Black Pepper Varieties Research Articles

Biochemical defence reactions of black pepper varieties against Colletotrichum gloeosporioides incitant of anthracnose disease

Anthracnose caused by Colletotrichum gloeosporioides in Black pepper is a severe disease that causes even up to 100 percent crop losses under epidemic conditions. Most of the cultivated varieties of black pepper are highly susceptible to the disease, especially Panniyur 1, the most predominant variety grown in the country. Our study tested 11 black pepper genotypes for their biochemical defense reaction to anthracnose disease. Field observations were initially recorded for two consecutive years in alternate germplasm sites, and the disease incidence ranged between 4.00 and 21.33. The disease incidence under glasshouse conditions upon challenge inoculation was minimal for the variety IISR Girimunda. Upon inoculation with C. gloeosporioides, resistant cultivars exhibited significantly higher activity levels of antioxidant enzymes such as peroxidase, polyphenol oxidase, catalase, phenylalanine ammonia-lyase, and superoxide dismutase compared to local check and uninoculated control plants. This suggests that the variety IISR Girimunda’s resistance to anthracnose may be attributed to its possession of robust biochemical defense molecules.

Influence of weather parameters on Anthracnose in black pepper (Piper nigrum L.) in the upper Brahmaputra valley zone of Assam

Black pepper (Piper nigrum L.) production faces several challenges due to various diseases, with anthracnose being the most significant. It is caused by Colletotrichum gloeosporioides (Penz.) Penz. and Sacc., a fungal plant pathogen that leads to severe infections in black pepper plants, both in nurseries and in the field. The occurrence of anthracnose disease is highly influenced by weather conditions. Epidemiological studies were conducted at Assam Agricultural University, Jorhat, Assam from 2019 to 2021 to determine the impact of weather factors such as temperature, rainfall, rainy days, and relative humidity on anthracnose incidence in seven different black pepper varieties. Upon analyzing the recorded data, it was found that rainfall, minimum temperature, rainy days, and morning relative humidity are the most significant contributors to disease occurrence. However, the role of maximum temperature, evening relative humidity, and bright sunshine hours was statistically non-significant. Data from 2019 and 2020 were further analyzed using stepwise multiple regression to estimate anthracnose incidence in individual black pepper varieties. These regression models were subsequently validated using data of 2021. The root mean square error values varied between 0.0001 and 0.0011, indicating that the models are acceptable.

Selection of stable housekeeping genes for gene expression studies in different varieties of black pepper (Piper nigrum L.)

Real Time quantitative PCR (RT-qPCR) is a widely used technique to study the transcript level modulation of genes during developmental stages of crop plants as well as in stress responses. Suitable reference genes have not been validated in many plants including black pepper. In this study, expression stability of six commonly used housekeeping genes viz., actin, ?-tubulin, elongation factor, initiation factor, ubiquitin and glyceraldehyde 3- phosphate dehydrogenase were evaluated by RT-qPCR during the growth of the black pepper inflorescence of varieties viz., Panniyur 1, Karimunda and Thekken. The results were analyzed using geNorm and Normfinder statistical algorithms. Stable reference gene is critical for the accurate normalization of target gene data in RT-qPCR. In this study actin, elongation factor and initiation factor were identified as the most stable housekeeping gene in different black pepper varieties viz., Thekken, Panniyur 1 and Karimunda respectively. Actin in combination with GAPDH and elongation factor were obtained as optimal reference genes for Thekken. It is the first report on identification of stable housekeeping gene in different varieties of black pepper and can aid in expression studies in black pepper for yield improvement. The study will aid in normalization of gene expression studies in different varieties of black pepper.

Physical Properties of Black Pepper for designing a Robotic Black Pepper Harvester

Agricultural robots were designed based on the characteristics of the target crop. In this study, two varieties of black pepper including Kaimunda and Panniyur 1 were evaluated for physical parameters to design a robotic black pepper harvester. The main objective of this study was to measure and analyze the physical properties of black pepper to design the robotic pepper harvester. In this regard, studies were conducted for pepper spike, pepper peduncle, pepper berry, and pepper vine separately. The results showed that the average length and diameter of pepper spikes of Karimunda and Panniyur 1 respectively as 10.4 cm and 1.10 cm; and 12.8 cm and 1.30 cm. In an average the tested peppers have a berry diameter of 0.42 cm and RGB value of (20, 39, 3) - (255, 224, 111) for Karimunda variety and 0.59 cm and (35, 54, 10) - (255, 240, 100) for Panniyur 1 variety. Based on the shear strength analysis, at a cutting speed of 0.1 mm s -1, the average shear strength of the peduncle was obtained as 1718.6 N mm-2 for Karimunda and 1671 N mm -2 for Panniyur 1. And at cutting speed 1 mm s-1, the average shear strength peduncle of Karimunda and Panniyur 1 respectively is 1535 N mm-2 and 1544 N mm-2. The average length of the peduncle of Karimunda and Panniyur 1 respectively as 1.2 cm and 1.3 cm, and the diameter of both varieties was 0.17 cm. The maximum leaf coverage of the pepper vine ranges from 10 to 91, and the 95th percentile of the data was 76 cm.

Genome-wide identification and characterization of tissue-specific non-coding RNAs in black pepper (Piper nigrum L.).

Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) are the two classes of non-coding RNAs (ncRNAs) present predominantly in plant cells and have various gene regulatory functions at pre- and post-transcriptional levels. Previously deemed as "junk", these ncRNAs have now been reported to be an important player in gene expression regulation, especially in stress conditions in many plant species. Black pepper, scientifically known as Piper nigrum L., despite being one of the most economically important spice crops, lacks studies related to these ncRNAs. From a panel of 53 RNA-Seq datasets of black pepper from six tissues, namely, flower, fruit, leaf, panicle, root, and stem of six black pepper cultivars, covering eight BioProjects across four countries, we identified and characterized a total of 6406 lncRNAs. Further downstream analysis inferred that these lncRNAs regulated 781 black pepper genes/gene products via miRNA-lncRNA-mRNA network interactions, thus working as competitive endogenous RNAs (ceRNAs). The interactions may be various mechanisms like miRNA-mediated gene silencing or lncRNAs acting as endogenous target mimics (eTMs) of the miRNAs. A total of 35 lncRNAs were also identified to be potential precursors of 94 miRNAs after being acted upon by endonucleases like Drosha and Dicer. Tissue-wise transcriptome analysis revealed 4621 circRNAs. Further, miRNA-circRNA-mRNA network analysis showed 432 circRNAs combining with 619 miRNAs and competing for the binding sites on 744 mRNAs in different black pepper tissues. These findings can help researchers to get a better insight to the yield regulation and responses to stress in black pepper in endeavor of higher production and improved breeding programs in black pepper varieties.

An Effective Inoculation Method for Phytophthora capsici on Black Pepper Plants.

Piper nigrum L. (black pepper) is a typical woody vine that is an economically important spice crop across the world. Black pepper production is significantly impacted by root rot disease caused by Phytophthora capsici, which has seriously influenced the industry development as a "choke point" problem. However, the molecular genetic mechanism of resistance in black pepper is unclear, leading to slow progress in the development of new black pepper varieties. An effective inoculation and precise sampling system for Phytophthora capsici on black pepper plants is essential for studying this plant-pathogen interaction. The main aim of this study is to demonstrate a detailed methodology where the basal head of black pepper is inoculated with Phytophthora capsici, while also providing a reference for the inoculation of woody vine plants. The basal head of the black pepper plant was pinpricked to damage it, and mycelial pellets covered the three holes to retain the moisture so the pathogen could infect the plant well. This method provides a better way of solving the instability that is caused by traditional inoculation methods including soil drench or root dipping. It also provides a promising means for studying the mode of action between plants and other soil-borne plant pathogens in agricultural precision breeding.

Screening of black pepper varieties against anthracnose under nursery conditions

Pathogen causing anthracnose of black pepper was isolated from symptomatic leaf sample and was identified as Colletotrichum gloeosporioides on the basis of morphological, cultural and molecular characterization. Later, pot culture experiment was conducted in greenhouse (year 2020-21) to determine resistance/susceptibility of seven different black pepper varieties viz., Arakkulamunda, Doddigya, Karimunda, Malligesara, Panniyur-1, Poonjarmunda and Uddagare, against anthracnose in nursery condition. It was observed that no variety was resistant but Karimunda variety was found to be highly tolerant against the disease. Whereas, Poonjarmunda and Panniyur-1 were classified as susceptible and highly susceptible, respectively.

Performance of black pepper varieties as intercrop in coconut gardens in the lower Brahmaputra valley of Assam state, India

Black pepper (Piper nigrum) is well habituated as an inter/under/mixed crop in plantation crops. A field experiment was conducted at Horticultural Research Station (AICRP on Palms), Kahikuchi of Assam Agricultural University for 12 consecutive years (2009-2021) for studying the performance of black pepper varieties/hybrids when grown as intercrop in 38 year old Assam Green Tall. Panniyur-1 produced a higher number of laterals with more spread compared to other varieties. Similarly, a significantly higher number of spikes (134.0), spike length (15.0 cm) and number of berries per spike (82.0) were also recorded in Panniyur-1. Sreekara recorded the lowest spike length (9.8 cm), while IISR Malabar Excel recorded the lowest number of spikes (85.0). Six-year mean dry berry yield indicated that the yield was significantly higher with Panniyur-1 (1.60 kg vine-1) followed by Sreekara (1.49 kg vine-1) and average yield of 1.00 kg vine-1 recorded in IISR Malabar Excel, IISR Thevam and IISR Shakthi. The oleoresin content (11.7%) and piperine content (5.2%) was found highest in Panniyur-1, followed by Sreekara (10.9 % and 4.5%) whereas, the lowest oleoresin content (8.8%) and piperine content (2.9%) were recorded in IISR Malabar Excel and IISR Thevam, respectively. Intercropping of black pepper in coconut garden recorded the highest net return (` 237088 ha-1) and B: C ratio (3.48) followed by Sreekara (` 212764 ha-1; B: C ratio 3.12) and the lowest net return (` 177938 ha-1) and B: C ratio (2.61) were obtained in IISR Malabar Excel.

Response of black pepper varieties for propagation by serpentine layering

In the present study response of light black pepper verities for propagation through serpentine layering was studied. Verities showed significant variations with respect to growth attributing parameters, survivability and numbers of layers per year. Maximum survivability (93.00 % and 88.33 %) at 30 and 90 days after cutting was found in Panniyur-1. Maximum planting material production per year was achieved in Panniyur-1 (51.17) which was higher than the rest of the varieties but was statistically at par with Panniyur-2 (50.50) and Pournami (50.17). These three varieties may be considered for higher production of planting materials through serpentine layering method.

Peroxidase activity as a marker to evaluate resistance in Black pepper against Phytophthora infection

Foot rot caused by Phytophthora capsici/P. tropicalis, is the most deleterious of all diseases affecting black pepper. Conventional pathogen inoculation and response to biochemical parameters such as lignin and peroxidase activity were targeted for locating source of resistance in black pepper. The direct response of infection as phenotypic symptoms and defense response imparted by lignin and peroxidase activity was studied in eight black pepper varieties, namely 04-P24, IISR Shakthi, Sreekara, Panniyur-1, Malabar Excel, Thevam, Panchami, Pournami and four germplasm accessions (7731, 7583, 8041, 8062) that showed differential response to Phytophthora infection. Among the varieties tested, 04-P24 showed no symptoms of infection and found as resistant. The response of lignin and peroxidase activity upon infection showed 04-P24 as having highest peroxidase activity with higher lignin content. Based on consecutive results, it is inferred that increased levels of lignin and peroxidase contributed to development of Phytophthora resistance in black pepper. The study suggests that peroxidase activity can be used as a biochemical marker for screening black pepper plants for Phytophthora resistance.

In silico assisted identification of peppery aroma compound ‘rotundone’ backbone genes from black pepper

Rotundone, an oxygenated sesquiterpene compound, responsible for the peppery aroma. The importance of the rotundone in the flavor industry warrants search for the precursor genes in plants. We report in this study, the first on the identification of rotundone backbone genes viz., α-guaiene synthase & α-guaiene oxidase in black pepper. We identified the precursor genes of rotundone using berry transcriptome profiling. The metabolite profiling using head space mass spectrometry showed the presence of the direct precursor compounds for rotundone biosynthesis in black pepper berries. The identification of the genes & compounds of the guaiene skeleton is expected to help in bioprospecting of black pepper varieties & also in recombinant production of the aroma compound. Communicated by Ramaswamy H. Sarma Identification of rotundone backbone genes & precursor compounds from Piper nigrum

The effect of light intensities on morpho-physiological and biochemical of black pepper (Piper nigrum L.)

The difference in the levels of light intensity was responded with changes in morphophysiological and biochemical characters of plants, especially in leaves of black pepper. The aim of this study was to determine the effect of several levels of light intensity on the morphophysiological and biochemical characters of leaves of black pepper. The research was conducted in July - November 2017 in Kemuja, Mendobarat, Bangka Belitung. This study used split-plot design with three replications. The main plots were the levels of light intensity, namely 100%, 75%, and 50%. Subplots were varieties of black pepper, namely Petaling 1, Petaling 2, and Nyelungkup. The results showed that there was no interaction between varieties and light intensities. The morphophysiological and biochemical responses of the leaves of the three varieties tested were the same at all levels of light intensity. Light intensity up to 50% has no effect on leaf morphological characters, but leaves become thinner at lower light intensities. Chlorophyll, nitrate reductase activity and leaf sucrose concentration were same at all light intensities up to 50%. Plants exposed to higher light intensity have a higher number of stomata. The results concluded that the light intensity of up to 50% did not cause changes in leaf morphology and biochemistry and only affected leaf stomata density.

The growth of three varieties of black pepper (Piper nigrum) under different light intensities related to indigenous hormones role

Abstract. Issukindarsyah, Sulistyaningsih E, Indradewa D, Putra ETS. 2020. The growth of three varieties of black pepper (Piper nigrum) under different light intensities related to indigenous hormones role. Biodiversitas 21: 1778-1785. Low light intensity causes the alteration of plant biochemical and morphological as the mechanism of adaptation. The experiment used split-plot design with three replications. The main plots were three light intensity levels, i.e. 100%, 75%, and 50% radiation; while subplots were three varieties namely Nyelungkup, Petaling 1 and Petaling 2. This research was conducted to figure out the effect of shadings on hormones and the growth of three varieties of black pepper (Piper nigrum L.). The results showed that in initial vegetative growth, varieties of Nyelungkup and Petaling 1 had higher growth of both ortotroph and plagiotroph branches, leaf number, leaf area, length of root, root surface area, plant dry weight, nett assimilation rate, and plant growth rate than the variety of Petaling 2. The light intensity of 50% and 75% increased the auxin and gibberellin contents of the leaf but they did not affect the zeatin. The maximum gibberellin and auxin contents of leaf were recorded at 75% light intensity. The 50% and 75% light intensity raised the length, diameter, and internode of ortotroph branch; number, length, and internode of plagiotroph branch; leaf number; leaf area; leaf area ratio; length of root; root surface area; plant growth rate and plant dry weight related to indigenous hormones role.

Transcriptional Sequencing and Gene Expression Analysis of Various Genes in Fruit Development of Three Different Black Pepper (Piper nigrum L.) Varieties.

Black pepper (Piper nigrum) is a vital spice crop with uses ranging from culinary to pharmacological applications. However, limited genetic information has constrained the understanding of the molecular regulation of flower and fruit development in black pepper. In this study, a comparison among three different black pepper varieties, Semengok Aman (SA), Kuching (KC), and Semengok 1 (S1), with varying fruit characteristics was used to provide insight on the genetic regulation of flower and fruit development. Next-generation sequencing (NGS) technology was used to determine the flower and fruit transcriptomes by sequencing on an Illumina HiSeq 2500 platform followed by de novo assembly using SOAPdenovo-Trans. The high-quality assembly of 66,906 of unigenes included 64.4% of gene sequences (43,115) with similarity to one or more protein sequences from the GenBank database. Annotation with Blast2Go assigned 37,377 genes to one or more Gene Ontology terms. Of these genes, 5,874 genes were further associated with the biological pathways recorded in the KEGG database. Comparison of flower and fruit transcriptome data from the three different black pepper varieties revealed a large number of DEGs between flower and fruit of the SA variety. Gene Ontology (GO) enrichment analysis further supports functions of DEGs between flower and fruit in the categories of carbohydrate metabolic processes, embryo development, and DNA metabolic processes while the DEGs in fruit relate to biosynthetic process, secondary metabolic process, and catabolic process. The enrichment of DEGs in KEGG pathways was also investigated, and a large number of genes were found to belong to the nucleotide metabolism and carbohydrate metabolism categories. Gene expression profiling of flower formation-related genes reveals that other than regulating the flowering in black pepper, the flowering genes might also be implicated in the fruit development process. Transcriptional analysis of sugar transporter and carbohydrate metabolism genes in different fruit varieties suggested that the carbohydrate metabolism in black pepper fruit is developmentally regulated, and some genes might serve as potential genes for future crop quality improvement. Study on the piperine-related gene expression analysis suggested that lysine-derived products might present in all stages of fruit development, but the transportation was only active at the early stage of fruit development. These results indicate several candidate genes related to the development of flower and fruit in black pepper and provide a resource for future functional analysis and potentially for future crop improvement.

Phyllogenetic of nine superior black pepper (Piper nigrum L.) varieties based on morphological and molecular markers

Understanding genetic relationship among varieties is necessary in crop improvement. The objective of the study was to determine phylogeny of nine black pepper varieties, based on morphology and molecular markers. The results showed that a dendrogram generated from morphological characters, at similairty about 50 %, the pepper varieties were divided into two groups. Group I consisted of Petaling 1, Petaling 2, Natar 1, and Natar 2 and group II consisted of Malonan, Ciinten, Chunuk, Bengkayang, and LDK. Polymorphism produced by DNA markers (RAPD and SSR) formed three groups that were distinguishable for Natar1, Natar2, Petaling 1 and Petaling2 in the first group relevant to morphological clustering. Chunuk, LDK and Malonan in the second group, and the rest belonging to the third cluster. Notably, Chunuk and LDK were far distant from other Sumatera origin. In contrast Chunuk was preferentially close to a variety from other geographical origin, Malonan. The farthest distance was shown between LDK and Petaling 2 originating from Sumatera which shared similarity of 43 %, indicating their different genetic background. These morphological and molecular markers complement each other to reveal the relationship of nine superior varieties of black peppers which could be beneficial for furher use in breeding scheme.

Hormonal and transcriptional analyses of fruit development and ripening in different varieties of black pepper (Piper nigrum).

Black pepper (Piper nigrum L.) is one of the most popular and oldest spices in the world with culinary uses and various pharmacological properties. In order to satisfy the growing worldwide demand for black pepper, improved productivity of pepper is highly desirable. A primary constraint in black pepper production is the non-synchronous nature of flower development and non-uniform fruit ripening within a spike. The uneven ripening of pepper berries results in a high labour requirement for selective harvesting contributes to low productivity and affects the quality of the pepper products. In Malaysia, there are a few recommended varieties for black pepper planting, each having some limitations in addition to the useful characteristics. Therefore, a comparative study of different black pepper varieties will provide a better understanding of the mechanisms regulates fruit development and ripening. Plant hormones are known to influence the fruit development process and their roles in black pepper flower and fruit development were inferred based on the probe-based gene expression analysis and the quantification of the multiple plant hormones using high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). In this study, jasmonic acid and salicylic acid were found to play roles in flowering and fruit setting, whereas auxin, gibberellin and cytokinins are important for fruit growth. Abscisic acid has positive role in fruit maturation and ripening in the development process. Distinct pattern of plant hormones related gene expression profiles with the hormones accumulation profiles suggested a complex network of regulation is involved in the signaling process and crosstalk between plant hormones was another layer of regulation in the black pepper fruit development mechanisms. The current study provides clues to help in elucidating the timing of the action of each specific plant hormone during fruit development and ripening which could be applied to enhance our ability to control the ripening process, leading to improving procedures for the production and post-harvest handling of pepper fruits.

Pathogenic variability in Phytophthora capsici from black pepper (Piper nigrum L.) as revealed by transcriptome analysis

Phytophthora capsici, the causal organism of foot rot disease of black pepper exhibits wide variation in their virulence among the isolates. To understand the underlying mechanisms RNA-Seq analysis was carried out using a highly virulent (05-06) and less virulent (98-49) isolate of P. capsici from black pepper. The isolates were inoculated separately on the black pepper variety “IISR-Subhakara”, susceptible to Phytophthora and the leaf samples collected at 8, 24 and 48 h post inoculation (hpi) were subjected to RNA-Seq analysis. The isolates showed stage specific and infection responsive expression of various effectors and other proteins. The highly virulent isolate, 05-06 was found to be in biotrophic stage at 8 hpi and expressed various apoplastic and cytoplasmic effectors, the expression of which was several folds higher than that in less virulent isolate 98-49. By 24 hpi, the virulent isolate was in necrotrophic stage. The less virulent isolate 98-49, was also in biotrophic stage at 8 hpi and at 24 hpi it was in a stage of transition between biotrophic and necrotrophic phase and was in complete necrotrophic stage at 48 hpi. The over expression of various effector proteins and their tight temporal expression during the process of infection is the cause for the variation in virulence of the P. capsici isolates from black pepper.

Genotype specific host resistance for Phytophthora in black pepper (Piper nigrum L.)

Phytophthora foot rot is a devastating disease in black pepper which is caused by P. capsici. Using host resistance is a major component in the integrated pest management of this disease. To explore the host resistance pattern, we studied the genotype specific differential expression of important pathogenesis related gene β 1, 3 glucanase and 5 R gene loci from resistant and susceptible varieties of black pepper. The relative expression of β 1, 3 glucanase was up regulated in resistant variety and down regulated in susceptible variety. R gene loci Pn CNBS 5, CNBS 3 and Pn CNBS 2 showed up regulation in susceptible variety in the early hours of infection while resistant genotype recorded its down regulation till 72 h suggesting that the selective down expression of these loci may be attributed to the resistance in the resistant variety. These R genes may be the susceptibility genes (S-genes) in black pepper for Phytophthora. The high relative expression of the R gene locus Pn CNBS 4 and Pn CNBS 1 in resistant genotype at early hours shows their involvement in resistance towards P. capsici. The differential expression of the R gene loci shows the genotype specific functional significance for Phytophthora resistance.

In vitro elimination of Piper yellow mottle virus from infected black pepper through somatic embryogenesis and meristem-tip culture

Piper yellow mottle virus (PYMoV) is known to infect black pepper (Piper nigrum) in India and other parts of the world. In the present study, somatic embryogenesis and meristem-tip culture alone and in combination with the antiviral agent ribavirin were attempted to eliminate PYMoV from infected black pepper explants. Cyclic somatic embryos obtained from the micropylar region of matured seeds collected from PYMoV-infected black pepper plants of six varieties were regenerated and hardened in the greenhouse. Testing of somatic embryo-derived plants by PCR showed virus elimination in 55–100% of the plants of the different varieties of black pepper. PYMoV elimination was increased when cyclic somatic embryos were pre-treated with ribavirin before regeneration. A protocol for meristem-tip culture of black pepper plants was developed that consisted of excising the meristem from PYMoV-infected black pepper plants and inoculating it in the regeneration medium containing antibiotics (to remove endophytic bacterial contamination), followed by rooting and hardening of the plants. Testing of the meristem-derived plants showed PYMoV elimination in 84% of the plants. Further elimination of the virus was achieved when meristem-tip culture was combined with ribavirin treatment.

γ-Aminobutyric acid (GABA) priming enhances the osmotic stress tolerance in Piper nigrum Linn. plants subjected to PEG-induced stress

The pretreatment of two black pepper varieties, Panniyur 1 (drought-sensitive) and Panniyur 5 (drought-tolerant) with GABA (2 mM) influenced various physiological and biochemical parameters positively and the PEG (poly ethylene glycol 6000; 10 % w/v)-induced stress tolerance was increased in both varieties of black pepper. Although both varieties primed with GABA showed positive responses while encountering PEG-stress, Panniyur 5 showed better performance. When compared to non-primed plants induced with PEG-stress, GABA primed black pepper plants showed enhanced rate of leaf RWC and also a faster reduction of cell osmotic potential. Proline and total sugars were found to accumulate earlier in primed plants and the activity of antioxidant enzymes like guaiacol peroxidase and superoxide dismutase also increased significantly, in response to PEG-stress. When compared to non-primed plants, GABA priming resulted in a reduced rate of lipid peroxidation, and comparatively lesser inhibition of photosynthetic and mitochondrial activity (measured in terms of O2 evolution/uptake) in primed plants during osmotic stress. Occurrence of GABA in plants of black pepper varieties was detected by HPTLC technique. In PEG-treated plants GABA content was higher than that of control; and a multifold enhancement of GABA was observed in black pepper plants subjected to PEG-stress, after priming with GABA.