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Surface characteristics and stress tolerance of submerged conidia, blastospores and aerial conidia of biocontrol fungus Cordyceps javanica IF-1106
GAO Meiyu, LI Junmei, LI Yihua, XIANG Huiming, MA Ruiyan, ZHOU Wenwen
Mycosystema ›› 2025, Vol. 44 ›› Issue (4) : 240288.
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Surface characteristics and stress tolerance of submerged conidia, blastospores and aerial conidia of biocontrol fungus Cordyceps javanica IF-1106
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Cordyceps javanica is an entomopathogenic fungus with biocontrol potential in control of many important pests belonging to Homoptera, Hemiptera, Lepidoptera, Thysanoptera and Coleoptera. Submerged conidia and blastospores can be obtained by liquid fermentation of C. javanica, and aerial conidia can be obtained by solid culture. The differences in morphology, size and surface ultrastructure of the three kinds of spores of C. javanica IF-1106 were compared. It is clear that aerial conidia, submerged conidia and blastospores have different morphology, and the average sizes are 4.45, 4.17 and 7.67 μm, respectively. A similar structure, the scar at one end of three kinds of spores, was observed by scanning electron microscope. The surface of the aerial conidia was rough and appeared to be covered with a layer of small rods. The surface of blastospores is smooth with obvious cracks, and sometimes segmented. The surface of the submerged conidia is smooth with a few thin cracks, and some of them have structures like bud scars. Image of transmission electron microscopy showed that the cell wall thickness and outer layer structure of the three kinds of spores were significantly different. The hydrophobicity of three kinds of spores of C. javanica IF-1106 was determined by the test of microbial adhesion to hydrocarbons (MATH) and the results showed the hydrophobicity ranked as aerial conidia > blastospore > submerged conidia. When pH ranging from 3.0 to 9.0, the Zeta potential of aerial conidia varied from +2.68 mV to -18.44 mV, that of blastospores ranged from +5.16 mV to -5.51 mV, and that of submerged conidia changed from +0.39 mV to -18.09 mV. The isoelectric points of the three kinds of spores were in acidic range and all spores were negatively charged in neutral condition. The germination rate and stress tolerance of the three kinds of spores were compared. It was found that blastospores germinated fastest but were least stress-tolerant; the aerial conidia were more stress-tolerant but slowest germinated, while germination rate of submerged conidia was close to that of blastospores and the stress-tolerance was the best, showing good potential for utilization and development. These results provide a theoretical basis for the application of C. javanica IF-1106 in production.
Cordyceps javanica / aerial conidia / submerged conidia / blastospore / surface characteristics / stress tolerance {{custom_keyword}} /
Fig. 1 Microscopic morphology and particle size distribution of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106. A, D: Aerial conidia; B, E: Blastospores; C, F: Submerged conidia. Bars=50 μm.图1 爪哇虫草IF-1106气生分生孢子、芽生孢子和液生分生孢子显微形态及粒径分布 A, D：气生分生孢子；B, E：芽生孢子；C, F：液生分生孢子. 标尺=50μm |
Fig. 4 MATH assay of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106. Data are means ± SD. Different lowercase letters indicate significant difference in one-way analysis of variance at α=0.05 level.图4 爪哇虫草IF-1106气生分生孢子、芽生孢子和液生分生孢子的碳氢吸附能力分析 数据代表平均值±标准差，不同字母表示在α=0.05水平上差异显著 |
Table 1 Contact angle and surface tension in suspension of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106表1 爪哇虫草IF-1106气生分生孢子、芽生孢子和液生分生孢子悬浮液的接触角与表面张力值 |
| 孢子类型 Spore type | 接触角 Contact angle | 表面张力 Surface tension |
|---|---|---|
| 气生分生孢子 Aerial conidia | (82.25±1.85)° a | 81.37±1.79 c |
| 芽生孢子 Blastospores | (81.88±0.8)° a | 91.34±1.12 b |
| 液生分生孢子 Submerged conidia | (78.81±0.96)° b | 97.13±2.49 a |
| 注：数据代表平均值±标准差，不同字母表示在α=0.05水平上差异显著. 下同 | |
| Note: Data are means ± SD. Different lowercase letters indicate significant difference in one-way analysis of variance at α=0.05 level. The same below. |
Fig. 7 The germination index-treatment time and UV-B irradiation energy-germination rate ExpDecl model fitting to three types of spores of Cordyceps javanica IF-1106.图7 爪哇虫草IF-1106 3种孢子热处理萌发指数-处理时间与UV-B紫外辐照能量-萌发率单指数衰弱模型拟合 |
Table 2 The germination index and treatment time fitting equation of three types of spores of Cordyceps javanica IF-1106表2 爪哇虫草IF-1106 3种孢子热处理萌发指数-处理时间拟合方程 |
| 孢子类型 Spore type | 萌发指数-处理时间拟合方程 Germination index-treatment time fitting equation | R2 | GT50 (h) |
|---|---|---|---|
| 气生分生孢子 Aerial conidia | Ig =1/(1+e(-2.16+1.65t)) | 0.948 7 | 1.31±0.02 b |
| 芽生孢子 Blastospores | Ig =1/(1+e(-2.22+2.42t)) | 0.937 8 | 0.91±0.02 c |
| 液生分生孢子 Submerged conidia | Ig =1/(1+e(-2.76+1.94t)) | 0.955 1 | 1.41±0.01 a |
Table 3 ExpDecl model fitting equation of UV-B irradiation energy-germination rate of three types of spores of Cordyceps javanica IF-1106表3 爪哇虫草IF-1106 3种孢子的UV-B紫外辐照能量-萌发率单指数衰弱模型拟合方程 |
| 孢子类型 Spore type | 单指数衰弱模型拟合方程 ExpDecl model fitting equation | | GD50 (J) |
|---|---|---|---|
| 气生分生孢子 Aerial conidia | y=-0.23+1.23e(-x/3.57) | 0.990 9 | 0.18±0.13 b |
| 芽生孢子 Blastospores | y=0.04+0.95e(-x/1.28) | 0.976 1 | 0.91±0.02 c |
| 液生分生孢子 Submerged conidia | y=-40.03+41.07e(-x/213.69) | 0.959 4 | 2.80±0.15 a |
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Fig. 1 Microscopic morphology and particle size distribution of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106. A, D: Aerial conidia; B, E: Blastospores; C, F: Submerged conidia. Bars=50 μm.Fig. 2 Morphology of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106 observed by SEM. A-C: Aerial conidia; D-F: Blastospores; G-I: Submerged conidia.Fig. 3 Transection morphology of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106 observed by TEM. A-D: Aerial conidia; E-H: Blastospores; I-L: Submerged conidia.Fig. 4 MATH assay of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106. Data are means ± SD. Different lowercase letters indicate significant difference in one-way analysis of variance at α=0.05 level.
Table 1 Contact angle and surface tension in suspension of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106Fig. 5 Zeta potential of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106 under different pH.Fig. 6 Germination rate of aerial conidia, blastospores and submerged conidia of Cordyceps javanica IF-1106.Fig. 7 The germination index-treatment time and UV-B irradiation energy-germination rate ExpDecl model fitting to three types of spores of Cordyceps javanica IF-1106.Table 2 The germination index and treatment time fitting equation of three types of spores of Cordyceps javanica IF-1106Table 3 ExpDecl model fitting equation of UV-B irradiation energy-germination rate of three types of spores of Cordyceps javanica IF-1106
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