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A computer-assisted comparative analysis of the amino acid sequences of (putative) thiol proteases encoded by the genomes of several diverse groups or positive-stranded RNA viruses and distantly related to the family of cellular papain-like proteases is presented. A high level of similarity was detected between the leader protease of foot-and-mouth-disease virus and the protease of murine hepatitis coronavirus which cleaves the N-terminal p28 protein from the polyprotein. Statistically significant alignment of a portion of the rubella virus polyprotein with cellular papain-like proteases was obtained, leading to tentative identification of the papain-like protease as the enzyme mediating processing of the non-structural proteins of this virus. Specific grouping between the sequences of the proteases of α-viruses, and poty- and bymoviruses was revealed. It was noted that papain-like proteases of positive-stranded RNA viruses are much more variable both in their sequences and in genomic locations than chymotrypsin-related proteases found in the same virus class. A novel conserved domain of unknown function has also been identified which flanks the papain-like proteases of α-, rubi- and coronaviruses.

▼ A computer-assisted comparative analysis of the amino acid sequences of (putative) thiol proteases encoded by the genomes of several diverse groups or positive-stranded RNA viruses and distantly related to the family of cellular papain-like proteases is presented. A high level of similarity was detected between the leader protease of foot-and-mouth-disease virus and the protease of murine hepatitis coronavirus which cleaves the N-terminal p28 protein from the polyprotein. Statistically significant alignment of a portion of the rubella virus polyprotein with cellular papain-like proteases was obtained, leading to tentative identification of the papain-like protease as the enzyme mediating processing of the non-structural proteins of this virus. Specific grouping between the sequences of the proteases of α-viruses, and poty- and bymoviruses was revealed. It was noted that papain-like proteases of positive-stranded RNA viruses are much more variable both in their sequences and in genomic locations than chymotrypsin-related proteases found in the same virus class. A novel conserved domain of unknown function has also been identified which flanks the papain-like proteases of α-, rubi- and coronaviruses.

▼ The iron storage protein ferritin acts as an antioxidant by sequestering excess iron, thereby limiting the availability of free excess iron and preventing the generation of OH-type radicals. Oxidative stress and ABA mediate ferritin induction in maize whereas only oxidative stress operates in Arabidopsis. Iron mediates oxidative stress in Vigna mungo (L.) Hepper as revealed by upregulation of activities of antioxidative enzymes and reduction of the activity in the presence of antioxidants and free radical scavengers. Pre-treatment of iron deficient de-rooted seedlings with free radical scavengers and antioxidants followed by co-treatment with ferric citrate inhibited ferritin induction. Pro-oxidant (H₂O₂) treatment resulted in induction of ferritin up to 2 mmol/L. ABA induced ferritin in a dose dependent manner. These results indicate that both iron mediated oxidative stress and ABA lead to ferritin induction. It was also observed that ferritin induction is specific for iron in comparison to other metals.

▼ The iron storage protein ferritin acts as an antioxidant by sequestering excess iron, thereby limiting the availability of free excess iron and preventing the generation of OH-type radicals. Oxidative stress and ABA mediate ferritin induction in maize whereas only oxidative stress operates in Arabidopsis. Iron mediates oxidative stress in Vigna mungo (L.) Hepper as revealed by upregulation of activities of antioxidative enzymes and reduction of the activity in the presence of antioxidants and free radical scavengers. Pre-treatment of iron deficient de-rooted seedlings with free radical scavengers and antioxidants followed by co-treatment with ferric citrate inhibited ferritin induction. Pro-oxidant (H₂O₂) treatment resulted in induction of ferritin up to 2 mmol/L. ABA induced ferritin in a dose dependent manner. These results indicate that both iron mediated oxidative stress and ABA lead to ferritin induction. It was also observed that ferritin induction is specific for iron in comparison to other metals.

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The morphogenic pathway of adventitious shoot regeneration at the ends of Vigna mungo epicotyl segments was determined by ontogenic age, orientation, polarity and position of the explant on mother seedling. The epicotyl explants excised from 3-day-old in vitro raised seedlings when planted vertically with basal end inserted in the medium containing 6-benzylaminopurine developed multiple shoots at the apical end by direct organogenesis while the basal end of the cutting formed callus which differentiated into shoots via indirect organogenesis. With increase in the age of the explants, the shoot forming response increased at the apical end while at the basal end it decreased and formed callus only. The 17-day-old explants produced an average of four shoots at the apical end in 78% of the cultures on medium containing MS salts, B₅ vitamins and BAP (5 μM) within 28 days. Substitution of BAP at an equimolar concentration with kinetin, 2-ip, TDZ and AdS, and BAP in combination with auxins (IAA or IBA or NAA) did not improve shoot regeneration. The shoot forming response of explants decreased as the distance of the segment increased from shoot apex of the mother seedling as well as when the orientation of explants deviates from the normal vertical upright position. Efficient rooting (100%) of the shoots was achieved on medium containing half MS salts, full MS vitamins and IBA (2.5 μM). Regenerated plantlets were established in soil with 90% survival rate and all surviving plants were morphologically normal and seed fertile. The regenerable cells of the explants were found to be competent for transformation with Agrobacterium tumefaciens.

▼ A cysteine endopeptidase named SH-EP was isolated as one of the major hydrolytic enzymes involved in the mobilization of storage globulin in the cotyledon of germinated seeds of Vigna mungo. The enzyme, by itself or in combination with a serine endopeptidase, digests the globulin subunits to smaller peptides in vitro. Protein immunoblot analysis with antiserum raised against SH-EP showed that this enzyme is synthesized in the cotyledon after the onset of imbibition and increases until day 4 and decreases thereafter. Application of plant hormones and growth regulators, as well as amino acids as proteolytic end-products, appears to affect the development of SH-EP to a limited extent in the cotyledon of the germinated seeds. SH-EP of 33 kDa is synthesized on membrane-bound polysomes as a large, inactive 45-kDa precursor, which is cotranslationally processed to a 43-kDa intermediate through cleavage of a signal peptide. The amino-terminal propeptide region of the intermediate is cleaved further to form the 33-kDa mature enzyme by a multistep processing. The 43-kDa intermediate is also subjected to the cleavage of the carboxy-terminal decapeptide containing a Lys-Asp-Glu-Leu tail, which is known as a retention signal for the endoplasmic reticulum lumen. An asparaginyl endopeptidase, designated VmPE-1, was isolated as one of the processing enzymes responsible for the cleavage of the amino-terminal propeptide region of the precursor to SH-EP.

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Regeneration has been achieved in Vigna mungo L. through organogenesis using explants from axillary shoots originating from the nodes of seedlings germinated in cytokinin containing medium. Seeds germinated in thidiazuron (TDZ) at 0.5 mg l⁻¹ supplemented MS medium produced ≈11 axillary shoots/cotyledonary node. Stem and petiole explants derived from these axillary-shoots produced callus along with shoot-buds after 2 weeks of culture on half strength MS supplemented with 0.1 mg l⁻¹ α-napthaleneacetic acid. Shoot-buds were also produced from various sites of injury caused by incisions on the stem explants. Full strength MS salts inhibited bud formation. Histological studies indicated the differentiation of shoot-buds from the cortical cells. The pH of the regeneration medium had a significant effect on regeneration efficiency. The shoot-buds elongated and rooted on one third strength MS medium. The plantlets were transferred to soil after 3 weeks and 90–95% of the plantlets thus obtained could survive transfer to soil. The regeneration protocol described is highly reproducible and equally effective for all the four genotypes tested, viz. T-9, Pusa-1, Pusa-2 and PS-1 yielding about 5 shoot-buds/stem explant (with apex). The regeneration system is efficient as it results in the recovery of 4–5 plants within a period of 8 weeks, starting from an explant.

▼ The occurrence of 24-epiclerosterol, three Δ^8^(^1^4^)-sterols [24α- and 24β-methyl-5α-cholest-8(14)-en-3β-ols and 24α-ethyl-5α-cholest-8(14)-en-3β-ol] and four 14α-methyl-Δ^9^(^1^1^)-sterols [14α,24α- and 14α,24β-dimethyl-5α-cholest-9(11)-en-3β-ols, 14α-methyl-24α-ethyl-5α-cholest-9(11)-en-3β-ol and 14α-methyl-24β-ethyl-5a-cholesta-9(11),25-dien-3β-ol] has been demonstrated in the seeds of four Leguminosae species, Cajanus cajan, Cicer arietinum, Pisum sativum and Vigna mungo. These compounds were minor sterol constituents. In addition, 24α-ethyl-5α-cholest-9(11)-en-3β-ol and 24-methylenepollinastanol were isolated and identified from V. mungo seeds. Sitosterol was the principal sterol in all of the four Leguminosae seeds investigated.

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Results are reported from on-farm surveys of N₂ fixation in Nepal, conducted between 1994 and 1999, involving the summer legumes soybean, mashbean and groundnut, and the winter legumes lentil and chickpea, at various locations in the Hill and Terai regions of Nepal. Additional less-detailed data were also collected for pigeonpea, grasspea and fababean. There were a total of 107 crops in the major and minor surveys. Estimates of the proportion of legume nitrogen (N) derived from N₂ fixation (Pfix) were determined using the natural ¹⁵N abundance method. Mean estimates of Pfix for the various species were 62% (soybean), 47% (mashbean), 57% (groundnut), 78% (lentil), 79% (chickpea), 75% (pigeonpea), 87% (grasspea) and 85% (fababean). Estimates of total N fixed (including roots) were 59kgNha⁻¹ (soybean), 28kgNha⁻¹ (mashbean), 153kgNha⁻¹ (groundnut), 72kgNha⁻¹ (lentil), 84kgNha⁻¹ (chickpea), 412Nha⁻¹ (pigeonpea) and 80Nha⁻¹ (grasspea and fababean). The on-farm measurements of N₂ fixation were generally similar to those of experimental crops in the same areas of the country. Correlation matrices of soil fertility parameters, shoot dry matter and N, and N₂ fixation revealed that the total amounts of N fixed were influenced primarily by crop growth. Based on the above figures, it was estimated that approximately 30,000t N were fixed annually in Nepal by legumes, valued at US$ 15 million.

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Summary

The inheritance of the dwarf plant type was studied in blackgram (V. mungo (L.) Hepper). ‘Type 9’ has erect plant type with normal internode length. The mutant line, ‘EMSD’ has reduced internode length. The F₁, F₂ and F₃ generations of a cross between ‘Type 9’ and ‘EMSD’ and its reciprocal were studied. The extreme dwarf plant type appeared to be governed by a single recessive gene, dw ₁ dw ₁ with no cytoplasmic effect.

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Seeds used to plant a crop may contain sufficient molybdenum (Mo) to prevent subsequent Mo deficiency in the crop even when they are sown on Mo deficient soils. However, little is known about either the sources of the Mo acquired by the seed, or the timing of its redistribution during seed development. A glasshouse experiment was set up to examine the effect of Mo supply and nitrogen source on the redistribution of Mo within black gram, from full flowering to seed maturity. Treatments comprised two sources of N (symbiotic N₂fixation, NH₄NO₃), two levels of Mo supply [nil (−Mo), 0.64 mg Mo kg⁻¹soil (+Mo)] and four harvests (full flowering, early pod setting, late pod filling and seed maturity). The redistribution of Mo in black gram was examined by determining changes over time in the content of Mo in plant parts at each growth stage.

Molybdenum supply and the plant growth stage strongly affected the redistribution of Mo to the seed. In −Mo plants reliant on symbiotic N₂fixation, Mo redistributed from roots, stems and leaves was the only source of Mo for reproductive development since, from full flowering until maturity, there was no net increase in whole plant Mo. For pod and early seed development, the roots were the major source of Mo in −Mo plants. After late pod filling, nodules replaced roots as the major source of Mo for seed fill in −Mo plants. By contrast, for +Mo plants reliant on symbiotic N₂fixation, Mo taken up from the soil after full flowering could have supplied nearly 50% of the seed Mo. The major sources of Mo for seed filling in +Mo plants were middle stem leaves during early podding, and middle stems and pod walls from late podding.

Supplying NH₄NO₃to plants from sowing had little effect on Mo distribution or redistribution in +Mo black gram plants. However, in −Mo plants it accelerated the loss of Mo from middle stems and their leaves compared to nodulated plants.

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Summary

To introduce resistance to fungal and viral diseases into urdbean (Vigna mungo), it was crossed with adzukibean (Vigna angularis) to achieve an interspecific hybrid between the two species by using different non-conventional breeding methods. Partial success was obtained with the use of UV irradiated pollen, intraspecific hybrids as parents and spray of immuno-suppressants on the female parent under glass house conditions and to the extent of callusing in aseptic culture.

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Cadmium (Cd)-induced oxidative stress and antioxidant defense mechanisms were analyzed in roots and leaves of Vigna mungo L. Seeds were germinated in perlite-vermiculite and irrigated with Hoagland nutrient solution. At day 6, seedlings were exposed to 40 μM Cd under semi-hydroponic conditions for a period of 12 days. Growth anomalies and abnormal chromatin condensation were observed in Cd-treated plants, in comparison with control ones. Cd accumulation was observed in roots of treated plants. The analyses of antioxidative defense and oxidative parameters in roots, stems and leaves showed different tissue-specific responses. Superoxide dismutase (SOD) and guaiacol peroxidase (GPx) activities and the level of lipid peroxidation (MDA content) decreased in roots. However, they increased in leaves. Catalase activity and chlorophyll content, on the other hand, decreased over exposure to Cd stress. Total glutathione, non-protein thiols, reduced glutathione (GSH) and phytochelatins increased significantly, while oxidized glutathione (GSSG) decreased, as compared with control plants. The present data suggest that the presence of Cd in soil and water can cause oxidative damage that may be detrimental for optimum production of nutritional mung.

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Summary

Interspecific hybrids have been obtained in an otherwise incompatible cross involving blackgram (Vigna mungo ♀) and greengram (V. radiata ♂). The application of a mixture of gibberellic acid, naphthaleneacetic acid and kintetin to the pollinated buds prevented early abscission of the pod and the abortion of the hybrid embryo. Hybrid embryos (11–17 days after pollination) excised from the young developing pods and cultured on modified Murashige & Skoogs' medium, supplemented with IAA, kinetin, casein hydrolysate or coconut water produced normal-looking plantlets. The younger embryos (less than 11 days after pollination) either proliferated to form callus, or occasionally produced plantlets which albino, spindly and weak. The F₁ plants were partially fertile, late-maturing, and intermediate between the two parents with respect to characters such as leaflet size, plant height and number of branches. However, the setting percentage and the number of seeds per pod were highly reduced because of the meiotic irregularities. In the F₂ generation, grown in the field as replicated rows, different combinations of desirable characters appeared and the setting percentage was also improved.

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Summary

Protoplasts were isolated from hypocotyl of V. mungo (L.) Hepper or hypocotyl-derived callus of V. sublobata (Phaseolus sublobata Roxb.) and V. unguiculata (L.) Walp (syn. V. sinensis (L.) Saviex Hassk) using an enzyme solution comprising Cellulase 2.5%, Macerozyme, Hemicellulase and Driselase each at a 0.5% level in 0.5 M sorbitol. Isolated protoplasts were cultured in Murashige and Skoog's (1962) basal liquid medium supplemented with BA, NAA, 2,4-D (1 mg/l each) and sucrose (14%). After four weeks, protoplast colonies were transferred to the same medium with a reduced level of sucrose (7%). Colonies proliferated into actively growing calli. Further attempts to regenerate plants from such calli were not successful. However, protoclones of V. unguiculata differentiated roots on auxin/cytokinin supplemented media. Alternative methods for shoot differentiation from protoplastderived cultures were tried by the use of Agrobacterium tumefaciens “shooter” strains pGV 2215 or pGV 2298 or wild type strain B6S3.

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A field study was conducted for six years (1981–1986) on sandy loam soil on intercropping hedgerows of Leucaena leucocephala (Lam) de Wit. with three field crops viz. maize (Zea mays L), black gram (Vigna mungo L) and cluster bean (Cyamopsis tetragonoloba L Taub.). In treatments 1 and 2 Leucaena hedges were planted as pure crops at close (25 cm × 75 cm) and wide (25 cm × 375 cm) spacings. In treatments 3, 4 and 5 the three field crops were intercropped between the hedgerows of Leucaena at the wide spacing, and in treatments 6, 7 and 8 the field crops were raised as pure crops. Leucaena was topped to 75 cm each time it attained a height of 175 cm.

The pure crop of Leucaena at close spacing produced an average, over the six years, of 34 t ha⁻¹a⁻¹ of green fodder and 9.4 t ha⁻¹a⁻¹ of air dry fuelwood. The Leucaena at wide spacing produced 18.9 t ha⁻¹a⁻¹ of green fodder and 6.3 t ha⁻¹a⁻¹ of fuelwood. Intercropping with field crops decreased the yield of green fodder and fuelwood. The yield of all the field crops was less when raised as intercrops than as pure crops.

Mean maximum net returns were obtained from intercrops of Leucaena and cluster bean (Rs 3540 ha⁻¹a⁻¹) which were significantly higher than the returns from pure crop of Leucaena at wide spacing but similar to the returns from pure crops of cluster bean. Leucaena with maize (Rs 3273 ha⁻¹a⁻¹) and black gram (Rs 3125 ha⁻¹a⁻¹) gave significantly higher net returns over pure crops of Leucaena at wide spacing, maize and black gram.

ICRISAT = International Crops Research Institute for the Semi-Arid Tropics- Hyderabad, India.

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Black gram (Vigna mungo L. Hepper) seed contains two D-galactose-specific lectin species, BGL-I and BGL-II, identified on the basis of elution from ion exchange column and immunochemical cross-reactivity. BGL-I consisted of two monomeric lectins, BGL-I-1 and BGL-I-2, of relative molecular weights 94 and 89 kDa, respectively. BGL-II is another monomeric lectin with a molecular weight of 83 kDa. The in vivo synthesis studies using pulse-chase experiment showed that BGL-II lectin was synthesized as early as 14 days after flowering (DAF). The 94-kDa BGL-I-1 lectin was synthesized around 17 DAF. There was no cotranslational or posttranslational modification of the lectin proteins. The amount of lectin in developing seeds was determined by radial immunodiffusion assay technique. The maximum amount of lectin per seed was found at 28 DAF.

▼ A study was conducted on nutritional constituents (total sugars, total proteins, total lipids and starch content) and antinutritional factors such as phenolic compounds, tannins, saponins, phytic acid, trypsin inhibitors and enzymes related to them such as acid- and alkaline phosphatases, α-galactosidase in eleven recommended cultivars and twenty one advance breeding lines of black gram (Vigna mungo L. Hepper) with an aim to identify genotypes containing high nutritional quality and low antinutritional content. The average content of starch, total soluble sugars, proteins and lipids was around 43.5, 4.84, 22.0 and 1.1%, respectively. Seven genotypes had higher levels of bound fructose contributed by sucrose and raffinose series oligosaccharides. A significant positive correlation was observed among total phenols, o-dihydroxy phenols and flavonols; and among trypsin inhibitors and saponins. The content of phytic acid and activity of trypsin inhibitors showed significant variation among these genotypes. However, not much variation was observed in the content of tannins and saponins. Activities of α-galactosidase, acid- and alkaline phosphatase were found to be related to the content of bound fructose of raffinose series oligosaccharides and phytic acid respectively. Genotypes having higher activity of these enzymes showed lower content of these antinutritional factors. The results showed that the observed diversity in developed cultivars and advance breeding lines could be further used by plant breeders.

▼ The polyamine (PA) concentration was greatest in the nodules at stage 2 (flowering) in Vigna mungo. The amount of putrescine (Put) was the highest and changed significantly with senescence, whereas the spermine (Spm) level was the least. During senescence, both arginine decarboxylase (ADC, EC 4.1.1.19) and ornithine decarboxylase (ODC, EC 4.1.1.17) were positively correlated with the endogenous PA titre, particularly in the late stages of development, while the catabolic enzyme, diamine oxidase (DAO, EC 1.4.3.6) increased with senescence, being highest (five-fold) in nodules at stage 5 (i.e. mature pod stage). In vivo labelling studies using l-[U-^1^4C]arginine with difluoromethylarginine (DFMA) and difluoromethylornithine (DFMO) indicated that both Put biosynthetic enzymes are involved during the process of senescence. Moreover, Spm promoted nitrogenase activity in vivo.

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Flavonoids in five lines ofVigna mungo, fifteen lines ofV. radiata var.radiata and two lines ofV. radiata var.sublobata, which belong to the subgenus Ceratotropis, were examined. In hypocotyls, seed-coats and mature leaves of those plants, twelve kinds of flavonoid including three anthocyanins, two leucoanthocyanins, two glycoflavones and five flavonol glycosides were found, and their distribution pattern in twenty-two lines of the legumes is discussed. The leaves ofV. radiata var.radiata and var.sublobata contained the glycosides (mainly rutin) of both quercetin and kaempferol, while those ofV. mungo contained only kaempferol glycosides, with robinin as the predominant pigment, and the purple-red hypocotyls of the former group contained delphinidin 3-p-coumaroylglucoside, while those of the latter contained cyanidin 3-glucoside, although delphinidin 3-glucoside was commonly found in all of the plants. With the exception of two lines, all of the seed-coats examined contained in common four compounds of vitexin, isovitexin, leucocyanidin and leucodelphinidin, whereas in addition to these pigments the black seed-coats ofV. mungo andV. radiata var.sublobata TC 1965 contained delphindin 3-glucoside.

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Vigna mungo is one of the large-seeded grain legumes that has not yet been transformed. We report here for the first time the production of morphologically normal and fertile transgenic plants from cotyledonary-node explants inoculated with Agrobacterium tumefaciens carrying binary vector pCAMBIA2301, the latter of which contains a neomycin phosphotransferase (nptII) gene and a β-glucuronidase (GUS) gene (uidA) interrupted with an intron. The transformed green shoots, selected and rooted on medium containing kanamycin, tested positive for nptII and uidA genes by polymerase chain reaction (PCR) analysis. These shoots were established in soil and grown to maturity to collect the seeds. Mechanical wounding of the explants prior to inoculation with Agrobacterium, time lag in regeneration due to removal of the cotyledons from explants and a second round of selection at the rooting stage were found to be critical for transformation. Analysis of T₀ plants showed the expression and integration of uidA into the plant genome. GUS activity in leaves, roots, flowers, anthers and pollen grains was detected by histochemical assay. PCR analysis of T₁ progeny revealed a Mendelian transgene inheritance pattern. The transformation frequency was 1%, and 6–8 weeks were required for the generation of transgenics.

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The efficiency of Vigna mungo L. Hepper transformation was significantly increased from an average of 1% to 6.5% by using shoot apices excised from embryonic axes precultured on 10 μM benzyl-6-aminopurine (BAP) for 3 days and wounded prior to inoculation in Agrobacterium tumefaciens strain EHA105 carrying the binary vector pCAMBIA2301, which contains a neomycin phosphotransferase gene (nptII) and a β-glucuronidase (GUS) gene (gusA) interrupted by an intron. The transformed green shoots that were selected and rooted on medium containing kanamycin, and which tested positive for nptII gene by polymerase chain reaction, were established in soil to collect seeds. GUS activity was detected in whole T₀ shoots and T₁ seedlings. All T₀ plants were morphologically normal, fertile and the majority of them transmitted transgenes in a 3:1 ratio to their progenies. Southern analysis of T₁ plants showed integration of nptII into the plant genome.

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A recombinant inbred line (RIL) mapping population (F₈) was generated by crossing Vigna mungo (cv. TU 94-2) with Vigna mungo var. silvestris and screened for mungbean yellow mosaic virus (MYMV) resistance. The inter simple sequence repeat (ISSR) marker technique was employed to identify markers linked to the MYMV resistance gene. Of the 100 primers screened, 54 showed amplification of which 36 exhibited polymorphism between the parents TU 94-2 (resistant) and V. mungo var. silvestris (susceptible). Individual plants from 53 RIL populations were analysed and one marker (ISSR811₁₃₅₇) was identified as tightly linked to the MYMV resistant gene at 6.8 cM. Both the phenotype as well as the ISSR811₁₃₅₇ marker segregated in a 1 : 1 ratio. The ISSR811₁₃₅₇ marker was sequenced and sequence characterized amplified region (SCAR) primers were designed (YMV1-F and YMV1-R) to amplify the marker. Screening for the SCAR marker in the RIL population distinguished the MYMV resistant and susceptible plants, agreeing well with the phenotypic data. The ISSR811₁₃₅₇ marker was validated using diverse blackgram genotypes differing in their MYMV reaction. The marker will be useful for the development of MYMV-resistant genotypes in blackgram.

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Intercropping of Vigna mungo (black gram) is prevalent for varied crop regimes in subtropical northern plains of India. In sugarcane, the negative impacts of a black gram intercrop on crop yields, rhizosphere soil properties and benefit: cost ratio have been reported. The possible allelopathic potential of black gram seeds on the germination, seedling emergence and root elongation of other commercial crops is reported here. The effects of imbibed seeds of black gram, their aqueous leachate and seed extracts on the germination and root elongation of seeds of four test crops viz. wheat, maize, gram and lentil, both under aseptic and soil conditions, were investigated. Inhibitory effects were evident in all the bioassays of seeds of these crops. The black gram seeds directly and leachates were highly inhibitory but the aqueous seed extract was less so. The observations indicate a release of inhibitory substances from black gram seeds leading to the observed inhibitory effects.

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The aim of the present study was to investigate the metabolic fate of guanine nucleotides in higher plants. The rate of uptake of [8-¹⁴C]; guanosine by suspension-cultured Catharanthus roseus cells was more than 20 times higher than that of [8-¹⁴C];jguanine. The rate of uptake of [8-¹⁴C];guanosine increased with the age of the culture. Pulse-chase experiments with [8-¹⁴C];guanosine revealed that some of the guanosine that had been taken up by the cells was converted to guanine nucleotides and incorporated into nucleic acids. A significant amount of [8-¹⁴C];guanosine was degraded directly to xanthine, allantoin and allantoic acid, with the generation of ¹⁴CO₂ as the final product. The rate of salvage of [8-¹⁴C];guanosine for the synthesis of nucleic acids was highest in young cells, while the rate of degradation increased with the age of the cells. In segments of roots from Vigna mungo seedlings, nearly 50% of the [8-¹⁴C];guanosine that had been absorbed over the course of 15 min was recovered in guanine nucleotides. A significant amount of the radioactivity in nucleotides became associated with nucleic acids and ureides during ‘chase’ periods. In segments of young leaves of Camellia sinensis, [8-¹⁴C];guanosine was initially incorporated into guanine nucleotides, nucleic acids, theobromine and ureides, and the radioactivity in these compounds was transferred to caffeine and CO₂ during a 24-h incubation. Our results suggest that guanosine is an intermediate in the catabolism of guanine nucleotides and that it is re-utilised for nucleotide synthesis by ‘salvage’ reactions. Guanosine was catabolised by the conventional degradation pathway via xanthine and allantoin. In some plants, guanosine is also utilised for the formation of ureide or the biosynthesis of caffeine.

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Summary

The inheritance of resistance to mungbean yellow mosaic virus (MYMV) was studied in blackgram (Vigna mungo (L.) Hepper). The highly resistant donors Pant U-84 and UPU-2 and a highly susceptible line, UL-2, their F₁'s, F₂'s and backcrosses were grown with spreader located every 5 to 6 rows. The resistance was found to be digenic and recessive in all the crosses and free from cytoplasmic effect.

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Summary

This review is given on the origin and interrelationship of blackgram and greengram: the symptoms, mode of transmission, and host range of important diseases, namely: mungbean yellow mosaic virus, leaf crinkle virus, leaf curl virus, mosaic mottle virus, Cercospora leaf spot, powdery mildew, root and stem rots, bacterial leaf spot and halo blight. The screening for resistance, sources of resistance, including interspecific hybridization, and induced mutations, as well as the genetics of resistance are treated along with suggestions for future breeding strategies of these crops.

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Summary

The resistance sources among various test cultivars of urdbean to Colletotrichum truncatum, a leaf spotting pathogen, were identified and genetics of resistance was worked out by studying F₁, F₂ and F₃ generations of crosses between resistant cultivars and the susceptible cv. Kulu 4 and of those among the resistant parents. The resistance was found to be controlled by single dominant genes and the resistance genes were non-allelic.

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Root and shoot tolerance indices and photosynthesis characteristics (CO₂-dependent-O₂ evolution; H₂O→MV electron transport; whole-leaf photosynthesis by infrared gas analyzer) indicated that ADT-36 and CR-1009 rice varieties were more tolerant than other varieties (IR-50, IR-20, and Ponni). Vigna varieties (T-9 and Krishna) were most susceptible to aqueous oil pollution. Since the oil-polluted soil contained a potentially toxic concentration of cadmium, tolerant (ADT-36) and susceptible (IR-50) varieties of Oryza were further analyzed for cadmium-binding components. Higher accumulations of cadmium were found in the roots than in the leaves of both rice varieties. Cadmium is associated with proteins of about 50,000 and 33,000-dalton in molecular mass, of which the 33-kdalton protein was significantly induced only in ADT-36. It is suggested by the present study that the ADT-36 rice variety is most tolerant to aqueous oil pollution, as evidenced by higher STI (shoot tolerance index) and RTI (root tolerance index) values, induction of Cd-binding proteins, and comparatively normal photosynthesis rates.

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The influence of endogenous root nodules phenolic acids on indoleacetic acid (IAA) production by its symbiont (Rhizobium) was examined. The root nodules contain higher amount of IAA and phenolic acids than non-nodulated roots. Presence of IAA metabolizing enzymes, IAA oxidase, peroxidase, and polyphenol oxidase indicate the metabolism of IAA in the nodules and roots. Three most abundant endogenous root nodule phenolic acids (protocatechuic acid, 4-hydroxybenzaldehyde and p-coumaric acid) have been identified and their effects on IAA production by the symbiont have been studied in l-tryptophan supplemented yeast extract basal medium. Protocatechuic acid (1.5 μg ml⁻¹) showed maximum stimulation (2.15-fold over control) of IAA production in rhizobial culture. These results indicate that the phenolic acids present in the nodule might serve as a stimulator for IAA production by the symbiont (Rhizobium).