Mustard Accessions Research Articles

Indexing heat stress-induced changes in Indian mustard germplasm using biochemical traits, stress tolerance indices and seed morphological features

Heat stress in Brassica is a great threat to its productivity and it is a major abiotic challenge in the current scenario of changing global climatic conditions. Oil production from Brassica is the second largest production after soybean, globally. In this study, 32 Indian mustard accessions were evaluated (post-anthesis stage) under heat stress in field conditions during the rabi season of 2019-20, by being exposed to 3 different growing conditions i.e., early, optimum and late sowing. Biochemical assays were performed at the post-anthesis stage to analyze the best-performing accessions under heat stress during the rabi season of 2021-22. Seed morphological parameters and stress indices (MDA, proline content) were used to find high-performing accessions. The results showed a significant correlation between yield under stress and STI (stress tolerance index), YI (yield index), SSPI (stress susceptibility percent index) and MP (mean productivity), indicating the utility of these indices in the selection of heat-tolerant and high-yielding lines. Based on the morphological, seed yield and quality parameters, accessions IC280920, IC401575, IC426400, IC491509 and IC570301 were found tolerant to heat stress as compared to other accessions. Therefore, the selected accessions can be utilized to improve crop Brassica, especially under heat stress.

Decoding genetic diversity and population structure of Brassica species by inter primer binding site (iPBS) retrotransposon markers

AbstractMarker-assisted breeding serves as a potent tool for screening target germplasm, assessing genetic diversity, and determining breeding potential of a crop. Therefore, inter primer binding site (iPBS)-retrotransposons marker system was employed to evaluate a collection of 33 Brassica genotypes, including 10 Brassica juncea, 5 B. oleracea, 7 Sinapis alba, 5 B. nigra, and 6 B. rapa, were utilized to evaluate their genetic diversity and variations 10 polymorphic primers that generated a total of 144 bands. Various diversity indices were calculated in the studied germplasm, including polymorphism information content (0.13–0.30), effective number of alleles (1.217–1.689), Shannon’s information index (0.244–0.531), and gene diversity (0.148–0.370). These indices collectively affirmed substantial genetic variations within the germplasm. Molecular variance analysis revealed that the majority (62%) of genetic variations were present within populations. The Brassica accessions were categorized into three populations utilizing a model-based structure algorithm. Evaluation of diversity indices based on the structure indicated that populations III and II exhibited higher diversity. Principal coordinate analysis and neighbor-joining analysis further corroborated the three distinct populations, confirming the reliability of the STRUCTURE analysis. Notably, the genetic distance assessment identified BN1 and BN3 from B. nigra species and the genotypes BO1 and BO3 from B. oleracea as genetically diverse mustard accessions. The extensive genetic diversity observed within the Brassica germplasm underscores its significance as a valuable genetic resource for comprehensive Brassica breeding programs. Moreover, these accessions hold promise as suitable candidates for heterosis breeding initiatives aimed at improving mustard production.

Characterization and evaluation of the morphological attributes of Ethiopian mustard (Brassica carinata A. Braun) landraces

Ethiopian mustard (Brassica carinata A. Braun) is one of the Brassica leafy vegetables and oilseed crops, which can withstand adverse environmental conditions. This study was conducted to characterize and evaluate the leaf attributes of 313 Ethiopian mustard accessions grown in the greenhouse and field in 2018/19 in Beijing, China. Data on 18 different leaf morphological attributes were collected based on the IBPGR for Brassica and Raphanus descriptor format and Fiji Image J. The collected data were subjected to descriptive statistics using JMP version 14 software. Results indicate that the majority of the accessions had serrated leaf margin, intermediate juvenile development, rounded apex leaf shape, absence of leaf pubescence, number of lobes > 5 and had intermediate number of leaves per plant with frequencies of 101, 213, 223, 244, 183 and 289, respectively. The accessions had also white midrib color, light green leaf color, purple petiole color, purple stem color and purple apex leaf color pigments with frequencies of 168, 165, 104, 113 and 122, respectively. Significant differences were observed among the accessions for leaf size attributes (p < 0.001) indicating their potential as leafy vegetables. Furthermore, there were significant accession × environment effects for the laminal length, total leaf length, leaf area, leaf weight and petiole length. Notably, 71% of the accessions had an average of 81 days flowering time. The multivariate cluster and principal component analyses divided the 313 accessions into eight groups with distinctive information; consisting of 81, 37, 79, 38, 14, 11, 6 and 47 accessions. Thus, this study provides important information about Ethiopian mustard germplasms that is vital for further advancement and genetic improvement of the crop.

Genome-wide association study of tocopherols (vitamin E) in Indian mustard (Brassica juncea)

A diverse set of 289 mustard accessions was used to establish variation for α-, γ- and total tocopherols in mustard germplasm. A large variation in our diversity panel for tocopherol isomers and total tocopherols. γtocopherols were observed to be more abundant than α-tocopherols in the mustard seeds. This tocopherol variation was used to identify the genetic loci related to tocopherols using GWAS. Various strong candidate genes such as VTE2-2, SAHH2, PP5.2, PES1, ANT1 etc. involved directly or indirectly in the tocopherol biosynthesis pathway were identified through this method.

Leaf Mustard (Brassica juncea) Germplasm Resources Showed Diverse Characteristics in Agro-Morphological Traits and Glucosinolate Levels.

Leaf mustard, characterized by its purple/red/green leaves with a green/white midrib, is known for its thick, tender, and spicy leaves with a unique taste and flavor. There were only a few studies reported on leaf mustard for its morphological and biochemical traits from Korea. A total of 355 leaf mustard accessions stored at the GenBank of the National Agrobiodiversity Center were evaluated for 25 agro-morphological traits and seven intact glucosinolates (GSLs). The accessions showed a wide variation in terms of most of the traits. The quantitative agro-morphological traits varied from 16.0 (leaf length) to 48.7% (petiole width) of the coefficient of variation (CV). The highest variation was observed in glucoiberin (299.5%, CV), while the total GSL showed a CV of 66.1%. Sinigrin, followed by gluconapin and gluconasturtiin, was the most abundant GSL, accounting for as high as 75% of the total GSLs, while glucobrassicanapin and glucoiberin were the least abundant, contributing 0.7% and 0.1% on average, respectively. Sinigrin had a positive significant correlation with all GSLs but gluconasturtiin, while glucobarbarin and gluconasturtiin were highly positively correlated to each other, but least correlated with other GSLs. The leaf length was negatively correlated with sinigrin and glucoiberin. The width of the petiole showed a positive correlation with gluconapin, glucobrassicanapin, and glucobrassicin, while the length of the petiole had a negative correlation with sinigrin, glucobrassicanapin, glucoiberin, glucobrassicin, and the total GSLs. A higher width of the midrib was associated with higher contents of gluconapin, glucobrassicanapin, and glucobrassicin. A PCA analysis based on the agro-morphological traits showed that the first and second principal components accounted for 65.2% of the overall variability. Accessions that form a head tend to exhibit a longer leaf length, a larger plant weight, a thicker midrib, and higher widths of the midrib, petiole, and leaf. The GSLs showed inconsistent inter-and intra-leaf variation. Accessions that identified for various traits in their performance, such as, for example, Yeosu66 and IT259487 (highest total glucosinolates) and IT228984 (highest plant weight), would be promising lines for developing new varieties.

A Set of Yellow Mustard (Sinapis alba L.) Germplasm with Polycotyledony

A world collection of 132 yellow mustard (Sinapis alba L.) accessions was characterized in a greenhouse to identify germplasm with polycotyledony and to assess the genetic segregation of tricot and tetracot seedlings in selfed S1 and S2 generations. The effort identified a set of 46 yellow mustard accessions with frequent occurrences of polycotyledony. The revealed genetic segregations seemed to suggest the development of tricot and tetracot seedlings in yellow mustard was largely controlled by a combination of genes at multiple diallelic loci. The identified tricot germplasm can be used to facilitate the genetic and/or genomic analysis of polycotyledonous germplasm for a better understanding of genetic and developmental mechanisms conditioning polycotyledony and the development of yellow mustard lines for explorable tricot breeding.

Optimization of sowing dates in Indian mustard (Brassica juncea L.) to combat yield losses caused by high temperature at reproductive stage

A field experiment was undertaken during the Rabi seasons of 2019-20 and 2021-22 at organic farm of Amity Institute of Organic Agriculture, Amity University, Noida, Uttar Pradesh, India, for the optimization of the sowing time period to reduce the effect of heat stress on Indian mustard (Brassica juncea L.) for increasing productivity. 32 Indian mustard germplasms were sown at three different time periods viz., the last week of September, the last fortnight of October, and the second week of November. Our results revealed that the mustard crop showed a substantial increase in yield supporting characters such as the number of siliqua and seeds per siliqua when sown at last week of September as compared to the second week of October, whereas the late sown crop resulted in less yield due to the heat stress faced by crop during the anthesis stage as compared to early and optimum sowing. The mean seed yield per plant showed a positive correlation with mean test weight. We established the positive effect of early sowing over optimal and late sowing in Indian mustard; further, we found a few mustard accessions were able to resist different climatic conditions. The mustard germplasm accessions IC296688, IC296703, IC296732, IC305130, IC401575, IC426385, and IC589669 were high yielding among all the accessions and can be considered as heat stress tolerant.

Genetic Diversity in Oilseed and Vegetable Mustard (Brassica juncea L.) Accessions Revealed by Nuclear and Mitochondrial Molecular Markers

Genetic diversity analysis is a fundamental work for effective management and utilization of plant germplasm. Brassica juncea is an economically important crop, including both oilseed and vegetable types. In the present study, a total of 99 accessions of Brassicaceae family, including 84 mustard (50 oilseed and 34 vegetable types) in China and 15 other Brassicaceae accessions were evaluated for their genetic diversity using nuclear and mitochondrial molecular markers. All accessions were evaluated using 18 simple sequence repeats, 20 sequence related amplified polymorphisms, and 7 intron-exon splice junction primers, and in total, 232 polymorphic fragments were obtained. The unweighted pair-group method with arithmetic mean cluster analysis indicated that all accessions could be divided into three major clusters, with cluster I including all 50 oilseed mustard, cluster II including 34 vegetable mustard, and cluster III containing 15 other Brassicaceae accessions. The results of principal component analysis and population structure analysis were in accordance with the cluster result. Molecular variance analysis revealed that the genetic variation was 34.07% among populations and 65.93% within Brassica species, which indicates existence of considerable genetic variation among oilseed and vegetable B. juncea species. Based on an InDel and a SNP locus reported in B. juncea mitochondrial genome, all the 84 B. juncea mitochondrial genomes were divided into three mitotypes (MTs1-3), 22 accessions of MT1, 20 accessions of MT2, and 42 accessions of MT3. In addition, the results of the modified multiplex PCR, Indel and SNP could identify pol-, cam-, nap- (or MT4), Bol-, Bni-, Esa-, and In-cytoplasmic types in 15 other Brassicaceae accessions. Together, oilseed and vegetable B. juncea can be used for broadening the genetic background for each other.

Genetic Diversity Analysis Reveals Potential of the Green Peach Aphid (Myzus persicae) Resistance in Ethiopian Mustard.

Brassica carinata (BBCC, 2n = 34) is commonly known as Ethiopian mustard, Abyssinian mustard, or carinata. Its excellent agronomic traits, including resistance to biotic and abiotic stresses, make it a potential genetic donor for interspecific hybridization. Myzus persicae (green peach aphid, GPA) is one of the most harmful pests of Brassica crops, significantly effecting the yield and quality. However, few aphid-resistant Brassica crop germplasms have been utilized in breeding practices, while the underlying biochemical basis of aphid resistance still remains poorly understood. In this study, we examined the genetic diversity of 75 B. carinata accessions and some plant characteristics that potentially contribute to GPA resistance. Initially, the morphological characterization showed abundant diversity in the phenotypic traits, with the dendrogram indicating that the genetic variation of the 75 accessions ranged from 0.66 to 0.98. A population structure analysis revealed that these accessions could be grouped into two main subpopulations and one admixed group, with the majority of accessions (86.67%) clustering in one subpopulation. Subsequently, there were three GPA-resistant B. carinata accessions, BC13, BC47, and BC51. The electrical penetration graph (EPG) assay detected resistance factors in the leaf mesophyll tissue and xylem. The result demonstrated that the Ethiopian mustard accessions were susceptible when the phloem probing time, the first probe time, and the G-wave time were 20.51-32.51 min, 26.36-55.54 s, and 36.18-47.84 min, respectively. In contrast, resistance of the Ethiopian mustard accessions was observed with the phloem probing time, the first probe time, and G-wave time of 41.18-70.78 min, 181.07-365.85 s, and 18.03-26.37 min, respectively. In addition, the epidermal characters, leaf anatomical structure, glucosinolate composition, defense-related enzyme activities, and callose deposition were compared between the resistant and susceptible accessions. GPA-resistant accessions had denser longitudinal leaf structure, higher wax content on the leaf surface, higher indole glucosinolate level, increased polyphenol oxidase (PPO) activity, and faster callose deposition than the susceptible accessions. This study validates that inherent physical and chemical barriers are evidently crucial factors in the resistance against GPA infestation. This study not only provide new insights into the biochemical basis of GPA resistance but also highlights the GPA-resistant B. carinata germplasm resources for the future accurate genetic improvement of Brassica crops.

Population structure and genetic diversity as revealed by SSR markers in Ethiopian mustard (Brassica carinata A. Braun): a potential edible and industrially important oilseed crop

Brassica carinata A. Braun (Ethiopian mustard) is an oilseed crop belonging to rapeseed-mustard group, with extensive food and industrial applications. It produces high quality oil ideal for aviation fuel, bio-jet for aircrafts and bio-diesel for airport vehicles besides its use as edible oil. In an attempt to analyze population structure and genetic diversity in a panel of 78 Ethiopian mustard accessions, 212 SSR markers had been employed. A total of 139 (65.57%) SSRs resulted into polymorphic amplicons, while 73 (34.43%) SSRs amplified monomorphic products. The allele number ranged from 1–7 with 3.03 average number of alleles per marker. PIC values were in the range of 0.02–0.53 with an average PIC value of 0.29 per marker. Gene diversity ranged from 0.02 to 0.50 with an average value of 0.37 per SSR marker. Overall, lower PIC values and gene diversity values indicated the presence of lesser genetic diversity among B. carinata genotypes. The unweighted pair group method with arithmetic average (UPGMA)-based dendrogram divided all the 78 accessions into two major groups, whereas, three subpopulations/subgroups were predicted by population STRUCTURE analysis. Further, this study provided a deeper insight into the population structure and genetic diversity of Ethiopian mustard in India and will help to improvise the breeding strategies for its genetic improvement.

Identification of New Source of Resistance to Powdery Mildew of Indian Mustard and Studying Its Inheritance.

Powdery mildew of Indian mustard (Brassica juncea), caused by Erysiphe cruciferarum, is emerging as major problem in India. All the Indian mustard cultivars presently grown in India are highly susceptible to powdery mildew and so far no resistance source has been reported. In this study, with an aim to identify resistant source, 1,020 Indian mustard accessions were evaluated against E. cruciferarum PMN isolate, at Wellington, The Nilgiris, Tamil Nadu, India under natural hot spot conditions. The study identified one accession (RDV 29) with complete resistance against E. cruciferarum PMN isolate for the first time, which was consistent in five independent evaluations. Genetic analysis of F1, F2 and backcross populations obtained from the cross RSEJ 775 (highly susceptible) × RDV 29 (highly resistant) for two season revealed that the resistance is governed by two genes with semi-dominant and gene dosage effect. Further, a new disease rating system using six scales (0, 1, 2, 3, 4, and 5) has also been proposed in this study to score powdery mildew based on progress of fungal growth in different plant parts of the F2 population.The outcome of this study viz. newly identified powdery mildew-resistant Indian mustard accession (RDV 29), information on inheritance of resistance and the newly developed disease rating scale will provide the base for development of powdery mildew-resistant cultivars ofIndian mustard.

Variation in Plant Morphology and Sinigrin Content in Ethiopian Mustard (Brassica carinata L.)

Ethiopian mustard (Brassica carinata) is mainly grown as a leafy vegetable and oilseed crop. Sinigrin is predominant glucosinolate in the leaves of Ethiopian mustard. It is hydrolyzed by enzyme myrosinase to produce bioactive product specifically allyl-isothiocyanates. Due to sinigrin content, Ethiopian mustard has a mild flavor and it is a healthy addition to human diet. However, sinigrin concentration depends on genotype. Understanding variations of plant morphology and sinigrin content may be the first step for crop improvement. According to the analyses of various plant characteristics among ninety nine Ethiopian mustard accessions, we found significant differences in plant height, chlorophyll content, and petiole length. In addition, sinigrin content was determined using ultra-performance liquid chromatography tandem quadrupole mass spectrometers/tunable ultraviolet detector (UPLC-TQS/TUV). We found a significant difference in sinigrin content among leaves of 94 Ethiopian mustard accessions. Except for petiole length, the sinigrin content was negatively correlated with leaf area, leaf width, number of primary branches, and plant height. This information will help Ethiopian mustard breeders in screening breeding lines for new accessions.

Prediction of Agro-Morphological and Nutritional Traits in Ethiopian Mustard Leaves (Brassica Carinata A. Braun) by Visible-Near-Infrared Spectroscopy.

The particular characteristics of some of the Ethiopian mustard accessions available from seed banks could be used to increase the production and the diversity of products available to consumers and to improve their general quality. The objectives of this study were to determine the genetic variability for agro-morphological (days to first flowering: DFF and leaf pubescence: LP) and nutritional traits (total phenolic content: TPC) among accessions, and to evaluate the potential of near-infrared spectroscopy (NIRS) to predict these traits in Ethiopian mustard leaves. A great variation was found for the traits evaluated. The reference values were regressed against different spectral transformations by modified partial least-squares (MPLS) regression. The coefficients of determination in cross-validation (R2cv) shown by the equations for DFF, LP and TPC were 0.95, 0.63 and 0.99, respectively. The standard deviation to standard error of cross-validation ratio (RPD), were for these traits, as follows: DFF: 4.52, LP: 1.53 and, TPC: 24.50. These results show that the equations developed for DFF and TPC in Ethiopian mustard, can be predicted with sufficient accuracy for screening purposes and quality control, respectively. In addition, the LP equation can be used to identify those samples with “low”, “medium” and “high” groups. From the study of the mean and deviation standard spectra, and regression vectors of MPLS models it can be concluded that some major cell components, highly participated in modelling the equations for these traits.

Eukaryotic translation initiation factor 2B-beta (eIF2Bβ), a new class of plant virus resistance gene.

Recessive resistances to plant viruses in the Potyvirus genus have been found to be based on mutations in the plant eukaryotic translation initiation factors, eIF4E and eIF4G or their isoforms. Here we report that natural, monogenic recessive resistance to the Potyvirus Turnip mosaic virus (TuMV) has been found in a number of mustard (Brassica juncea) accessions. Bulked segregant analysis and sequencing of resistant and susceptible plant lines indicated the resistance is controlled by a single recessive gene, recessive TuMV resistance 03 (retr03), an allele of the eukaryotic translation initiation factor 2B-beta (eIF2Bβ). Silencing of eIF2Bβ in a TuMV-susceptible mustard plant line and expression of eIF2Bβ from a TuMV-susceptible line in a TuMV-resistant mustard plant line confirmed the new resistance mechanism. A functional copy of a specific allele of eIF2Bβ is required for efficient TuMV infection. eIF2Bβ represents a new class of virus resistance gene conferring resistance to any pathogen. eIF2B acts as a guanine nucleotide exchange factor (GEF) for its GTP-binding protein partner eIF2 via interaction with eIF2·GTP at an early step in translation initiation. Further genotyping indicated that a single non-synonymous substitution (A120G) in the N-terminal region of eIF2Bβ was responsible for the TuMV resistance. A reproducible marker has been developed, facilitating marker-assisted selection for TuMV resistance in B. juncea. Our findings provide a new target for seeking natural resistance to potyviruses and new opportunities for the control of potyviruses using genome editing techniques targeted on eIF2Bβ.

Identification and evaluation of Indian mustard genotypes for white rust resistance and agronomic performance

The screening of 2000 Indian mustard accessions against white rust and phenotypic evaluation of resistant accessions to assess the nature and magnitude of genetic diversity including their agronomic potential was carried out at three locations during rabi of 2014–2016. Out of 2000 germplasm accessions, 168, 46 and 185 accessions were found resistant at Ludhiana, Pantnagar, and Hissar, respectively but only 27 were identified as resistant across the locations indicating the pathogenic variability at different locations. These 27 accessions were further validated under artificial inoculation and eight of them, namely, IC265495, IC313380, EC766091, EC766133, EC766134, EC766192, EC766230 and EC766272 were identified as highly resistant with disease severity reaction (PDI = 0) to A. candida at both cotyledonary and true leaf stages. Agronomic evaluation of these 27 accessions facilitated the identification of superior genotypes with high magnitude of genetic diversity for their use in breeding. As compared to check varieties, elite genotype(s) such as IC313380 was found promising for days to flowering (40), silique on main stem (52.6), silique length (4.2 cm), seeds per silique (17.2) and oil content (41.4%); EC766230 for no. of primary branches (8), seeds/silique (16.8), seed yield/plant (16.0g), oil content (38.7%) while EC766272 for silique on main stem (55.50), seed yield/plant (18g) and oil content (40.5%). The resistant accessions coupled with agronomic superiority may be useful genetic resources for improvement of Indian mustard. In addition, the resistant accessions can serve as a rich gene pool for breeding programmes.

Genetic diversity analysis of yellow mustard (Sinapis alba L.) germplasm based on genotyping by sequencing

Recent advances in next generation sequencing technologies make genotyping by sequencing (GBS) more feasible for molecular characterization of plant germplasm with complex and unsequenced genomes. We used a GBS protocol consisting of Roche 454 pyrosequencing, genomic reduction and advanced bioinformatics tools to analyze genetic diversity of 24 diverse yellow mustard accessions. One and one half 454 pyrosequencing runs generated roughly 1.2 million sequence reads totaling about 392 million nucleotides. Application of the computational pipeline DIAL identified 512 contigs and 828 SNPs. The BLAST algorithm revealed alignments of 214 contigs with the sequences reported in NCBI nr/nt database. Sanger sequencing confirmed 95 % of 41 selected contigs and 94 % of 240 putative SNPs. The 454 scored SNPs were highly imbalanced among assayed samples. Diversity analysis of these SNPs revealed that 26.1 % of the total variation resided among landrace, cultivar and breeding lines and 24.7 % between yellow- and black-seeded germplasm. Cluster analysis showed that the black-seeded accessions were largely clustered together and the breeding lines were grouped with known origin. Computer simulation was performed to assess the impact of 454 SNPs missing and revealed considerable changes in allelic count, bias in detection of genetic structure, and large deviations from the expected genetic-distance matrix. These findings are useful for parental selection consideration in yellow mustard breeding, and our detailed analyses help illustrate the utility of GBS in genetic-diversity analysis of plant germplasm, particularly for genetic-relationship assessment.

Genetic Variability of Ethiopian Mustard (Brassica carinata A. Brun) Accessions Based on Some Morphological Characters

Genetic Variability of Ethiopian Mustard (Brassica carinata A. Brun) Accessions Based on Some Morphological Characters

Seasonal variation of growth and yield performance of mustard (&lt;i&gt;Brassica juncea&lt;/i&gt; (L.) Czern &amp; Coss) genotypes in Sri Lanka

Seasonal variations affect growth and yield of a crop, primarily by changing its phenological developmental processes. A study was conducted to establish the relationship between growth, yield and their seasonal variations using ten mustard accessions (AC 501, 515, 580, 790, 1099, 1814, 2122, 5088, 7788 and 8831). The field study was conducted in a site at Nagollagama in Kurunegala District during two growing seasons, Maha and Yala. There was a significant variation in agronomic and phenological characters in different mustard accessions between two seasons, Maha and Yala, and among the accessions (p ≤ 0.05). Plant growth was affected by variations in climatic conditions. Soil moisture was unlimited and comparatively steady in Maha, but significantly fluctuated during Yala. Difference in soil nutrients, temperature and relative humidity during two seasons also contributed the variation in plant growth. Significantly high yields were obtained from all mustard accessions during the Maha season. There is a substantial variability of yield potential in different mustard genotypes in studied. Three mustard accessions (AC 580, AC 5088 and AC 7788) produced significantly higher yield in Maha and AC 7788 produced highest yield in Yala season as well, showing adaptability to seasonal variations. Key words: Growth; Maha and Yala seasons; mustard accessions; yield; phenological developmentDOI: http://dx.doi.org/10.4038/jas.v6i1.3807 The Journal of Agricultural Sciences, 2011 Vol.6(1) 1-15

Phytoextractive potential among mustard (&lt;i&gt;Brassica juncea&lt;/i&gt;) genotypes in Sri Lanka

Heavy metal pollution in soil and water is a global environmental concern. In Sri Lanka, accumulation of heavy metals in soil, water and plant/animal biomass has been widely reported. Phytoremediation, the use of plants and their associated microbes, is an emerging, low-cost, environmental-friendly approach in the cleanup and prevention of environmental pollution. Indian Mustard (Brassica juncea) has been widely used to extract toxic metals from contaminated soils worldwide. Sri Lanka has a genetically diverse mustard collection, but their phytoextarctive potentials are yet to be determined. Present study was conducted to evaluate variation in phytoextractive ability of soil-borne heavy metals by ten different mustard accessions. Heavy metal contents (Mn, Co, Pb and Zn) in 12-week-old mustard plants (whole plant) were estimated during Maha and Yala in 2007-2008 using Atomic Absorption Spectroscopy. Heavy metal content in soils where the plants were grown was also assessed during the two seasons. Soil Mn and Co concentrations were significantly high in Maha than in Yala. Difference in heavy metal concentrations in mustard accessions between the two seasons was not significant. However, significantly high concentrations of Mn were found in accessions 7788, 515 and 8831 (236, 225, 220x102 μg/g). Cobolt (Co) was significantly high in accession 5088 (238x102 μg/g). Lead (Pb) concentrations were significantly high in accessions 8831 (156x102 μg/g) and 5088 (148x102 μg/g) and Zn was significantly high in accession 501 (6413x102 μg/g). The study suggests that screening the entire mustard germplasm in Sri Lanka is worthwhile to identify potential heavy metal accumulators. Key words: heavy metal hyperaccumulation; phytoremediation DOI: 10.4038/cjsbs.v38i2.1862 Cey. J. Sci. (Bio. Sci.) 38 (2): 85-93, 2009

Influence of Ammonium and Nitrate Nutrition on Plant Growth and Zinc Accumulation by Indian Mustard

ABSTRACT The source of nitrogen (N) used in soil fertility practices affects plant growth, nutrient absorption, and the availability of nutrients. Consequently, the potential of plants to extract zinc (Zn) from soils may be increased by controlling the ratio of NH4 + to NO3 − to maximize growth and Zn accumulation. The objectives of this research were to determine the effects of Zn supply and different molar ratios of NH4 + to NO3 − on growth and Zn accumulation in Indian mustard (Brassica juncea Czern.). In a factorial experiment with solution culture, Indian mustard (accession 182921) was supplied with two concentrations of Zn (0.05 and 4.0 mg L−1) in combination with six N treatments with different molar percentage ratios of NH4 + to NO3 − (0:100, 10:90, 20:80, 30:70, 40:60, and 50:50) for three weeks. Zinc supplied at 0.05 mg Zn L−1 represented a common concentration of Zn in solution culture, whereas 4.0 mg Zn L−1 was excessive for plant nutrition. If the supply of Zn in solution was excessive, plants developed symptoms of foliar chlorosis, which became severe if plants were supplied with 80% of N as NO3 −. Supplying high proportions of NO3 − in the nutrient medium stimulated Zn accumulation, whereas increasing proportions of NH4 + (up to 50% of the total N) enhanced shoot growth. The pH of nutrient solutions generally decreased with increasing proportion of NH4 + in solutions and with increased Zn supply. The Zn phytoextraction potential of Indian mustard was maximized, at about 15 mg Zn plant−1, if plants received 10% of the total N as NH4 + and 90% as NO3 −.