Effects of co-cropping Bidens pilosa (L.) and Tagetes minuta (L.) on bioaccumulation of Pb in Lactuca sativa (L.) growing in polluted agricultural soils

Polluted agricultural soils are a serious problem for food safety, with phytoremediation being the most favorable alternative from the environmental perspective. However, this methodology is generally time-consuming and requires the cessation of agriculture. Therefore, the purpose of this study was to evaluate two potential phytoextractor plants (the native species Bidens pilosa and Tagetes minuta) co-cropped with lettuce growing on agricultural lead-polluted soils. The concentrations of Pb, as well as of other metals, were investigated in the phytoextractors, crop species, and in soils, with the potential risk to the health of consumers being estimated. The soil parameters pH, EC, organic matter percentage and bioavailable lead showed a direct relationship with the accumulation of Pb in roots. In addition, the concentration of Pb in roots of native species was closely related to Fe (B. pilosa, r = 0.81; T. minuta r = 0.75), Cu (T. minuta, r = 0.93), Mn (B. pilosa, r = 0.89) and Zn (B. pilosa, r = 0.91; T. minuta, r = 0.91). Our results indicate that the interaction between rhizospheres increased the phytoextraction of lead, which was accompanied by an increase in the biomass of the phytoextractor species. However, the consumption of lettuce still revealed a toxicological risk from Pb in all treatments.     

Effects of Acacia (Acacia auriculaeformis A. Cunn)‐associated fungi on mustard (Brassica juncea (L.) Coss. var. foliosa Bailey) growth in Cd‐ and Ni‐contaminated soils

Aims: To evaluate the effect of Acacia auriculaeformis‐associated fungi on the growth of mustard [Brassica juncea (L.) Coss. var. foliosa Bailey] in Cd‐ and Ni‐contaminated soils and design novel plant–fungi associations for bioremediation purpose. Methods and Results: Endophytic Trichoderma H8 and rhizosphere Aspergillus G16 were applied for rhizoremediation of Cd‐, Ni‐, and Cd–Ni combination‐contaminated soils through association with B. juncea (L.) Coss. var. foliosa. Compared with the noninoculated control plants, inoculation with Trichoderma H8 produced 109%, 41% and 167% more fresh weight (FW) plant yields in the Cd‐, Ni‐, and Cd–Ni‐contaminated soils, respectively (P < 0·05). Similarly, plants inoculated with Aspergillus G16 produced 109%, 47% and 44% more FW plant yields in these contaminated soils, respectively. Plants co‐inoculated with these two strains produced 118%, 100% and 178% more FW plant yields, respectively. The inoculations also increased the translocation factors and metal bioconcentration factors. Conclusions: The efficiency of phytoextraction for B. juncea (L.) Coss. var. foliosa was enhanced after inoculating with Acacia‐associated fungi. Significance and Impact of the study: The use of plant–fungi association may be a promising strategy to remediate metal‐contaminated soils.     

Intraspecific variability of cadmium tolerance in hydroponically grown Indian mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) Czern.) seedlings

Indian mustard (Brassica juncea (L.) Czern.) is a promising plant species for phytoremediation of heavy metal polluted soils. However, genetic variability of metal tolerance in Indian mustard has not been studied. We evaluated intraspecific variation of Cd tolerance of this species by screening 64 varieties in hydroponics. The tolerance index (TI), calculated as percentage of root length of Cd-treated (7 μM CdCl₂) over untreated control seedlings, significantly varied from 34 to 79%, depending on the variety. Information about phenotypic and economic traits of the studied varieties was taken from the literature and subjected to a cluster analysis. The varieties were distributed into three clusters and most of the varieties characterized by the highest TI values (TI > 65%) were grouped together in one cluster. Moreover, TI negatively correlated with the following characteristics: yellow seed colour (R = −0.35, P = 0.005), total oil content (R = −0.33, P = 0.008), oleic acid (R = −0.25, P = 0.047) and linoleic acid (R = −0.36, P = 0.004) contents in seeds. The results showed the presence of significant variability for Cd tolerance in Indian mustard. The knowledge about correlations between Cd tolerance and phenotypic characteristics of plants might be utilized for rapid selection of cultivars to be used for phytoremediation of polluted soils.     

Mobilization of cadmium and other metals from two soils by root exudates of Zea mays L., Nicotiana tabacum L. and Nicotiana rustica L.

Soluble root exudates were collected from three plants (Nicotiana tabacum L., Nicotiana rustica L. and Zea mays L.), grown under axenic and hydroponic conditions, in order to study their metal-solubilizing ability for Cd and other cations (Cu, Fe, Mn, Ni, Zn). Nicotiana spp. and Zea mays L. root exudates differed markedly in C/N ratio, sugars vs. amino acids ratio and organic acids content. Metals from two soils were extracted with either root exudate solutions, containing equal amounts of organic carbon, or distilled water as control. In the presence or absence of root exudates, the solubility of Fe and Mn was much higher than of the four other metals tested. Root exudates increased the solubilities of Mn and Cu, whereas those of Ni and Zn were not affected. Root exudates of Nicotiana spp. enhanced the solubility of Cd. The extent of Cd extraction by root exudates (N. tabacum L. N. rustica L. Zea mays L.) was similar to the order of Cd bioavailability to these three plants when grown on soil. An increase in Cd solubility in the rhizosphere of apical root zones due to root exudates is likely to be an important cause of the relatively high Cd accumulation in Nicotiana spp.     

Comparison of tolerance of <Emphasis Type="Italic">Brassica juncea</Emphasis> and <Emphasis Type="Italic">Vigna radiata</Emphasis> to cadmium

The effect of different cadmium concentrations (6–120 μM) on Hill reaction activity (HRA) of isolated chloroplasts, contents of chlorophylls (Chls) and carotenoids (Cars), and Cd uptake and accumulation in plant organs of Indian mustard (Brassica juncea L. cv. Vitasso) and mung bean [Vigna radiata (L.) Wilczek] were determined. The Cd stress inhibited photochemical activity of isolated chloroplasts of both species and in both tested developmental stages. On the basis of EC₅₀ values, the mung bean showed a higher sensitivity to Cd treatment than Indian mustard. The higher sensitivity of both species was determined in the earlier than in the older developmental stage. The leaves of Cd-treated plants possessed lower contents of Chls and Cars in both species and the negative effect increased with Cd concentration. A difference between species was also found in Cd uptake and accumulation. In both species, Cd was accumulated more in roots than in shoots, with higher accumulation in Indian mustard than in mung bean.     

In vitro breeding of Brassica juncea L. to enhance metal accumulation and extraction properties

In vitro breeding and somaclonal variation were used as tools to improve the potential of Indian mustard (Brassica juncea L.) to extract and accumulate toxic metals. Calli from B. juncea were cultivated on a modified MS medium supplemented with 10–200 μM Cd or Pb. Afterwards, new B. juncea somaclones were regenerated from metal-tolerant callus cells. Three different phenotypes with improved tolerance of Cd, Zn and Pb were observed under hydroponic conditions: enhanced metal accumulation in both shoots and roots; limited metal translocation from roots to shoots; reduced accumulation in shoots and roots. Seven out of thirty individual variants showed a significantly higher metal extraction than the control plants. The improvement of metal shoot accumulation of the best regenerant (3× Cd, 1.6× Zn, 1.8× Pb) and metal extraction (6.2× Cd, 3.2× Zn, 3.8× Pb) indicated a successful breeding and selection of B. juncea, which could be used for phytoremediation purpose.     

Use of Brassicaceous seed meals to improve seedling emergence of tomato and pepper in Pythium ultimum infested soils

Growth room studies were conducted to determine the impact of Brassicaceae seed meals on the emergence of tomato and pepper seedlings in Pythium ultimum infested soils. Pasteurised Burch sandy loam soils were amended with intact and denatured seed meal of rape seed and mustard. Brassica juncea or Brassica napus intact seed meal increased the tomato and pepper seedling emergence. Interestingly, B. napus amended soils resulted in the same seedling emergence with B. juncea regardless of their relatively lower glucosinolate content compared to mustard-based seed meals. Seedling emergence in soils amended with intact Sinapis alba seed meal was significantly the lowest for both tomato and pepper seedlings. In contrast, seedling emergence was higher in soils amended with denatured than intact S. alba seed meals suggesting some glucosinolate-related inhibitory effect on seedling emergence of both crops. Glycine max seed meal amendment improved the seedling emergence better than the control but to a lower-level when compared to glucosinolate containing seed meals. This finding suggests that even though improvement of seedling emergence of tomato and pepper in P. ultimum infested soils can be achieved using Brassicaceae seed meals, it cannot be entirely attributed to glucosinolate-related processes. These studies demonstrate that intact B. napus and B. juncea seed meals can be used to improve tomato and pepper seedling emergence in P. ultimum infested soils.     

Association genetics of the parameters related to nitrogen use efficiency in Brassica juncea L.

Key message

Genome wide association studies allowed prediction of 17 candidate genes for association with nitrogen use efficiency. Novel information obtained may provide better understanding of genomic controls underlying germplasm variations for this trait in Indian mustard.

Abstract

Nitrogen use efficiency (NUE) of Indian mustard (Brassica juncea (L.) Czern & Coss.) is low and most breeding efforts to combine NUE with crop performance have not succeeded. Underlying genetics also remain unexplored. We tested 92 SNP-genotyped inbred lines for yield component traits, N uptake efficiency (NUPEFF), nitrogen utilization efficiency (NUTEFF), nitrogen harvest index (NHI) and NUE for two years at two nitrogen doses (N_o without added N and N₁₀₀ added @100 kg/ha). Genotypes IC-2489-88, M-633, MCP-632, HUJM 1080, GR-325 and DJ-65 recorded high NUE at low N. These also showed improved crop performance under high N. One determinate mustard genotype DJ-113 DT-3 revealed maximum NUTEFF. Genome wide association studies (GWAS) facilitated recognition of 17 quantitative trait loci (QTLs). Environment specificity was high. B-genome chromosomes (B02, B03, B05, B07 and B08) harbored many useful loci. We also used regional association mapping (RAM) to supplement results from GWAS. Annotation of the genomic regions around peak SNPs helped to predict several gene candidates for root architecture, N uptake, assimilation and remobilization. CAT9 (At1g05940) was consistently envisaged for both NUE and NUPEFF. Major N transporter genes, NRT1.8 and NRT3.1 were predicted for explaining variation for NUTEFF and NUPEFF, respectively. Most significant amino acid transporter gene, AAP1 appeared associated with NUE under limited N conditions. All these candidates were predicted in the regions of high linkage disequilibrium. Sequence information of the predicted candidate genes will permit development of molecular markers to aid breeding for high NUE.

     

Effects of liming and mycorrhizal colonization on soil phosphate depletion and phosphate uptake by maize (Zea mays L.) and soybean (Glycine max L.) grown in two tropical acid soils

The effects of liming and inoculation with the arbuscular mycorrhizal fungus, Glomus intraradices Schenck and Smith on the uptake of phosphate (P) by maize (Zea mays L.) and soybean (Glycine max [L.] Merr.) and on depletion of inorganic phosphate fractions in rhizosphere soil (Al-P, Fe-P, and Ca-P) were studied in flat plastic containers using two acid soils, an Oxisol and an Ultisol, from Indonesia. The bulk soil pH was adjusted in both soils to 4.7, 5.6, and 6.4 by liming with different amounts of CaCO₃.In both soils, liming increased shoot dry weight, total root length, and mycorrhizal colonization of roots in the two plant species. Mycorrhizal inoculation significantly increased root dry weight in some cases, but much more markedly increased shoot dry weight and P concentration in shoot and roots, and also the calculated P uptake per unit root length. In the rhizosphere soil of mycorrhizal and non-mycorrhizal plants, the depletion of Al-P, Fe-P, and Ca-P depended in some cases on the soil pH. At all pH levels, the extent of P depletion in the rhizosphere soil was greater in mycorrhizal than in non-mycorrhizal plants. Despite these quantitative differences in exploitation of soil P, mycorrhizal roots used the same inorganic P sources as non-mycorrhizal roots. These results do not suggest that mycorrhizal roots have specific properties for P solubilization. Rather, the efficient P uptake from soil solution by the roots determines the effectiveness of the use of the different soil P sources. The results indicate also that both liming and mycorrhizal colonization are important for enhancing P uptake and plant growth in tropical acid soils.     

Identification of an ISSR Marker for 2-propenyl glucosinolate Content in <Emphasis Type="Italic">Brassica juncea</Emphasis> L. and Conversion to a SCAR Marker

Research was undertaken to identify molecular markers using the ISSR technique for 2-propenyl glucosinolate in Brassica juncea. Bulked segregant analysis was used based on three bulks: (1) low 2-propenyl, low 3-butenyl glucosinolate, (2) high 2-propenyl glucosinolate, low 3-butenyl and (3) low 2-propenyl, high 3-butenyl glucosinolate. An ISSR marker was found to be tightly linked to high 2-propenyl glucosinolate. The ISSR fragment was cloned and sequenced and resulted in a 505 bp fragment bordered by the inverted SSR. An improved primer was designed based on the cloned sequence which resulted in a clear, simple to score, band associated with high 2-propenyl glucosinolate. The marker was screened against a range of canola and mustard quality B. juncea and was found to be widely applicable. The potential usefulness of the marker for canola quality and mustard B. juncea breeding programs is also discussed.     

Induction of phytochelatins and antioxidant defence system in <Emphasis Type="Italic">Brassica juncea</Emphasis> and <Emphasis Type="Italic">Vigna radiata</Emphasis> in response to chromium treatments

Growth performance, chromium (Cr) accumulation potential and induction of antioxidative defence system and phytochelatins (PCs) were studied in hydroponically grown Brassica juncea (Indian mustard) and Vigna radiata (mungbean) at various levels of Cr treatments (0, 50, 100, 200 μM Cr). B. juncea accumulated twofolds and threefolds higher Cr in root and shoot, respectively than in V. radiata. Compared to B. juncea, V. radiata was found to be particularly sensitive to Cr as observed by the severity and development of Cr toxicity symptoms and decreased growth. Induction of PC and enzymes of antioxidant defence system were monitored as plant’s primary and secondary metal detoxifying responses, respectively. There was induction of PC and enzymes of antioxidant defence system in both the plants. PCs were induced significantly in roots and shoot of both the plants at all the levels of Cr treatments. Significantly higher activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) were observed in shoot of B. juncea than V. radiata at all the levels of Cr treatments. Induction of PCs along with antioxidant defence system in response to Cr stress suggests the cumulative role of PCs and antioxidants in conferring tolerance against accumulated Cr in B. juncea, and thereby signifies the suitability of this plant as one of the potential remediators of Cr.     

Rhizosphere Bacteria Enhance Selenium Accumulation and Volatilization by Indian Mustard

Indian mustard (Brassica juncea L.) accumulates high tissue Se concentrations and volatilizes Se in relatively nontoxic forms, such as dimethylselenide. This study showed that the presence of bacteria in the rhizosphere of Indian mustard was necessary to achieve the best rates of plant Se accumulation and volatilization of selenate. Experiments with the antibiotic ampicillin showed that bacteria facilitated 35% of plant Se volatilization and 70% of plant tissue accumulation. These results were confirmed by inoculating axenic plants with rhizosphere bacteria. Compared with axenic controls, plants inoculated with rhizosphere bacteria had 5-fold higher Se concentrations in roots (the site of volatilization) and 4-fold higher rates of Se volatilization. Plants with bacteria contained a heat-labile compound in their root exudate; when this compound was added to the rhizosphere of axenic plants, Se accumulation in plant tissues increased. Plants with bacteria had an increased root surface area compared with axenic plants; the increased area was unlikely to have caused their increased tissue Se accumulation because they did not accumulate more Se when supplied with selenite or selenomethionine. Rhizosphere bacteria also possibly increased plant Se volatilization because they enabled plants to overcome a rate-limiting step in the Se volatilization pathway, i.e. Se accumulation in plant tissues.     

Turgor Maintenance by Osmoregulation inBrassica napusandB. junceaunder Field Conditions

Indian mustard (Brassica juncea(L) Czernjacw) maintains higherleaf turgor than canola (B. napusL.) under water deficits andthis is related to the greater yield of mustard under theseconditions. The work reported in this paper was designed tostudy the way mustard maintains this turgor advantage. It wasbased on three field experiments that each used at least twocultivars or lines of each species. The leaf water potentialat which leaves reached zero turgor was consistently lower inmustard than in canola (up to 1.1 MPa lower). This differencearose from a greater rate of decline in leaf osmotic potentialwith declining water potential in mustard rather than from anydifference in the osmotic potential at full turgor. Calculationsof solute accumulation showed that mustard had a greater capacityto osmoregulate than canola, with this capacity being the basisfor its advantage in turgor maintenance. Other differences inplant water relations were consistent with the differences inosmoregulation, with the predicted relative water content ofleaves at an osmotic potential of -2.5 MPa being 0.43 for canolaand 0.61 for mustard. Mustard's greater capacity to accumulatesolutes is concluded to be a major factor in its greater yieldunder water deficits. Brassica napusL.; Brassica juncea(L) Czernjacw; Indian mustard; canola; water deficit; plant water relations; osmoregulation; osmotic adjustment; turgor     

Gene transfer between canola (Brassica napus L. and B. campestris L.) and related weed species

Brassica species are particularly receptive to gene transformation techniques. There now exists canola genotypes with transgenic herbicide resistance for glyphosate, imidazolinone, sulfonylurea and glufosinate herbicides. The main concern of introducing such herbicide resistance into commercial agriculture is the introgression of the engineered gene to related weed species. The potential of gene transfer between canola (Brassica napus and B. campestris) and related weed species was determined by hand pollination under controlled greenhouse conditions. Canola was used as both male and female parent in crosses to the related weed species collected in the Inland Northwest region of the United States. Weed species used included: field mustard (B. rapa), wild mustard (S. arvensis) and black mustard (B. nigra). Biological and cytological aspects necessary for successful hybrid seed production were investigated including: pollen germination on the stigma; pollen tube growth down the style; attraction of pollen tubes to the ovule; ovule fertilisation; embryo and endosperm developmental stages. Pollen germination was observed in all 25 hybrid combinations. Pollen tubes were found in the ovary of over 80% of combinations. About 30% of the hybrid combinations developed to the heart stage of embryo development or further. In an additional study involving transgenic glufosinate herbicide resistant B. napus and field mustard it was found that hybrids occurred with relatively high frequency, hybrids exhibited glufosinate herbicide resistance and a small proportion of hybrids produced self fertile seeds. These fertile plants were found to backcross to either canola or weed parent.     

鬼针草(Bidens pilosa L.)对镉污染农田的修复潜力

为探究富集植物鬼针草对镉(Cd)污染农田土壤的修复潜力,通过野外调查,原土盆栽试验和田间试验,测定鬼针草及其根系土壤Cd含量,计算鬼针草的富集系数和去除率。结果表明,野外调查中不同铅锌矿区生长的鬼针草叶片中Cd含量最大值为53.3 mg/kg。盆栽试验中,低浓度Cd土壤处理(T1),鬼针草地上部Cd的富集系数为4.70,转运系数1.59,大于1。高浓度Cd土壤处理(T2 13.4 mg/kg),其地上部Cd积累量达到43.1 mg/kg,其地上部Cd富集系数为3.51。鬼针草对Cd表现出稳定的积累特性。田间试验小区中,土壤Cd含量均值为2.66 mg/kg,鬼针草中地上部Cd含量均值为10.9 mg/kg,富集系数为4.16,使用鬼针草修复Cd污染土壤每公顷地种植一茬鬼针草的去除率为4.3%—6.2%。使用富集植物鬼针草修复农田Cd污染具有较好的工程应用前景。     

Low Allozymic Variation in the Bidens pilosa L. Complex (Asteraceae)

Bidens alba, B. subalternans, and B. pilosa form a complex group based on their morphological similarities. Bidens pilosa L. and B. subalternans DC. are herbs with a wide distribution in agricultural and disturbed areas. Bidens alba (L.) DC. varies in size from herb to subshrub and has a coastal distribution. Enzyme electrophoresis was used to evaluate genetic diversity in 12 populations of Bidens. All but three loci (Lap-1, Est, and Got) were monomorphic. Est-1 and Got were polymorphic only in B. alba. Lap-1 was polymorphic only in B. pilosa and B. subalternans. The estimates of genetic variability were low for all three taxa and all of the populations studied. Genetic diversity varied from 0.01 to 0.03. Mean genetic identities were high among populations of each species (0.99 for B. alba and 1.00 for B. pilosa and B. subalternans) and among the three species (1.00). Bidens pilosa and B. subalternans could be considered a single species if the taxonomy of the group were based solely on isozyme data.     

Copper concentration in plants and in the rhizosphere as influenced by the iron status of tomato (Lycopersicon esculentum L.)

Changes of metal concentration that occur in the rhizosphere may arise from several processes including variation in the concentration of complexing ligands, pH or redox potential that can be influenced by the Fe status of the plant. The aim of this study was to assess for both acidic and calcareous, Cu-contaminated soils how Cu concentration in plants and in the rhizosphere was affected by the Fe status of a strategy I plant species. The change of soil solution pH, total solution Cu concentration and soil redox potential was monitored for 8 days in the rhizosphere of tomato (Lycopersicon esculentum L.) in response to contrasting Fe supply. The concentration of Cu in roots was enhanced under Fe deficiency in the acidic soils. Shoot Cu however did not vary with the Fe status of the plant. The plant Fe status had little effect on rhizosphere pH, redox potential or Cu concentration in solution in either acidic or calcareous soils. Marked differences in pH and solution Cu concentration were observed between rhizosphere and uncropped soils. Roots induced an increase in pH of acidic soils and a decrease in solution Cu concentration in all soils. The decrease in solution Cu concentration in acidic soils may be explained by the increase in rhizosphere pH. The proposed device provided new data on the fate of Cu in the rhizosphere and showed a positive correlation for the four soils considered together between the total Cu concentration in soil solution and root Cu concentration.     

Thiophenes and benzofurans in the undisturbed rhizosphere ofTagetes patula L.

Summary Marigold (Tagetes patula L.) contains secondary metabolites toxic to various organisms. While these compounds may function as defensive agents in the plant, it is not clear whether they are exuded into the rhizosphere. Using a continuous root exudate trapping system and capillary column gas chromatography/mass spectrometry/data system, four thiophenes and two benzofurans were identified in the root exudates collected from the undisturbed rhizosphere of marigold. The importance of rhizospheric chemistry in the study of allelopathy is stressed.     

POTENTIAL OF BRASSICA JUNCEA IN ORDER TO TREAT TEXTILE—EFFLUENT—CONTAMINATED SITES

Three plant species (Brassica juncea, Sorghum vulgare, and Phaseolus mungo) of different agronomic consequence were evaluated for the decolorization of the dyes from textile effluent. B. juncea, S. vulgare, and P. mungo showed textile effluent decolorization up to 79, 57, and 53%, respectively. A significant decrease in shoot and root height, but no significant injury, was observed in the case of P. mungo and S. vulgare. B. juncea (Indian mustard), the most tolerant and more effective metals accumulator than other tested agricultural plant species, showed enhanced growth with respect to the height of the shoot and root, 129 and 178%, respectively, when grown using original textile effluent. Textile effluent induced intracellular nicotinamide adenine dinucleotide reduced (NADH)–dichlorophenol indophenol reductase significantly in the case of S. vulgare and B. juncea with 209 and 194%, respectively. The extracellular riboflavin reductase activity was induced by 223% in the case of P. mungo as compared to control plants. Significant induction of intracellular laccase (266%) was observed in the case of B. juncea, indicating their crucial role for a potential metabolism and further degradation of the textile effluent. The metabolites were identified as napthalenesufamide (m/z 372) and 2-amino-4, 6-dichlorotriazine (m/z 167), when B. juncea was used to degrade a model dye, Reactive red 2.     

Remediation of Nickel-Contaminated Soil by Brassica juncea L. cv. T-59 and Effect of the Metal on Some Metabolic Aspects of the Plant

Among four cultivars of Brassica juncea L., viz., TM-4, TM-2, RH-30, and T-59, cv. T-59 was relatively more tolerant to nickel (Ni) toxicity based on the growth parameters, seedling vigor index, and metal tolerance index. Nickel application inhibited the activity of the nitrate-assimilating enzyme nitrate reductase in the roots, stem, and leaves, whereas the total organic nitrogen, proline, and activity of a polyamine-metabolizing enzyme, diamine oxidase, increased in this tolerant cultivar (T-59). It accumulated a good amount of Ni from the soil in its root and shoot (i.e., 6.0–6.51 μg Ni g^?1 dry weight) during 2 months of cultivation with an 8.0 mM Ni supply in the soil. The data presented in this paper indicate that Ni tolerance and its removal by Indian mustard from subtropical Indian soil is cultivar dependent, possibly due to different genetic and physiological adaptations of the cultivars.