Plant Genetic Improvement Research Articles

The influence of plant genomics on plant evolution

With the increasing demand for high-quality tea, the genetic basis of ideal traits of tea plants has been widely concerned. The research on tea tree genomics, specifically focusing on “Longjing 43”, provides significant insights into plant evolution and breeding. “Longjing 43” was chosen due to its complex genome and economic importance. The study successfully assembled its genome to the chromosome level, revealing a large and heterogeneous genome with numerous repetitive sequences. Comparative genomics showed that hybridization has been a key driver of genetic diversity and adaptability in tea plants. These findings are crucial for developing marker-assisted selection (MAS) techniques, improving traits such as disease resistance, flavor, and stress response. Moreover, the research underscores the role of tea tree genomics in preserving cultural heritage and promoting economic benefits through enhanced tea quality. This study contributes to the broader understanding of plant genomics by illustrating the evolutionary processes and potential applications in agriculture, conservation, and industry, thus offering a comprehensive tool for future plant breeding and genetic improvement strategies.

Recent Progress on Plant Apomixis for Genetic Improvement

Apomixis is a reproductive process that produces clonal seeds while bypassing meiosis (or apomeiosis) without undergoing fertilization (or pseudo-fertilization). The progenies are genetically cloned from their parents, retaining the parental genotype, and have great potential for the preservation of genes of interest and the fixing of heterosis. The hallmark components of apomixis include the formation of female gametes without meiosis, the development of fertilization-independent embryos, and the formation of functional endosperm. Understanding and utilizing the molecular mechanism of apomixis has far-reaching implications for plant genetic breeding and agricultural development. Therefore, this study focuses on the classification, influencing factors, genetic regulation, and molecular mechanism of apomixis, as well as progress in the research and application of apomixis-related genes in plant breeding. This work will elucidate the molecular mechanisms of apomixis and its application for plant genetic improvement.

A broad analysis of vegetative rescue and propagation of Moquiniastrum polymorphum (Less.) G. Sancho

Background: The primary method for propagating forest species is through seeds, which is cost-effective and ensures genetic adaptability to environmental changes. However, germination issues and genetic variability can hinder standardisation of productivity. In the case of Moquiniastrum polymorphum, a species known for its remarkable wood quality and pharmacological potential, seedling production and genetic improvement efforts have been limited. This study focused on the rescue and vegetative propagation of M. polymorphum, which are crucial steps for species selection and genetic enhancement. Methods: Protocols were tested to rescue and propagate propagules from different individuals collected in Lages, Santa Catarina (2020/2022). The vegetative rescue tests were: (I) epicormic sprouting induction through girdling techniques and detached branches; and (II) influence of individuals, disposition sense and time on the epicormic sprouting of detached branches. Vegetative propagation analyses included: (I) cutting according to individuals; and (II) relation between rooting environments and individuals on cutting. Results: The results indicated that the girdling techniques were not efficient for vegetative rescue, as only 8% of individuals produced epicormic sprouts. In contrast, detached branches showed a much higher success rate of 80% for epicormic sprouting, revealing significant differences in sprout development among individuals over time. Vertically oriented branches produced nearly three times more sprouts compared to horizontally oriented branches. Regarding vegetative propagation, certain individuals exhibited remarkable rooting rates of over 75%. However, no conclusive results were obtained when using epicormic materials or when considering different rooting environments. Conclusions: Given the significance of rescue and vegetative propagation in plant genetic improvement and the limited research addressing these aspects in M. polymorphum, this study holds substantial importance for future investigations. It is recommended to expand rescue and vegetative propagation studies to encompass additional populations, different individuals, and rooting environments, further advancing our understanding and efforts to enhance this species.

Deciphering the fiber quality of Gossypium barbadense L. var. brasiliensis in La Convención, Cusco, Perú

BackgroundThe quality of cotton fiber determines its value in the textile market, influencing agricultural profitability and the efficiency of textile processing. The selection of genotypes with superior fibers is a key factor for genetic improvement programs seeking adaptability and sustainability in the face of climate change. This demonstrates the strategic importance of this plant for sustainable agriculture and the global textile industry. The objective of this research was to decipher the fiber quality of Gossypium barbadense var. brasiliensis in the native Amazonian communities of La Convención, Cusco-Perú, and to evaluate other critical aspects of native cotton that have not yet been identified. The methodology included non-probability sampling for accessibility, qualitative and quantitative analyses, and multivariate analyses. The fiber length (mm), micronaire index (maturity/fineness), fiber strength (gf/tex), length uniformity index (%), fiber elongation (%), maturation index (%), and short fiber index (%) were the fiber characteristics evaluated using the HVI method in cotton genotypes.ResultsCotton accessions collected from Koribeni (Gossypium spp.) and Shivankoreni (Gossypium barbadense var. brasiliensis) stood out for their fiber quality properties, especially length, strength, and uniformity, which highlights their relevance for advanced textile applications and potential for use in plant genetic improvement programs.ConclusionThese findings reinforce the need to conserve and study these native cotton accessions from the Peruvian Amazon region, which can offer promising perspectives for the textile industry and agricultural biodiversity.

The association analysis of DNA methylation and transcriptomics identified BpCYCD3;2 as a participant in influencing cell division in autotetraploid birch (Betula pendula) leaves

Polyploidization plays a crucial role in plant breeding and genetic improvement. Although the phenomenon of polyploidization affecting the area and number of plant epidermal pavement cells is well described, the underlying mechanism behind this phenomenon is still largely unknown. In this study, we found that the leaves of autotetraploid birch (Betula pendula) stopped cell division earlier and had a larger cell area. In addition, compared to diploids, tetraploids have a smaller stomatal density and fewer stomatal numbers. Genome-wide DNA methylation analysis revealed no significant difference in global DNA methylation levels between diploids and tetraploids. A total of 9154 differential methylation regions (DMRs) were identified between diploids and tetraploids, with CHH-type DMRs accounting for 91.73% of all types of DMRs. Further research has found that there are a total of 2105 differentially methylated genes (DMEGs) with CHH-type DMRs in birch. The GO functional enrichment results of DMEGs showed that differentially methylated genes were mainly involved in terms such as cellular process and metabolic process. The analysis of differentially methylated genes and differentially expressed genes suggests that hyper-methylation in the promoter region may inhibit the gene expression level of BpCYCD3;2 in tetraploids. To investigate the function of BpCYCD3;2 in birch, we obtained overexpression and repressed expression lines of BpCYCD3;2 through genetic transformation. The morphogenesis of both BpCYCD3;2-OE and BpCYCD3;2-RE lines was not affected. However, low expression of BpCYCD3;2 can lead to inhibition of cell division in leaves, and this inhibition of cell proliferation can be compensated for by an increase in cell size. Additionally, we found that the number and density of stomata in the BpCYCD3;2-RE lines were significantly reduced, consistent with the tetraploid. These data indicate that changes in cell division ability and stomatal changes in tetraploid birch can be partially attributed to low expression of the BpCYCD3;2 gene, which may be related to hyper-methylation in its promoter region. These results will provide new insights into the mechanism by which polyploidization affects plant development.

PfbZIP85 Transcription Factor Mediates ω-3 Fatty Acid-Enriched Oil Biosynthesis by Down-Regulating PfLPAT1B Gene Expression in Plant Tissues.

The basic leucine zipper (bZIP) transcription factor (TF) family is one of the biggest TF families identified so far in the plant kingdom, functioning in diverse biological processes including plant growth and development, signal transduction, and stress responses. For Perilla frutescens, a novel oilseed crop abundant in polyunsaturated fatty acids (PUFAs) (especially α-linolenic acid, ALA), the identification and biological functions of bZIP members remain limited. In this study, 101 PfbZIPs were identified in the perilla genome and classified into eleven distinct groups (Groups A, B, C, D, E, F, G, H, I, S, and UC) based on their phylogenetic relationships and gene structures. These PfbZIP genes were distributed unevenly across 18 chromosomes, with 83 pairs of them being segmental duplication genes. Moreover, 78 and 148 pairs of orthologous bZIP genes were detected between perilla and Arabidopsis or sesame, respectively. PfbZIP members belonging to the same subgroup exhibited highly conserved gene structures and functional domains, although significant differences were detected between groups. RNA-seq and RT-qPCR analysis revealed differential expressions of 101 PfbZIP genes during perilla seed development, with several PfbZIPs exhibiting significant correlations with the key oil-related genes. Y1H and GUS activity assays evidenced that PfbZIP85 downregulated the expression of the PfLPAT1B gene by physical interaction with the promoter. PfLPAT1B encodes a lysophosphatidate acyltransferase (LPAT), one of the key enzymes for triacylglycerol (TAG) assembly. Heterogeneous expression of PfbZIP85 significantly reduced the levels of TAG and UFAs (mainly C18:1 and C18:2) but enhanced C18:3 accumulation in both seeds and non-seed tissues in the transgenic tobacco lines. Furthermore, these transgenic tobacco plants showed no significantly adverse phenotype for other agronomic traits such as plant growth, thousand seed weight, and seed germination rate. Collectively, these findings offer valuable perspectives for understanding the functions of PfbZIPs in perilla, particularly in lipid metabolism, showing PfbZIP85 as a suitable target in plant genetic improvement for high-value vegetable oil production.

Effect of Media and Photoperiod on Embryogenic and Organogenic Callus Induction from Mature Seed in Oryza sativa L.

Rice is the staple food for billions of people and a source of income for hundreds of millions. This food security crop production needs to be improved to face the projected demands of the exponentially augmenting world’s population and overcome biotic and abiotic stress in the fields. Optimized in vitro culture protocols are a prerequisite to genetic engineering which appears to be the best potential way to improve the rice plant. In this study, ‘Nerica 3’ and ‘Nerica L36’ seeds were in vitro culture tested into 4 media (m1-4), in dark and photoperiod environments. The percentage of callus induction was calculated and callus weight was recorded. Results show that callus induction was influenced by variety × environment and medium × environment interactions, with a strong influence of the environment used. ‘Nerica 3’ showed the highest mean (88.25%) callus induction after six weeks of incubation on different media. m1 and m2 media showed greater mean callus induction (more than 86%). Higher callus induction came from m1 (82% and 91%) and m2 (81% and 93%) media, while lower rates came from m3 (73%) and m4 (69%) media for embryogenic and organogenic calli respectively. Culturing the explant in dark environment to produce embryogenic callus, resulted in greater callus weight for ‘Nerica 3’ (1.03 g) and ‘Nerica L36’ (0.79 g). This study is a contribution to the rice plant genetic improvement by proposing protocols for somatic embryogenesis of two Nerica rice varieties.

Assessing Genetic Relationships, Trait Associations and Diversity Patterns in Sorghum Germplasm Through Correlation, Cluster and Principal Component Analysis

Background: The loss of biodiversity has a significant impact on the fundamental services provided by ecosystems to humanity, including plant development and genetic improvement. Germplasm serves as the foundational material for identifying genetic variations. In this context, the examination of sorghum germplasm diversity has been conducted. Methods: The study involved 86 different sorghum germplasm samples that were assessed alongside three control groups, each replicated three times, during the Rabi season of 2021. This evaluation was conducted using augmented block design I (ABD I) at the Department of Millets, Tamil Nadu Agricultural University in Coimbatore. Result: The results of the Pearson correlation analysis revealed significant relationships notably, traits such as plant height, number of leaves, panicle length, panicle width, panicle weight, hundred seed weight and dry fodder yield exhibited positive and significant correlations with grain yield per plant. Cluster analysis identified four distinct groupings among the 86 accessions, with clusters 1 and 4 displaying the greatest diversity. Principal component analysis indicated that PC1 accounted for the largest variability. The genotypes were identified through PCA analysis is having greater variation and better performance. The findings of this study suggest that the identified sorghum genotypes could serve as valuable genetic resources for enhancing sorghum productivity in dry and semi-arid regions, particularly in the face of unpredictable climate change.

An efficient genetic transformation system mediated by Rhizobium rhizogenes in fruit trees based on the transgenic hairy root to shoot conversion.

Genetic transformation is a critical tool for gene editing and genetic improvement of plants. Although many model plants and crops can be genetically manipulated, genetic transformation systems for fruit trees are either lacking or perform poorly. We used Rhizobium rhizogenes to transfer the target gene into the hairy roots of Malus domestica and Actinidia chinensis. Transgenic roots were generated within 3 weeks, with a transgenic efficiency of 78.8%. Root to shoot conversion of transgenic hairy roots was achieved within 11 weeks, with a regeneration efficiency of 3.3%. Finally, the regulatory genes involved in stem cell activity were used to improve shoot regeneration efficiency. MdWOX5 exhibited the most significant effects, as it led to an improved regeneration efficiency of 20.6% and a reduced regeneration time of 9 weeks. Phenotypes of the overexpression of RUBY system mediated red roots and overexpression of MdRGF5 mediated longer root hairs were observed within 3 weeks, suggesting that the method can be used to quickly screen genes that influence root phenotype scores through root performance, such as root colour, root hair, and lateral root. Obtaining whole plants of the RUBY system and MdRGF5 overexpression lines highlights the convenience of this technology for studying gene functions in whole plants. Overall, we developed an optimized method to improve the transformation efficiency and stability of transformants in fruit trees.

GhRCD1 promotes cotton tolerance to cadmium by regulating the GhbHLH12-GhMYB44-GhHMA1 transcriptional cascade.

Heavy metal pollution poses a significant risk to human health and wreaks havoc on agricultural productivity. Phytoremediation, a plant-based, environmentally benign, and cost-effective method, is employed to remove heavy metals from contaminated soil, particularly in agricultural or heavy metal-sensitive lands. However, the phytoremediation capacity of various plant species and germplasm resources display significant genetic diversity, and the mechanisms underlying these differences remain hitherto obscure. Given its potential benefits, genetic improvement of plants is essential for enhancing their uptake of heavy metals, tolerance to harmful levels, as well as overall growth and development in contaminated soil. In this study, we uncover a molecular cascade that regulates cadmium (Cd2+) tolerance in cotton, involving GhRCD1, GhbHLH12, GhMYB44, and GhHMA1. We identified a Cd2+-sensitive cotton T-DNA insertion mutant with disrupted GhRCD1 expression. Genetic knockout of GhRCD1 by CRISPR/Cas9 technology resulted in reduced Cd2+ tolerance in cotton seedlings, while GhRCD1 overexpression enhanced Cd2+ tolerance. Through molecular interaction studies, we demonstrated that, in response to Cd2+ presence, GhRCD1 directly interacts with GhbHLH12. This interaction activates GhMYB44, which subsequently activates a heavy metal transporter, GhHMA1, by directly binding to a G-box cis-element in its promoter. These findings provide critical insights into a novel GhRCD1-GhbHLH12-GhMYB44-GhHMA1 regulatory module responsible for Cd2+ tolerance in cotton. Furthermore, our study paves the way for the development of elite Cd2+-tolerant cultivars by elucidating the molecular mechanisms governing the genetic control of Cd2+ tolerance in cotton.

An Introduction to Plant Cell, Tissue, and Organ Culture: Current Status and Perspectives.

Plant cell, tissue, and organ cultures (PCTOC) have been used as experimental systems in basic research, allowing gene function demonstration through gene overexpression or repression and investigating the processes involved in embryogenesis and organogenesis or those related to the potential production of secondary metabolites, among others. On the other hand, PCTOC has also been applied at the commercial level for the vegetative multiplication (micropropagation) of diverse plant species, mainly ornamentals but also horticultural crops such as potato or fruit and tree species, and to produce high-quality disease-free plants. Moreover, PCTOC protocols are important auxiliary systems in crop breeding crops to generate pure lines (homozygous) to produce hybrids for the obtention of polyploid plants with higher yields or better performance. PCTOC has been utilized to preserve and conserve the germplasm of different crops or threatened species. Plant genetic improvement through genetic engineering and genome editing has been only possible thanks to the establishment of efficient in vitro plant regeneration protocols. Different companies currently focus on commercializing plant secondary metabolites with interesting biological activities using in vitro PCTOC. The impact of omics on PCTOC is discussed.

Preliminary results of mutagenesis by irradiation in E. globulus and E. nitens seeds

Although ionizing radiation is a tool widely used in plant genetic improvement, generating genetic diversity and improving yields and traits in crops throughout the world with 3,275 mutant cultivars. Climatic change affects native forest ecosystems and plantations leading to significant reductions in tree production. In 2020, INFOR and CCHEN initiated the CHI5052 project for mutagenesis of forest species affected by climate change in Chile with funding from International Atomic Energy Agency (IAEA), and recently received a Grant from Government of Biobio, Innovation Fund for Competitiveness (FIC-R). Seed irradiation treatments were carried out in a self-shielded Gamma Cell 220R irradiator equipped with CO60 and an irradiation rate of 8.9 Gy|min established by the Fricke dosimetric system. It involved the effects of gamma irradiation treatments (0, 10, 20, 30, 40, 50 Gy) on seed germination and initial growth of Eucalyptus nitens at 8 months-old. It also included determination of gamma radiation dosimetry for LD30 and LD50 doses for Eucalyptus globulus. The results obtained on gamma radiation seeds on Eucalyptus nitens confirm the positive effect on germination and initial growth of seedlings in the field in doses of 10 Gy at 8-months-old. The preliminary LD30 radiations dosimetry of E. globulus have generated seedlings with leaf aberration, pleiocotyly, that possible correspond to knock-out mutation of a dominant allele at a heterozygous locus or a dominant mutation that needs to be confirmed by molecular markers. The preliminary results provide guidance regarding the magnitude of gamma radiation to be used and confirm that relatively low doses would be the most effective to improve germination and initial seedling growth for Eucalyptus nitens; but considering the differences between species and the diversity of existing results in the bibliography, the doses to test must be defined for each particular species.

CRISPR Variants for Gene Editing in Plants: Biosafety Risks and Future Directions.

The CRISPR genome editing technology is a crucial tool for enabling revolutionary advancements in plant genetic improvement. This review shows the latest developments in CRISPR/Cas9 genome editing system variants, discussing their benefits and limitations for plant improvement. While this technology presents immense opportunities for plant breeding, it also raises serious biosafety concerns that require careful consideration, including potential off-target effects and the unintended transfer of modified genes to other organisms. This paper highlights strategies to mitigate biosafety risks and explores innovative plant gene editing detection methods. Our review investigates the international biosafety guidelines for gene-edited crops, analyzing their broad implications for agricultural and biotechnology research and advancement. We hope to provide illuminating and refined perspectives for industry practitioners and policymakers by evaluating CRISPR genome enhancement in plants.

EARLY FLOWERING is a dominant gain-of-function allele of FANTASTIC FOUR 1/2c that promotes early flowering in tomato.

Flowering time, an important factor in plant adaptability and genetic improvement, is regulated by various genes in tomato (Solanum lycopersicum). In this study, we characterized a tomato mutant, EARLY FLOWERING (EF), that developed flowers much earlier than its parental control. EF is a dominant gain-of-function allele with a T-DNA inserted 139 bp downstream of the stop codon of FANTASTIC FOUR 1/2c (FAF1/2c). The transcript of SlFAF1/2c was at elevated levels in the EF mutant. Overexpressing SlFAF1/2c in tomato plants phenocopied the early flowering trait of the EF mutant. Knocking out SlFAF1/2c in the EF mutant reverted the early flowering phenotype of the mutant to the normal flowering time of the wild-type tomato plants. SlFAF1/2c promoted the floral transition by shortening the vegetative phase rather than by reducing the number of leaves produced before the emergence of the first inflorescence. The COP9 signalosome subunit 5B (CSN5B) was shown to interact with FAF1/2c, and knocking out CSN5B led to an early flowering phenotype in tomato. Interestingly, FAF1/2c was found to reduce the accumulation of the CSN5B protein by reducing its protein stability. These findings imply that FAF1/2c regulates flowering time in tomato by reducing the accumulation and stability of CSN5B, which influences the expression of SINGLE FLOWER TRUSS (SFT), JOINTLESS (J) and UNIFLORA (UF). Thus, a new allele of SlFAF1/2c was discovered and found to regulate flowering time in tomato.

Genoplasmics: Advancing Plant Germplasm Research through Genomics

Plant genetic resources (PGR) are crucial for crop improvement programs. The National Genebank (NGB) at ICAR-NBPGR is responsible for collecting, conserving, and facilitating the utilization of genetic diversity in crop plants. Plant germplasm forms the foundation for plant genetic improvement. Extensive germplasm collections have been amassed and stored, presenting the challenge of effectively harnessing and exploiting this valuable resource. Genomics-based plant germplasm research (GPGR), or genoplasmics, is an emerging interdisciplinary field that applies genomic principles and methods to germplasm study. This article outlines the concept, strategy, and approach of GPGR, highlighting recent advancements in core collection creation, germplasm enhancement through core collections, and gene discovery from core collections. GPGR represents a significant milestone in germplasm research, ushering in a new scientific investigation and innovation era.

Cytogenetic activity of a mutagenic factor with high damaging capacity in winter wheat

The analysis of cytological abnormalities is an important method for identifying the potential of a chemical as a mutagen for future heritable genetic changes, the level of genotype-mutagen interaction and site-specific activity for the nature and/or different concentrations of the mutagen. The research aims to determine the limits of the variability of genotypes of different origins, especially those with wide ecological and genetic variability, and to show the interaction between the variety and the mutagen. Winter wheat grains of several varieties (Balaton, Borovytsia, Zelenyi Hai, Zoloto Ukrainy, Kalancha, Niva Odeska, Polianka, Pochayna) were treated with dimethyl sulphate at concentrations of 0.0125%, 0.025%, 0.05%, and exposure was 24 hours. The cytogenetic activity was studied by the frequency and spectrum of chromosomal rearrangements in the corresponding phases of cell division, depending on the variety and concentration of the mutagen as the main factors affecting these parameters, as well as the main features of the spectrum, such as the overall rate of chromosomal rearrangements, the number of fragments and double fragments, bridges, micronuclei, and lagging chromosomes. The studied concentrations of the supermutagen were found to have a significant effect on all analysed parameters and can be classified as optimal and high concentration levels in terms of the effect on cytological activity and mitotic problems for the factor, despite previous studies. The variety factor has a much greater impact on the nature and frequency of certain types of aberrations than an increase in the mutagen concentration, it was characterised by a much greater site-specific effect than other chemical agents, and various variants in mutagenic effects were identified according to the subject’s genotype. It was generalised that the features that reproduced the effect of the mutagen, according to the discriminant analysis, were the total frequency, the frequency of fragments and double fragments, and bridges. In practical use in the genetic improvement of plants and for obtaining valuable traits, the optimal concentrations are 0.0125%, and 0.025%, which is planned to be further confirmed on a wider range of genotypes and by mutation studies for the next (second or third) generations

A homolog of AtCBFs, SmDREB A1-4, positively regulates salt stress tolerance in Arabidopsis thaliana and Salix matsudana

CBFs (C-repeat binding factors) have multiple functions in abiotic stress adaption; functional research of these genes will provide precious gene resources for plant genetic improvement. In this study, a homolog of AtCBFs, SmDREB A1-4 was cloned and its role in salt tolerance was explored. SmDREB A1-4 is a member of DREB A1 subgroup with 10 members. SmDREB A1-4 localized in nuclei and cytoplasm and expressed ubiquitously in different tissue and organs. The expression level of SmDREB A1-4 could be induced by NaCl treatment and the TC-rich repeat and DREB motif on the SmDREB A1-4 gene promoter may mediate the NaCl-induced expression pattern. Overexpression of the SmDREB A1-4 gene in Arabidopsis enhanced the salt tolerance of transgenic Arabidopsis lines, while down-regulated the expression level in Salix plantlets by Virus induce gene silencing decreased the salt tolerance capacity in VIGS Salix plantlets. Experiments data from both sides confirmed that SmDREB A1-4 is a positive regulatory factor in salt stress tolerance. qRT-PCR and luciferase reporter assays revealed that SOS1 and DREB2A are downstream genes of SmDREB A1-4. Through upregulating the expression of SOS1 and DREB2A, SmDREB A1-4 enhanced plant tolerance to salinity by regulating ion homeostasis, reduction of Na+/K+ ratio, and improvement of proline biosynthesis. This research offers a potentially valuable gene resource for the stress-resistant varieties breeding of Salix matsudana in the future.

Genetic Components and Variability Assessment for Grain Yield and Its Accrediting Traits in Maize (Zea mays L.)

Understanding the variability, heritability, and genetic advance in maize is crucial for efficient plant breeding and genetic improvement programmes. The present investigation was conducted to evaluate the various parameters related to assessment of genetic variability and nature of associations among traits affecting grain yield in 80 genotypes of maize (Zea mays L.) at the Research Farm, Department of Genetics & Plant Breeding, College of Agriculture, Gwalior, M.P., India during the Rabi seasons of 2019-20 and Kharif 2020-21. The analysis of variance revealed that highly significant differences exist among the inbred lines, their hybrids and checks for all the characters. Under irrigated and partial irrigated conditions, traits viz., days to 50 percent tasselling and silking, anthesis silking interval (ASI), plant height and membrane stability index exhibited high GCV and PCV. The characters with the highest heritability coupled with higher genetic advance were found for the traits namely: days to 50% silking and 50% tasselling, anthesis silking interval, plant height, numbers of kernel rows per cob, numbers of kernel per rows, seed yield per plant (g), numbers of cobs per plant, days to maturity, cob girth (cm), turgid weight (g), saturation water deficit and membrane stability index for both under irrigated and partial irrigated conditions. High heritability with higher genetic advance as percent of mean indicated the preponderance of additive gene action in controlling the traits. Hence direct selection of such characters would be effective in improving the yield in maize.

Chemical emasculation in cowpea (Vigna unguiculata (L.) Walp.) and dicotyledonous model species using trifluoromethanesulfonamide (TFMSA)

Hybridization plays an indispensable role in creating the diversity associated with plant evolution and genetic improvement of crops. Production of hybrids requires control of pollination and avoidance of self-pollination for species that are predominantly autogamous. Hand emasculation, male sterility genes or male gametocides have been used in several plant species to induce pollen sterility. However, in cowpea (Vigna unguiculata (L.) Walp), a self-pollinated cleistogamous dryland crop, only hand emasculation is used, but it is tedious and time-consuming. In this study, male sterility was effectively induced in cowpea and two dicotyledonous model species (Arabidopsis thaliana (L.) Heynh. and Nicotiana benthamiana Domin) using trifluoromethanesulfonamide (TFMSA). Pollen viability assays using Alexander staining showed that 30 ml of 1000 mg/l TFMSA with two-time treatments of one-week interval at the early stage of the reproductive phase under field or greenhouse conditions induced 99% pollen sterility in cowpea. TFMSA treatment induced non-functional pollen in diploid A. thaliana at two-time treatment of 10 ml of 125–250 mg/l per plant and N. benthamiana at two-time treatment of 10 ml of 250–1000 mg/l per plant. TFMSA-treated cowpea plants produced hybrid seeds when used as the female parent in crosses with non-treated plants used as male parents, suggesting that TFMSA had no effect on female functionality in cowpea. The ease of TFMSA treatment and its effectiveness to induce pollen sterility in a wide range of cowpea genotypes, and in the two model plant species tested in this study, may expand the scope of techniques for rapid pollination control in self-pollinated species, with potential applications in plant breeding and plant reproduction science.

Seleção de caracteres para programas de melhoramento genético do mamoeiro sob estresse hídrico e térmico

ABSTRACT Papaya cultivation is widespread in Brazil, particularly in the states of Bahia and Espírito Santo, where most commercial plantations are concentrated. Owing to the economic and social importance of papaya, the present study aimed to determine the explanatory variables between the genotypes of two cultivars: Golden (from the Soil group) and Tainung Nº 1 hybrid (from the Formosa group), cultivated under high temperatures and hydric stress. The genotypes containing more desirable agronomic characteristics were identified for use in plant genetic improvement programs. Principal component analysis (PCA) was applied to select the desirable genotypes for Golden and Tainung Nº 1 cultivars based on specific variables analyzed for two groups of variables; for group 1, the plant height, stem diameter, leaf length, leaf width, and leaf number were analyzed, whereas for group 2, the leaf and root dry mass, stem dry mass and fresh mass of 10 discs, fresh mass, and stem and root fresh mass were analyzed. When exposed to hydric and thermal stress, the Tainung Nº 1 cultivar outperformed the Golden cultivar for the evaluation characteristics selected for use in genetic improvement programs.