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Both the biotic and abiotic stressors restrict the yield potential of many crops, including bananas. Bananas belong to the genus Musa and are the world’s most popular and widely produced fruit for their nutritional and industrial importance. The demand for bananas is growing each day worldwide. However, different pest infestations are hampering the production of bananas, making it a matter of concern for global food security. Several biotechnological tools and applications including RNA interference (RNAi) have been employed to enhance the biotic stress resistance in plants. The capacity to silence targeted genes at transcriptional and post-transcriptional levels makes the RNAi technique a popular choice for gene knock-down and functional genomics studies in crops. Silencing of different suppressor molecule coding genes through RNAi helps crops to combat the detrimental effects of plant pathogens. The host-induced gene silencing (HIGS) technology, also known as the host-delivered RNAi (HD-RNAi), is nowadays gaining popularity due to its ability to target an array of pathogens, comprising bacteria, nematodes, fungi, viruses, and insects. This methodology is employed to manage disease pest outbreaks in a diverse range of crop species, including bananas. Besides HIGS, virus-induced and spray-induced gene silencing (VIGS and SIGS, respectively) are the potential approaches where RNAi technology is exploited to control plant-pathogenic diseases. The current review emphasizes the different kinds of diseases of bananas and the potential of HD-RNAi, a new-age and promising technology to build a barrier against significant crop and economic loss.

Molecular markers are one of the expandable inventions in agricultural science. After decades of their introduction, these still are an integral part of crop genotyping and crop improvement. The present scenario offers to choose from different molecular marker types based on their principle, methodologies and extent of applications. Several markers have been used to identify and map abiotic stress related genes and quantitative trait loci (QTL) onto the chromosomes of different crops. The genetic mapping of these identified genetic elements by using different markers provides the scope of selective breeding in the agricultural crops to tackle abiotic stresses. Moreover, recent progress achieved in genetics, molecular breeding and genomic selection has facilitated a comprehensive understanding of the molecular markers and unlocked new insights into marker-assisted breeding. The advent of new technologies like association mapping (AM) and genome-wide association studies has unveiled the highthroughput application of molecular markers. In this review, a focused representation of the use of different molecular markers in the identification of tolerant crop genotypes and associated genes/QTLs against major abiotic stresses, including salinity, drought and temperature has been provided. Additionally, the application of molecular markers in AM and AM-based breeding of some important agricultural crops has been discussed.

BACKGROUND Use of RNA interference (RNAi) technology in effective pest management has been explored for decades. Henosepilachna vigintioctopunctata is a major solanaceous crop pest in Asia. In this study, the effects of the RNAi-mediated silencing of clathrin heavy chain in H. vigintioctopunctata were investigated. RESULTS Feeding either the in vitro-synthesized or the bacterially expressed double-stranded RNAs (dsRNAs) significantly impaired the normal physiology of H. vigintioctopunctata instars and adults. However, the bacterially expressed dsHvChc caused higher mortality than the in vitro-synthesized ones in the larvae and adults. Moreover, on evaluating the potential risk of dsHvChc on Propylea japonica, significant transcriptional effects of dsHvChc1 were observed, while the organismal level effects were not significant. On the contrary, dsHvChc2 did not affect P. japonica at either level. A similar test revealed significant transcriptional effects of dsPjChc1 on H. vigintioctopunctata, while staying ineffective at the organismal levels. Conversely, dsPjChc2 did not affect H. vigintioctopunctata at either level. Importantly, no effect of dsPjChc1 exposure on H. vigintioctopunctata suggested that other factors besides the 21-nucleotide (nt) matches between sequences were responsible. Finally, ingestion of dsHvmChc1 derived from H. vigintioctomaculata, containing 265-nt matches with dsHvChc1, caused 100% mortality in H. vigintioctopunctata. CONCLUSIONS We conclude that (i) species with numerous 21-nt matches in homologous genes are more likely to be susceptible to dsRNA; (ii) dsRNA can be safely designed to avoid negative effects on non-target organisms at both transcriptional and organismal levels; (iii) HvChc can be used as an efficient RNAi target gene to effectively manage H. vigintioctopunctata.

The GATA transcription factors (TFs) play a crucial role in regulating various physiological processes in plants. Identification and characterization of the GATA TF family has been carried out in several important grass species, including rice, maize, and bamboo. However, no information is available on the GATA TFs in the C3 grass species Dichanthelium oligosanthes. In the current study, 31 GATA genes have been identified in the D. oligosanthes genome by stringent bioinformatics analysis. The exon-intron arrangement analysis of the DoGATAs via the Gene Structure Display Server (GSDS 2.0) revealed the redundancy and differences in their gene structural organization. In addition, the sequence comparisons within the DoGATAs via BLAST revealed 11 numbers of putative paralogs. Similarly, the BLAST comparisons among the OsGATAs and DoGATAs resulted in the identification of 21 orthologs. Structural analysis of the identified DoGATAs through Simple Modular Architecture Research Tool (SMART), Conserved Domain Database (CDD), and Multiple Expectation Maximization for Motif Elicitation (MEME) revealed that all of them possess the signature GATA domain and the C-X2-C-X18-C-X2-C consensus sequence. The phylogenetic analysis via MEGA divided the DoGATAs into four groups along with rice and Arabidopsis GATAs. In addition, the subcellular localization, gene ontology, and other peptide functional prediction results further supported the DoGATAs to be putative GATA genes. Moreover, the findings of this study can serve as a basic framework for the isolation and functional characterization of GATA genes in D. oligosanthes.

Tyrosine hydroxylase (TH), a melanin synthesis pathway enzyme hydroxylating tyrosine into 3,4-dihydroxyphenylalanine, is involved in the pigmentation and sclerotization of insect cuticles. However, the role of TH in 28-spotted potato ladybeetle (Henosepilachna vigintioctopunctata), an emerging pest of the solanaceous crops has been explored to a limited extent. In this study, we integrated dietary RNA interference (RNAi) and hematoxylin and eosin (HE) staining with various bioassays to analyze the role of tyrosine hydroxylase (HvTH) throughout the developmental processes of Henosepilachna vigintioctopunctata.The results revealed that ingestion of dsHvTH led to cuticle tanning impairment, arrested larval feeding in the first and second instars of Henosepilachna vigintioctopunctata, and subsequently resulted in 100% mortality. The HE staining assays revealed that dsHvTH prevented new abdominal cuticle formation. A pharmacological study using 3-iodo-tyrosine (3-IT), a HvTH inhibitor, disrupted larval-larval-pupal cuticle tanning during the third-fourth instar larval development and eventually failed to pupate. Similarly, dsHvTH fed to fourth instars hindered larval-pupal-adult cuticle tanning, and the eclose adults were 100% malformed. Ingestion of dsHvTH or 3-IT significantly down-regulated HvTH, HvDDC, Hvebony, and Hvlaccase2 expression and reduced dopamine levels. Finally, HvTH silencing in adult females substantially reduced the offspring hatching rates.The collective results of the study suggested that HvTH plays conserved roles in larval-pupal-adult cuticle melanization and sclerotization while exhibiting a novel function in Henosepilachna vigintioctopunctata reproduction. © 2022 Society of Chemical Industry.

Salinity stress is one of the most devastating abiotic stresses affecting rice growth and productivity. Several phytohormones in rice contribute towards salinity response, including ethylene (ET). Furthermore, priming of rice seedlings with different chemicals has revealed new insights in rice stress physiology. Therefore, the hydroponic culture experiment under completely randomized design (CRD) factorial was conducted to study the effects of seed priming with two contrasting chemicals 1-Methylcyclopropene (1-MCP) and Ethephon with respect to ET production under salinity stress levels 0 (control, CK) and 25 mM NaCl (salinity stress, SS) on cultivar Zhongzheyou 1 (indica) with five replications. Results revealed that the use of 1-MCP and Ethephon improved overall rice seedling germination and growth as compared to the unprimed one under salinity stress. Early germination rate was found to be higher in the Ethephon primed seedlings. However, the late germination rate, overall seedling vigor index (SVI), total plant dry biomass (higher as 37.8 and 42% in 1-MCP-primed seeds, and 28.1 and 21.3% higher in Ethephon-primed seeds than no primed seeds under both salinity levels), other agronomic traits, and SPAD value were found to be higher in the 1-MCP primed seedlings. Further, the production of reactive oxygen species was comparatively higher in the Ethephon primed seedlings than the 1-MCP-primed seedlings. In addition, evaluation of ET levels and expression profiling (qRT-PCR) of some ET signaling genes revealed that Ethephon priming resulted in elevated ET concentration and upregulated ET signaling genes, including OsACS1 and OsEIN2. Overall, our results provide a basic idea of the role of rice seed priming with Ethephon and 1-MCP under salinity condition and their effects on the ET interplay. Ethylene response of salt stressed rice seedlings following Ethephon and 1-methylcyclopropene seed priming. SG speed of germination, GE germination energy percentage, 3rd and 6th DAS 3rd and 6th day after sowing, FG final germination.

The striped flea beetle (SFB, Phyllotreta striolata) is an important pest of the cruciferous crops in Asia. SFB is regarded as the most destructive pest of cruciferous crops in China due to the severe crop loss and frequent infestation incidents. As no SFB resistant cultivar is available at present, therefore, application of insecticides is the primary method of SFB control. On the contrary, the exploitation of chemical insecticides causes severe environmental issues and is not cost-effective. The use of a seed-pelletized coating of spinetoram effectively reduced SFB feedings on the flowering cabbage seedlings, whereas in combination with the insect-proof net, it controlled the SFB infestation throughout the cabbage growth period. The analysis of the pesticide residues in soil and different cabbage parts indicated the degradation dynamics of spinetoram. Furthermore, estimation of the half-life of spinetoram revealed that via seed-palletized application spinetoram half-life was found to be 2.82 days in soil, 4.21 days in the root, 5.77 days in the stem, and 3.57 days in the leaf, respectively. Both the lower pesticide residues and the half-life of spinetoram in soil and cabbage parts suggested it to be a promising environment and food-safe pesticide in controlling SFB. Moreover, the seed-pelletized coating ensured a sustainable release of spinetoram that can reduce the pesticide application frequency and be cost-effective and pocket-friendly for the farmers.

Fushi-tarazu factor 1 (FTZF1) is an ecdysone-inducible transcription factor that plays a vital role during the metamorphosis in insects. In this study, we functionally characterized HvFTZ-F1 in H. vigintioctopunctata, a dreadful solanaceous crop pest, by using a dietary RNA interference technique. The HvFTZ-F1 expression levels were elevated in the 1st and 2nd-instars before molting and declined immediately after ecdysis. The HvFTZ-F1 silencing led to high mortality in the 1st instars, while the expression of the osmosis-regulative gene, HvAQPAn.G, was significantly increased in the 1st instars. HvFTZ-F1 silencing downregulated the Halloween and 20E-related genes, decreased the ecdysteroids titer, suppressed the expression of pigmentation-related genes, and reduced the catecholamines titer. In the 4th instars, HvFTZ-F1 silencing caused 100% mortality by arresting the development at the prepupal stage and preventing new abdominal cuticle formation. In the female adults, HvFTZ-F1 silencing caused an evident decrease in fecundity, prolonged the pre-oviposition period, reduced the number of eggs and hatching rate, severely atrophied the ovaries. Moreover, the 20E-related genes and the dopamine synthesis genes were suppressed in the dsHvFTZ-F1-treated females. Overall, our results revealed that HvFTZ-F1 regulates ecdysis, pupation, and reproduction in H. vigintioctopunctata, thereby could be a promising molecular target for the development of RNAi-based biopesticides to control H. vigintioctopunctata.

The Bph1 gene was the first reported brown planthopper (BPH, Nilaparvata lugens) resistance gene in Mudgo rice and was widely used as a commercial cultivar for controlling BPH infestations. However, rapid adaptations of BPH on the Mudgo rice resulted in its resistance breakdown and the emergence of virulent BPH populations. Thus, specific BPH populations and rice varieties can serve as good model systems for studying the roles of different bio-compounds and proteins in the insect-plant interactions. Although our understandings have been improved on the complexity of BPH and rice interactions, the underlying molecular mechanisms remain largely unknown. Here we analyzed the feeding performances and the transcriptomic responses of two BPH populations (Mugdo-BPH and TN1-BPH) during compatible (Mudog-BPH feeding on Mudgo rice) and incompatible (TN1-BPH feeding on Mudgo rice) interactions. The electrical penetration graph (EPG) results indicated that the BPH feeding and performances during the incompatible interaction are significantly affected in terms of decreased honeydew, loss of weight, decreased phloem sap ingestion (N4 waveform), but increased non-penetration (NP waveform) phase. Abundance of glucose and trehalose was reduced in BPH during the incompatible interaction. Transcriptomic surveys of insects in both interactions revealed that genes involved in cuticle formation, detoxification, metabolite transport, digestion, RNA processing, lipid or fatty acid metabolism, and proteolysis were significantly down-regulated during the incompatible interaction, whereas genes involved in insulin signaling were significantly upregulated. Knockdown of four genes, including the sugar transporter NlST45, the serine and arginine-rich protein NlSRp54, the cytochrome P450 gene NlCYP6AY1, and the cuticle protein NlCPR70 through RNA-interference revealed thess genes are important for BPH survival. Overall, the results of this study will be helpful for the future researches on BPH virulence shifts.

Rice production and sustainability are challenged by its most dreadful pest, the brown planthopper (Nilaparvata lugens Stål, BPH). Therefore, the studies on rice-BPH interactions and their underlying mechanisms are of high interest. The rice ontogenetic defense, such as the role of microRNAs (miRNAs) has mostly been investigated against the pathogens, with only a few reports existing against the insect infestations. Thus, revealing the involvement of rice miRNAs in response to BPH infestations will be beneficial in understanding these complex interactions. In this study, the small RNA profiling of the IR56 rice in response to separate BPH infestations of varied virulence levels identified the BPH-responsive miRNAs and revealed the differential transcript abundance of several miRNAs during a compatible and incompatible rice-BPH interaction. The miRNA sequence analysis identified 218 known and 28 novel miRNAs distributed in 54 miRNA families. Additionally, 138 and 140 numbers of differentially expressed (DE) miRNAs were identified during the compatible and incompatible interaction, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed the target gene candidates of DE miRNAs (including osa-miR2871a-3p, osa-miR172a, osa-miR166a-5p, osa-miR2120, and osa-miR1859) that might be involved in the IR56 rice defense responses against BPH infestation. Conversely, osa-miR530-5p, osa-miR812s, osa-miR2118g, osa-miR156l-5p, osa-miR435 and two of the novel miRNAs, including novel_16 and novel_52 might negatively modulate the IR56 rice defense. The expressional validation of the selected miRNAs and their targets further supported the IR56 rice defense regulatory network. Based on our results, we have proposed a conceptual model depicting the miRNA defense regulatory network in the IR56 rice against BPH infestation. The findings from the study add further insights into the molecular mechanisms of rice-BPH interactions and will be helpful for the future researches.

In the current scenario of global climate change, the utmost desire to ensure food security is to maintain and increase agricultural production. But, due to rapid climate change, many abiotic factors such as rainfall, drought, flooding, temperature and solar radiations are severely affecting the production of rice at various growth stages. It is predicted that almost 51% of rice cultivation and production would be reduced during the next century due to global climate change. However, agriculture activities are also contributing to global warming by 10–14% of total global greenhouse gas emissions and 18% of the total methane is emitted from paddy rice fields. Therefore, mitigating and adaptation strategies such as alternate wetting and drying, inter cropping with short term vegetation, limiting chemical fertilizers by precise farming, usage of rice cultivars with low methane emission, improved tillage, recycling of farm waste into organic fertilizers, and by developing integrated rice farming system, are needed to hinder greenhouse gas emissions from rice fields. Furthermore, strategies are required to cope with effects of climate change on rice production by application of anaerobic methanotrops to oxidize the CH4, and the development of high-yielding and abiotic stresses-tolerant (temperature, drought) and resistance rice cultivars by using different new breeding, genetic engineering and genomic tools. Besides that, other management options such as development of weather-proofed farm equipment, shifting of planting and adjustments in cropping dates and use of climate forecasting by using remote sensing and modeling can also be used to sought out the climatic issues.

Chitinases are glycoside hydrolase (GH) family of proteins having multifaceted roles in plants. It is of interest to identify and characterize chitinase-encoding genes from the popular bulbous plant onion (Allium cepa L.). We have used the EST sequences for onion chitinases to elucidate its functional features using sequence, structure and functional analysis. These contigs belong to the GH19 chitinases family according to domain architecture analysis. They have highly conserved chitinase motifs including motifs exclusive to plant chitinases as implied using the MEME based structural characterization. Estimation of biochemical properties suggested that these proteins have features to form stable and hydrophilic proteins capable of localizing extracellular and in vacuoles. Further, they have multiple cellular processes including defense role as inferred by DeepGO function prediction. Phylogenetic analysis grouped them as class I and class VII plant chitinase, with possible abundance of class I chitinase in onion. These observations help in the isolation and functional validation of onion chitinases.

Auxins (IAA) and cytokinins (CKs) are the most influential phytohormones, having multifaceted roles in plants. They are key regulators of plant growth and developmental processes. Additionally, their interplay exerts tight control on plant development and differentiation. Although several reviews have been published detailing the auxin-cytokinin interplay in controlling root growth and differentiation, their roles in the shoot, particularly in leaf morphogenesis are largely unexplored. Recent reports have provided new insights on the roles of these two hormones and their interplay on leaf growth and development. In this review, we focus on the effect of auxins, CKs, and their interactions in regulating leaf morphogenesis. Additionally, the regulatory effects of the auxins and CKs interplay on the phyllotaxy of plants are discussed.

Anthracnose disease caused by Colletotrichum truncatum is a major economic constraint to chilli production in the tropical and subtropical regions of the world including India. To understand the molecular mechanisms of defense against anthracnose, we used a differential chilli-C. truncatum system consisting of two cultivars of chilli (Susceptible; Teja Jhal, TJ and resistant; Bhut Jolokia, BJ) and a highly virulent C. truncatum isolate to evaluate the temporal expression of seventeen defense-related genes associated with multiple defense signaling pathways. Quantitative real time PCR demonstrated rapid induction and significant accumulation of jasmonic acid (JA) and ethylene (ET) responsive genes such as plant defensin 1.2, Lypoxygenase 3, Allene oxide synthase and ACC synthase 2 in the resistant cultivar post treatment with C. truncatum. Significant induction of these genes was also realized upon exogenous treatment with JA and ET. The salicylic acid (SA) responsive phenylalanine ammonia-lyase 2 gene was upregulated only under incompatible interaction. Further, the transcript levels of pathogenesis related proteins PR2 and PR5 was significantly higher in the resistant genotype whereas PR1 and PR3 were moderately responsive. In addition, the expression of defense responsive transcription factors increased gradually in the resistant cultivar and remained significantly higher at 9 dpi as opposed to the susceptible one. Combined result analyses revealed that chilli adopts multiple defense strategies in mediating defence responses against the C. truncatum infection. Overall, this work represents a valuable resource for future functional genomics experiments to unravel the molecular mechanisms of host resistance and pathogen virulence in the agriculturally important chilli-C. truncatum pathosystem.

The rhizome soft rot caused by the necrotrophic oomycete, Pythium aphanidermatum is a serious constraint to turmeric ( Curcuma longa L.) production worldwide. The molecular mechanisms underlying the pathological response of turmeric to P. aphanidermatum are not fully understood. In the present study, we performed a deep transcriptome profiling of a resistant turmeric genotype (Cl210-27) post inoculation with P. aphanidermatum . De novo assembly of 146 million clean RNA-Seq reads resulted in 55,014 contigs with length >200 bp. Of these, 34,185 (62.14%) contigs showed significant similarity to the protein sequences from the non-redundant (nr) protein database. 2978 contigs were identified as differentially expressed between infected and mock samples, 2231 of which were up-regulated and 747 were down-regulated. Functional annotation revealed high enrichment of transcripts associated with plant-pathogen interaction, defense signalling and plant secondary metabolism. Rapid induction of pathogen responsive genes encoding NBS-LRRs, glucanases, peroxidases, receptor kinases as well as those associated with jasmonate and ethylene signalling suggest that C. longa adopts multiple strategies to defend against pathogen attack. Further, the identification of multiple miRNA targets confirms the critical involvement of post-transcriptional gene silencing mechanisms in regulating resistance response in C. longa . Overall, the present study represents a comprehensive picture of genes associated with rhizome rot resistance and represents a valuable resource for future functional genomics studies to unravel the molecular mechanisms of C. longa-P. aphanidermatum interaction.

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules that transduce the externally perceived signals and play crucial role in plant defense against pathogen attack. In the present study, a turmeric (Curcuma longa L.) complementary DNA (cDNA) encoding a MAPK gene responsive to Pythium aphanidermatum infection was isolated using rapid amplification of cDNA ends (RACE)-PCR. It was designated as ClMPK6 based on its high homology with Arabidopsis AtMPK6. The full-length cDNA of 1484 bp length carried an open reading frame (ORF) of 1176 bp encoding a 391 amino acid polypeptide. ClMPK6 protein contains Thr-Glu-Tyr (TEY) motif on its activation loop with a common docking (CD) domain at the C-terminal end and belong to subgroup A of MAPK family. Southern hybridization revealed single copy of ClMPK6 in turmeric genome, and its intron-exon composition showed highly conserved nature of these signaling kinases across different species. Quantitative RT-PCR showed high expression of ClMPK6 in rhizome tissues of mature turmeric plants. Analysis of temporal expression revealed significant induction of ClMPK6 transcript in response to defense signaling molecules and pathogen attack at the early stages. Ectopic overexpression of ClMPK6 in Arabidopsis plants resulted in enhanced resistance to Botrytis cinerea and constitutively high expression of defense responsive genes like PDF1.2, PAD3, AOS, ACS2, ACS6, etc. Our results suggest that ClMPK6 substantiate the characteristics of AtMPK6 orthologs in defense against necrotrophic infection in plants.

The conserved mitogen-activated protein kinase (MAPK) cascades play vital roles in plant defense responses against pathogens and insects. In the current study, the expression profiles of 17 OsMPKs were determined in the TN1 and IR56 rice varieties under the infestation of brown planthopper (BPH), one of the most destructive hemimetabolous rice pests. The virulent IR56 BPH population (IR56-BPH) and the avirulent TN1 BPH population (TN-BPH) were used to reveal the roles of OsMPKs in the compatible (IR56-BPH infested on the TN1 and IR56 rice varieties, and TN1-BPH infested on the TN1 rice variety) and the incompatible (TN1-BPH infested on the IR56 rice variety) interaction. The statistical analysis revealed that rice variety, BPH population type, and infestation period have significant effects on the transcription of OsMPKs. Out of these genes, five OsMPKs (OsMPK1, OsMPK3, OsMPK7, OsMPK14, and OsMPK16) were found to exhibit upregulated expression only during incompatible interaction. Six OsMPKs (OsMPK4, OsMPK5, OsMPK8, OsMPK9, OsMPK12, and OsMPK13) were associated with both incompatible and compatible interactions. The transcription analysis of salicylic acid, jasmonic acid, and ethylene phytohormone signaling genes revealed their roles during the rice–BPH interactions. The upregulated expression of OsC4H, OsCHS, and OsCHI in the incompatible interaction implied the potential defense regulatory roles of phenylpropanoids. In both varieties, the elevated transcript accumulations of OsGST and OsSOD, and the increased enzyme activities of POD, SOD, and GST at 1 day post-infestation (dpi), but not at 3 dpi, indicated that reactive oxygen species (ROS) signaling might be an early event in rice–BPH interactions. Furthermore, upregulated transcription of OsLecRK3 and OsLecRK4 was found only during an incompatible interaction, suggesting their involvement in the BPH resistance response in the IR56 rice variety. Lastly, based on the findings of this study, we have proposed a model of interactions of IR56 rice with TN1-BPH and IR56-BPH that depicts the resistance and susceptibility reactions, respectively.

Purple blotch (PB), caused by Alternaria porri (Ellis) Cifferi is the most devastating foliar disease of onion worldwide. However, no attempt has been made so far to detect or map a PB-resistant locus in the onion genome. The present investigation was performed to study the inheritance and develop molecular markers linked to PB resistance by using F1, F2, and BC1 populations developed from a cross between the PB-resistant onion cultivar ‘Arka Kalyan’ and the susceptible parent ‘Agrifound Rose’. Disease evaluation with a virulent isolate of A. porri revealed that the F1 was resistant while 498 F2 plants segregated in a 3:1 resistant (R) to susceptible (S) phenotypic ratio and 128 BC1 lines segregated in 1R:1S ratio, suggesting that the PB resistance is controlled by a single dominant gene designated as ApR1. Out of 288 ISSRs and SSRs primer sets, 59 distinguished the two parental lines and were used in bulk segregant analysis to link them with the presumed ApR1 gene. Seven markers viz. 3 ISSRs (AcISSR471257, AcISSR681600, and AcISSR1031416) and four SSRs (AcSSR7, AcSSR22, AcSSR31, and AcSSR33) showed specific polymorphism between resistant and susceptible bulks and were used for genotyping F2 and BC1 mapping populations. The three ISSR fragments were converted into sequence-tagged markers, and southern blotting confirmed their association with the resistant locus and the single-copy status. Molecular mapping revealed that the SSR marker AcSSR7 and STS marker ApR-450 were closely linked to the ApR1 locus in coupling at distances of 1.3 and 1.1 cM, respectively. Further, both of these markers could not be amplified in 23 susceptible onion genotypes with different genetic backgrounds. This is the first report of identification of markers linked to PB-resistant locus in onion. Hence, SSR marker AcSSR7 and STS marker ApR-450 identified in this study could be recommended for facilitating the introgression of ApR1 into susceptible onion variants for the development of high yielding PB-resistant genotypes.

Pathogenesis-related protein-5 (PR5) is encoded by a complex group of gene family that are involved in host defense against biotic and abiotic stresses as well as regulation of physiological processes in a wide range of plants and animals. In the present study, we isolated and characterized a PR5 gene, designated as AsPR5, induced in response to Fusarium oxysporum f. sp. cepae (FOC) infection in garlic (Allium sativum). AsPR5 cDNA encoded a protein of 223 amino acids including a 22 amino acid signal peptide at the N-terminus suggesting that it is an apoplast secreted acidic protein. AsPR5 protein contains 16 conserved cysteine residues and five additional conserved amino acids- an arginine, a glutamic acid and three aspartic acids related with antifungal activity of most plant thaumatin like proteins. Semi-quantitative RT-PCR showed that the transcript levels of AsPR5 was higher in stem tissues, the primary site of FOC infection, followed by leaves, roots and flowers. Temporal expression analysis using qPCR revealed high expression of AsPR5 upon infection with FOC as well as various phytohormones (JA, ET and ABA) and stress stimuli (wounding, high temperature and salinity) indicating its involvement in both biotic and abiotic stresses. Analyses of purified recombinant protein against different fungal pathogens showed improved antifungal activity compared to other reported PR5 proteins. Furthermore, the Arabidopsis plants ectopically expressing AsPR5 showed enhanced resistance to fungal pathogen, Botrytis cinerea and constitutively higher expression of defense responsive genes such as Lox3, PDF1.2, PAD3, AOS, and AOC. These results suggest that, besides antifungal activities against the necrotrophs, AsPR5 also play significant role in activating multiple defense pathways for enhancing stress resistance in crop plants.