Endophytic Bacillus spp. from medicinal plants inhibit mycelial growth of Sclerotinia sclerotiorum and promote plant growth

Plant growth promoting bacteria that are also capable of suppressing plant pathogenic fungi play an important role in sustainable agriculture. There is a critical need of conducting research to discover, characterize and evaluate efficacy of new strains of such bacteria in controlling highly aggressive plant pathogens. In this study, we isolated endophytic bacteria from medicinal plants of Bangladesh and evaluated their antagonistic capacity against an important phytopathogenic fungus Sclerotinia sclerotiorum. Growth promoting effects of those isolates on cucumber and rice seedlings also were assessed. Among 16 morphologically distinct isolates, BDR-2, BRtL-2, and BCL-1 significantly inhibited the growth of S. sclerotiorum through induction of characteristic morphological alterations in hyphae and reduction of mycelial dry weight. When cucumber and rice seeds were treated with these endophytic bacteria, seven isolates (BCL-1, BDL-1, BRtL-2, BRtL-3, BDR-1, BDR-2 and BBoS-1) enhanced seed germination, seedling vigor, seedling growth, and number of roots per plant at varying level compared to untreated controls. All isolates produced high levels of indole-3-acetic acid (6.3 to 63μg mL−1) in vitro. Two most potential isolates, BDR-2 and BRtL-2 were identified 34 as Bacillus amyloliquefaciens and B. subtilis, respectively based on the 16S rRNA gene sequencing. These results suggest that endophytic Bacillus species from native medicinal plants have great potential for using as natural plant growth promoter and biopesticides in sustainable crop production

까막전복(Haliotis discus, Reeve 1846) 치패용 배합사료내 미역(Undaria pinnatifida) 대체원으로서 미이용해조류인 구멍갈파래(Ulva australis)와 괭생이모자반(Sargassum horneri) 및 이들 혼합분의 대체 효과

1. Dietary Substitution Effect of Ulva australis for Undaria pinnatifida on Growth, Body Composition and Air Exposure of Juvenile Abalone (Haliotis discus, Reeve 1846) Substitution effect of Undaria pinnatifida with Ulva australis in formulated diet on growth, body composition and air exposure of abalone (Haliotis discus) was investigated. A total of 1260 juvenile abalone were distributed into 21 cages. Six formulated diets and dry U. pinnatifida were prepared. The control (UA0) diet contained 20% U. pinnatifida. Twenty, 40, 60, 80 and 100% U. pinnatifida were substituted with the same amount of U. australis, referred to as the UA20, UA40, UA60, UA80 and UA100 diets, respectively. U. pinnatifida was prepared to compare effect of formulated diet on performance of abalone. Abalone were fed with one of the experimental diets for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure for 24 h and then cumulative mortality was monitored for the next 4 days. Higher survival, weight gain and specific growth rate (SGR) were observed in abalone fed all formulated diets than the U. pinnatifida. Abalone fed the UA60 diet produced the greatest weight gain and SGR. No difference in proximate compositions of the soft body of abalone was observed. The cumulative mortality of abalone fed the U. pinnatifida was higher than all formulated diets at 84 h until the end of the 4-day post observation after 24-h air exposure. Abalone fed the UA0 diet showed higher mortality than other formulated diets at 84 h until the end of the 4-day post observation. In conclusion, U. pinnatifida could be completely replaced with U. australis in abalone feed. The best growth was obtained in abalone fed the UA60 diet. Keywords: Abalone (Haliotis discus), air exposure, dietary substitution, formulated diets, Ulva australis, Undaria pinnatifida 2. Substitution effect of Undaria pinnatifida with Sargassum horneri in formulated diet on growth performance, body composition and air exposure stress of juvenile abalone (Haliotis discus, Reeve 1846) Dietary substitution effect of Undaria pinnatifida with Sargassum horneri on growth performance, proximate composition and air exposure stress on juvenile abalone was investigated. A total of 1260 juvenile abalone were randomly distributed in 21, 100-L net cages (60 per cage). Six formulated diets were prepared. Twenty percent U. pinnatifida powder was included in the control (SH0) diet. The U. pinnatifida component of the experimental diets was substituted with S. horneri at the rates of 20, 40, 60, 80, and 100%, referred to as the SH20, SH40, SH60, SH80, and SH100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare effect of the formulated diet on abalone. Abalone were fed with one of the experimental diets once a day for 16 weeks. Water stability of nutrient content in all formulated diets was changed with time. Survival of abalone fed all formulated diets was higher than that of abalone fed the U. pinnatifida. Abalone fed the SH0, SH20, SH40, SH60, and SH80 diets achieved greater weight gain and specific growth rate (SGR) than those of abalone fed the SH100 diet and U. pinnatifida. The greatest weight gain and SGR were obtained in abalone fed the SH60 diet. The proximate composition of the soft body of abalone, except for crude protein, was not affected by the experimental diets. Higher cumulative mortality was observed in abalone fed the U. pinnatifida than that of abalone fed the all formulated diets, except for SH0 diet at 84 h until the end of the 4-day post observation after 24-h air exposure. In conclusion, U. pinnatifida up to 80% could be substituted with S. horneri when 20% U. pinnatifida was included in formulated abalone feed. The SH60 diet achieved the best growth performance of abalone. Keywords: Abalone (Haliotis discus), air exposure, phaeophyta, Sargassum horneri, substitution effect, Undaria pinnatifida 3. Substitution effect of the combined fouling macroalgae, Ulva australis and Sargassum horneri for Undaria pinnatifida in formulated diets on growth and body composition of juvenile abalone (Haliotis discus, Reeve 1846) subjected to air exposure stressor The effect of substituting the combined macroalgae Ulva australis and Sargassum horneri for Undaria pinnatifida in formulated diets on growth and body composition of abalone subjected to air exposure stressor was investigated. A total of 1260 juvenile abalone were distributed into 21 cages. Six formulated diets were prepared. The control (CUS0) diet contained 20% U. pinnatifida. Twenty, 40, 60, 80 and 100% of U. pinnatifida were substituted with an equal amount of the combined U. australis and S. horneri, referred to as the CUS20, CUS40, CUS60, CUS80 and CUS100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare the growth performance of abalone. Abalone were fed with one of the experimental diets once a day for 16 weeks and then subjected to air stressor for 24 h. The cumulative mortality of abalone was monitored for the following 4 days after 24 h of air exposure. Abalone fed all formulated diets attained higher survival, weight gain and specific growth rate (SGR) than U. pinnatifida. Abalone fed the CUS100 diet achieved the greatest weight gain and SGR, followed by the CUS80 and CUS60 diets. The greatest shell growth and heaviest soft body weight were obtained in abalone fed the CUS100 diet. Proximate composition of the soft body of abalone, except for moisture content was not affected by the experimental diets. The cumulative mortality of abalone fed the U. pinnatifida was higher than that of abalone fed all formulated diets at 84 h until the end of the 4-day post observation. The lowest cumulative mortality was obtained in abalone fed the CUS80 diet at the end of the 4-day post observation. Therefore, U. pinnatifida could be completely replaced with the combined U. australis and S. horneri in abalone (H. discus) feed. Keywords: Abalone (Haliotis discus), air exposure stressor, Sargassum horneri, substitution effect, Ulva australis, Undaria pinnatifidaChapter 1. General Introduction 1 Chapter 2. Dietary substitution effect of Ulva australis for Undaria pinnatifida on growth, body composition and air exposure of juvenile abalone, Haliotis discus (Reeve 1846) 6 2.1 Introduction 6 2.2 Materials and methods 9 2.2.1 Preparation of U. australis 9 2.2.2 Rearing conditions of abalone 9 2.2.3 Preparation of the experimental diets 9 2.2.4 Growth and biological measurements of abalone 13 2.2.5 Chemical analysis of the experimental diets and soft body of abalone 13 2.2.6 Observation of cumulative mortality of abalone subjected to air exposure 13 2.2.7 Statistical analysis 14 2.3 Results 15 2.3.1 Growth performance of abalone 15 2.3.2 Biological measurement of abalone 17 2.3.3 Chemical composition of the soft body of abalone 17 2.3.4 Cumulative mortality of abalone subjected to air exposure stressor 20 2.4 Discussion 22 Chapter 3. Substitution effect of Undaria pinnatifida with Sargassum horneri in formulated diet on growth performance, body composition and air exposure stress of juvenile abalone (Haliotis discus, Reeve 1846) 25 3.1 Introduction 25 3.2 Materials and methods 28 3.2.1 Collection of S. horneri 28 3.2.2 Experimental conditions of abalone 28 3.2.3 Experimental diets 28 3.2.4 Sample collection and measurement of abalone growth 32 3.2.5 Chemical analysis of the experimental diets and soft body of abalone 32 3.2.6 Water stability of the experimental diets 32 3.2.7 Investigation of the cumulative mortality of abalone subjected to air exposure 33 3.2.8 Statistical analysis 33 3.3 Results 34 3.3.1 Water stability of the experimental diets over time 34 3.3.2 Effect of formulated diets substituting U. pinnatifida with S. horneri on performance of abalone 37 3.3.3 Biological parameters of abalone fed the formulated diets substituting U. pinnatifida with S. horneri 39 3.3.4 Chemical composition of the soft body of abalone 41 3.3.5 Cumulative mortality of abalone subjected to air exposure stressor 43 3.4 Discussion 45 Chapter 4. Substitution effect of the combined fouling macroalgae, Ulva australis and Sargassum horneri for Undaria pinnatifida in diets on growth and body composition of juvenile abalone (Haliotis discus, Reeve 1846) subjected to air exposure stressor 49 4.1 Introduction 49 4.2 Materials and methods 52 4.2.1 Collection of macroalgae 52 4.2.2 Preparation of the experimental area and rearing of abalone 52 4.2.3 Preparation of the experimental diets 52 4.2.4 Sample collection and measurement of abalone growth 56 4.2.5 Proximate analysis of the soft body of abalone and experimental diets 56 4.2.6 Calculation of the cumulative mortality of abalone subjected to air stressor 56 4.2.7 Water stability of the experimental diets 57 4.2.8 Statistical analysis 57 4.3 Results 58 4.3.1 Water stability of the nutrient content in experimental diets 58 4.3.2 Growth performance of abalone 60 4.3.3 Proximate composition of the soft body of abalone 63 4.3.4 Cumulative mortality of abalone subjected to air stressor 63 4.4 Discussion 66 Chapter 5. General Discussion 71 References 75 Abstract (in Korean) 89 Acknowledgments 94Docto