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.

First Report of Candidatus Phytoplasma asteris (16SrI-B Subgroup) associated with phyllody disease of moth bean in world.

Moth bean (Vigna aconitifolia), a drought and heat-resistant legume from the Fabaceae family, is commonly cultivated in arid and semi-arid regions of the Indian subcontinent In September 2022, phyllody symptoms (Figure 1) were observed on 50-days-old moth bean plants at the ICAR-NBPGR research farm in Jodhpur, Rajasthan, India. The disease incidence ranged from 10 to 25%. To investigate the cause, ten symptomatic VacoJod (1-10) and ten asymptomatic VacoJod (11-20) Vigna aconitifolia plants were collected. Insect populations were also collected from the vicinity using the sweep-net method to examine the role of insect vectors. The leafhopper was identified based on morphological characterization as Empoasca sp. at the Division of Entomology, ICAR-IARI, New Delhi. DNA was extracted from midribs of all collected plants and the Empoasca sp., using Qiagen DNeasy Plant Mini Kit and Blood and Tissue kit, respectively. Nested polymerase chain reaction (Nested-PCR) with universal primers P1/P7 and R16F2n/R16R2 (Deng and Hiruki, 1991; Gundersen and Lee, 1996), and secA gene primers (secAfor1/secArev3 and secAfor2/secArev3) (Hodgetts et al., 2008) were employed to determine phytoplasma species association. Out of the 10 symptomatic plants and 10 leafhopper samples, 6 leafhopper samples and all symptomatic plants produced expected band sizes for the 16S rRNA (approximately 1.25 kb) and secA gene (480 bp). The PCR products were cloned, sequenced, and sequences (two each from moth bean and leafhopper) were submitted to NCBI GenBank with accession numbers OP941130, OP941132, OP941133 and OP941134 for 16S rRNA and OP958868, OP958869, OP958870, and OP958871 for secA gene sequences. Nucleotide BLAST analysis of 16S rRNA sequences revealed a minimum of 99.92% similarity with 'Primula acaulis' yellows phytoplasma (KJ494340) from Czech Republic. All 100% hits corresponded to 16SrI-B group phytoplasmas, for example rapeseed phyllody phytoplasma (CP055264) from Taiwan. Similarly, nucleotide BLAST analysis of secA sequences revealed a minimum of 99.15% sequence similarity with Paulownia witches'-broom phytoplasma (secA) (OP124308) from China. All 100% hits were of 16SrI-B group phytoplasmas, for example Ageratum conyzoides yellowing phytoplasma (MW401697, secA) from India. Phylogenetic analysis using MEGA11 (Tamura et al., 2021) clustered the moth bean and Empoasca sp. phytoplasma strains with 16SrI-B phytoplasma reference strains. iPhyClassifier tool classified the 16S rRNA gene sequences into 16Sr group I, subgroup B, with a similarity coefficient of 1.0 (Figure 2a, 2b). This marks the first report of the association of 'Ca. P. asteris' 16SrI-B related phytoplasma strain with moth bean plants globally. The 16SrI-B phytoplasma strain is prevalent in various crops in India (Singh et al., 2023). This report emphasizes the epidemiological studies and highlights the need for further research and preventive measures to manage the spread of this phytoplasma strain, which could impact crop production and food security in hot and dry regions.

Identification of new stable resistant sources and assessing agro-morphological performance of sponge gourd germplasm against Tomato Leaf curl New Delhi Virus incidence.

Tomato leaf curl New Delhi virus (TolCNDV) causes yellow mosaic disease, which poses a significant biotic constraint for sponge gourd cultivation, potentially resulting in crop loss of up to 100%. In the present investigation, 50 diverse genotypes were screened for 3 years under natural epiphytotic conditions. A subset of 20 genotypes was further evaluated across four different environments. The combined analysis of variance revealed a significant genotype × environment interaction. Eight genotypes consistently exhibited high and stable resistance in the preliminary screening and multi-environment testing. Furthermore, genotype plus genotype × environment interaction biplot analysis identified DSG-29 (G-3), DSG-7 (G-2), DSG-6 (G-1), and DSGVRL-18 (G-6) as the desirable genotypes, which have stable resistance and better yield potential even under diseased conditions. The genotype by yield × trait biplot analysis and multi-trait genotype-ideotype distance index analysis further validated the potential of these genotypes for combining higher yield and other desirable traits with higher resistance levels. Additionally, resistant genotypes exhibited higher activities of defense-related enzymes as compared to susceptible genotypes. Thus, genotypes identified in our study will serve as a valuable genetic resource for carrying out future resistance breeding programs in sponge gourd against ToLCNDV.

Corrigendum: Temporal transcriptome of tomato elucidates the signaling pathways of induced systemic resistance and systemic acquired resistance activated by Chaetomium globosum.

[This corrects the article DOI: 10.3389/fgene.2022.1048578.].

Marker-assisted enhancement of bacterial blight (Xanthomonas oryzae pv. oryzae) resistance in a salt-tolerant rice variety for sustaining rice production of tropical islands.

Introduction: Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae is a major disease of rice, specially in the tropical regions of the world. Developing rice varieties with host resistance against the disease is the most effective and economical solution for managing the disease. Methods: Pyramiding resistance genes (Xa4, xa5, xa13,and Xa21) in popular rice varieties using marker-assisted backcross breeding (MABB) has been demonstrated as a cost-effective and sustainable approach for establishing durable BB resistance. Here, we report our successful efforts in introgressing four resistance genes (Xa4, xa5, xa13, and Xa21) from IRBB60 to CARI Dhan 5, a popular salt-tolerant variety developed from a somaclonal variant of Pokkali rice, through functional MABB. Results and discussion: Both BB and coastal salinity are among the major challenges for rice production in tropical island and coastal ecosystems. Plants with four, three, and two gene pyramids were generated, which displayed high levels of resistance to the BB pathogen at the BC3F2 stage. Under controlled salinity microplot environments, the line 131-2-175-1223 identified with the presence of three gene pyramid (Xa21+xa13+xa5) displayed notable resistance across locations and years as well as exhibited a salinity tolerance comparable to the recurrent parent, CARI Dhan 5. Among two BB gene combinations (Xa21+xa13), two lines, 17-1-69-334 and 46-3-95-659, demonstrated resistance across locations and years, as well as salt tolerance and grain production comparable to CARI Dhan 5. Besides salinity tolerance, five lines, 17-1-69-179, 46-3-95-655, 131-2-190-1197, 131-2-175-1209, and 131-2-175-1239, exhibited complete resistance to BB disease. Following multilocation testing, potential lines have been identified that can serve as a prospective candidate for producing varieties for the tropical Andaman and Nicobar Islands and other coastal locations, which are prone to BB and coastal salinity stresses.

Temporal transcriptome of tomato elucidates the signaling pathways of induced systemic resistance and systemic acquired resistance activated by Chaetomium globosum.

C. globosum is an endophytic fungus, which is recorded effective against several fungal and bacterial diseases in plants. The exclusively induce defense as mechanism of biocontrol for C. globosum against phyto-pathogens is reported. Our pervious study states the effectiveness of induced defense by C. globosum (Cg), in tomato against Alternaria solani. In this study the temporal transcriptome analysis of tomato plants after treatment with C. globosum was performed for time points at 0 hpCi, 12 hpCi, 24 hpCi and 96 phCi. The temporal expression analysis of genes belonging to defense signaling pathways indicates the maximum expression of genes at 12 h post Cg inoculation. The sequential progression in JA signaling pathway is marked by upregulation of downstream genes (Solyc10g011660, Solyc01g005440) of JA signaling at 24 hpCi and continued to express at same level upto 96 hpCi. However, the NPR1 (Solyc07g040690), the key regulator of SA signaling is activated at 12 h and repressed in later stages. The sequential expression of phenylpropanoid pathway genes (Solyc09g007920, Solyc12g011330, Solyc05g047530) marks the activation of pathway with course of time after Cg treatment that results in lignin formation. The plant defense signaling progresses in sequential manner with time course after Cg treatment. The results revealed the involvement of signaling pathways of ISR and SAR in systemic resistance induced by Cg in tomato, but with temporal variation.

Spatial and temporal variation of heavy metals in atmospheric aerosol of Delhi.

The levels of Suspended Particulate Matter (SPM) and heavy metals viz. Pb, Cd, Cr, Ni and Fe were measured. Aerosol samples from four different locations in Delhi were collected by High-volume samplers for a period of one year from July 1997 June 1998. Metal concentration was determined by Atomic Absorption Spectrometry. The annual average concentration of SPM in Delhi was found to be 416.34 +/- 223 microg m(-3). The atmospheric aerosol samples were highly enriched with elements viz. Pb and Cd, which originate from various human activities like transportation and industrial processes. Principal Component Analysis (PCA) showed vehicular traffic and industrial emission as the major contributors of metals. The annual average concentration of Pb did not exceed the national standard of 0.75 microg m(-3).