**4.5 Infection process of** *M. acerina* **conidia on** *P. notoginseng* **leaves**

The different infection stages of *M. acerina* conidia on *P. notoginseng* leaves were observed and photographed. For microscopic observation, we used fluorescence staining with calcofluor white. Under excitation with ultraviolet light, conidia and hyphae emit blue fluorescence. The development of conidia on *P. notoginseng* leaves between 0 and 18 h is shown in **Figure 7**. At 6 h, the conidia had grown multiple primary hyphae from cells at different locations. Between 6 and 12 h, the primary hyphae continued to elongate, and at 12 h, some of the hyphal ends were expanded to form an appressorium. At 18 h, lesions had appeared on the leaf surface, which indicated that hyphae had invaded the *P. notoginseng* leaves. The development of conidia on *P. notoginseng* leaves between 24 and 96 h is shown in **Figure 6**. By 24 h, the lesion area had expanded and the lesion became conspicuous, with an appressorium in the center. By 48 h, the lesion center had turned yellow and hyphae on the leaf surface no longer elongated. At 72 h, the lesion was further enlarged and the color of the lesion center changed from yellow to brown. At 96 h, multiple conidia appeared on the lesion surface. The conidia were formed by the mycelium growing and developing in the lesions. The lifecycle of *M. acerina*, from conidial inoculation to the production of conidia, is completed in 4 days (**Figure 8**).

#### **Figure 7.**

*Development of* Mycocentrospora acerina *conidia on* P. notoginseng *leaves. (A–D) conidia were observed on the leaves of P. notoginseng at 0, 6, 12, and 18 h, respectively. The blue color shows* Mycocentrospora acerina *conidia and hyphae stained with calcofluor white stain. The bright-field image shows* P. notoginseng *leaf epidermal cells, and the merged image shows the germination and invasion of* Mycocentrospora acerina *conidia on* P. notoginseng *leaves. Bar = 50 μm.*

*Cultivation Practice of Chinese Medicinal Herbs DOI: http://dx.doi.org/10.5772/intechopen.104859*

#### **Figure 8.**

*Development of* Mycocentrospora acerina *conidia on* P. notoginseng *leaves. (A–D) conidia were observed on the leaves of* P. notoginseng *at 24, 48, 72, and 96 h, respectively. The blue color shows* Mycocentrospora acerina *conidia and hyphae stained with calcofluor white stain. The bright-field image shows P. notoginseng leaf epidermal cells, and the merged image shows the germination and invasion of* M. acerina *conidia on*  P. notoginseng *leaves. Bar = 50 μm.*

#### **4.6 Control of round spot disease by rain-shelter cultivation**

In 2020, the rainy season in Lancang County began in June. At the end of June, a rain shelter was built in the *P. notoginseng* field and an open-field control treatment was set up simultaneously. On July 10, the first round spot disease incidence survey was conducted. Neither sheltered nor non-sheltered *P. notoginseng* plants developed the disease (**Figure 9**). However, on July 20, round spot disease started to occur in some areas of the open field. In contrast, the sheltered plants remained healthy. Subsequently, round spot disease began to spread in the open field. By August 10, the average round spot disease incidence in the open field was 18.07%, and the disease index was 8.89. However, the incidence in sheltered plants was still 0.00%. Over time, the disease incidence in the open field increased. As of September 30, the incidence

#### **Figure 9.**

*Effect of rain-shelter cultivation on the incidence rate and disease index of round spot disease. (A) Incidence and (B) disease index of round spot disease in rain-shelter and open-field cultivation.*

#### **Figure 10.**

*Effects of rain-shelter cultivation and open-field cultivation on the occurrence of round spot disease. (A)*  P. notoginseng *plants grown under shelter cultivation remained healthy. (B) Round spot disease occurred in open-field cultivation.*

had reached 77.70%, covering nearly the entire open-field treatment area. However, sheltered plants still remained healthy (**Figure 10**). These data indicated that rainshelter cultivation has good preventive and control effects on the occurrence of round spot disease, with an average preventive effect of 100%.
