Unleashing the Potential of Bacterial Isolates from Apple Tree Rhizosphere for Biocontrol of Monilinia laxa: A Promising Approach for Combatting Brown Rot Disease.

peer reviewedMonilinia laxa, a notorious fungal pathogen responsible for the devastating brown rot disease afflicting apples, wreaks havoc in both orchards and storage facilities, precipitating substantial economic losses. Currently, chemical methods represent the primary means of controlling this pathogen in warehouses. However, this study sought to explore an alternative approach by harnessing the biocontrol potential of bacterial isolates against brown rot in apple trees. A total of 72 bacterial isolates were successfully obtained from the apple tree rhizosphere and subjected to initial screening via co-cultivation with the pathogen. Notably, eight bacterial isolates demonstrated remarkable efficacy, reducing the mycelial growth of the pathogen from 68.75 to 9.25%. These isolates were subsequently characterized based on phenotypic traits, biochemical properties, and 16S rRNA gene amplification. Furthermore, we investigated these isolates' production capacity with respect to two enzymes, namely, protease and chitinase, and evaluated their efficacy in disease control. Through phenotypic, biochemical, and 16S rRNA gene-sequencing analyses, the bacterial isolates were identified as Serratia marcescens, Bacillus cereus, Bacillus sp., Staphylococcus succinus, and Pseudomonas baetica. In dual culture assays incorporating M. laxa, S. marcescens and S. succinus exhibited the most potent degree of mycelial growth inhibition, achieving 68.75 and 9.25% reductions, respectively. All the bacterial isolates displayed significant chitinase and protease activities. Quantitative assessment of chitinase activity revealed the highest levels in strains AP5 and AP13, with values of 1.47 and 1.36 U/mL, respectively. Similarly, AP13 and AP6 exhibited the highest protease activity, with maximal enzyme production levels reaching 1.3 and 1.2 U/mL, respectively. In apple disease control assays, S. marcescens and S. succinus strains exhibited disease severity values of 12.34% and 61.66% (DS), respectively, highlighting their contrasting efficacy in mitigating disease infecting apple fruits. These findings underscore the immense potential of the selected bacterial strains with regard to serving as biocontrol agents for combatting brown rot disease in apple trees, thus paving the way for sustainable and eco-friendly alternatives to chemical interventions

From soil to host: Discovering the tripartite interactions between entomopathogenic nematodes, symbiotic bacteria and insect pests and related challenges

peer reviewedEntomopathogenic nematodes (EPNs) are emerging as key agents in ecological networks, exhibiting a wide range of interactions with other biotic components, in particular their symbiotic relationships with the bacteria Xenorhabdus and Photorhabdus. This comprehensive study reveals their global distribution and local benefits and highlights their historical background and taxonomic grouping. The importance of the secreted compounds of EPNs in pest management is highlighted by an in-depth exploration of their potential as biocontrol agents. The complex interactions between nematodes and endosymbiotic bacteria are dissected to understand their mutualistic relationships and subsequent effects on host organisms. The strategies used by EPNs to locate, recognize, and invade hosts will be carefully analyzed to understand their pathogenic phase and the resulting immune responses elicited in insect hosts. Infection strategies employed by the EPN-bacteria complex will be examined to assess their efficacy and real-world challenges. The challenges associated with the effective use of EPNs, including environmental constraints and the need for improved efficacy, will be thoroughly investigated to propose viable solutions. This study paves the way for harnessing the biocontrol potential of EPNs and provides a robust framework for future research to improve the efficacy of EPNs in sustainable agriculture and pest management while addressing the challenges identified

Biodiversity of Nematode Communities Associated with Wheat (<i>Triticum</i><i> aestivum</i> L.) in Southern Morocco and Their Contribution as Soil Health Bioindicators

Soil nematodes are major soil organisms known to reduce wheat production worldwide. However, they are a crucial part of soil biodiversity. Due to the limited data available regarding nematode biodiversity associated with cereal crops in Morocco, a survey was conducted in 2019 across 80 wheat fields. Thirty-three nematode taxa were obtained with different trophic groups: 11 bacterivores (i.e., Rhabditis and Cephalobus spp.), 11 herbivores (i.e., Pratylenchus and Heterodera spp.), 6 fungivores (i.e., Ditylenchus and Aphelenchoides spp.), 4 omnivores (i.e., Dorylaimus and Aporcelaimus spp.) and one predator (Mononchus spp.). For each locality, the diversity of nematode communities was assessed through multiple diversity indices. Three areas (Ait Melloul, Oulad Dahou, and Sidi Boushab) were more diversified and had pronounced nematode occurrence. Moreover, few localities (e.g., Ait Amira and Lqliaa) were shown to be disturbed. Our study underlined that several nematode taxa were significantly correlated with edaphic and climatic/geographic properties. On the other hand, the spatial and parsimony analyses revealed that plant feeders were most associated with bacterial feeders in disturbed soils. This work revealed that the soil nematodes associated with wheat crops are diverse and can serve as an important tool for soil biomonitoring at a large scale

Biodiversity of nematode communities associated with wheat (Triticum aestivum L.) in Southern Morocco and their contribution as soil health bioindicators

Soil nematodes are major soil organisms known to reduce wheat production worldwide. However, they are a crucial part of soil biodiversity. Due to the limited data available regarding nematode biodiversity associated with cereal crops in Morocco, a survey was conducted in 2019 across 80 wheat fields. Thirty-three nematode taxa were obtained with different trophic groups: 11 bacterivores (i.e., Rhabditis and Cephalobus spp.), 11 herbivores (i.e., Pratylenchus and Heterodera spp.), 6 fungivores (i.e., Ditylenchus and Aphelenchoides spp.), 4 omnivores (i.e., Dorylaimus and Aporcelaimus spp.) and one predator (Mononchus spp.). For each locality, the diversity of nematode communities was assessed through multiple diversity indices. Three areas (Ait Melloul, Oulad Dahou, and Sidi Boushab) were more diversified and had pronounced nematode occurrence. Moreover, few localities (e.g., Ait Amira and Lqliaa) were shown to be disturbed. Our study underlined that several nematode taxa were significantly correlated with edaphic and climatic/geographic properties. On the other hand, the spatial and parsimony analyses revealed that plant feeders were most associated with bacterial feeders in disturbed soils. This work revealed that the soil nematodes associated with wheat crops are diverse and can serve as an important tool for soil biomonitoring at a large scale

Évaluation de la résistance aux nématodes à kystes des céréales, Heterodera avenae dans les lignées élites marocaines de blé dur et blé tendre

Les nématodes à kystes des céréales (Heterodera avenae) constituent une menace importante pour la production de blé en Afrique du Nord. Cette étude a évalué la résistance de 100 lignées élites de blé (51 lignées de blé dur et 49 lignées de blé tendre) du Maroc contre H. avenae. En utilisant une seule population du pathogène de la région de Zaers, la résistance a été évaluée en fonction des facteurs de reproduction des nématodes, classés en cinq catégories allant de résistant à hautement sensible. Trois lignées de blé dur (L7, L19 et L41) et six lignées de blé tendre (L8, L12, L14, L29, L38 et L44) ont montré une résistance modérée. Ces résultats fournissent des informations précieuses sur les sources potentielles de résistance au sein du germoplasme de blé marocain, qui peuvent contribuer au développement de variétés améliorées pour une production durable des céréales dans la région. Des recherches supplémentaires sont nécessaires pour identifier et utiliser les gènes et mieux comprendre les mécanismes spécifiques responsables de la résistance observée dans ces lignées prometteuses de blé

Évaluation de la résistance aux nématodes à kystes des céréales, Heterodera avenae dans les lignées élites marocaines de blé dur et blé tendre

Cereal cyst nematodes (Heterodera avenae) pose a significant threat to wheat production in North Africa. This study assessed the resistance of 100 elite wheat breeding lines (51 durum and 49 bread wheat) from Morocco against H. avenae. Using a single population of the pathogen from the Zaers region, resistance was evaluated based on nematode reproduction factors, categorized into five classes ranging from resistance to high susceptibility. Three durum wheat lines (L7, L19, and L41) and six bread wheat lines (L8, L12, L14, L29, L38, and L44) displayed moderate resistance. These findings offer valuable insights into potential sources of resistance within Moroccan wheat germplasm, that could contribute to the development of improved varieties for sustainable cereal production in the region. Further future investigations could help to identify and utilize the specific genes and understand mechanisms responsible for the observed resistance in these promising wheat lines.Les nématodes à kystes des céréales (Heterodera avenae) constituent une menace importante pour la production de blé en Afrique du Nord. Cette étude a évalué la résistance de 100 lignées élites de blé (51 lignées de blé dur et 49 lignées de blé tendre) du Maroc contre H. avenae. En utilisant une seule population du pathogène de la région de Zaers, la résistance a été évaluée en fonction des facteurs de reproduction des nématodes, classés en cinq catégories allant de résistant à hautement sensible. Trois lignées de blé dur (L7, L19 et L41) et six lignées de blé tendre (L8, L12, L14, L29, L38 et L44) ont montré une résistance modérée. Ces résultats fournissent des informations précieuses sur les sources potentielles de résistance au sein du germoplasme de blé marocain, qui peuvent contribuer au développement de variétés améliorées pour une production durable des céréales dans la région. Des recherches supplémentaires sont nécessaires pour identifier et utiliser les gènes et mieux comprendre les mécanismes spécifiques responsables de la résistance observée dans ces lignées prometteuses de blé

Counter-attack of biocontrol agents: Environmentally benign Approaches against Root-knot nematodes (Meloidogyne spp.) on Agricultural crops

Root-knot nematodes (Meloidogyne spp.) are obligate sedentary endoparasites, considered severe crop-damaging taxa among all plant-parasitic nematodes globally. Their attacks through parasitic proteins alter the physiology and machinery of the host cells to favour parasitism and reduction in crop yield. Currently, the use of excessive pesticides as a fast remedy to manage this pest is hazardous for both the environment and humans. Keeping this view in mind, there is an urgent need for developing efficient eco-friendly strategies. Bio-control as an eco-friendly is considered the best approach to manage nematodes without disturbing non-target microbes. In bio-control, living agents such as fungi and bacteria are the natural enemies of nematodes and the best substitute for pesticides. Fungi, including nematode-trapping fungi, can sense host signals and produce special trapping devices viz., constricting rings and adhesive knobs/loops, to capture nematodes and kill them. Whereas, endo-parasitic fungi kill nematodes by enzymatic secretions and spore adhesion through their hyphae. Bacteria can also control nematodes by producing antibiotic compounds, competing for nutrients and rhizosphere, production of hydrolytic enzymes viz., chitinases, proteases, lipases, and induction of systemic resistance (ISR) in host plants. Scientists throughout the world are trying to evolve environmentally benign methods that sustain agricultural production and keep nematodes below a threshold level. Whatever methods evolve, in the future the focus should be on important aspects like green approaches for managing nematodes without disturbing human health and the environment

Screening of Rhizobacterial Isolates from Apple Rhizosphere for Their Biocontrol and Plant Growth Promotion Activity

Apple crops are prone to several diseases that limit their production—in particular, root rot caused by a new genus of oomycetes, mainly Phytopythium vexans. This study aims to screen antagonistic bacteria that can play an important role in the biological control of this pathogenic oomycete and to evaluate their capacity to promote plant growth. The dual culture test revealed that, out of 200 bacterial isolates, 16 have been able to inhibit the mycelial growth of P. vexans with inhibition rates greater than 50%. The selected isolates were identified based on the 16S rDNA genes: 14 bacteria belonging to the genus Bacillus, Stenotrophomonas, and the family Enterobacteriaceae. Notably, two isolates, B1 and M2-6 (identified as Bacillus velezensis), demonstrated the highest inhibition rates of 70% and 68%, respectively. These selected isolates were examined for their ability to produce different compounds related to biocontrol and plant growth promotion. Furthermore, the 16 selected isolates were evaluated for their ability to produce compounds associated with biocontrol and plant growth promotion, including hydrolytic enzymes (cellulases, proteases, and amylases), HCN (hydrogen cyanide) production, phosphate solubilization, IAA (indole-3-acetic acid) production, pectinase production, and stimulation of sorghum bicolor growth in vivo. Variations were observed among the bacterial isolates in terms of their compound production and phytostimulation capabilities. However, the secretion of proteases was consistently detected in all antagonistic isolates. The presence of genes responsible for the production of antifungal lipopeptides (bacillomycin, fengycin, and iturin) in the selected bacterial isolates was determined using polymerase chain reaction (PCR) techniques, while the absence of genes involved in surfactin biosynthesis was also confirmed through PCR studies. These isolates demonstrated inhibitory activity through the production of proteases and antifungal lipopeptides. Further research is needed to explore their potential use in biological control strategies and to improve apple crop productivity