Screening, Identification and Control Effects of Biocontrol Strain TN2 against Pepper Anthracnose

doi:10.13560/j.cnki.biotech.bull.1985.2024-0719

Abstract

Abstract:

【Objective】To screen and identify a biocontrol strain with the ability to control pepper anthrax, and to evaluate its control effect, and to explore its effect on disease activity and antibacterial stability of pepper fruit.【Method】A single strain isolated from soil samples was screened by plate confrontation test and pepper isolation test, finally a bacterial strain with significant antibacterial activity was obtained. It was identified by morphological observation, physiological and biochemical characteristics and 16S rRNA sequence determination, and the malondialdehyde（MDA）content, defense enzyme activity and stability of antibacterial substances in pepper after inoculation were determined.【Result】In the plate antagonism test, the TN2 strain had a strong inhibitory effect on Colletotrichum acutatum, and the antibacterial rate reached > 70%. Meanwhile, the disease index of the pepper plants after TN2 treatment was significantly lower than that of the positive control group, as verified by in vitro biocontrol test. Combining the morphological, physiological and biochemical characteristics of strain TN2 and the phylogenetic tree analysis of 16S rRNA sequence, we identified TN2 as Bacillus velezensis. TN2 enhanced the activity of peroxidase（POD）, superoxide dismutase（SOD）, phenylalnine ammonialyase（PAL）, catalase（CAT）, but reducing the MDA content to positive control treatment, and its antibacterial substances were relatively stable under different treatments.【Conclusion】B. velezensi TN2 strain has promising potential to control anthrax in capsicum, and can be used as an effective biocontrol strain in the biological control of pepper anthrax, which has important practical application value.

Key words: pepper anthracnose, Bacillus velezensis, biological control, identification, antibiotic active substance

LIU Qian, MA Lian-jie, ZHANG Hui, WANG Dong, FAN Mao, LIAO Dun-xiu, ZHAO Zheng-wu, LU Wen-cai. Screening, Identification and Control Effects of Biocontrol Strain TN2 against Pepper Anthracnose[J]. Biotechnology Bulletin, 2025, 41(1): 287-297.

Figures/Tables 13

Table 1 Antagonism of antagonistic strains against Colle-totrichum acutatum

菌株编号 Strain number	菌落直径 Colony diameter/mm	抑菌率 Antibacterial rate/%
TN2	15.54±0.14e	71.23±0.26a
CB2	16.4±0.21d	67.91±2.36b
BSJ4	18.65±0.11c	64.62±0.96c
BSJ12	19.4±0.16b	61.48±2.22d
YC8	21.36±0.27a	60.44±0.49d

Fig. 1 Inhibition of strain TN2 on C. acutatum（scale: 5 mm）

Fig. 2 Colony morphology and the morphology of strain TN2 observed by SEM

Table 2 Physiological and biochemical characteristics of strain TN2

测试项目 Test item	特征 Characteristic	测试项目 Test item	特征 Characteristic
接触酶	+	MR	-
氧化酶	+	葡萄糖产酸	+
明胶液化	+	葡萄糖产气	-
V-P	+	蔗糖产酸	+
pH 5.5	+	蔗糖产气	-
20% NaCl	+	吲哚乙酸	+
50℃生长温度	+	固氮	+
淀粉水解	+	解磷	-

Fig. 3 A phylogenetic tree of strain TN2 and other strains constructed based on the 16S rRNA sequence

Fig. 4 Inhibition of VOCs and cell-free filtrate of strain TN2 to C. capsici（scale: 5 mm） A: Inhibition of strain TN2 VOCs against anthracnose. C: Inhibition of strain TN2 cell-free filtrate against anthracnose. B, D: Anthrax colonies（CK）

Fig. 5 Inhibitory effect of strain TN2 on 7 plant pathogens on PDA plate（scale: 5 mm） A1-G1 is the treatment group, and A2-G2 is the control group. A: Fusarium oxysporum; B: Fusarium annuum; C: Haematonectria; D: Botrytis cinerea; E: Verticillium dahliae;F: Sclerotinia sclerotiorum; G: Guignardia

Table 3 Inhibitory effects of strain TN2 on various fungal pathogens

病原菌 Pathogen	菌落直径 Colony diameter/mm	抑菌率 Antibacterial rate/%
尖孢镰刀菌Fusarium oxysporum	34.47±0.77a	53.92±1.26e
辣椒枯萎病菌Fusarium annuum	29.05±0.27c	64.14±0.3c
茄镰刀菌Haematonectria	31.37±0.83b	58.17±1.08d
灰葡萄孢菌Botrytis cinerea	32.26±2.96b	61.48±2.22d
大丽轮枝菌Verticillium dahliae	7.92±0.37f	89.29±0.47a
核盘菌Sclerotinia sclerotiorum	27.36±0.75d	63.99±0.97c
芒果囊孢菌Guignardia	21.42±0.69e	73.87±0.81b

Fig. 6 Effects of strain TN2 treatment on the MDA contents of pepper fruits

Fig. 7 Effects of strain TN2 treatment on antioxidant enzyme activity in pepper fruits

Fig. 8 Effect of different temperatures（A）, pH（B）, ultrasonic duration（C）, and UV irradiation duration（D）on the inhibitory stability of TN2 fermentation filtrate against C. acutatum Different letters indicate significant difference（P <0.05）

Fig. 9 Biocontrol effects of strain TN2 on pepper anthracnose（scale: 10 mm） CK: Sterile water + pepper anthrax（positive control）; TN2: TN2 + anthrax

Table 4 Efficacy of strain TN2 against anthrax in pepper fruits

处理 Treatment	第1天 Day 1		第3天 Day 3		第7天 Day 7
处理 Treatment	病情指数 Disease index	相对防效 Relative control effect/%	病情指数 Disease index	相对防效 Relative control effect/%	病情指数 Disease index	相对防效 Relative control effect/%
对照 CK	9.44±8.28d	-	47.59±9.67b	-	72.22±3.79a	-
TN2	0.56±1.36e	94.12±0.14a	8.06±4.52d	83.07±0.10ab	20.19±4.93c	72.05±0.07b

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