Breeding Tools Research Articles

The Exceptionally Large Genomes of the Fabeae Tribe: Comparative Genomics and Applications in Abiotic and Biotic Stress Studies

The Fabeae tribe comprises five legume genera, which include some of the most ancient and important crops, like peas, lentils, and faba beans. Biotic and environmental stresses are major threats to the stable and high productivity of Fabeae crops. The use of omics resources can provide breeders with the tools needed to develop new crop varieties in a more efficient and sustainable way. However, the genomic efforts on Fabeae crops have lagged behind compared to other legume species, mainly due to their large genome size and repeat content. The first annotated chromosome-level reference genome assembly in Fabeae was published for pea (Pisum sativum cv. Caméor) in 2019. Since then, many efforts have been made to sequence the genome of other species from this tribe. Currently, 17 genomes of Fabeae species are available for the scientific community; five of them are at the chromosome level. Fundamental knowledge and molecular tools for breeding have been boosted on the legume resistance/tolerance against biotic and abiotic stresses by the availability of some of these recent reference genomes, especially the pea cv. Caméor genome. This review provides a comparison of the Fabeae tribe genomes available and an overview of recent accomplishments in their application in abiotic and biotic stress research.

Phenotypic Variation in Flower Color and Morphology in the Gerbera (Gerbera hybrida) F1 Hybrid Population and Their Association with EST-SSR Markers.

Gerbera (Gerbera hybrida) is a widely cultivated ornamental plant. However, its genetic improvement is limited by the lack of genetic analysis and molecular markers for traits. In this study, we analyzed the phenotypic and genotypic variation of 140 F1 progeny from two gerbera varieties with different flower types and colors. We evaluated the flower's morphology, color, and pigment content of the F1 population and performed cluster principal component analysis (PCA) and correlation analysis. The results showed that the main ornamental traits of the hybrid progeny varied greatly. The segregation ratios of single and double flowers and ligulate and split ray florets were both 1:1. The flower colors of the F1 progeny were mainly red and purple-red, similar to the male parent's color. Furthermore, we conducted a genetic analysis of the hybrid progeny using EST-SSR markers and performed association analysis with phenotypic traits. We identified 2, 2, 3, 1, and 2 loci to be associated with peduncle length (PL), ray floret length (RFL), and outer ray floret; the level of apex relative to the top of involucre (LAI); outer corolla lips (OCL); and the b* of ray floret color, respectively. Our results reveal the genetic patterns of important ornamental traits and provide a theoretical basis and practical tools for gerbera genetic breeding.

CottonSense: A high-throughput field phenotyping system for cotton fruit segmentation and enumeration on edge devices

High-throughput phenotyping (HTP) has become a powerful tool for gaining insights into the genetic and environmental factors that affect cotton (Gossypium spp.) growth and yield. With the recent advances in the field of computer vision, namely the integration of deep learning algorithms, the accuracy and efficiency of HTP systems have improved dramatically, enabling them to automatically quantify such fundamental phenotypic traits as fruit identification and enumeration. However, there is currently no HTP system available for counting all the reproductive phases of cotton crop that can be deployed in agronomic field conditions throughout the growing season. This study presents CottonSense, an advanced HTP system that overcomes the challenges of deployment across multiple growth periods by effectively segmenting and enumerating cotton fruits at four stages of growth, including square, flower, closed boll, and open boll. Consequently, CottonSense enhances agronomic management through increased opportunities for data collection and analysis. Using RGB-D cameras, it captures and processes both two and three-dimensional data, facilitating a wider range of phenotypic trait extractions such as crop biomass and plant architecture. To segment the cotton fruits, a Mask-RCNN model is trained and optimized for faster inference using TensorRT. The model yields an average AP score of 79% in segmentation across the four fruit categories. Moreover, the model's accuracy in estimating total fruit count per image is validated by a strong agreement with the counts given by ten domain experts, as reflected by an R2 value of 0.94. Furthermore, to accurately count the segmented fruits over large populations of plants, an enumeration algorithm based on a tracking strategy is developed that achieves an R2 value of 0.93 when compared to hand-counted fruits in the field. The proposed HTP system, which is implemented entirely on an edge computing device, is cost-effective and power-efficient, making it an effective tool for high-yield cotton breeding and crop improvement. The code for CottonSense is publicly available at https://github.com/FeriBolour/CottonSense.

The Genetic Dissection of Nitrogen Use-Related Traits in Flax (Linum usitatissimum L.) at the Seedling Stage through the Integration of Multi-Locus GWAS, RNA-seq and Genomic Selection.

Nitrogen (N), the most important macro-nutrient for plant growth and development, is a key factor that determines crop yield. Yet its excessive applications pollute the environment and are expensive. Hence, studying nitrogen use efficiency (NUE) in crops is fundamental for sustainable agriculture. Here, an association panel consisting of 123 flax accessions was evaluated for 21 NUE-related traits at the seedling stage under optimum N (N+) and N deficiency (N-) treatments to dissect the genetic architecture of NUE-related traits using a multi-omics approach integrating genome-wide association studies (GWAS), transcriptome analysis and genomic selection (GS). Root traits exhibited significant and positive correlations with NUE under N- conditions (r = 0.33 to 0.43, p < 0.05). A total of 359 QTLs were identified, accounting for 0.11% to 23.1% of the phenotypic variation in NUE-related traits. Transcriptomic analysis identified 1034 differentially expressed genes (DEGs) under contrasting N conditions. DEGs involved in N metabolism, root development, amino acid transport and catabolism and others, were found near the QTLs. GS models to predict NUE stress tolerance index (NUE_STI) trait were tested using a random genome-wide SNP dataset and a GWAS-derived QTLs dataset. The latter produced superior prediction accuracy (r = 0.62 to 0.79) compared to the genome-wide SNP marker dataset (r = 0.11) for NUE_STI. Our results provide insights into the QTL architecture of NUE-related traits, identify candidate genes for further studies, and propose genomic breeding tools to achieve superior NUE in flax under low N input.

Molecular and Morphological Characterization of Wheat Genotypes under Drought Condition in Nigerian Sudan Savannah

Drought stress is one of the most important abiotic constrains affecting cereal crop in the world that causes serious yield loses and threat to sustainability and food security especially in wheat thereby causing the insufficient supply of food. Therefore, understanding the genetic characterization of drought stress response is very important. This study was designed to reveal the morphological and molecular characterization of wheat genotypes using simple sequence repeat (SSR) markers and to estimate the genetic diversity and relationships among the cultivars subjected to drought conditions. A total of 15 wheat genotypes were evaluated for quantitative morphological traits such as plant height, number of seeds per spike, 1000 seed weight, spike length, flag leaf length, grain weight and proline content. Molecular characterization was done using a set of simple sequence repeat (SSR) markers. A total of 12 SSR markers were used to analyze the varieties and the genetic diversity and relationship among them. The results showed that, the drought-stressed plants had lower plant height, number of seeds per spike, 1000 seed weight, spike length, flag leaf length and grain weight than the non-stressed plants, while proline content was found to be higher in stressed plants than the non-stressed. Molecular analyses indicated significant variation among the genotypes with the mean PIC value of 0.64, mean heritability ratio of 0.67 and mean allele number of 8.9. This study also indicates the significance of SSRs as a useful tool in marker-assisted breeding about drought tolerance and for developing strategies for improving drought tolerance in cereals.

Genetic aspects in working with the kholmogory cattle breed in the arkhangelsk region

Monitoring of the genetic structure of cattle breeds allows conducting studies that provide information about the cross-section in the timeline by the frequencies of genotypes of blood groups. In particular, the study was carried out on 10 time intervals of observations in herds for the Kholmogorsky breed of breeding plants of the Arkhangelsk region (n = 10983). The dynamics is shown by the decrease and increase in the frequencies of individual alleles. The genetic structure of the herd becomes more homozygous, as the loss of alleles goes on. A similar situation has developed in the samples of cows of the first and ninth generations, their genetic structures are sharply different. According to the results of the research, it was found that the quantitative and qualitative composition of the allelofund of the Kholmogorsky cattle of the Arkhangelsk region has changed under the influence of breeding processes. It was found that the degree of homozygosity (theoretical) tends to decrease from 10.5% (3rd generation) to 6.5% (9th, 10th generation) in the context of the analyzed generations of females, and the number of effective alleles, respectively, increases from 9.4% to 15.4%. At the same time, it was revealed that the breeding stock of the herds of breeding plants of the Arkhangelsk region was heterogeneous according to the genetic panel of the EAV locus. The greatest genetic distance is shown by purebred cows of the Kholmogorsky breed of cattle of the 1-2 observation intervals with Holstein in the 9-10 intervals. Breeding work and assessment of genetic variability is a tool for successful breeding in cattle herds of breeding plants by generations. The event to create new and improve existing factory lines using genetic markers of breed affiliation is promising. This will reduce the negative consequences of related mating of parent pairs, as well as avoid an increase in the level of homozygosity in the controlled herds of the Arkhangelsk population of the Kholmogorsky cattle breed.

Haploids can be induced in knockout mutants of OsPLA1, but not OsDMP3 or OsDMP6, in rice

Doubled haploid (DH) technology is an important tool in crop breeding because it can significantly accelerate the breeding process. ZmPLA1/MATL/NLD and ZmDMP are two key genes controlling haploid induction (HI) in maize, exhibiting a synergistic effect. However, it is unknown whether knock out of ZmDMP orthologs can stimulate HI in rice. In this study, a ZmPLA1 ortholog (OsPLA1) and two ZmDMP orthologs (OsDMP3 and OsDMP6) were identified in rice. All three genes encode plasma membrane-localized proteins and were highly expressed in mature anthers. Knockout of OsPLA1 in both Minghui 63 and Nipponbare resulted in reduced seed setting rate (SSR) and caused HI. The osdmp3, osdmp6 and the double mutant failed to trigger HI independently, nor increased the haploid induction rate (HIR) when combined with ospla1. Repeated pollinations operations of QX654A with the ospla1 mutant significantly improve SSR, while reducing HIR. RNA-seq profiling of mature ospla1 mutant anthers indicated that a large number of differentially expressed genes (DEGs) were enriched in redox homeostasis and lipid metabolic GO terms, plant hormone signal transduction, and MAPK signaling pathways. These findings provide important insights towards construction of an efficient DH breeding technology and study of the molecular mechanism of HI in rice.

Bayesian and classical approaches for the estimation of genetic parameters and coefficients of repeatability of acerola quality traits

Although acerola (Malpighia emarginata DC.) is a tropical fruit of high interest due to its high ascorbic acid content and attractive sensory attributes, fruit production is characterized by high genetic variability. Additionally, the use of new biometric tools for acerola breeding is scarce. This study aimed to estimate genetic parameters and the coefficient of repeatability, as well as determine the optimal number of fruits for quality trait analyses in different acerola genotypes, using different approaches. Twenty-three (Experiment I) and thirty-five (Experiment II) genotypes were evaluated in a randomized block design with four replicates and three plants per plot. Twenty fruits per plant were harvested and evaluated for the following quality traits: diameter, mass, skin color (lightness, chroma and hue), firmness, soluble solids (SS), titratable acidity (TA), SS/TA ratio, and ascorbic acid content. The genetic parameters and the coefficient of repeatability were estimated for each experiment using classical and Bayesian methods. Both approaches achieved similar results on estimating variance components, genetic parameters and the coefficient of repeatability. Genetic parameters showed favorable conditions for acerola selection. The coefficient of repeatability was high for all acerola quality traits. A total of 17 fruits are required for the effective selection of acerola genotypes with an accuracy of 95%.

Identification of genetic variants and individual genes associated with postpartum hypocalcemia in Holstein cows

Periparturient hypocalcemia is a complex metabolic disorder that occurs at the onset of lactation because of a sudden irreversible loss of Ca incorporated into colostrum and milk. Some cows are unable to quickly adapt to this demand and succumb to clinical hypocalcemia, commonly known as milk fever, whereas a larger proportion of cows develop subclinical hypocalcemia. The main goal of this study was to identify causative mutations and candidate genes affecting postpartum blood calcium concentration in Holstein cows. Data consisted of blood calcium concentration measured in 2513 Holstein cows on the first three days after parturition. All cows had genotypic information for 79 k SNP markers. Two consecutive rounds of imputation were performed: first, the 2513 Holstein cows were imputed from 79 k to 312 k SNP markers. This imputation was performed using a reference set of 17,131 proven Holstein bulls with 312 k SNP markers. Then, the 2513 Holstein cows were imputed from 312 k markers to whole-genome sequence data. This second round of imputation used 179 Holstein animals from the 1000 Bulls Genome Project as a reference set. Three alternative phenotypes were evaluated: (1) total calcium concentration in the first 24 h postpartum, (2) total calcium concentration in the first 72 h postpartum calculated as the area under the curve; and (3) the recovery of total calcium concentration calculated as the difference in total calcium concentration between 72 and 24 h. The identification of genetic variants associated with these traits was performed using a two-step mixed model-based approach implemented in the R package MixABEL. The most significant variants were located within or near genes involved in calcium homeostasis and vitamin D transport (GC), calcium and potassium channels (JPH3 and KCNK13), energy and lipid metabolism (CA5A, PRORP, and SREBP1), and immune response (IL12RB2 and CXCL8), among other functions. This work provides the foundation for the development of novel breeding and management tools for reducing the incidence of periparturient hypocalcemia in dairy cattle.

Exploring the efficacy of targeted fingerprinting marker techniques in genetic studies of the Indian poppy (Papaver somniferum L.): A comparative analysis

Targeted fingerprinting marker techniques have emerged as promising tools in plant sciences, particularly in plant breeding. To initiate an effective breeding program for a licit but industrially potential plant, the opium poppy, a comparative assessment of these markers was conducted. In this study, we compared the Start Codon Targeted polymorphism (SCoT), CAAT box-derived polymorphism (CBDP), and Expressed sequence tag-simple sequence repeats (EST-SSRs) markers for their competence and informativeness in revealing genetic identity, relatedness, and diversity among ten released varieties of the Indian opium poppy. Among the markers studied, EST-SSR markers demonstrated higher discriminating power, attributed to their ability to unveil comparatively higher polymorphic information content, marker index, and effective marker index. While all three marker systems effectively discriminated the poppy varieties, EST-SSR markers showed greater genetic diversity and a more informative ancestral history-based dendrogram topology. Significant correlation coefficients were observed between EST-SSR and CBDP markers, particularly in the combined marker dataset. Furthermore, the co-phenetic correlation was significant for three marker systems, with EST-SSR markers showing maximum correlation. Notably, the dendrograms constructed using EST-SSR markers and combined marker data displayed a significant and positive correlation with phenotypic traits assessed for the ten poppy varieties. Overall, the findings highlight the superiority of EST-SSR markers in deciphering genetic relationships among Indian opium poppy varieties and suggest their potential as valuable tools in breeding and genetic diversity studies.

Histological and biophysical changes of cassava roots during retting, a key step of fufu processing.

Retting is a key step of cassava processing into widely consumed foods (fufu, chikwangue, miondo and bobolo) in sub-Saharan Africa. For some populations, retting ability is a major quality criterion that drives the adoption of new cassava varieties. Despite this importance, the physiological basis associated with this process remains poorly understood, and should lead to improved screening tools for breeding. Eight cassava varieties contrasting in retting ability properties were used in the present study. Roots and soaking water were sampled during retting and characterized at both histological and biochemical levels. Histological data highlighted the degradation of root cell wall during retting. The average pH of soaking water decreased from 5.94 to 4.31 and the average simple sugars decreased from 0.18 to 0 g L-1, whereas the organic acids increased up to 5.61 g L-1. In roots tissue, simple sugars and organic acid contents decreased from 22.9 to 0 g kg-1 and from 80 to 0 g kg-1, respectively. The total pectin content of roots among varieties at harvest was similar, and decreased during the retting process. Overall, there was a negative correlation between total pectins content and root softening, although this did not reach statistical significance. Major histological and biochemical changes occurred during cassava root retting, with some of them associated with the process. Retting affected starch pasting properties more than starch content. Although this process is characterized by root softening and degradation of cell wall structure, the present study strongly suggested that pectin is not the only cell wall component involved in these changes. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Genomic tools in poultry breeding: Harnessing molecular markers for progress

Genomic tools in poultry breeding: Harnessing molecular markers for progress

Genome editing in plants: a tool for precision breeding and functional genomics

Genome editing in plants: a tool for precision breeding and functional genomics

Comprehensive characterization of SBP genes revealed their role under multifactorial stress combinations in dragon fruit (Selenicereus undatus L.)

The SQUAMOSA PROMOTER BINDING PROTEIN (SBP) gene family is essential for plant growth and development. However, little is known about the SBP gene family in pitaya (Selenicereus undatus L.); a fruit crop cultivated in tropical climates, severely affected by abiotic stress factors. These stresses produce excessive reactive oxygen species (ROS), affecting pitaya growth and development. In this study, we identified 17 SBP genes in the pitaya genome (HuSBP) and classified them into seven distinct clusters based on their phylogeny. The HuSBP genes exhibited a conserved intron-exon structure and motif domain organization. These SBP genes were differentially expressed in 15 developmental stages of flower (F), flower buds (FB), pericarp (PeriC), and pulp. In addition, specific HuSBP genes exhibited higher expression under single-factor, double-factor, and multifactorial stresses, revealing their diverse role in the growth and development of pitaya. Exogenous application of melatonin with known antioxidant and stress-protective properties, was also applied. The expression pattern of RNA-Seq data was validated by RT-qPCR analysis. Based on genome-wide results and transcriptome-based data under multifactorial stresses, we predicted five putative candidate genes (HuSBP1/3/7/11/14) that might play diverse roles in pitaya growth and development. These genes contain vital enzymes that play a role in the production of phenylpropanoid and glutathione metabolism. These results provide valuable insights into the role of HuSBP genes in pitaya stress tolerance and could be used to develop innovative strategies to create resilient and adaptable pitaya genotypes using conventional breeding and modern biotechnological tools.

Comparative Cytogenetic Analysis of Diploid and Triploid Pacific Abalone, Haliotis discus hannai

Introduction: The Pacific abalone, Haliotis discus hannai, is one of the most commercially important marine shellfish in China. Cell engineering breeding is an important tool in abalone genetic breeding, and the triploids obtained through this method have high commercial value. However, current research mainly focuses on establishing induction methods and evaluating the growth traits of triploids, while there is a lack of basic research on triploid cytogenetics. Method: In this study, Cytogenetic analysis of triploid Haliotis discus hannai larvae (produced by chemical treatment) and diploid larvae was performed. Result: The results showed that triploid H. discus hannai had a chromosome number of 3n = 54, consisting of 30 metacentric (m) and 24 submetacentric (sm) chromosomes, while the diploids had a chromosome number of 2n = 36, consisting of 20 metacentric (m) and 16 submetacentric (sm) chromosomes. Notably, both triploids and diploids displayed variation in the number of NORs and/or their diameter. The average number of NORs in triploid was significantly higher than that in diploids (p < 0.05), but the average diameter of NORs of triploid was no significant different from that of diploid (p > 0.05). Additionally, 5S rDNA localization to 3 submetacentric chromosomes was observed in triploids, compared to 2 submetacentric chromosomes in diploids. The number of 18S rDNA sites displayed positional conservancy and quantitative variability in both diploids and triploids. Specifically, 18S rDNA was found at the end of the chromosome in both groups, with triploids exhibiting a significantly higher number of loci than diploids (p < 0.01). Conclusion: This study provides valuable insights into the cytogenetic characteristics of triploid H. discus hannai, which could facilitate further research on the stability of the chromosome set in this species.

Rapid determination of rice protein content using near-infrared spectroscopy coupled with feature wavelength selection

Protein content is a key indicator for rice nutritional value, and its accurate determination has become a necessary tool for rice quality evaluation and breeding. To solve the shortcomings of slow and costly testing by traditional methods, a rapid detection model of rice protein content was constructed based on near-infrared spectroscopy coupled with feature wavelength selection. The backward interval partial least squares (BiPLS) was combined with the genetic simulated annealing algorithm (GSA) and the simulated annealing binary particle swarm optimization algorithm (SABPSO), respectively, to construct BiPLS-GSA and BiPLS-SABPSO for selecting protein feature wavelengths, thereby establishing a corresponding partial least squares quantitative calibration model. Among them, the regression model established using feature wavelengths selected by BiPLS-SABPSO had the best performance. The determination coefficient of the model for the validation set and the independent test set were 0.949 and 0.956, the root mean square error were 0.174% and 0.214%, the relative root mean square error were 2.621% and 3.118%, and the residual predictive deviation being 4.235 and 4.500, respectively, which could meet the requirement for rapid and accurate determination of rice protein content. The combination of BiPLS-SABPSO and near-infrared spectroscopy has developed into a new method to achieve fast and reliable determination of rice protein content, providing an alternative strategy for rapid qualitative detection of related agricultural products.

Transcriptomics integrated with metabolomics reveals the effect of cold stress on rice microspores

BackgroundMicrospore culture is one of the important biotechnological tools in plant breeding. The induction of microspore embryogenesis is a critical factor that affects the yield of microspore-derived embryo productions. Cold treatment has been reported to reprogram the gametophytic pathway in various plant species. However, the exact mechanism(s) underlying the effect of cold pre-treatment of floral buds on the efficiency of ME is still not clear.ResultsIn this study, the effects of cold stress on the microspore totipotency of rice cultivar Zhonghua 11 were investigated. Our results revealed that a 10-day cold treatment is necessary for microspore embryogenesis initiation. During this period, the survival rate of microspores increased and reached a peak at 7 days post treatment (dpt), before decreasing at 10 dpt. RNA-seq analysis showed that the number of DEGs increased from 3 dpt to 10 dpt, with more downregulated DEGs than upregulated ones at the same time point. GO enrichment analysis showed a shift from ‘Response to abiotic stimulus’ at 3 dpt to ‘Metabolic process’ at 7 and 10 dpt, with the most significant category in the cellular component being ‘cell wall’. KEGG analysis of the pathways revealed changes during cold treatment. Mass spectrometry was used to evaluate the variations in metabolites at 10 dpt compared to 0 dpt, with more downregulated DEMs being determined in both GC-MS and LC-MS modes. These DEMs were classified into 11 categories, Most of the DEMs belonged to ‘lipids and lipid-like molecules’. KEGG analysis of DEMs indicates pathways related to amino acid and nucleotide metabolism being upregulated and those related to carbohydrate metabolism being downregulated. An integration analysis of transcriptomics and metabolomics showed that most pathways belonged to ‘Amino acid metabolism’ and ‘Carbohydrate metabolism’. Four DEMs were identified in the interaction network, with stearidonic acid involving in the most correlations, suggesting the potential role in microspore totipotency.ConclusionsOur findings exhibited the molecular events occurring during stress-induced rice microspore. Pathways related to ‘Amino acid metabolism’ and ‘Carbohydrate metabolism’ may play important roles in rice microspore totipotency. Stearidonic acid was identified, which may participate in the initiation of microspore embryogenesis.

Target genes utilized for drought tolerance enhancement in maize

Among the most widely grown cereal crops is maize, which is a staple food for millions of people worldwide. It is primarily used for human consumption in various forms, animal feed, and industrial applications. In many countries like Mexico, Africa, and South America, it is the main source of calories in their daily diet, making it crucial for food security. Many nations worldwide are more at risk of drought as global warming continues to accelerate. One of the major hurdles to food production in the twenty-first century and a serious threat to our present and future food security is a water crisis. Crop failure due to water scarcity can put millions of lives at risk. Along with traditional breeding, transgenic approaches are an essential tool in modern plant breeding. They allow the introduction of beneficial genes from other organisms or within the same organism to improve plant characteristics. This review focuses on specific genes that are stably expressed and tested for drought tolerance in maize. Several genes have been identified as potential targets for improving drought tolerance in maize. Although mechanisms of target genes overlap to some extent, we attempted to divide the selected research articles according to the mechanism of the targeted gene into categories and reviewed them.

CRISPR/Cas9 Editing Sites Identification and Multi-Elements Association Analysis in Camellia sinensis.

CRISPR/Cas9 is an efficient genome-editing tool, and the identification of editing sites and potential influences in the Camellia sinensis genome have not been investigated. In this study, bioinformatics methods were used to characterise the Camellia sinensis genome including editing sites, simple sequence repeats (SSRs), G-quadruplexes (GQ), gene density, and their relationships. A total of 248,134,838 potential editing sites were identified in the genome, and five PAM types, AGG, TGG, CGG, GGG, and NGG, were observed, of which 66,665,912 were found to be specific, and they were present in all structural elements of the genes. The characteristic region of high GC content, GQ density, and PAM density in contrast to low gene density and SSR density was identified in the chromosomes in the joint analysis, and it was associated with secondary metabolites and amino acid biosynthesis pathways. CRISPR/Cas9, as a technology to drive crop improvement, with the identified editing sites and effector elements, provides valuable tools for functional studies and molecular breeding in Camellia sinensis.

Mutation breeding as a tool for improving plant characters: A review

Identifying plants with desirable traits among existing plant varieties is the initial and most important step in plant breeding. Plant breeding requires the genetic variation of useful traits for crop improvement or crop betterment. The plant breeding depends upon the genetic variation. In nature, variation occurs mainly as a result of mutation and without it, plant breeding would be impossible. Mutation as a mechanism of creating variability was identified by Hugo de Vries while experimenting on the rediscovery of Mendel’s Law of Inheritance.17 Mutation arises in two ways; First, spontaneous mutation which occurs without treatment of the organism with an exogenous mutagen and secondly induced mutation which occurs due to the treatment of a plant or plant parts such as seed, stem, cuttings, pollen and ovules with the help of mutagens. The purposeful employment of the induced mutation for crop improvement is known as mutation breeding. The mutation breeding is also known as the variation breeding.There are mainly two types of mutagens (agent to cause mutation) i.e. physical and chemical mutagens. The mutant shows higher potential for improving plant architecture leading to better crop improvement and used as complementary and rational tool in plant breeding. Mutation breeding programme should be clearly planned and should be large enough with sufficient facilities to screen large population in short time. This review highlights the role of mutation breeding in improvement of qualitative and quantitative characters of crop plant.