Genetic Improvement Of Crop Plants Research Articles

Morpho-phenological characterization and genetic analysis of dolichos bean germplasm from Uttar Pradesh, India

Abstract The true characterization of elite germplasm is of utmost importance for accelerating the crop breeding programme. The Indian dolichos bean [Lablab purpureus (L.) var. typicus Prain] has the potential to improve nutritional and food security. In the present investigation, a total of 21 genotypes of dolichos bean, comprising local collections mainly, along with one standard check (Kashi Sheetal) were evaluated in a complete randomized block design with three replications for two consecutive years, 2021–22 to 2022–23 for the perusal of the genetic variability. Analysis of variance revealed significant differences among all the genotypes for all the characters. PCV and GCV estimates revealed very little influence of environment on the expression of traits under study. High heritability (>90%) estimates coupled with high genetic advance as a percent of the mean were observed for flower attributes, pod length, average weight of 10 pods, pod yield and protein content. The principal component analysis revealed that the first two components cumulatively accounted for more than 50% of total variability. The present investigation revealed that the genotypes, RLBDL-S-8, RLBDL-S-14 and RLBDL-S-4-5 were stable across the years and genotype RLBDL-S-8 exhibited the highest yield potential, which can be used effectively in the development of high yielding varieties of dolichos bean in the Bundelkhand region. The study also revealed the presence of wide genetic variability in the studied local accessions which is a prerequisite for the genetic improvement of crop plants. High heritability and genetic advancement indicated the scope of selection in the crop improvement.

MYB Transcription Factor Family in Pearl Millet: Genome-Wide Identification, Evolutionary Progression and Expression Analysis under Abiotic Stress and Phytohormone Treatments.

Transcription factors (TFs) are the regulatory proteins that act as molecular switches in controlling stress-responsive gene expression. Among them, the MYB transcription factor family is one of the largest TF family in plants, playing a significant role in plant growth, development, phytohormone signaling and stress-responsive processes. Pearl millet (Pennisetum glaucum L.) is one of the most important C4 crop plants of the arid and semi-arid regions of Africa and Southeast Asia for sustaining food and fodder production. To explore the evolutionary mechanism and functional diversity of the MYB family in pearl millet, we conducted a comprehensive genome-wide survey and identified 279 MYB TFs (PgMYB) in pearl millet, distributed unevenly across seven chromosomes of pearl millet. A phylogenetic analysis of the identified PgMYBs classified them into 18 subgroups, and members of the same group showed a similar gene structure and conserved motif/s pattern. Further, duplication events were identified in pearl millet that indicated towards evolutionary progression and expansion of the MYB family. Transcriptome data and relative expression analysis by qRT-PCR identified differentially expressed candidate PgMYBs (PgMYB2, PgMYB9, PgMYB88 and PgMYB151) under dehydration, salinity, heat stress and phytohormone (ABA, SA and MeJA) treatment. Taken together, this study provides valuable information for a prospective functional characterization of the MYB family members of pearl millet and their application in the genetic improvement of crop plants.

Comparative genomic analysis of the aldehyde dehydrogenase gene superfamily in Arabidopsis thaliana - searching for the functional key to hypoxia tolerance.

Flooding entails different stressful conditions leading to low oxygen availability for respiration and as a result plants experience hypoxia. Stress imposed by hypoxia affects cellular metabolism, including the formation of toxic metabolites that dramatically reduce crop productivity. Aldehyde dehydrogenases (ALDHs) are a group of enzymes participating in various aspects of plant growth, development and stress responses. Although we have knowledge concerning the multiple functionalities of ALDHs in tolerance to various stresses, the engagement of ALDH in plant metabolism adjustment to hypoxia is poorly recognized. Therefore, we explored the ALDH gene superfamily in the model plant Arabidopsis thaliana. Genome-wide analyses revealed that 16 AtALDH genes are organized into ten families and distributed irregularly across Arabidopsis 5 chromosomes. According to evolutionary relationship studies from different plant species, the ALDH gene superfamily is highly conserved. AtALDH2 and ALDH3 are the most numerous families in plants, while ALDH18 was found to be the most distantly related. The analysis of cis-acting elements in promoters of AtALDHs indicated that AtALDHs participate in responses to light, phytohormones and abiotic stresses. Expression profile analysis derived from qRT-PCR showed the AtALDH2B7, AtALDH3H1 and AtALDH5F1 genes as the most responsive to hypoxia stress. In addition, the expression of AtALDH18B1, AtALDH18B2, AtALDH2B4, and AtALDH10A8 was highly altered during the post-hypoxia-reoxygenation phase. Taken together, we provide comprehensive functional information on the ALDH gene superfamily in Arabidopsis during hypoxia stress and highlight ALDHs as a functional element of hypoxic systemic responses. These findings might help develop a framework for application in the genetic improvement of crop plants.

The Adaptation and Tolerance of Major Cereals and Legumes to Important Abiotic Stresses.

Abiotic stresses, including drought, extreme temperatures, salinity, and waterlogging, are the major constraints in crop production. These abiotic stresses are likely to be amplified by climate change with varying temporal and spatial dimensions across the globe. The knowledge about the effects of abiotic stressors on major cereal and legume crops is essential for effective management in unfavorable agro-ecologies. These crops are critical components of cropping systems and the daily diets of millions across the globe. Major cereals like rice, wheat, and maize are highly vulnerable to abiotic stresses, while many grain legumes are grown in abiotic stress-prone areas. Despite extensive investigations, abiotic stress tolerance in crop plants is not fully understood. Current insights into the abiotic stress responses of plants have shown the potential to improve crop tolerance to abiotic stresses. Studies aimed at stress tolerance mechanisms have resulted in the elucidation of traits associated with tolerance in plants, in addition to the molecular control of stress-responsive genes. Some of these studies have paved the way for new opportunities to address the molecular basis of stress responses in plants and identify novel traits and associated genes for the genetic improvement of crop plants. The present review examines the responses of crops under abiotic stresses in terms of changes in morphology, physiology, and biochemistry, focusing on major cereals and legume crops. It also explores emerging opportunities to accelerate our efforts to identify desired traits and genes associated with stress tolerance.

The Exocytosis Associated SNAP25-Type Protein, SlSNAP33, Increases Salt Stress Tolerance by Modulating Endocytosis in Tomato

In plants, vesicular trafficking is crucial for the response and survival to environmental challenges. The active trafficking of vesicles is essential to maintain cell homeostasis during salt stress. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are regulatory proteins of vesicular trafficking. They mediate membrane fusion and guarantee cargo delivery to the correct cellular compartments. SNAREs from the Qbc subfamily are the best-characterized plasma membrane SNAREs, where they control exocytosis during cell division and defense response. The Solanum lycopersicum gene SlSNAP33.2 encodes a Qbc-SNARE protein and is induced under salt stress conditions. SlSNAP33.2 localizes on the plasma membrane of root cells of Arabidopsis thaliana. In order to study its role in endocytosis and salt stress response, we overexpressed the SlSNAP33.2 cDNA in a tomato cultivar. Constitutive overexpression promoted endocytosis along with the accumulation of sodium (Na+) in the vacuoles. It also protected the plant from cell damage by decreasing the accumulation of hydrogen peroxide (H2O2) in the cytoplasm of stressed root cells. Subsequently, the higher level of SlSNAP33.2 conferred tolerance to salt stress in tomato plants. The analysis of physiological and biochemical parameters such as relative water content, the efficiency of the photosystem II, performance index, chlorophyll, and MDA contents showed that tomato plants overexpressing SlSNAP33.2 displayed a better performance under salt stress than wild type plants. These results reveal a role for SlSNAP33.2 in the endocytosis pathway involved in plant response to salt stress. This research shows that SlSNAP33.2 can be an effective tool for the genetic improvement of crop plants.

Genetic diversity and identification of interspecific hybrids of Anacardium species using microsatellites

Study of genetic diversity and interspecific hybridizations plays an imperative role in the genetic improvement of crop plants. Microsatellite or simple sequence repeats (SSRs) markers have been the marker of choice for many genetic studies in perennial tree crops. In this study, genetic diversity of 23 cashew (Anacardium occidentale L.) germplasm accessions with unique traits was carried out using the cashew SSR (CSSR) markers. Besides, true hybridity of the interspecific hybrids of A. occidentale and A. microcarpum Ducke was investigated. Eight of the 21 CSSRs screened in 10 diverse accessions were polymorphic and used for genetic diversity analysis in 23 accessions. Major allele frequency ranged from 0.50 to 0.98; gene diversity ranged from 0.10 to 0.50, and polymorphism information content (PIC) ranged from 0.10 to 0.38 for the surveyed SSR loci. Dendrogram analysis of 23 accessions formed two main clusters with two sub-clusters in each. Clustering of the accessions had no relationship with the geographic region of collection. In tree hybridizations, early screening methods are becoming indispensable to ascertain the true hybridity of progenies to save the costs and resources. For the first time, three CSSR markers that detect the true hybridity of interspecific hybrids of cashew and its wild relative A. microcarpum were identified. Hybrid purity index of the progenies in interspecific crosses varied from 67 to 100%. These three CSSR markers capable of distinguishing the two Anacardium species could be useful in evolutionary studies involving these species and their natural hybrids in the wilds.

Comprehensive proteomic analysis revealing multifaceted regulatory network of the xero-halophyte Haloxylon salicornicum involved in salt tolerance

Haloxylon salicornicum is a xero-halophyte which grow predominantly in dry saline areas. However, the proteomic approach for revealing the regulatory network involved in salt adaptation of this important xerohalophyte has not been studied so far. In the present investigation, the label-free quantitative proteomic analysis was carried out in shoot of H. salicornicum to get an insight into the functional network of proteins involved in salt tolerance. Comparative proteomic analysis in control and salt treated plants of H. salicornicum by nano-ESI-LC–MS and MS/MS, and data base searching led to the identification of 723 proteins. Pathway enrichment analysis by KEGG uncovered various biological pathways to which salinity induced differentially regulated proteins are involved. In H. salicornicum, out of 723 identified proteins, 187 proteins were differentially regulated in response to salinity. In addition to significant up-regulation of stress responsive proteins, other proteins involved in carbohydrate metabolism, TCA cycle, protein synthesis, antioxidative defense systems, energy transfer, ion transport, nucleotide binding, and proteosomal proteins also significantly up-regulated under salinity in H. salicornicum. The major photosynthetic proteins up-regulated were RuBisCo, D1 protein, photosystem II-CP47, and cytochrome b599. TCA cycle component proteins such as citrate synthase, succinate dehydrogenase, and malate dehydrogenase upregulated indicating their significant roles in providing vital energy for salinity tolerance. Salinity induced higher expressions of ion transporters in H. salicornicum suggest efficient compartmentalization of toxic sodium ions. In addition, up-regulation of antioxidative defense system can be correlated with effective scavenging of salinity induced ROS, hence imparting salt tolerance. In H. salicornicum, protein synthesis was boosted under salinity as confirmed from the salinity-induced up-regulation of the ribosome associated proteins. Salinity induced significantly changed proteins of the ribosomal pathway include ribosomal protein components such as elongation factor-Tu (EF-Tu), initiation factor 1 and 2 (IF1, 2), Rpo cluster C and B, etc. Functional integrity of protein synthesis machinery in H. salicornicum is maintained under high salinity by higher abundance of ribosomal subunit proteins in NaCl-treated plants. We assume that consistent energy supply by the up-regulation of TCA cycle along with uninterrupted protein synthesis and maintenance of structural integrity of the photosynthetic machinery are the primary mechanism of salinity tolerance of H. salicornicum. In the present study, we comprehensively elucidated possible mechanisms associated with systematic salt tolerance of H. salicornicum employing proteomic approach. The information from this study will contribute to the genetic improvement of crop plants that can be grown in saline marginal lands.

Transcriptional Factors Regulate Plant Stress Responses through Mediating Secondary Metabolism.

Plants are adapted to sense numerous stress stimuli and mount efficient defense responses by directing intricate signaling pathways. They respond to undesirable circumstances to produce stress-inducible phytochemicals that play indispensable roles in plant immunity. Extensive studies have been made to elucidate the underpinnings of defensive molecular mechanisms in various plant species. Transcriptional factors (TFs) are involved in plant defense regulations through acting as mediators by perceiving stress signals and directing downstream defense gene expression. The cross interactions of TFs and stress signaling crosstalk are decisive in determining accumulation of defense metabolites. Here, we collected the major TFs that are efficient in stress responses through regulating secondary metabolism for the direct cessation of stress factors. We focused on six major TF families including AP2/ERF, WRKY, bHLH, bZIP, MYB, and NAC. This review is the compilation of studies where researches were conducted to explore the roles of TFs in stress responses and the contribution of secondary metabolites in combating stress influences. Modulation of these TFs at transcriptional and post-transcriptional levels can facilitate molecular breeding and genetic improvement of crop plants regarding stress sensitivity and response through production of defensive compounds.

Polyploidization for the Genetic Improvement of Cannabis sativa.

Cannabis sativa L. is a diploid species, cultivated throughout the ages as a source of fiber, food, and secondary metabolites with therapeutic and recreational properties. Polyploidization is considered as a valuable tool in the genetic improvement of crop plants. Although this method has been used in hemp-type Cannabis, it has never been applied to drug-type strains. Here, we describe the development of tetraploid drug-type Cannabis lines and test whether this transformation alters yield or the profile of important secondary metabolites: Δ9-tetrahydrocannabinol (THC), cannabidiol (CBD), or terpenes. The mitotic spindle inhibitor oryzalin was used to induce polyploids in a THC/CBD balanced drug-type strain of Cannabis sativa. Cultured axillary bud explants were exposed to a range of oryzalin concentrations for 24 h. Flow cytometry was used to assess the ploidy of regenerated shoots. Treatment with 20–40 μM oryzalin produced the highest number of tetraploids. Tetraploid clones were assessed for changes in morphology and chemical profile compared to diploid control plants. Tetraploid fan leaves were larger, with stomata about 30% larger and about half as dense compared to diploids. Trichome density was increased by about 40% on tetraploid sugar leaves, coupled with significant changes in the terpene profile and a 9% increase in CBD that was significant in buds. No significant increase in yield of dried bud or THC content was observed. This research lays important groundwork for the breeding and development of new Cannabis strains with diverse chemical profiles, of benefit to medical and recreational users.

Phylogeny-dominant classification of J-proteins in Arabidopsis thaliana and Brassica oleracea.

Hsp40s or DnaJ/J-proteins are evolutionarily conserved in all organisms as co-chaperones of molecular chaperone HSP70s that mainly participate in maintaining cellular protein homeostasis, such as protein folding, assembly, stabilization, and translocation under normal conditions as well as refolding and degradation under environmental stresses. It has been reported that Arabidopsis J-proteins are classified into four classes (types A-D) according to domain organization, but their phylogenetic relationships are unknown. Here, we identified 129 J-proteins in the world-wide popular vegetable Brassica oleracea, a close relative of the model plant Arabidopsis, and also revised the information of Arabidopsis J-proteins based on the latest online bioresources. According to phylogenetic analysis with domain organization and gene structure as references, the J-proteins from Arabidopsis and B. oleracea were classified into 15 main clades (I-XV) separated by a number of undefined small branches with remote relationship. Based on the number of members, they respectively belong to multigene clades, oligo-gene clades, and mono-gene clades. The J-protein genes from different clades may function together or separately to constitute a complicated regulatory network. This study provides a constructive viewpoint for J-protein classification and an informative platform for further functional dissection and resistant genes discovery related to genetic improvement of crop plants.

Next Generation Sequencing: A Step toward Unraveling of Biosynthetic Pathways in Plants

Plant science is largely driven by DNA sequence data, which has been fundamentally changed in last decade due to the development and emergence of next-generation sequencing (NGS) technologies. NGS has played a vital role in the advancement of plant genomics, which has opened the opportunities for genetic improvement of crop plants and identification of biosynthetic pathways of important pharmaceutical biomolecules (tanshinones, forskolin, artemisinin etc.).

RNA Silencing in Plants: Mechanisms, Technologies and Applications in Horticultural Crops.

Understanding the fundamental nature of a molecular process or a biological pathway is often a catalyst for the development of new technologies in biology. Indeed, studies from late 1990s to early 2000s have uncovered multiple overlapping but functionally distinct RNA silencing pathways in plants, including the posttranscriptional microRNA and small interfering RNA pathways and the transcriptional RNA-directed DNA methylation pathway. These findings have in turn been exploited for developing artificial RNA silencing technologies such as hairpin RNA, artificial microRNA, intrinsic direct repeat, 3’ UTR inverted repeat, artificial trans-acting siRNA, and virus-induced gene silencing technologies. Some of these RNA silencing technologies, such as the hairpin RNA technology, have already been widely used for genetic improvement of crop plants in agriculture. For horticultural plants, RNA silencing technologies have been used to increase disease and pest resistance, alter plant architecture and flowering time, improve commercial traits of fruits and flowers, enhance nutritional values, remove toxic compounds and allergens, and develop high-value industrial products. In this article we aim to provide an overview of the RNA silencing pathways in plants, summarize the existing RNA silencing technologies, and review the current progress in applying these technologies for the improvement of agricultural crops particularly horticultural crops.

Mining for Candidate Genes in an Introgression Line by Using RNA Sequencing: The Anthocyanin Overaccumulation Phenotype in Brassica.

Introgression breeding is a widely used method for the genetic improvement of crop plants; however, the mechanism underlying candidate gene flow patterns during hybridization is poorly understood. In this study, we used a powerful pipeline to investigate a Chinese cabbage (Brassica rapa L. ssp. pekinensis) introgression line with the anthocyanin overaccumulation phenotype. Our purpose was to analyze the gene flow patterns during hybridization and elucidate the genetic factors responsible for the accumulation of this important pigment compound. We performed RNA-seq analysis by using two pipelines, one with and one without a reference sequence, to obtain transcriptome data. We identified 930 significantly differentially expressed genes (DEGs) between the purple-leaf introgression line and B. rapa green cultivar, namely, 389 up-regulated and 541 down-regulated DEGs that mapped to the B. rapa reference genome. Since only one anthocyanin pathway regulatory gene was identified, i.e., Bra037887 (bHLH), we mined unmapped reads, revealing 2031 de novo assembled unigenes, including c3563g1i2. Phylogenetic analysis suggested that c3563g1i2, which was transferred from the Brassica B genome of the donor parental line Brassica juncea, may represent an R2R3-MYB transcription factor that participates in the ternary transcriptional activation complex responsible for the anthocyanin overaccumulation phenotype of the B. rapa introgression line. We also identified genes involved in cold and light reaction pathways that were highly upregulated in the introgression line, as confirmed using quantitative real-time PCR analysis. The results of this study shed light on the mechanisms underlying the purple leaf trait in Brassica plants and may facilitate the use of introgressive hybridization for many traits of interest.

Analysis of the siRNA-Mediated Gene Silencing Process Targeting Three Homologous Genes Controlling Soybean Seed Oil Quality.

In the past decade, RNA silencing has gained significant attention because of its success in genomic scale research and also in the genetic improvement of crop plants. However, little is known about the molecular basis of siRNA processing in association with its target transcript. To reveal this process for improving hpRNA-mediated gene silencing in crop plants, the soybean GmFAD3 gene family was chosen as a test model. We analyzed RNAi mutant soybean lines in which three members of the GmFAD3 gene family were silenced. The silencing levels of FAD3A, FAD3B and FAD3C were correlated with the degrees of sequence homology between the inverted repeat of hpRNA and the GmFAD3 transcripts in the RNAi lines. Strikingly, transgenes in two of the three RNAi lines were heavily methylated, leading to a dramatic reduction of hpRNA-derived siRNAs. Small RNAs corresponding to the loop portion of the hairpin transcript were detected while much lower levels of siRNAs were found outside of the target region. siRNAs generated from the 318-bp inverted repeat were found to be diced much more frequently at stem sequences close to the loop and associated with the inferred cleavage sites on the target transcripts, manifesting “hot spots”. The top candidate hpRNA-derived siRNA share certain sequence features with mature miRNA. This is the first comprehensive and detailed study revealing the siRNA-mediated gene silencing mechanism in crop plants using gene family GmFAD3 as a test model.

Use of Molecular Markers to Improve the Agro-Industrial Productivity in the North West of Argentina

Genetic improvement of crop plants through conventional breeding has been the cornerstone to improve global agricultural production. Nowadays, different molecular biology techniques have become available to supplement and assist conventional breeding, among them the utilization of molecular markers. The generation of molecular, or DNA, markers are based on two basic molecular biology methods in order to be able to detect polymorphism: Southern blotting, a nucleic acid hybridization technique, and the amplification in vitro of specific DNA segments by the Polymerase Chain Reaction (PCR) technique . By using these two methods and several variations of the basic technologies, many different kind of molecular markers have been developed during the last decades. It is important to note that for a molecular marker to be efficient in crop breeding it should meet most of the following criteria [: high level of polymorphism; even distribution across the whole genome (not clustered in certain regions); co-dominance (or capacity to identify at heterozygous); clear distinct allelic features; single copy; low cost to use (or cost-efficient marker development and genotyping); easy assay/detection and automation; high availability (un-restricted use) and suitability to be duplicated/multiplexed (so that the data can be accumulated and shared between laboratories); genome-specific in nature (especially with polyploids) and have no detrimental effect on phenotype. However, the choice of the best marker system depends on many other factors as well including crop genetics and available resources (time, reagents, equipments, etc).

Quantitative trait loci mapping for kernel row number using chromosome segment substitution lines in maize

Unveiling the genetic architecture of grain yield and yield-related traits is useful for guiding the genetic improvement of crop plants. Kernel row number (KRN) per ear is an important yield component, which directly affects the grain yield of maize. In this study, we constructed a set of 130 chromosome segment substitution lines (CSSLs), using Nongxi531 as the donor parent and H21 as recipient parent, by continuous backcrossing and selfing. In total, 11 quantitative trait loci (QTL) were detected for KRN by stepwise regression under 3 environmental settings, with 9.87-19.44% phenotypic variation being explained by a single QTL. All 11 QTL were also detected by single-factor ANOVA across the 3 environments tested. Of these 11 QTL, 4 were identified across more than 2 environments, indicating that they are authentically expressed under different environments to control the formation and development of KRN in female maize inflorescences. The CSSLs harbored a greater number of favorable alleles for KRN compared to the H21 line, and could be employed as improved H21 lines in maize breeding programs.

The potential of unintended effects in potato glycoalkaloids

Unintended changes have long been considered as byproducts associated with genetic improvement of crop plants. The issue has been hotly debated during recent years following the identification of some unwanted characters in genetically engineered crop plants. In this context, the subject of unintended effects of plant transformation on known toxic compounds has been an area of immense interest. Compositional changes in these toxins may have a profound impact on human and animal health. Potato glycoalkaloids are known toxic compounds to humans and animals. These days, food safety evaluation tests of transgenic potato varieties are conducted on routine basis to keep the glycoalkaloid levels below a threshold level. Some transgenic potato varieties have been found with altered glycoalkaloid levels, which have created doubts on the process of transformation and tissue culture conditions. In this review, we summarize recent work on unintended effects in crop plants with special emphasis on compositional changes in potato glycoalkaloids as a result of genetic transformation. Keywords : Unintended effects, transgenic potato, glycoalkaloids, food safety, environmental stress African Journal of Biotechnology Vol. 12(8), pp. 754-766

Mejoramiento vegetal usando genes con funciones conocidas

El mejoramiento de plantas mediante la inserción de un fragmento de ADN usando ingeniería genética representa una oportunidad para desarrollar cultivares o variedades con características económicamente deseables, como conferir ventajas adaptativas al medio ambiente, mejores propiedades nutrimentales y disminución del uso de agroquímicos. Dada la polémica alrededor de este tipo de tecnologías la justificación de su desarrollo y uso dependerá del entorno sociocultural y deberá ser estudiado caso por caso. El presente documento tiene el objetivo de plantear un panorama de los Organismos Genéticamente Modificados (OGM), sus ventajas y desventajas, y establecer el porqué constituyen una oportunidad para desarrollar cultivares con características que por métodos tradicionales no podrían obtenerse.

Variability, heritability and genetic advance in mulberry (<i>Morus</i> spp.) for growth and yield attributes

Genetic improvement of crop plants is brought about by manipulating the genetic makeup through systematic breeding techniques or by employing modern biotechnological tools. Application of systematic breeding technique to a large extent is decided by the knowledge on the genetic control of the traits. Keeping this in view, nine mulberry genotypes were evaluated for different growth and yield attributing traits viz., number of tillers (NT), plant height (PH), total shoot length (TSL), nodal distance (ND), leaf fall % (LF), number of leaves/plant (NLP), weight of 100 fresh leaves (WFL), weight of 100 dry leaves (WDL), single leaf area (LA), leaf area index (LAI), aboveground biomass (AGB), leaf harvest index (LHI) and leaf yield (LY) and estimated the magnitude of genotypic and phenotypic variation, heritability, genetic advance and correlation coefficients. The broad sense heritability for these traits ranged from 63.942 (WFL) to 13.261 (PH). High heritability coupled with high genetic advance was recorded for the characters WFL, LF, LA, WDL and LY suggesting the higher genetic control over these traits. Leaf yield showed significantly positive phenotypic and genotypic correlations with all other growth traits except PH and LF. Leaf fall had significant negative correlations with all the highly heritable yield attributes viz., ND (-0.379), WDL (-0.225), LA (-0.346), LAI (-0.233) at 1% level and AGB (-0.148), LHI (-0.122) and LY (-0.146) at 5% level. Likewise, it showed positive correlations with TSL (0.558), NLP (0.264) and PH (0.221). Since mulberry is mainly cultivated for leaf yield, genotypes having higher WFL, LA, WDL and LY and less LF must be given importance during parent selection to evolve high yielding varieties with less leaf fall across different seasons in mulberry.

Reduction of inositol (1,4,5)-trisphosphate affects the overall phosphoinositol pathway and leads to modifications in light signalling and secondary metabolism in tomato plants.

The phosphoinositol pathway is one of the major eukaryotic signalling pathways. The metabolite of the phosphoinositol pathway, inositol- (1,4,5) trisphosphate (InsP3), is a regulator of plant responses to a wide variety of stresses, including light, drought, cold, and salinity. It was found that the expression of InsP 5-ptase, the enzyme that hydrolyses InsP3, also dramatically affects the levels of inositol phosphate metabolites and the secondary metabolites in transgenic tomato plants. Tomato plants expressing InsP 5-ptase exhibited a reduction in the levels of several important inositol phosphates, including InsP1, InsP2, InsP3, and InsP4. Reduced levels of inositol phosphates accompanied an increase in the accumulation of phenylpropanoids (rutin, chlorogenic acid) and ascorbic acid (vitamin C) in the transgenic fruits of tomato plants. The enhanced accumulation of these metabolites in transgenic tomato plants was in direct correspondence with the observed up-regulation of the genes that express the key enzymes of ascorbic acid metabolism (myo-inositol oxygenase, MIOX; L-galactono-γ-lactone dehydrogenase, GLDH) and phenylpropanoid metabolism (chalcone synthase, CHS1; cinnamoyl-CoA shikimate/quinate transferase, HCT). To understand the molecular links between the activation of different branches of plant metabolism and InsP3 reduction in tomato fruits, the expression of transcription factors known to be involved in light signalling was analysed by real-time RT-PCR. The expression of LeHY5, SIMYB12, and LeELIP was found to be higher in fruits expressing InsP 5-ptase. These results suggest possible interconnections between phosphoinositol metabolism, light signalling, and secondary metabolism in plants. Our study also revealed the biotechnological potential for the genetic improvement of crop plants by the manipulation of the phosphoinositol pathway.