Phytophthora species are well-known destructive forest pathogens, especially in natural ecosystems. The wild apple (Malus sieversii (Ledeb.) Roem.) is the primary ancestor of M. domestica (Borkh.) and important germplasm resource for apple breeding and improvement. During the period from 2016 to 2018, a survey of Phytophthora diversity was performed at four wild apple forest plots (Xin Yuan (XY), Ba Lian (BL), Ku Erdening (KE), and Jin Qikesai (JQ)) on the northern slopes of Tianshan Mountain in Xinjiang, China. Phytophthora species were isolated from baiting leaves from stream, canopy drip, and soil samples and were identified based on morphological observations and the rDNA internal transcribed spacer (ITS) sequence analysis. This is the first comprehensive study from Xinjiang to examine the Phytophthora communities in wild apple forests The 621 resulting Phytophthora isolates were found to reside in 10 different Phytophthora species: eight known species (P. lacustris being the most frequent, followed by P. gonapodyides, P. plurivora, P. gregata, P. chlamydospora, P. inundata, P. virginiana, and P. cactorum) and two previously unrecognized species (P. sp. CYP74 and P. sp. forestsoil-like). The highest species richness of Phytophthora occurred at BL, followed by XY. P. lacustris was the dominant species at BL, XY, and JQ, while P. gonapodyides was the most common at KE. In the present paper, the possible reasons for their distribution, associated implications, and associated diseases are discussed.

During surveys conducted in 2020, severe symptoms associated with death and decline were observed on more than 30-year-old Metasequoia glyptostroboides (Chinese redwood) trees in the shelter forests along the Yangtze River in Jingzhou City, Hubei Province, China. A previous study showed that Phytophthora acerina was one of the causal agents of the decline of the Chinese redwood. In this study, a total of 147 fungal isolates were obtained from the diseased roots and xylem of trunks of declining M. glyptostroboides trees. Through morphology and multilocus phylogenetic analysis, these isolates were identified as eight species belonging to the genera Fusarium and Neocosmospora, including F. fujikuroi, F. irregulare, F. odoratissimum, F. reticulatum, N. falciformis, N. keratoplastica, N. solani, and N. tonkinensis. Single inoculation and coinoculation with P. acerina assays of these Fusarium and Neocosmospora species were then performed to test pathogenicity on 3-year-old seedlings of M. glyptostroboides. Lesions (i.e., on seedling stems) caused by species of the genera Neocosmospora and Fusarium were smaller than those caused by P. acerina. Coinoculation of F. fujikuroi and P. acerina, as well as the coinoculation of F. reticulatum and P. acerina, caused larger lesions than inoculation with P. acerina alone. All these species of Fusarium and Neocosmospora were shown to have the potential to be pathogenic to M. glyptostroboides. This study provided evidence that the decline of M. glyptostroboides in Jingzhou is a disease complex.

Hylurgus ligniperda (Fabricius) is an important pest that attacks Pinus species in China. It impacts the vitality of local pine vegetation, reduces the ability to prevent windbreak and sand fixation, and causes ecological loss. MaxEnt and ArcGIS are used to predict and analyze the changes in suitable distribution areas of H. ligniperda under current and future climate scenarios, based on 12 climate factor datasets and 1,001 field distribution data points for this pest. The environmental variables used significantly influence the potential distribution of H. ligniperda. Highly suitable areas of this beetle are located in western Europe, central Asia, and the southeastern regions of Oceania, with sporadic occurrences across North America, South America, and Africa. Highly suitable areas in China occur across the east, central south, and southwest regions. There is a significant increase in the high and medium suitability areas, while the area of low suitability decreases under the 4 future climate scenarios (SSP126, SSP245, SSP370, and SSP585). The suitable distribution area for H. ligniperda shows an overall trend of moving northwestward. The purpose of this current study is to provide important theoretical support for the prevention and management of this pest by predicting and analyzing suitable distribution areas under current and future climate scenarios.