Harnessing nature's defenders: unveiling the potential of microbial consortia for plant defense induction against Alternaria blight in cumin.

Present study was aimed to develop an efficient microbial consortium for combating Alternaria blight disease in cumin. The research involved isolating biocontrol agents against Alternaria burnsii, characterizing their biocontrol and growth promotion traits, and assessing compatibility. A pot experiment was conducted during rabi season of 2022-2023 to evaluate the bioefficacy of four biocontrol agents (1F, 16B, 31B, and 223B) individually and in consortium, focusing on disease severity, plant growth promotion, and defense responses in cumin challenged with A. burnsii. Microbial isolates 1F, 16B, 31B, and 223B significantly inhibited A. burnsii growth in dual plate assays (~ 86%), displaying promising biocontrol and plant growth promotion activities. They were identified as Trichoderma afroharzianum 1F, Aneurinibacillus aneurinilyticus 16B, Pseudomonas lalkuanensis 31B, and Bacillus licheniformis 223B, respectively. The excellent compatibility was observed among all selected biocontrol agents. Cumin plants treated with consortia of 1F + 16B + 31B + 223B showed least percent disease index (32.47%) and highest percent disease control (64.87%). Consortia of biocontrol agents significantly enhanced production of secondary metabolites (total phenol, flavonoids, antioxidant, and tannin) and activation of antioxidant-defense enzymes (POX, PPOX, CAT, SOD, PAL, and TAL) compared to individual biocontrol treatment and infected control. Moreover, consortium treatments effectively reduced electrolyte leakage over the individual biocontrol agent and infected control treatment. The four-microbe consortium significantly enhanced chlorophyll (154%), carotenoid content (88%), plant height (78.77%), dry weight (72.81%), and seed yield (104%) compared to infected control. Based on these findings, this environmentally friendly four-microbe consortium may be recommended for managing Alternaria blight in cumin.

Formulations of synergistic microbial consortia for enhanced systemic resistance against Fusarium wilt in cumin.

The study aimed to understand the dynamic interplay between plants and their associated microbes to develop an efficient microbial consortium for managing Fusarium wilt of cumin. A total of 601 rhizospheric and endophytic bacteria and fungi were screened for antagonistic activity against Fusarium oxysporum f.sp. cumini (Foc). Subsequently, ten bacteria and ten fungi were selected for characterizing their growth promotion traits and ability to withstand abiotic stress. Furthermore, a pot experiment was conducted to evaluate the bioefficacy of promising biocontrol isolates-1F, 16B, 31B, and 223B in mono and consortium mode, focusing on disease severity, plant growth, and defense responses in cumin challenged with Foc. Promising isolates were identified as Trichoderma atrobruneum 15F, Pseudomonas sp. 2B, Bacillus amyloliquefaciens 9B, and Bacillus velezensis 32B. In planta, results revealed that cumin plants treated with consortia of 15F, 2B, 9B, and 32B showed highest percent disease control (76.35%) in pot experiment. Consortia of biocontrol agents significantly enhanced production of secondary metabolites and activation of antioxidant-defense enzymes compared to individual strain. Moreover, consortium treatments effectively reduced electrolyte leakage over the individual strain and positive control. The four-microbe consortium significantly enhanced chlorophyll (~ 2.74-fold), carotenoid content (~ 2.14-fold), plant height (~ 1.8-fold), dry weight (~ 1.96-fold), and seed yield (~ 19-fold) compared to positive control in pot experiment. Similarly, four microbe consortia showed highest percent disease control (72.2%) over the positive control in field trial. Moreover, plant growth, biomass, yield, and yield attributes of cumin were also significantly increased in field trial over the positive control as well as negative control.

Association of a novel begomovirus species with fenugreek yellow vein disease in India.

BACKGROUND: Fenugreek (Trigonella foenum-graecum L.) is an annual medicinal and spice crop belonging to the family Fabaceae. The occurrence of a yellow vein disease was recorded in fenugreek in Jodhpur (India) in 2022. The infection of begomoviruses in legume crops results in significant yield loss and major economic loss. The current study reports an association of a novel begomovirus species associated with yellow vein disease in Fenugreek. METHODS AND RESULTS: In symptomatic fenugreek plants, geminivirus-like particles were visible under a transmission electron microscope. Further, nucleotide sequence analysis of the rolling circle amplified product revealed 2743 nucleotide DNA-A genome with close relatedness to French bean leaf curl virus (88.21%) and Senna leaf curl virus (87.63%). It was proposed as a new begomovirus species, Fenugreek yellow vein Rajasthan virus. The genome organization suggested the presence of a typical nonanucleotide sequence along with 7 ORFs in DNA-A. A possible recombination event took place in the coat protein (V1) region with Pedilanthus leaf curl virus and Chilli leaf curl virus as major and minor parents. The recombinant virus poses possible threats to several other legume crops. To the best of our knowledge, this is the first report of the association of FeYVRaV with fenugreek yellow vein disease from northwestern India. CONCLUSIONS: In conclusion, the presence of a novel begomovirus species associated with yellow vein disease in fenugreek is alarming and needs further studies on its infectivity to prevent its spread to legume crops.

First Report of Candidatus Phytoplasma asteris (16SrI-B subgroup) associated with phyllody disease of fenugreek in the world.

Fenugreek (Trigonella foenum-graecum) is a leafy vegetable and spice crop, native to Indian subcontinent and Eastern Mediterranean region. Phytoplasma infection symptoms were observed in fenugreek at ICAR-National Bureau of Plant Genetic Resources Regional Station, Jodhpur and Agricultural Research Station Mandore Jodhpur, Rajasthan, India. The first appearance of phytoplasma suspected symptoms of little leaf was recorded after 50 days of sowing in the months of January 2022. The major symptoms recorded were virescence, phyllody, shoot proliferation, witches-broom, little leaf, yellowing and overall stunted growth in 146 germplasm accessions at NBPGR research farm, Jodhpur and one major commercially cultivated variety RMT 305 at Mandore Jodhpur. Ten samples from symptomatic and five samples from asymptomatic fenugreek plants were collected and processed for total DNA extraction using the Qiagen DNeasy plant mini kit (Germany). The extracted DNA was amplified using nested PCR assays with universal phytoplasma detection primers for 16S rRNA gene (P1/P7 and R16F2n/R16R2) and secA gene specific primers (SecAfor1/SecArev3 and SecAfor2/SecArev3) (Schneider et al. 1995; Gundersen and Lee 1996; Hodgetts et al. 2008). The amplicons of ∼1.25 kb with 16S rRNA and ∼480 bp with secA gene specific primers were amplified in all symptomatic fenugreek samples. In negative control (asymptomatic plants) no amplification was observed with either of gene specific primers in gel electrophoresis. PCR amplified products from the six selected positive samples (FPP-NBPGR-J-01 to FPP-NBPGR-J-04 and FPP-MND-01 to FPP-MND-02) of 16S rRNA and secA gene, were sequenced from both ends. Sequences were deposited in the NCBI GenBank with accession numbers ON756108-ON756113 for 16S rRNA gene sequences and ON745809 to ON745814 for secA gene sequences. BLAST analysis of 16S rRNA and secA sequences revealed 100% sequence identity among themselves and 99.95 to 100% sequence identity with the earlier reported phytoplasma strains of aster yellows group related phytoplasma strains (GenBank Acc. No. MN239504, MN080270) belonging to Ca. P. asteris (16SrI group). Further analyses of the 16S rRNA and secA gene-based phylogenetic tree and the iPhyClassifier-based virtual RFLP analysis of 16S rRNA gene study demonstrated that the phytoplasma associated with fenugreek phyllody belonged to 16Sr group I ('Ca. P. asteris') and subgroup B (GenBank accession AP006628), with similarity coefficient of 1.0. Earlier association of 16Sr-II-D subgroup (Ca. P. australasiae) with fenugreek as host was reported from Pakistan (Malik et al., 2020). To the best of our knowledge, this is the first report of a 'Ca. P. asteris', 16SrI-B subgroup related phytoplasma strain associated with fenugreek phyllody in the world. The 16SrI-B phytoplasma strain is a widely distributed strain associated with several agricultural and horticultural crops of India (Rao 2021). This is not only the first instance of fenugreek phyllody disease found in India, but also the first instance of fenugreek phyllody caused by 16SrI-B subgroup phytoplasma worldwide. This report has epidemiological significance and needs immediate attention, as fenugreek is one of the most common seed spice crop being grown all over India.

Management of blight of bell pepper (Capsicum annuum var. grossum) caused by Drechslera bicolor

Abstract Sweet or bell pepper is a member of the Solanaceae family and is regarded as one of the most popular and nutritious vegetable. Blight, in the form of leaf and fruit blight, has been observed to infect bell pepper crops cultivated at the horticulture farm in Rajasthan College of Agriculture, Udaipur, India. Based on disease severity, we attempted to curb this newly emerged problem using different fungicides, plant extracts, bio-control agents, and commercial botanicals against the fungus in laboratory and pot experiments. Bio-control agent Trichoderma viride and plant growth promoting Rhizobacteria (PGPR) isolate Neist-2 were found to be quite effective against bell pepper blight. All evaluated fungicides, botanicals, commercial botanicals, and bio-control agents in vitro were further studied as seed dressers and two foliar sprays at ten days interval in pot experiments. The combinations of Vitavax, PGPR isolate Neist-2, and Mehandi extract were found to be very effective against bell pepper blight followed by Vitavax, T. viride, and Mehandi extract used individually. All treatments in the pot experiments were found to significantly reduce seedling mortality and enhance plant biomass of bell pepper. Thus, these experimental findings suggest that a better integrated management of bell pepper blight could be achieved by conducting field trials in major bell pepper- and chilli-cultivated areas of the state. Besides fungicides, different botanicals and commercial botanicals also seem to be promising treatment options. Therefore, the outcome of the present study provides an alternate option of fungicide use in minimizing loss caused by Drechslera bicolor.

Management of blight of bell pepper (Capsicum annuum var. grossum) caused by Drechslera bicolor.

Sweet or bell pepper is a member of the Solanaceae family and is regarded as one of the most popular and nutritious vegetable. Blight, in the form of leaf and fruit blight, has been observed to infect bell pepper crops cultivated at the horticulture farm in Rajasthan College of Agriculture, Udaipur, India. Based on disease severity, we attempted to curb this newly emerged problem using different fungicides, plant extracts, bio-control agents, and commercial botanicals against the fungus in laboratory and pot experiments. Bio-control agent Trichoderma viride and plant growth promoting Rhizobacteria (PGPR) isolate Neist-2 were found to be quite effective against bell pepper blight. All evaluated fungicides, botanicals, commercial botanicals, and bio-control agents in vitro were further studied as seed dressers and two foliar sprays at ten days interval in pot experiments. The combinations of Vitavax, PGPR isolate Neist-2, and Mehandi extract were found to be very effective against bell pepper blight followed by Vitavax, T. viride, and Mehandi extract used individually. All treatments in the pot experiments were found to significantly reduce seedling mortality and enhance plant biomass of bell pepper. Thus, these experimental findings suggest that a better integrated management of bell pepper blight could be achieved by conducting field trials in major bell pepper- and chilli-cultivated areas of the state. Besides fungicides, different botanicals and commercial botanicals also seem to be promising treatment options. Therefore, the outcome of the present study provides an alternate option of fungicide use in minimizing loss caused by Drechslera bicolor.