Characterization of Induced High Yielding Cowpea Mutant Lines Using Physiological, Biochemical and Molecular Markers

Gamma ray induced significant phenotypic and metabolite changes in sugarcane variants derived through in vitro mutagenesis

Sugarcane is an economically important polyploid crop whose genetic complexity and limited fertility poses a challenge for crop improvement programs. Gamma radiation-induced mutagenesis is an alternate approach for generating a diverse array of agronomically useful mutants, accelerating varietal development in a long-duration crop like sugarcane. To develop agronomically useful mutants of a commercial sugarcane genotype Co 99004, gamma ray induced in vitro mutagenesis was carried out. The phenotypic variants of Co 99004 in V1 generation could be categorized into five distinct phenotypically scorable classes, including three chlorophyll mutants (albina, chlorina and chlorina pigmented) and two green mutants like wild type control. SRAP marker analyses indicated distinct genomic variation among the phenotypic mutants and control plants, with the polymorphic information content (PIC) ranging from 0 to 0.472. Further, the phylogenetic dendrogram derived from the SRAP marker data grouped the mutants into four distinct clusters clearly differentiating the phenotypic classification. Sequencing of selected SRAP amplicons indicated deletion/insertion of gene specific fragments. Interestingly, the loss of chlorophyll in albina and chlorina mutants showed gamma irradiation-induced deletions in the gene encoding FAR1-RELATED SEQUENCE 5-like protein, which is involved in chlorophyll biosynthesis. GC-MS based metabolome profiling showed alteration in tetrapyrrole biosynthesis, MEP (Methylerythritol Phosphate), and fatty acid biosynthesis pathways, indicating a significant metabolic variation in the chlorophyll mutants. Further characterization of the genetically distinct, non-lethal green wild type mutants can lead to the identification of agronomically useful mutants. In addition, the loss-of-function chlorophyll mutants can serve as a good source for comparative genomics studies aimed at gene-trait association.

Biochemical and molecular profiling of induced high yielding M3 mutant lines of two Trigonella species: Insights into improved yield potential

Trigonella, commonly known as Fenugreek, is among the most promising medicinal herbs consumed worldwide due its protein rich dietary contributions. This study involved induced mutagenesis on two Trigonella species (Trigonella foenum-graecum var. PEB and Trigonella corniculata var. Pusa kasuri) using caffeine and sodium azide as mutagens, resulting in the identification of nine high-yielding mutant lines in the M3 generation. Molecular characterization using SCoT markers revealed a high polymorphism of 28.3% and 46.7% in PEB and Pusa kasuri, respectively, facilitating the investigation of genetic divergence among the control and mutant lines. Similarity correlation analysis indicated a high similarity between mutant A and mutant C (0.97) and between mutant J and mutant O (0.88), while the lowest similarity was observed between mutant B and mutant F (0.74) and between control and mutant L (0.58). Mutant F and Mutant J displayed the highest seed yield and its attributing traits, and seed protein content in PEB and Pusa kasuri, respectively. Physiological parameters, including chlorophyll content (Mutants A and N) and carotenoids (mutant A and J), exhibited improvements. Assessment of stomatal and seed characteristics using scanning electron microscopy may lead to improved physiological processes and distinction at the interspecific level, respectively. Methanolic extracts of the control and the mutant lines of both species were subjected to GC-MS analysis, revealing 24 major phytocompounds known for their pharmacological activities (antioxidant, anti-inflammatory, anticancer, etc.). Statistical methods such as Pearson correlation heatmap and pairwise scatter plot matrix provided insights into the correlations and linear associations among parameters for both PEB and Pusa kasuri. The strong correlation between iron content and seeds per pod in the mutant lines suggests a promising avenue for further research. Continued research and breeding efforts using these mutants can lead to significant advancements in agriculture and medicine, benefiting farmers, consumers, and industries alike.

Mutations induced in some Egyptian cowpea varieties with yield characteristics and high nutritional value using gamma rays and evaluation by microsatellite markers

PURPOSE

In order to achieve mutations with enhanced economic, productive, and nutritional characteristics in the two Egyptian cowpea varieties, Dokki 331 and Kaha 1, the application of gamma irradiation at different doses is employed. Additionally, this method aids in distinguishing between these mutations using simple sequence repeat (SSR) analysis.

MATERIALS AND METHODS

Two different cowpea cultivars were subjected to varying doses of gamma radiation ranging from 50 to 300 Gy. In order to analyze the effects of radiation, both unirradiated and irradiated seeds from both cultivars were planted using a randomized complete block design. This experiment was conducted over a span of six generations, namely M1, M2, M3, M4, M5, and M6, starting from April 2017 and continuing until 2022. Among the various radiation doses, the cultivar Kaha 1 produced promising traits when exposed to a dose of 150 Gy, while the cultivar Dokki 331 showed favorable traits when exposed to a dose of 300 Gy. These traits were further cultivated and studied until the M6 generation.

RESULTS

Induced mutations in two Egyptian cowpea varieties, Kaha 1 and Dokki 331, are subjected to varying doses of gamma radiation (0, 50, 100, 150, 200, 250, and 300 Gy). Morphological and genetic variations were observed, with mutations being induced at doses of 150 Gy for Kaha 1 and 300 Gy for Dokki 331. The mutation in Kaha 1 (beam 1) resulted in dwarfism, altered leaf shape, early flowering, increased peduncles, pods, and pod seed numbers, ultimately leading to enhanced seed production and acreage productivity. In Dokki 331, the mutations primarily affected pod color, resulting in greenish-brown pods with mosaic seeds, segregating black and gray seeds from the mosaic ones. These mutations led to an increase in the nutritional value of the seeds, including higher nitrogen content, total free amino acids, crude protein, total carbohydrates, and total sugars. The genetic diversity of the seven cowpea mutations was assessed using 20 microsatellite markers. The analysis revealed a total of 60 alleles, with an average of three alleles per locus. The allele frequency ranged from 0.2857 to 1.0, with an average of 0.6036. Gene diversity varied from 0.0 to 0.8163, while the heterozygosity was mostly zero, except for one primer (VM 37) with an average of 0.0071. The polymorphic information content (PIC) ranged from 0.7913 to 0.0, with an average of 0.4323. The Marker Index value ranged from 0.36 to 0.0, with an average of 0.152. Overall, our findings demonstrate the successful induction of mutations in Egyptian cowpea varieties using gamma rays, resulting in improved yield characteristics and nutritional value.

CONCLUSIONS

Radiation as a physical mutagen is highly regarded for its effectiveness, affordability, speed, and safety in inducing mutations. Utilizing gamma rays, we successfully derived a novel cowpea variety called beam 1 mutation, which has gained approval from the Egyptian Ministry of Agriculture.

Gamma rays and sodium azide induced variations in bio-physiological and agronomical traits in linseed (Linum usitatissimum L.)

Linseed is a valuable oilseed crop with huge therapeutic importance due to its high content of omega-3 fatty acids in the form of Alpha-linolenic acid (ALA). It is a self-pollinated crop with a low-yielding potential that restricts its improvement endeavors. To overcome low-yielding potential, individual and combination treatments of gamma rays and sodium azide were employed in widely grown linseed varieties. The results revealed a dose-dependent decline in seed germination, seedling height, pollen fertility, chlorophyll, and carotenoid contents and a dose-independent decline in carbonic anhydrase activity. Bio-physiological parameters decreased substantially in combination treatments compared to individual treatments of gamma rays and sodium azide. In contrast, lower doses of gamma rays, sodium azide, and their combinations effectively increased mean values of yield and yield-attributing traits in a few putative mutants. Such putative mutants represent a valuable genetic resource that could be used in future breeding programs for the genetic improvement of linseed and related medicinal plants.

Gamma-rays induced genome wide stable mutations in cowpea deciphered through whole genome sequencing

PURPOSE

Gamma rays are the most widely exploited physical mutagen in plant mutation breeding. They are known to be involved in the development of more than 60% of global cowpea (Vigna unguiculata (L.) Walp.) mutant varieties. Nevertheless, the nature and type of genome-wide mutations induced by gamma rays have not been studied in cowpea and therefore, the present investigation was undertaken.

MATERIALS AND METHODS

Genomic DNAs from three stable gamma rays-induced mutants (large seed size, small seed size and disease resistant mutant) of cowpea cultivar 'CPD103' in M6 generation along with its progenitor were used for Illumina-based whole-genome resequencing.

RESULTS

Gamma rays induced a relatively higher frequency (88.9%) of single base substitutions (SBSs) with an average transition to transversion ratio (Ti/Tv) of 3.51 in M6 generation. A > G transitions, including its complementary T > C transitions, predominated the transition mutations, while all four types of transversion mutations were detected with frequencies over 6.5%. Indels (small insertions and deletions) constituted about 11% of the total induced variations, wherein small insertions (6.3%) were relatively more prominent than small deletions (4.8%). Among the indels, single-base indels and, in particular, those involving A/T bases showed a preponderance, albeit indels of up to three bases were detected in low proportions. Distributed across all 11 chromosomes, only a fraction of SBSs (19.45%) and indels (20.2%) potentially altered the encoded amino acids/peptides. The inherent mutation rate induced by gamma rays in cowpea was observed to be in the order of 1.4 × 10-7 per base pair in M6 generation.

CONCLUSION

Gamma-rays with a greater tendency to induce SBSs and, to a lesser extent, indels could be efficiently and effectively exploited in cowpea mutation breeding.

A Genome-Wide Association Study Reveals Region Associated with Seed Protein Content in Cowpea

Cowpea (Vigna unguiculata L. Walp., 2n = 2x = 22) is a protein-rich crop that complements staple cereals for humans and serves as fodder for livestock. It is widely grown in Africa and other developing countries as the primary source of protein in the diet; therefore, it is necessary to identify the protein-related loci to improve cowpea breeding. In the current study, we conducted a genome-wide association study (GWAS) on 161 cowpea accessions (151 USDA germplasm plus 10 Arkansas breeding lines) with a wide range of seed protein contents (21.8~28.9%) with 110,155 high-quality whole-genome single-nucleotide polymorphisms (SNPs) to identify markers associated with protein content, then performed genomic prediction (GP) for future breeding. A total of seven significant SNP markers were identified using five GWAS models (single-marker regression (SMR), the general linear model (GLM), Mixed Linear Model (MLM), Fixed and Random Model Circulating Probability Unification (FarmCPU), and Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK), which are located at the same locus on chromosome 8 for seed protein content. This locus was associated with the gene Vigun08g039200, which was annotated as the protein of the thioredoxin superfamily, playing a critical function for protein content increase and nutritional quality improvement. In this study, a genomic prediction (GP) approach was employed to assess the accuracy of predicting seed protein content in cowpea. The GP was conducted using cross-prediction with five models, namely ridge regression best linear unbiased prediction (rrBLUP), Bayesian ridge regression (BRR), Bayesian A (BA), Bayesian B (BB), and Bayesian least absolute shrinkage and selection operator (BL), applied to seven random whole genome marker sets with different densities (10 k, 5 k, 2 k, 1 k, 500, 200, and 7), as well as significant markers identified through GWAS. The accuracies of the GP varied between 42.9% and 52.1% across the seven SNPs considered, depending on the model used. These findings not only have the potential to expedite the breeding cycle through early prediction of individual performance prior to phenotyping, but also offer practical implications for cowpea breeding programs striving to enhance seed protein content and nutritional quality.

Assessment of Bio-physiological damages and cytological aberrations in cowpea varieties treated with gamma rays and sodium azide

The assessment of mutagen induced biological damage forms an important study in determining the mutagenic potency and genotypic sensitivity, a vital aspect in mutation breeding programs. A prior assessment of lethal dose (LD50), mutagen induced biological damage (alterations in bio-physiological traits and frequency of cytological aberrations) is a prerequisite for determining an optimum mutagen dose in a successful mutation breeding experiment. Therefore, in a multi-year project of mutation breeding, two widely cultivated varieties of cowpea viz., Gomati VU-89 and Pusa-578, were treated with gamma (γ) rays and sodium azide (SA) doses. The results reflected a proportionate increase in bio-physiological damages with the increase in mutagenic doses and caused a substantial reduction in mean seed germination and seedling height. Different cytological aberrations such as cytomixis, univalents, chromosome stickiness, precocious separation, unequal separation, bridges, laggards, disturbed polarity, dyads, triads, and polyads were observed in both varieties. All the mutagen doses induced a broader spectrum of cytological aberrations with varying frequencies.

Field assessment of yield and its contributing traits in cowpea treated with lower, intermediate, and higher doses of gamma rays and sodium azide

Across the globe, plant breeders of different organizations are working in collaboration to bring preferred traits to crops of economic importance. Among the traits, "high yielding potential" is the most important as it is directly associated with food security and nutrition, one of the sustainable development goals. The Food and Agriculture Organization acknowledges plant breeders' role and efforts in achieving local and global food security and nutrition. Recognizing the importance of pulses and increasing pressure on food security, the United Nations General Assembly declared 2016 the "International year of Pulses" owing to their preferred traits such as climate change resilience, wide adaptability, low agriculture input, and protein- and nutrient-rich crops. Keeping all these developments in consideration, we initiated an induced mutagenesis program by treating cowpea (Vigna unguiculata L. Walp.) with different doses of gamma rays and sodium azide aiming to enhance the yielding potential of an otherwise outstanding variety viz., Gomati VU-89 and Pusa-578. We noticed a substantial increase in mean values of agronomic traits in putative mutants raised from seeds treated with lower and intermediate doses of mutagens. Statistical analysis such as correlation, path, hierarchical clustering analysis (HCA), and principal component analysis (PCA) were used to assess the difference between mutagenized and control populations. A significant and positive correlation of yield with yield-attributing traits was recorded. However, among all the yield attributing traits, seeds per pod (SPP) depicted the maximum direct impact upon yield, and therefore, working on this trait may yield better results. A widely used PCA revealed 40.46% and 33.47% of the total variation for var. Gomati VU-89 and var. Pusa-578, respectively. Cluster analysis clustered treated and control populations into separate clusters with variable cluster sizes. Cluster V in the variety Gomati VU-89 and cluster V and VI in the variety Pusa 578 comprised of putative mutants were higher yielding and hence could be recommended for selection in future breeding programs. We expect to release such mutant lines for farmer cultivation in Northern parts of India depending on the performance of such high-yielding mutant lines at multilocations.

Comparative effects of caffeine and lead nitrate on the bio-physiological and yield associated traits of lentil (Lens culinaris Medik.)

Lentil belonging to the fabaceae family is a proteinaceous cool-season legume consumed across the world. However, lentil is low yielding with a narrow genetic base compared to other grain legumes such as chickpea, faba bean, and cowpea. In the present study, we intended to investigate the effect of two different mutagens viz., caffeine and lead nitrate on the bio-physiological and agronomical traits of lentil. Unlike other mutagens like ethyl methanesulphonate, sodium azide, and hydrazine hydrates very little is known about the mutagenic potency of caffeine and lead nitrate. The results revealed contrasting effects as lower doses of caffeine-induced a substantial increase in mean values of physiological and agronomical traits whereas both lower and higher doses of lead nitrate negatively impacted the agronomical traits of lentil. Among the mutagen doses, 0.1% caffeine was most efficient in inducing a substantial increase in mean values of bio-physiological and quantitative traits. The present study also revealed the successful conduct of induced mutagenesis in lentil and present a protocol that could be followed in future breeding programs aimed at increasing the yielding potential of legumes.

Cowpea Constraints and Breeding in Europe

Cowpea (Vigna unguiculata (L.) Walp.) is a legume with a constant rate of cultivation in Southern European countries. Consumer demand for cowpea worldwide is rising due to its nutritional content, while Europe is constantly attempting to reduce the deficit in the production of pulses and invest in new, healthy food market products. Although the climatic conditions that prevail in Europe are not so harsh in terms of heat and drought as in the tropical climates where cowpea is mainly cultivated, cowpea confronts with a plethora of abiotic and biotic stresses and yield-limiting factors in Southern European countries. In this paper, we summarize the main constraints for cowpea cultivation in Europe and the breeding methods that have been or can be used. A special mention is made of the availability plant genetic resources (PGRs) and their potential for breeding purposes, aiming to promote more sustainable cropping systems as climatic shifts become more frequent and fiercer, and environmental degradation expands worldwide.

Conventional and new-breeding technologies for improving disease resistance in lentil (Lens culinaris Medik)

Lentil, an important cool season food legume, is a rich source of easily digestible protein, folic acid, bio-available iron, and zinc nutrients. Lentil grows mainly as a sole crop in the winter after harvesting rice in South Asia. However, the annual productivity is low due to its slow growth during the early phase, competitive weed infestation, and disease outbreaks during the crop growth period. Disease resistance breeding has been practiced for a long time to enhance resistance to various diseases. Often the sources of resistance are available in wild crop relatives. Thus, wide hybridization and the ovule rescue technique have helped to introgress the resistance trait into cultivated lentils. Besides hybridization, induced mutagenesis contributed immensely in creating variability for disease tolerance, and several disease-resistant mutant lines have been developed. However, to overcome the limitations of traditional breeding approaches, advancement in molecular marker technologies, and genomics has helped to develop disease-resistant and climate-resilient lentil varieties with more precision and efficiency. This review describes types of diseases, disease screening methods, the role of conventional and new breeding technologies in alleviating disease-incurred damage and progress toward making lentil varieties more resilient to disease outbreaks under the shadow of climate change.

The TaGSK1, TaSRG, TaPTF1, and TaP5CS Gene Transcripts Confirm Salinity Tolerance by Increasing Proline Production in Wheat (Triticum aestivum L.)

Salinity is an abiotic stress factor that reduces yield and threatens food security in the world's arid and semi-arid regions. The development of salt-tolerant genotypes is critical for mitigating yield losses, and this journey begins with the identification of sensitive and tolerant plants. Numerous physiologic and molecular markers for detecting salt-tolerant wheat genotypes have been developed. One of them is proline, which has been used for a long time but has received little information about proline-related genes in wheat genotypes. In this study, proline content and the expression levels of proline-related genes (TaPTF1, TaDHN, TaSRG, TaSC, TaPIMP1, TaMIP, TaHKT1;4, TaGSK, TaP5CS, and TaMYB) were examined in sensitive, moderate, and tolerant genotypes under salt stress (0, 50, 150, and 250 mM NaCl) for 0, 12, and 24 h. Our results show that salt stress increased the proline content in all genotypes, but it was found higher in salt-tolerant genotypes than in moderate and sensitive genotypes. The salinity stress increased gene expression levels in salt-tolerant and moderate genotypes. While salt-stress exposure for 12 and 24 h had a substantial effect on gene expression in wheat, TaPTF1, TaPIMP1, TaMIP, TaHKT1;4, and TaMYB genes were considerably upregulated in 24 h. The salt-tolerant genotypes showed a higher positive interaction than a negative interaction. The TaPTF1, TaP5CS, TaGSK1, and TaSRG genes were found to be more selective than the other analyzed genes under salt-stress conditions. Despite each gene's specific function, increasing proline biosynthesis functioned as a common mechanism for separating salt tolerance from sensitivity.

Improvement in cowpea variety Videza for traits of extra earliness and higher seed yield

The cowpea variety Videza, which was used as the control, matures early (70 days after planting), although it produces low yields. Gamma irradiation mutagenesis was used to induce Videza into extra-early maturing and higher yielding mutant genotypes. A single seed descend population was developed for radio-sensitivity test, and a Lethal Dose 50 (LD₅₀) of 240.5 Gy was determined, and applied from a cobalt-60 (⁶⁰Co) source, to acutely mass irradiate 1800 Videza seeds, at the Ghana Atomic Energy Commission. The irradiated seeds (M1) were planted to produce M2 seeds bearing plants and subsequently advanced to M3 plants for selection of nine induced plants based on extra earliness and significantly higher seed yields than the parental control. It took 48 days after planting (DAP) for the genotype coded P1N02#1 to reach 50 % maturity followed by 52 DAP for genotypes with codes P4N03#3; P3N01#5; P5N05#6, P4N14#7, P5N07#8, P5N05#10 and 54 DAP for genotype P4N14#11. P1N06#9 had the highest yield (97.38 g/plant), followed by P5N05#10 (95.97 g/plant), P1N08#13 (81.24 g/plant), P2N09#12 (73.94 g/plant), P6N10#19 (70.83 g/plant), P1N06#20 (65.36 kg/plant), P5N07#14 (61.23 g/plant), P4N14# (58.05 g/plant) and P1N08#17 (56.23 g/plant). M3 seeds were advanced to M4 plants for a Preliminary Yield Trial which revealed that induced plants P5N05#10 (1235 kg/ha), P2N09#12 (1206 kg/ha), P5N07#14 (1185 kg/ha), P1N06#20 (1171 kg/ha), P1N06#9 (1051 kg/ha), P1N08#13 (1041 kg/ha), and P6N10#19 (999 kg/ha) outperformed the control (517 kg/ha) and two other commercial varieties. Overall, the two highest performing candidates for further evaluation for varietal release were P5N05#10 and P2N09#12.

Disease Resistance and Molecular Variations in Irradiation Induced Mutants of Two Pea Cultivars

Induced mutation is useful for improving the disease resistance of various crops. Fusarium wilt and powdery mildew are two important diseases which severely influence pea production worldwide. In this study, we first evaluated Fusarium wilt and powdery mildew resistance of mutants derived from two elite vegetable pea cultivars, Shijiadacaiwan 1 (SJ1) and Chengwan 8 (CW8), respectively. Nine SJ1 and five CW8 M3 mutants showed resistant variations in Fusarium wilt, and the same five CW8 mutants in powdery mildew. These resistant variations were confirmed in M4 and M5 mutants as well. Then, we investigated the genetic variations and relationships of mutant lines using simple sequence repeat (SSR) markers. Among the nine effective SSR markers, the genetic diversity index and polymorphism information content (PIC) values were averaged at 0.55 and 0.46, which revealed considerable genetic variations in the mutants. The phylogenetic tree and population structure analyses divided the M3 mutants into two major groups at 0.62 genetic similarity (K = 2), which clearly separated the mutants of the two cultivars and indicated that a great genetic difference existed between the two mutant populations. Further, the two genetic groups were divided into five subgroups at 0.86 genetic similarity (K = 5) and each subgroup associated with resistant phenotypes of the mutants. Finally, the homologous PsMLO1 cDNA of five CW8 mutants that gained resistance to powdery mildew was amplified and cloned. A 129 bp fragment deletion was found in the PsMLO1 gene, which was in accord with er1-2. The findings provide important information on disease resistant and molecular variations of pea mutants, which is useful for pea production, new cultivar breeding, and the identification of resistance genes.

Chemical mutagenesis: role in breeding and biofortification of lentil (Lens culinaris Medik) mutant lines

BACKGROUND

Induced mutagenesis is a quick and effective breeding strategy to enhance genetic variability, an important prerequisite for the genetic improvement of existing lentil cultivars. Lentil is an important cool season food legume with low productivity due to the low yielding potential of existing lentil cultivars. The present study aimed at increasing the yielding potential, resulted in the isolation of six high-yielding mutant lines with dense micronutrients.

METHODS AND RESULTS

Two lentil varieties were treated with different doses of ethyl methanesulphonate, hydrazine hydrate, and sodium azide, followed by phenotypic selection for consecutive three generations. In the M₂ generation, six high-yielding mutant lines with stable phenotypes were isolated. The results revealed a substantial increase in mean values for quantitative and physiological traits coupled with a manifold increase in the genotypic coefficient of variation (GCV), heritability (h²), and genetic advance (GA). Correlation analysis revealed that plant yield was significantly and positively influenced (P < 0.001) by fertile branches per plant, pods per plant, and seed weight. Principal component analysis revealed two principal components contributed 63.5 and 62.5% of the total variation in the varieties Pant L-639 and Pant L-406, respectively.

CONCLUSION

The isolated high-yielding mutant lines with dense micronutrients that serve as rich genetic resources could be subjected to further breeding trials. After attaining yield stability, these might be registered and released as new improved lentil varieties.

Gamma Rays and Sodium Azide Induced Genetic Variability in High-Yielding and Biofortified Mutant Lines in Cowpea [Vigna unguiculata (L.) Walp.]

With the twin pressures of high population growth and extreme weather events, developing countries are the worst hit in meeting the food demands of their people, with millions unable to access adequate and nutritionally balanced food. Crop production must be increased by 70% to keep up with the food demands of a rapidly growing population, which is expected to rise to 9.6 billion by 2050. Legumes are ideal food crops to increase agricultural productivity and achieve sustainable development goals. Cowpea, a warm-season grain legume, is often categorized as a neglected crop with immense scope for genetic improvement through proper breeding strategies. A multi-year field experiment of induced mutagenesis was conducted to increase seed yield and genetic variability in the agro-economic traits of two cowpea varieties treated with different doses of gamma (γ) rays and sodium azide (SA). The study was also aimed to optimize different doses of γ rays and SA employed individually and in combinations. Quantitative trait analysis revealed a maximum increase in seed yield from M₂ to M₃ generation. Among the 10 quantitative traits studied, seeds per pod and seed weight positively correlated with a major direct impact on yield. An extensive phenotypic selection cycle from M₂-M₄ generations resulted in isolating new high-yielding and nutrient-dense mutant lines. Such high-yielding biofortified mutant lines with enhanced genetic variability could serve as a donor of elite genes and represent a valuable genetic resource for improving low-yielding warm-season grain legumes.

Comparative Mutagenic Effectiveness and Efficiency of Gamma Rays and Sodium Azide in Inducing Chlorophyll and Morphological Mutants of Cowpea

Mutagenic effectiveness and efficiency are the most important factors determining the success of mutation breeding, a coherent tool for quickly enhancing genetic diversity in crops. However, conclusive evidence of using an effective and efficient dose of gamma (γ) rays and sodium azide (SA) for genetic improvement is scant. The present study assesses genetic diversity in M₂ mutants of cowpea and evaluates mutagenic effectiveness and efficiency of the single and combination doses of γ rays and SA. In M₀ generation, 7200 M₁ seeds obtained by SA treatment (0.01-0.1%) and γ irradiation (100-1000 Gy) at a dose rate of 11.58 Gy/min were sown to raise M₁ generation. A total of 57,620 M₂ seeds were generated from the M₁ generation of two varieties-Gomati VU-89 and Pusa-578, from which 47,650 seeds germinated. Moreover, plants (38,749) that survived were screened for chlorophyll and morphological mutations. Among the mutagens, SA followed by γ rays + SA and γ rays was most effective in inducing higher frequency and a broader spectrum of chlorophyll mutants. A wide range of morphological mutants affecting every growth stage was recorded with the highest frequency in 400 Gy γ rays + 0.04% SA treatment. These morphological mutants with desirable agronomic traits represent a valuable genetic resource for future breeding programs. This study revealed the potency of γ rays and SA in increasing genetic diversity and demonstrated the successful conduct of induced mutagenesis in the cowpea.

Genetic and phenotypic diversity of selected Kenyan mung bean (Vigna radiata L. Wilckzek) genotypes

BACKGROUND

Mung bean is a pulse crop principally grown in the tropic and subtropic parts of the world for its nutrient-rich seeds. Seven mung beans accessions from Eastern Kenya were evaluated using thirteen phenotypic traits. In addition, 10 SSR markers were used to determine their genetic diversity and population structure. This aimed at enhancing germplasm utilization for subsequent mung bean breeding programs.

RESULTS

Analysis of variance for most of the phenology traits showed significant variation, with the yield traits recording the highest. The first three principal components (PC) explained 83.4% of the overall phenotypic variation, with the highest (PC1) being due to variation of majority of the traits studied such as pod length, plant height, and seeds per pod. The dendogram revealed that the improved genotypes had common ancestry with the local landraces. The seven mung beans were also genotyped using 10 microsatellite markers, eight of which showed clear and consistent amplification profiles with scorable polymorphisms in all the studied genotypes. Genetic diversity, allele number, and polymorphic information content (PIC) were determined using powermarker (version 3.25) and phylogenetic tree constructed using DARWIN version 6.0.12. Analysis of molecular variance (AMOVA) was calculated using GenALEx version 6.5. A total of 23 alleles were detected from the seven genotypes on all the chromosomes studied with an average of 2.875 across the loci. The PIC values ranged from 0.1224 (CEDG056) to 0.5918 (CEDG092) with a mean of 0.3724. Among the markers, CEDG092 was highly informative while the rest were reasonably informative except CEDG056, which was less informative. Gene diversity ranged from 0.1836 (CEDG050) to 0.5102 (CDED088) with an average of 0.3534. The Jaccards dissimilarity matrix indicated that genotypes VC614850 and N26 had the highest level of dissimilarity while VC637245 and N26 had lowest dissimilarity index. The phylogenetic tree grouped the genotypes into three clusters as revealed by population structure analysis (K = 3), with cluster III having one unique genotype (VC6137B) only. AMOVA indicated that the highest variation (99%) was between individual genotype. In addition, marker traits association analysis revealed 18 significant associations (P < 0.05).

CONCLUSION

These findings indicate sufficient variation among the studied genotypes that can be considered for germplasm breeding programs.

Mechanisms of Genome Maintenance in Plants: Playing It Safe With Breaks and Bumps

Maintenance of genomic integrity is critical for the perpetuation of all forms of life including humans. Living organisms are constantly exposed to stress from internal metabolic processes and external environmental sources causing damage to the DNA, thereby promoting genomic instability. To counter the deleterious effects of genomic instability, organisms have evolved general and specific DNA damage repair (DDR) pathways that act either independently or mutually to repair the DNA damage. The mechanisms by which various DNA repair pathways are activated have been fairly investigated in model organisms including bacteria, fungi, and mammals; however, very little is known regarding how plants sense and repair DNA damage. Plants being sessile are innately exposed to a wide range of DNA-damaging agents both from biotic and abiotic sources such as ultraviolet rays or metabolic by-products. To escape their harmful effects, plants also harbor highly conserved DDR pathways that share several components with the DDR machinery of other organisms. Maintenance of genomic integrity is key for plant survival due to lack of reserve germline as the derivation of the new plant occurs from the meristem. Untowardly, the accumulation of mutations in the meristem will result in a wide range of genetic abnormalities in new plants affecting plant growth development and crop yield. In this review, we will discuss various DNA repair pathways in plants and describe how the deficiency of each repair pathway affects plant growth and development.

The Effect of Processing on Bioactive Compounds and Nutritional Qualities of Pulses in Meeting the Sustainable Development Goal 2

Diversification of plant-based food sources is necessary to improve global food and nutritional security. Pulses have enormous nutritional and health benefits in preventing malnutrition and chronic diseases while contributing positively to reducing environmental footprint. Pulses are rich in diverse nutritional and non-nutritional constituents which can be classified as bioactive compounds due to their biological effect. These bioactive compounds include but are not limited to proteins, dietary fibres, resistant starch, polyphenols, saponins, lectins, phytic acids, and enzyme inhibitors. While these compounds are of importance in ensuring food and nutritional security, some of the bioactive constituents have ambivalent properties. These properties include having antioxidant, anti-hypertensive and prebiotic effects. Others have a deleterious effect of decreasing the digestibility and/or bioavailability of essential nutrients and are therefore termed antinutritional factors/compounds. Various processing techniques exist to reduce the content of antinutritional factors found in pulses. Traditional processing of pulses comprises soaking, dehulling, milling, germination, fermentation, and boiling, while examples of emerging processing techniques include microwaving, extrusion, and micronization. These processing techniques can be tailored to purpose and pulse type to achieve desired results. Herein, the nutritional qualities and properties of bioactive compounds found in pulses in meeting the sustainable development goals are presented. It also discusses the effect of processing techniques on the nutritional and non-nutritional constituents in pulses as well as the health and environmental benefits of pulse-diet consumption. Major challenges linked to pulses that could limit their potential of being ideal crops in meeting the sustainable development goal 2 agenda are highlighted.

Phenotypic diversity in mutagenized population of urdbean (Vigna mungo (L.) Hepper)

The present study was conducted to assess the extent of induced genetic variability and to determine the inheritance pattern of various yield contributing phenotypic traits in M₂ and M₃ generations of urdbean following mutagenesis with single and combination treatments of gamma rays and ethyl methanesulphonate (EMS). The mean number of seeds per pod and 100-seed weight increased in all the mutagenic treatments in both the varieties with few exceptions in M₂ generation. Mean pod length although increased considerably, however it did not differ significantly in most of the mutagenic treatments. In M₃ generation, 0.2% EMS and 300 Gy γ rays+0.2% EMS treatments induced maximum increase in mean pod length, seeds per pod and 100-seed weight in both the varieties. Genetic parameters showed manifold increase in most of the mutagenic treatments and varied from trait to trait. Increased genetic variability for economically important traits in the selected mutant lines has successfully contributed in diversifying the accessible genetic base which could be exploited for subsequent improvement of urdbean through phenotypic selection.