported that the Pestalotiopsis spp. mainly take the soil, diseased seedlings and organization as the transmission carriers, which prefer to grow in the high humidity environment. The younger the infected tissue is more likely to get infected and tissue damage is also conducive to pathogen infection (Ge QX et al., 2009). Morchella is suited to grow in high humidity environment, and its tissue is very fragile and vulnerable to mechanical and insect damage, which increase the possibility of Morchella infection (Ruíz-Herrera J and Osorio E, 1974, Sambyal K and Singh RV, 2021). Most importantly, as an edible commercial mushroom, Morchella grows and is harvested in a short time(Zhi CY et al., 2021). Once infected, it loses all commercial value, therefore, we should pay more attention to the soil quarantine work in the cultivation process of Morchella.