The Effects of Trichoderma spp. and Saccharomyces cerevisiae on the Growth of Pepper (Capsicum annuum L.) Plant and Root Rot Disease Caused by Phytophthora capsici Leonian

The Effects of Trichoderma spp. and Saccharomyces cerevisiae on the Growth of Pepper (Capsicum annuum L.) Plant and Root Rot Disease Caused by Phytophthora capsici Leonian

Emre Demirer Durak

Yuzuncu Yil University, Agriculture Faculty, Plant Protection Department, 65080, Van, Turkey

Abstract – Pepper (Capsicum annuum L.) is an important vegetable crop in Turkey. Phytophthora root rot, caused by Phytophthora capsici Leonian, is an important soilborne plant disease that causes economic losses inTurkey and world-wide. Biological control of different plant diseases was focused primarily using fungi. In this study, the effects of Trichoderma spp. and yeast were investigated on the growth of pepper and P. capsici disease. Trichoderma spp., has potential as a biological control agent against several soilborne pathogens and shown to be capable of increasing plant growth and yields. Application of yeasts as biocontrol agents acts as a new trend against different pathogens. Especially Saccharomyces cerevisiae is considered a new promising plant growth promoting yeast for different crops. Under controlled conditions, two F1 pepper cultivars were inoculated (Bafra and Sirena) with three different Trichoderma strains (Trichoderma harzianum, Trichoderma virens and Trichoderma asperellum) and yeast (Saccharomyces cerevisiae) in order to determine the most appropriate combination of P. capsici. Inoculated pepper seedlings were grown in a greenhouse for about 10 weeks at 22-24 C. The experiment was conducted two times in three replications. At the end of the study, it was found that Trichoderma spp. and yeast application significantly increased the growth components (plant height, shoot fresh and dry weights, root fresh and dry weights) compared to control pepper plants or inoculated with P. capsici alone. Similarly Trichoderma spp. and yeast significantly reduced the harmful effects of the disease. The best affinity was determined T. harzianum x S. cerevisiae combination. Also, the results indicate that S. cerevisiae have strong potential as plant growth promoters and as biocontrol agents of the soil-borne fungal plant pathogen P. capsici causing root rot in pepper.

Key words: Pepper, Phytophthora capsici Leonian, Saccharomyces cerevisiae, Trichoderma spp.

1. INTRODUCTION

   Pepper (Capsicum annuum L.), a member of the Solanaceae family, is an economically important vegetable crop cultivated worldwide. However, its production is severely constrained by numerous diseases and pests that lead to significant yield and quality losses. Among these diseases, Phytophthora blight caused by Phytophthora capsici Leonian is considered one of the most destructive pathogens affecting pepper cultivation. This soil-borne pathogen is widely distributed in pepper-growing regions and can infect plants at all developmental stages. During the seedling stage, it causes root and collar rot, leading to plant wilting and death, whereas in later stages it infects roots, stems, leaves, and fruits, resulting in severe economic losses [1,2,3]. Due to the pathogens biological characteristics and persistence in soil, the management of P. capsici remains difficult. Although chemical fungicides and cultural practices are commonly used, their effectiveness against soil-borne pathogens is often limited and may raise environmental and health concerns. Therefore, environmentally friendly and sustainable alternatives such as biological control have gained increasing importance in plant disease management [4].

   Among microbial biocontrol agents, species of the genus Trichoderma have been widely studied because of their strong antagonistic activity against plant pathogens and their plant growthpromoting properties. Trichoderma species are commonly found in soils rich in organic matter and are characterized by rapid growth, high competitive ability, and the production of various antimicrobial metabolites [5,6]. These fungi suppress pathogens through several mechanisms, including mycoparasitism, antibiosis, competition for nutrients and space, and the activation of plant defense responses [7,8]. Numerous studies have demonstrated the effectiveness of Trichoderma spp. against P. capsici. For example, Trichoderma harzianum has been shown to significantly reduce disease severity and mitigate pathogen-induced reductions in plant biomass [9], while other species such as T. viride and T. reesei can inhibit the mycelial growth of P. capsici and improve plant growth parameters [10]. Additionally, Trichoderma spp. are capable of parasitizing P. capsici hyphae and degrading its reproductive structures, thereby limiting pathogen development [11].

   In addition to filamentous fungi, yeasts have recently emerged as promising biological control agents in plant disease management. Yeasts can suppress plant pathogens through mechanisms such as competition for nutrients and space, production of

   antifungal metabolites, and induction of plant defense responses. Among them, Saccharomyces cerevisiae, commonly known as bakers yeast, has received considerable attention due to its safety, natural occurrence, and ease of cultivation [12]. Previous studies have reported that S. cerevisiae can inhibit plant pathogens such as Fusarium oxysporum while simultaneously enhancing plant growth parameters and chlorophyll content [13]. Moreover, yeast applications have been shown to reduce disease severity and improve plant biomass in several crops [14]. Despite these promising findings, studies evaluating the combined or comparative effects of Trichoderma spp. and yeasts on pepper growth and Phytophthora capsici disease remain limited. Therefore, the aim of this study was to investigate the effects of Trichoderma spp. and Saccharomyces cerevisiae on the growth of pepper plants and the development of root rot disease caused by Phytophthora capsici, and to assess their potential as environmentally friendly biological control agents.

   The results of this study are expected to contribute to the development of sustainable and environmentally friendly disease management strategies for pepper cultivation by highlighting the potential of microbial biocontrol agents as alternatives to chemical fungicides.

2. MATERIALS AND METHODS

   Under controlled conditions, two F1 pepper cultivars were inoculated (Bafra and Sirena) with three different Trichoderma strains (Trichoderma harzianum, Trichoderma virens and Trichoderma asperellum) and yeast (Saccharomyces cerevisiae) in order to determine the most appropriate combination of P. capsici Leonian. These pepper cultivars are used often in Turkey. Isolates were provided by the Collection of Mycology, Plant Pathology Department, University of Yuzuncu Yil. Isolates were identified with molecular techniques previously. Trichoderma isolates were obtained from soil and P. capsici was obtained from pepper. The bio- compound used in this study is active dry yeast of S. cerevisiae. The seeds were sown to pot including sterile mixture of peat and sand. Trichoderma species were grown on PDA incubated for 7 days at 24 °C. The spore suspensions were prepared 1×106 conidia/ml with the aid of a haemacytometer slide. These suspansions were added to soil 10 ml separately . Yeast application was conducted as soil inoculation using concentration of 5 g L-1. Two weeks later, the plants were inoculated with 10 ml of a zoospore suspension of

   P. cactorum (105 ml-1 zoospores) to each plant with a pipette. Inoculated pepper seedlings were grown in a greenhouse for about 10 weeks at 22-24 C. The experiment was conducted two times in three replications. Disease severity was dtermined with a (05) scale (0 = no symptom and 5 = plant death), plant height, shoot and root fresh and dry weights (oven-dried at 70ºC for 48 h) were recorded [15,16]. Data were subjected to analysis of variance (ANOVA), and mean comparisons were performed using the Waller Duncan multiple range test at P < 0.05.

3. RESULTS AND DISCUSSION

   The results of the present study demonstrate the effects of Trichoderma spp. and Saccharomyces cerevisiae on pepper plant growth and the suppression of Phytophthora capsici. Overall, microbial treatments improved plant growth parameters and reduced disease severity compared with the pathogen-inoculated control, highlighting the potential of these microorganisms as biological control agents in sustainable pepper production systems. The effects of different microbial treatments on growth parameters and disease incidence of pepper plants are presented in Table 1.

   TABLE 1. Effects of P. capsici, T. harzianum, T. virens, T. asperellum, and S. cerevisiae treatments on growth parameters and disease incidence in pepper plants.

   Treatments	Shoot height (cm)	Root height (cm)	Shoot fresh weight (g)	Shoot dry weight (g)	Root fresh weight (g)	Root dry weight(g)	Disease incidenc e (%)
   Control	13.8 bc*	19.2 ab	17.8 bc	2.2 a	6.4	1.5	–
   T. harzianum	15.5 b	22.4 a	21.4 a	2.0 ab	6.5 bc	1.3 b	–
   T. virens	14.3 b	18.7 b	17.5 c	1.5 c	7.4 b	1.4 b	–
   T.asperellum	13.2c	17.4 c	18.7 b	1.9 b	5.5 c	1 c	–
   S. cerevisiae	15.6 b	17.0 c	18.0 b	1.8 b	6.2 c	1.2 b	–

   T. harzianum+ S. cerevisiae	19.0 a	21.1 a	19.4 ab	1.9 b	9.0 a	1.8 a	–
   T. virens+ S. cerevisiae	14.6 b	19.0 ab	17.0 c	1.6 c	7.7 b	1.3 b	–
   T. asperellum+ S. cerevisiae	16.1 ab	17.3 c	15.4 d	1.8 b	6.5 bc	1.2 b	–
   T.harzianum+T.virens +T.asperellum+ S.cerevisiae	13.0 c	15.9 c	16.8 c	1.2 d	5.2 c	1.4 b	–
   P.capsici	13.2c	16.4 c	16.3 d	1.3 d	7.0 b	1.4 b	78.8
   T. harzianum + P.capsici	18.4 a	17.8 bc	20.4 a	1.6 c	9.3 a	1.7 a	42.6
   T. virens+ P.capsici	16.0 ab	21.5 a	18.6 b	1.9 b	4.4 cd	1.1 c	47.3
   T. asperellum + P.capsici	12.5cd	18.7 b	16.3 d	1.5 c	4.0 d	0.8 c	59.6
   S. cerevisiae + P.capsici	11.6 d	16.8 c	17.4 c	1.8 b	5.4 c	1 c	54.9
   T.harzianum+T.virens +T.asperellum+ S.cerevisiae + P.capsici	16.5 ab	18.0 b	15.2 d	1.6 c	5.5 c	1.1 c	45.1

   *values within columns followed by different letters were significantly different (P < 0.05) according to the Waller-Duncan procedure.

   Microbial applications generally improved plant growth compared with the untreated control. Among the treatments without pathogen inoculation, the combination of T. harzianum + S. cerevisiae produced the highest shoot height (19.0 cm) and root fresh weight (9.0 g), indicating a strong plant growthpromoting effect. In contrast, the treatment including all tested microorganisms (T. harzianum + T. virens + T. asperellum + S. cerevisiae) resulted in comparatively lower growth parameters, which may indicate competition among microbial agents within the rhizosphere environment.

   In plants inoculated with P. capsici, disease incidence reached 78.8% and was associated with significant reductions in plant growth parameters. However, the application of microbial agents substantially reduced disease incidence and mitigated the negative effects of the pathogen. Among the tested treatments, T. harzianum showed the highest level of disease suppression and significantly improved plant growth compared with the pathogen-only treatment. The combination of T. harzianum and S. cerevisiae further enhanced plant growth performance, suggesting a possible synergistic interaction between fungal and yeast-based biocontrol agents. No significant differences were observed between the two F1 pepper cultivars; therefore, the results were evaluated collectively.

   This synergistic interaction between Trichoderma spp. and yeasts may be explained by their complementary modes of action in the rhizosphere environment. While Trichoderma species are known to suppress pathogens through mycoparasitism, production of antifungal metabolites, and induction of systemic resistance, yeasts can contribute to pathogen inhibition through nutrient competition, antibiosis, and secretion of lytic enzymes. The combined presence of these microorganisms may therefore create a more suppressive rhizosphere environment, enhancing both pathogen inhibition and plant growth promotion. Similar synergistic effects between fungal and yeast biocontrol agents have been reported in several studies, suggesting that multi-microbial approaches may provide more stable and effective biological control strategies than single-agent applications.

   The effectiveness of Trichoderma species in suppressing Phytophthora capsici has been widely reported in previous studies. For example, [17] reported that T. asperellum (T34 strain) reduced disease severity by up to 71% in pepper under greenhouse conditions and significantly increased plant biomass. Similarly, [18] demonstrated that T. longibrachiatum and T. aggressivum f. europaeum reduced disease severity caused by P. capsici by 76% and 54%, respectively. The antagonistic activity of Trichoderma spp. is generally attributed to several mechanisms, including mycoparasitism, competition for nutrients and space, and the production of antifungal metabolites and cell walldegrading enzymes.

   In addition to filamentous fungi, yeasts have also been reported as promising biological control agents against several plant pathogens. Yeasts are known to suppress pathogens through mechanisms such as antibiosis, nutrient competition, production of lytic enzymes, and the induction of plant defense responses. In the present study, S. cerevisiae also contributed to plant growth promotion and disease suppression, supporting its potential role as a plant growthpromoting microorganism.

   Previous studies have also demonstrated that Trichoderma spp. can stimulate plant growth by enhancing nutrient uptake, producig phytohormone-like compounds, and improving root development. For instance, [9] reported that T. harzianum alleviated the reduction in plant biomass caused by P. capsici infection and helped maintain plant growth under pathogen pressure.

   Furthermore, the combined application of different biological control agents may enhance disease suppression through complementary mechanisms. [19] demonstrated that the combination of Trichoderma spp. and yeast culture filtrates effectively suppressed damping-off and root rot pathogens while simultaneously stimulating plant defense enzymes and improving plant physiological traits. Such synergistic interactions between beneficial microorganisms may increase the effectiveness and reliability of biological control strategies.

   Overall, the results of this study confirm that Trichoderma spp., particularly T. harzianum, and Saccharomyces cerevisiae can significantly improve pepper plant growth and reduce disease severity caused by Phytophthora capsici. These findings highlight the potential of combining beneficial fungi and yeasts as an environmentally friendly strategy for sustainable management of soil- borne diseases in pepper cultivation.

4. CONCLUSION

The results of this study demonstrate that Trichoderma spp. and Saccharomyces cerevisiae significantly improved pepper plant growth and reduced disease severity caused by Phytophthora capsici. Among the tested treatments, T. harzianum alone and in combination with S. cerevisiae showed the most promising effects on plant growth promotion and disease suppression. The microbial applications enhanced plant growth parameters while mitigating the negative effects of pathogen infection. These findings highlight the potential of beneficial fungi and yeasts as environmentally friendly biological control agents for the management of soil-borne diseases in pepper production. Further studies under field conditions are recommended to confirm the effectiveness of these microorganisms in practical agricultural systems.

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