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Brinjal is one of the most important vegetable crops grown in India for a wide range of culinary and medicinal purposes. Many fungal and viral diseases infect the crop, but the well-known disease that causes complete yield loss is phytoplasma. Phytoplasmas in brinjal belong to the 16SrI and 16SrVI groups in India and the characteristic symptoms are yellowing, severe stunting, reduced leaf size, necrosis, reduced internodes and dispersal of flowers before maturity, causing severe yield loss. Till now, there are not many studies on the detection and characterization of phytoplasmas infecting brinjal in Tamil Nadu. Therefore, a survey was conducted in major brinjal growing districts (Thiruvallur, Coimbatore, Thiruvannamalai, Krishnagiri, Vellore, Dindigul, Pudukottai, Ramanathapuram) of Tamil Nadu to monitor the disease incidence and yield loss caused by the phytoplasmas infecting brinjal. During the survey, the disease incidence ranged from 5.0 to 95.0 per cent, with Coimbatore district recording the highest incidence of 95.0 per cent. Nested PCR testing of the symptomatic samples collected from the different districts showed that all the samples collected were positive. Sequencing results also showed that all the samples belonged to the 16SrVI group and virtual RFLP analysis of the sequences indicated that the phytoplasmas infecting brinjal in the major brinjal-growing districts of Tamil Nadu belonged to the 16SrVI-D subgroup. [ABSTRACT FROM AUTHOR]

Abstract Background Little leaf disease caused by phytoplasma infection is a significant threat to eggplant (also known as brinjal) cultivation in India. This study focused on the molecular characterisation of the phytoplasma strains and insect vectors responsible for its transmission and screening of brinjal germplasm for resistance to little leaf disease. Results Surveys conducted across districts in the Tamil Nadu state of India during 2021–2022 showed a higher incidence of phytoplasma during the Zaid (March to June), followed by Kharif (June to November) and Rabi (November to March) seasons with mean incidence ranging from 22 to 27%. As the name indicates, phytoplasma infection results in little leaf (reduction in leaf size), excessive growth of axillary shoots, virescence, phyllody, stunted growth, leaf chlorosis and witches’ broom symptoms. PCR amplification with phytoplasma-specific primers confirmed the presence of this pathogen in all symptomatic brinjal plants and in Hishimonus phycitis (leafhopper), providing valuable insights into the role of leafhoppers in disease transmission. BLAST search and phylogenetic analysis revealed the phytoplasma strain as “Candidatus Phytoplasma trifolii”. Insect population and disease dynamics are highly influenced by environmental factors such as temperature, relative humidity and rainfall. Further, the evaluation of 22 eggplant accessions revealed immune to highly susceptible responses where over 50% of the entries were highly susceptible. Finally, additive main effect and multiplicative interaction (AMMI) and won-where biplot analyses identified G18 as a best-performing accession for little leaf resistance due to its consistent responses across multiple environments. Conclusions This research contributes essential information on little leaf incidence, symptoms, transmission and resistance profiles of different brinjal genotypes, which together ensure effective and sustainable management of this important disease of eggplants.

Background: Little leaf disease caused by phytoplasma infection is a significant threat to eggplant (also known as brinjal) cultivation in India. This study focused on the molecular characterisation of the phytoplasma strains and insect vectors responsible for its transmission and screening of brinjal germplasm for resistance to little leaf disease. Results: Surveys conducted across districts in the Tamil Nadu state of India during 2021–2022 showed a higher incidence of phytoplasma during the Zaid (March to June), followed by Kharif (June to November) and Rabi (November to March) seasons with mean incidence ranging from 22 to 27%. As the name indicates, phytoplasma infection results in little leaf (reduction in leaf size), excessive growth of axillary shoots, virescence, phyllody, stunted growth, leaf chlorosis and witches' broom symptoms. PCR amplification with phytoplasma-specific primers confirmed the presence of this pathogen in all symptomatic brinjal plants and in Hishimonus phycitis (leafhopper), providing valuable insights into the role of leafhoppers in disease transmission. BLAST search and phylogenetic analysis revealed the phytoplasma strain as "Candidatus Phytoplasma trifolii". Insect population and disease dynamics are highly influenced by environmental factors such as temperature, relative humidity and rainfall. Further, the evaluation of 22 eggplant accessions revealed immune to highly susceptible responses where over 50% of the entries were highly susceptible. Finally, additive main effect and multiplicative interaction (AMMI) and won-where biplot analyses identified G18 as a best-performing accession for little leaf resistance due to its consistent responses across multiple environments. Conclusions: This research contributes essential information on little leaf incidence, symptoms, transmission and resistance profiles of different brinjal genotypes, which together ensure effective and sustainable management of this important disease of eggplants. [ABSTRACT FROM AUTHOR]

A survey assessed cucumber phyllody disease incidence in Chikkaballapura, Bengaluru Rural, Bengaluru Urban, and Bagalkote districts of Karnataka, India. The average disease incidence ranged from 8 to 18 %. A total of 9 samples showing phyllody and little leaf symptoms were collected and association of phytoplasma was confirmed through 16S rRNA gene amplification, using universal primer pair P1/P7, and followed by nested PCR using primer R16F2n/R16R2. Further, characterization through multilocus sequence analysis targeting secY and rpl22 genes confirmed all nine strains as part of the 16SrI group ('Candidatus Phytoplasma asteris'). Additionally, four weed species (Lecusa aspera, Parthenium hysterophorus, Acaranthus sp., and Amaranthus viridis) found in cucumber fields tested positive for phytoplasma (16SrI) disease. In-silico RFLP analysis of the amplified F2n/R2 region of the 16S rRNA gene indicated that two phytoplasma strains (CuPP1 and CuPP3) from Chikkaballapura belonged to subgroup X (16SrI-X), one phytoplasma strain (CuPP2) belonged to subgroup B (16SrI–B). While the remaining strains from Bangalore Urban, Bengaluru Rural, and Bagalkote districts belonged to subgroup B (16SrI–B). A loop-mediated isothermal amplification (LAMP) detection protocol was also developed for 'Ca P. asteris', targeting the phytoplasma 16S ribosomal DNA. Comparison of assay sensitives demonstrated that LAMP technique is highly efficient and could detect the presence of phytoplasma up to 50 fg of template DNA. LAMP-based detection offers superior ease of use, cost-effectiveness, and rapid results. To the best of our knowledge, this is the first report of phytoplasma causing phyllody disease in cucumber crop in India. • Infected cucumber plants showed little leaf, phyllody, leaf proliferation, and shortened internodes. • ' Ca. Phytoplasma asteris' strain (16SrI) detected in cucumber phyllody symptoms via multi-locus gene sequence analysis (MLST). • A Loop‐mediated isothermal amplification (LAMP) assay was developed for detecting phytoplasma. • The present study reveals genetic diversity and impact of phyllody phytoplasma on cucumbers. • This is the first report of ' Ca. Phytoplasma asteris' (16SrI) causing cucumber phyllody in India. [ABSTRACT FROM AUTHOR]

Cathranthus roseus also known as periwinkle, an ornamental plant contains several medicinal values, was found with the symptoms of little leaf and witches’ broom at Shahjahanpur location with the incidence of up to 8%. The phytoplasma etiology was confirmed through scanning electron microscopy examination in all the four-leaf samples. Molecular analysis through PCR with universal primer pairs P1/P6 followed by nested PCR with R16F2n/R16r2 primers yielded ~1.2kbp amplicons in all the four symptomatic leaf samples. One amplicon was eluted, purified, sequenced, and used in BLASTn searches, which showed maximum identity of periwinkle isolate with several isolates of 16SrIX group of phytoplasma. Further, phylogenic analysis and in silico RFLP confirmed the association of 16SrIX-C subgroup phytoplasma in little leaf and witches broom plants which is the first report from India.

Phytoplasmas are minute phytopathogenic bacteria that induce excessive vegetative growth, known as witches'-broom (WB), in many infected plant species during the later stages of infection. The WB structure is characterized by densely clustered little (small) leaves, which are frequently accompanied by chlorosis (yellowing). The mechanisms behind the formation of little leaves within WB structures (LL-WB) are poorly understood. To address this gap, the LL-WB formation was extensively studied using sweet cherry virescence (SCV) phytoplasma-infected sweet cherry plants. Based on morphological examinations, signs of premature leaf senescence were observed in LL-WB samples, including reduced leaf size, chlorosis, and alterations in shape. Subsequent physiological analyses indicated decreased sucrose and glucose levels and changes in hormone concentrations in LL-WB samples. Additionally, the transcriptomic analysis revealed impaired ribosome biogenesis and DNA replication. As an essential process in protein production, the compromised ribosome biogenesis and the inhibited DNA replication led to cell cycle arrest, thus affecting leaf morphogenesis and further plant development. Moreover, the expression of marker genes involved in premature leaf senescence was significantly altered. These results indicate a complicated interplay between the development of leaves, premature leaf senescence, and the pathogen-induced stress responses in SCV phytoplasma-infected sweet cherry trees. The results of this study provide insight into understanding the underlying molecular mechanisms driving the formation of little leaves and interactions between plants and pathogens. The findings might help control phytoplasma diseases in sweet cherry cultivation.

Cathranthus roseus also known as periwinkle, an ornamental plant contains several medicinal values, was found with the symptoms of little leaf and witches' broom at Shahjahanpur location with the incidence of up to 8%. The phytoplasma etiology was confirmed through scanning electron microscopy examination in all the four-leaf samples. Molecular analysis through PCR with universal primer pairs P1/P6 followed by nested PCR with R16F2n/R16r2 primers yielded ~1.2kbp amplicons in all the four symptomatic leaf samples. One amplicon was eluted, purified, sequenced, and used in BLASTn searches, which showed maximum identity of periwinkle isolate with several isolates of 16SrIX group of phytoplasma. Further, phylogenic analysis and in silico RFLP confirmed the association of 16SrIX-C subgroup phytoplasma in little leaf and witches broom plants which is the first report from India. [ABSTRACT FROM AUTHOR]

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Aim of study: The application of pre-trained deep learning models, AlexNet and VGG16, for classification of five diseases (Epilachna beetle infestation, little leaf, Cercospora leaf spot, two-spotted spider mite and Tobacco Mosaic Virus (TMV)) and a healthy plant in Solanum melongena (brinjal in Asia, eggplant in USA and aubergine in UK) with images acquired from smartphones. Area of study: Images were acquired from fields located at Alangudi (Pudukkottai district), Tirumalaisamudram and Pillayarpatti (Thanjavur district) – Tamil Nadu, India. Material and methods: Most of earlier studies have been carried out with images of isolated leaf samples, whereas in this work the whole or part of the plant images were utilized for the dataset creation. Augmentation techniques were applied to the manually segmented images for increasing the dataset size. The classification capability of deep learning models was analysed before and after augmentation. A fully connected layer was added to the architecture and evaluated for its performance. Main results: The modified architecture of VGG16 trained with the augmented dataset resulted in an average validation accuracy of 96.7%. Despite the best accuracy, all the models were tested with sample images from the field and the modified VGG16 resulted in an accuracy of 93.33%. Research highlights: The findings provide a guidance for possible factors to be considered in future research relevant to the dataset creation and methodology for efficient prediction using deep learning models.

Abstract: A large‐scale survey was conducted on pistachio plants exhibiting foliar symptoms including scorch, little leaf, yellows and reddish in pistachio growing areas in the Qom, Yazd and Qazvin provinces of Iran. Total DNA was extracted from symptomatic and symptomless pistachio and used in nested PCR assays with phytoplasma universal primers. Nested PCR products were obtained for symptomatic plant samples while the symptomless plants yielded no PCR products. Virtual restriction fragment length polymorphism, phylogenetic and DNA homology analyses of partial 16S ribosomal sequences of phytoplasma strains associated with symptomatic plants revealed the presence of phytoplasmas referable to two ribosomal groups; in particular, “Candidatus Phytoplasma solani” and “Ca. P. phoenicium” were identified. The presence of these phytoplasmas in pistachio is of great phytosanitary significance due to its commercial interest. [ABSTRACT FROM AUTHOR]

During 2012–2014 surveys for the presence of phytoplasma diseases in Fars province (Iran), pomegranate little leaf symptoms were observed in several orchards in Khafr and Neyriz areas. Samples collected from symptomatic plants positively reacted in nested PCR assays using P1/P7 followed by R16F2n/R16R2 primer pairs producing the expected 1,250 bp DNA fragments. Real and virtual RFLP analysis showed that the sequences of phytoplasma strains from Khafr and Neyriz (KPLL and NPLL strains, respectively) were identical to each other and belong to 16SrII phytoplasma group, subgroup D. Phylogenetic analysis of the R16F2n⁄R16R2 DNA region confirmed that KPLL and NPLL phytoplasmas were enclosed in the same clade as other 16SrII-D subgroup phytoplasmas. This is the first reported occurrence of a 16SrII phytoplasma infecting pomegranate trees. [ABSTRACT FROM AUTHOR]

Symptomatological and histopathological studies of phytoplsama on Ocimum gratissimum L. and Petunia species, growing in Patanjali campus, Haridwar, Uttarakhand were recorded. O. gratissimum L. showed symptoms as little leaf and witches' broom while Petunia sp. showed yellowing of leaves, witches' broom and stunting of stem. Phloem necrosis was also reported in infected plants of both genera. [ABSTRACT FROM AUTHOR]

A recombinant inbred line (RIL) population derived from two cultivated cucumber (Cucumis sativus var. sativus L., 2n = 2x = 14) lines, Gy7 (synonym G421) and H-19, was previously used to map yield and fruit quality components. However, the map consisted mainly of dominant markers (i.e., random amplified polymorphic DNAs or amplified fragment length polymorphisms) limiting its use in plant improvement and map-based gene cloning. We report here a moderately saturated genetic map derived from this RIL population that incorporates codominant microsatellite [simple sequence repeat (SSR)] markers and two architectural traits, little leaf (ll) and determinate (de), growth habit. Of 821 cucumber genomic SSR primer pairs evaluated for map construction, 140 (17.0%) were polymorphic between the mapping parents. In combination with 42 previously mapped sequence characterized amplified region (SCAR) and SSR makers, these polymorphic markers were used to construct a linkage map with 46 RILs and 176 mapped loci spanning ≈400 cM across seven linkage groups (LG). The numbers of loci mapped on LG 1 through 7 were 11, 6, 35, 18, 46, 45, and 15, respectively. The ll locus was flanked by SSR02355 and SSR03940 (4.2 and 3.6 cM from ll, respectively), and de was flanked by CSWCTT14b and SSR13251 (1.4 and 4.2 cM from the de, respectively). The SSR markers linked with the de and ll genes were mapped to Chromosome 6. No recombination suppression was detected among the mapped loci examined. This Gy7 x H-19 RIL-based genetic map shared 94 marker loci with a previously reported RIL-based linkage map derived from a wide cross between C. sativus var. sativus line Gy14 and C. sativus var. hardwickii Alef. R. PI 183967. Comparative mapping supported previous findings that genomic differences (likely chromosomal rearrangements) exist between Gy14 and PI 183967. [ABSTRACT FROM AUTHOR]

In recent years, almond witches’-broom disease has been prevalent in almond growing areas in the centre and south of Iran. Furthermore, almond trees showing different symptoms of phytoplasma diseases such as little leaf, leaf rolling, dieback of branches, rosette and yellowing were observed in the central regions of Iran. DNA isolated from symptomatic almond trees was used to amplify 16S rDNA and 16S-23S rDNA intergenic spacer (IS) fragments by nested polymerase chain reaction (PCR) using phytoplasma universal primer pairs (P1/P7, R16F2/R2, PA2F/R and NPA2F/R). Phytoplasmas were detected in symptomatic almonds in two major almond-growing regions, Isfahan and ChaharMahal-O-Bakhtiari. Restriction fragment length polymorphism analyses of nested PCR products using endonuclease enzymes HpaII and TaqI revealed that phytoplasmas associated with infected almonds are genetically different. Sequence analyses of amplified fragments of 16S rDNA and IS region indicated that the almond phytoplasmas in Iran are closely related to ‘ Candidatus ( Ca.) Phytoplasma aurantifolia’, ‘ Ca. Phytoplasma phoenicium’, ‘ Ca. Phytoplasma solani’ and ‘ Ca. Phytoplasma trifolii’. The phytoplasmas related to ‘ Ca. Phytoplasma aurantifolia’ were more prevalent than other phytoplasmas in the central regions of Iran. [ABSTRACT FROM AUTHOR]

The article presents a study conducted to gain information regarding the diseases affecting bamboos planted in nurseries and plantations in Wayanad, India. During the study, causal agents of disease underwent isolation and there pathogens tested. The study found out that causal agents including Fusarium moniliforme and Botryobasidium salmonicolor caused culm rot and thread blight respectively. The diseases found in bamboos can be eliminated through fungicides and surface burning.

Porocca is a lethal disease of coconut (Cocos nucifera) emerging in Central America. Previously known only from Colombia, it has spread across the Isthmus of Panama in the last decade. Porroca is characterized by the production of stiff, dwarfed leaves, usually followed by the death of the palms within 2 years. We describe the long-distance spread of the disease as determined from regular censuses of more than 200,000 coconut palms in the indigenous Comarca of Kuna Yala and the Republic of Panama. Spread is temporally and spatially variable, with the disease moving across the landscape as much as 40 km per year. Porroca may represent a significant new threat to coconut production in the Caribbean Region. [ABSTRACT FROM AUTHOR]

White clover plants showing little leaf and leaf reddening symptoms were observed in Isfahan Province in central Iran. Restriction fragment length polymorphism analyses of nested PCR-amplified fragments from Iranian clover little leaf phytoplasma isolates and representative phytoplasmas from other phytoplasma groups using Alu I, Cfo I, Kpn I and Rsa I restriction enzymes indicated that the clover phytoplasma isolates are related to the peanut WB group. Sequence analyses of partial 16 S r RNA fragments showed that Iranian clover little leaf phytoplasma has 99% similarity with soybean witches'-broom phytoplasma, a member of the peanut WB (16 Sr II) phytoplasma group. This is the first report of clover infection with a phytoplasma related to the 16 Sr II group. [ABSTRACT FROM AUTHOR]

Sugar beet ( Beta vulgaris L. subsp. vulgaris var. altissima) is a biennial, sugar-producing tuber crop grown in different parts of the world. Diseased sugar beets with symptoms of little leaf were observed during 2008 in Tamil Nadu, India. Phytoplasmas were detected in symptomatic leaves of three separate plants using PCR with primer pair fU5/rU3, which amplify an 880-bp fragment of the 16S rRNA region of phytoplasmas. The nucleotide sequence analysis of a 766-bp fragment had 100% identity among the sequence from the three plants (GQ184437) and 96% nucleotide sequence identity with 16S ribosomal RNA gene sequences of eggplant phyllody phytoplasma. [ABSTRACT FROM AUTHOR]