Interactive effects of UV-B irradiation and triadimefon on nodulation and nitrogen metabolism in Vigna radiata plants

Supply of aqueous solution of triadimefon (20 mg dm⁻³) to unstressed green gram plants increased the contents of soluble proteins, amino acids, nitrate and nitrite, and the activity of nitrate reductase in the leaves and nitrate reductase in nodules. The nitrogenase activity in nodules and roots was also increased. Number and fresh mass of nodules and their nitrate and nitrite contents were also higher than those of the controls. In contrast, the UV-B stress (12.2 kJ m⁻² d⁻¹) suppressed nodulation and nitrogen metabolism in leaves and roots compared to plants under natural UV-B (10 kJ m⁻² d⁻¹). Triadimefon-treated plants did not show such severe inhibitions after exposure to elevated UV-B. Thus triadimefon increased their tolerance to UV-B stress.     

Culture conditions effecting plant regeneration from cotyledons of Vigna radiata (L.) Wilczek

Conditions for plant regeneration from excised cotyledons of Vigna radiata were studied. Complete plant developed from the uncallused proximal ends of cotyledons on Murashige & Skoog's (MS), Gamborg's (B₅) and C (MS salts + B₅ vitamins) basal media. The basal medium C was found to be best for plant regeneration. Regeneration frequency, however, varied with genotype, size, orientation and age of explant and the different plant growth regulators combination in the medium. Addition of cytokinins induced callusing at the proximal ends of cotyledons followed by multiple shoot formation. Out of 6-benzyl aminopurine (BAP), kinetin (KIN), N (^–2 isopentyl) adenine (2iP) and adenine sulphate (AS), only BAP and KIN were found to be more effective in enhancing the frequency of shoot regeneration. BAP at 1×10^-1M induced maximum (60%) shoot regeneration whereas maximum number of shoots (8 to 9 shoots) per explant was observed with 5×10^-6M BAP. Cotyledons excised from two-day old seedlings were most regenerative. The regenerative response of cotyledons decreased when sliced into two equal parts either longitudinally or transversely. Callusing and organogenic differentiation occured only if the petiolar end of cotyledons was in contact with medium. None of the tested treatments were effective in inducing shoot bud differentiation from subcultured callus. Well developed shoots rooted when incubated on half strength MS, MS and MS basal medium supplemented with IAA (5×10^-6M). The rooted plants were transferred to pots and later established in the field with 60% success.Abbreviations AS adenine sulphate - BAP 6-benzylaminopurine - B₅ medium after Gamborg et al. [6], - C Medium with MS salts + B₅ vitamins - 2iP N (^–2 isopentyl) adenine - IAA indole-3-acetic acid - KIN Kinetin - MS medium after Murashige & Skoog [21] - NAA 1-napthaleneacetic acid     

Enhancement of Peroxidase, Polyphenol Oxidase and Superoxide Dismutase Activities by Triadimefon in NaCl Stressed Raphanus Sativus L.

The activities of peroxidase, polyphenol oxidase and superoxide dismutase was significantly lower in roots and leaves of NaCl stressed radish (Raphanus sativus L.) plants. Addition of triadimefon to the NaCl stressed plants increased peroxidase, polyphenol oxidase and superoxide dismutase activities, and thereby ameliorated the negative effect of NaCl stress.     

Thidiazuron-induced high-frequency axillary and adventitious shoot regeneration in Vigna radiata (L.) Wilczek

Summary Prolific shoot regeneration was achieved in mungbean Vigna radiata (L.) Wilczek from 3-d-old in vitro cotyledonary node and hypocotyl explants from seedlings derived from mature seeds on Murashige and Skoog (MS) medium supplemented with thidiazuron (TDZ) (0.9 μM). An initial exposure to TDZ for 20 d and three successive transfers to fresh medium with reduced thidiazuron levels (0.09 μM) resulted in the regeneration of 104 shoots/explant from the cotyledon and 30 shoots/explant from the hypocotyl. Thidiazuron-associated abnormalities such as short compact shoots, fasciation and leaf growth in the form of rosettes were observed in shoots regenerated from hypocotyl explants. Both axillary and adventitious shoot formation from the explants were confirmed by histology. Through repectitive cycles of regeneration in the presence of TDZ, the number of shoots that could be obtained from the two explant classes within 80 d was significantly higher than with previous reports in mungbean     

Selection and characterization of mannitol-tolerant callus lines of Vigna radiata (L.) Wilczek

An osmotically (mannitol) tolerant callus line of Vigna radiata (L.) Wilczek has been isolated from callus cultures grown on modified PC-L2 medium supplemented with increasing concentrations of mannitol. The tolerance was stable and retained after growth in the absence of mannitol selection for 2 months. The growth of the tolerant line, in the presence of mannitol (540 mol m^-3) was comparable to that of a sensitive callus line growing in the absence of mannitol. This line not only grew well on media containing up to 720 mol m^-3 mannitol, but also required 450 mol m^-3 mannitol for its optimal growth. Osmotically tolerant callus also showed increased tolerance to NaCl (0–250 mol m^-3) stress as compared to sensitive callus. Accumulation of Na⁺ was lower, and the level of K⁺ was more stable in osmotically tolerant than in sensitive calli, when both were exposed to salt. The free proline content of both tolerant and sensitive calli increased on media supplemented with mannitol or NaCl. However, the proline content of sensitive callus was higher than in tolerant callus in the presence of same concentrations of mannitol or NaCl.Abbreviations NAA -naphthaleneacetic acid - 2,4-d 2,4-dichlorophenoxyacetic acid - BAP 6-benzylaminopurine     

Root initiation in Vigna radiata (L.) Wilczek hypocotyl cuttings is stimulated by smoke-derived extracts

Aqueous extracts of smoke, derived from Themeda triandra, a fire-climax grass, and Passerina vulgaris, a fynbos plant, stimulated root initiation and development in the hypocotyls of mung beans. Immersion time and the dilution of the smoke extracts were important in optimising the rooting response.     

Alleviation of Ultraviolet-B Radiation-Induced Growth Inhibition of Green Gram by Triadimefon

Supplementary UV-B (12.2 kJ m⁻² d⁻¹ UV-B_BE) provided to Vigna radiata for 2 h d⁻¹ suppressed the length of root, shoot and whole plants, number of leaves, total leaf area, leaf area index, specific leaf mass, fresh and dry mass of leaves and shoot, relative growth rate and net productivity. In unstressed green gram plants (10 kJ m⁻² d⁻¹ UV-B_BE), triadimefon (TRIAD) (20 mg dm⁻³) enhanced growth in all parameters over control. The growth promoting effect of TRIAD enabled the UV-B impacted plants to overcome the growth inhibitions to varying degrees indicating its protective potential against UV-B stress. This revised version was published online in July 2006 with corrections to the Cover Date.     

Halopriming of seeds imparts tolerance to NaCl and PEG induced stress in Vigna radiata (L.) Wilczek varieties

The investigation was carried out to study the effect of halopriming on NaCl and polyethylene glycol-6000 (PEG-6000) induced stress tolerance potential of three Vigna radiata (L.) Wilczek varieties, with varied abiotic stress tolerance potential. Halopriming is a seed priming technique in which the seeds were soaked in various salt solutions (in this study NaCl was used). The results of the study indicated that the application of stresses (both NaCl and PEG) induced retardation of growth attributes (measured in terms of shoot length, fresh weight, dry weight) and decrease in physiological attributes like total chlorophyll content, metabolites, photosynthetic and mitochondrial activity of the seedlings in all three V. radiata (L.) varieties. However, halopriming of the seeds could reduce the extent of decrease in these biological attributes. NaCl and PEG stress also caused increase in MDA content (a product of membrane lipid peroxidation) in all the varieties studied and this increase was significantly minimized under halopriming. From the present investigation it was evident that among the green gram varieties studied, Pusa Vishal, a NaCl tolerant variety showed enhanced tolerance to NaCl and PEG induced stress, when the seeds were subjected to halopriming followed by Pusa Ratna (stress sensitive variety). Pusa 9531 (drought tolerant variety) also showed positive halopriming effects but it was less significant when compared to other two varieties. It could be concluded that halopriming improved the drought and salinity stress tolerance potential of all varieties and it was significantly higher in the Pusa Vishal as compared to Pusa 9531 and Pusa Ratna.     

Carbon allocation and partitioning in Vigna radiata (L.) Wilczek as affected by additional carbon gain

Carbon allocation to the source leaf, export and partitioning to the sink were studied in mungbean supplied by additional carbon from the source leaves subjected to high CO2 concentrations (600 and 900 cm3 m-3) in three metabolic and functional source-sink combinations. The plants were pruned to a source-path-sink system. With CO2 enrichment there was an appreciable increase in net photosynthetic CO2 uptake in earlier formed and physiologically younger leaves. Most of the carbon fixed as a result of enrichment was translocated out of the source leaf within one diurnal cycle. The carbon remaining in the source leaf was unchanged. Partitioning of extra carbon into starch or sugar depended upon the amount of extra carbon synthesized. The unloading of the extra carbon into sinks depended on whether it was used for growth or stored. Under increased carbon content, the leaf as a sink was able to reorganize its metabolic reactions more rapidly to maintain the required gradient for unloading than the pod acting as the sink.     

Carbon allocation and partitioning in Vigna radiata (L.) Wilczek as affected by additional carbon gain

Carbon allocation to the source leaf, export and partitioning to the sink were studied in mungbean supplied by additional carbon from the source leaves subjected to high CO2 concentrations (600 and 900 cm3 m-3) in three metabolic and functional source-sink combinations. The plants were pruned to a source-path-sink system. With CO2 enrichment there was an appreciable increase in net photosynthetic CO2 uptake in earlier formed and physiologically younger leaves. Most of the carbon fixed as a result of enrichment was translocated out of the source leaf within one diurnal cycle. The carbon remaining in the source leaf was unchanged. Partitioning of extra carbon into starch or sugar depended upon the amount of extra carbon synthesized. The unloading of the extra carbon into sinks depended on whether it was used for growth or stored. Under increased carbon content, the leaf as a sink was able to reorganize its metabolic reactions more rapidly to maintain the required gradient for unloading than the pod acting as the sink.     

In vitro induction of multiple shoots and plant regeneration from shoot tips of mung bean (Vigna radiata (L.) Wilczek)

Conditions for plant regeneration from excised shoot tips of Vigna radiata were studied. Complete plants were regenerated directly without an intervening callus phase from shoot tips on basal medium (MS salts+B₅vitamins). Regeneration frequency varied with genotype, explant size and growth regulator combinations in the medium. Addition of cytokinins induced a variable amount of callus at the base of the shoot tip, followed by multiple shoot formation. Benzyladenine (BA), kinetin and zeatin at 5×10^-6 M each induced multiple shoots in 100% of the explants but the highest number of regenerants per explant (9) was produced with BA. The efficacy of BA for shoot multiplication was not improved when it was supplemented with naphthaleneacetic acid (NAA) or indoleacetic acid (IAA). NAA or adenine sulphate, when applied alone, induced complete plantlets. The growth regulator requirement of explants for the induction of multiple shoots varied with explant size. The shoot tip explants maintained proliferation ability on subculture. None of the treatments was effective in inducing shoot bud differentiation from callus. Regenerated shoots were rooted on MS basal medium and MS supplemented with either IAA or indolebutyric acid. The rooted plants were transferred to the field; 60% subsequently survived and grew.Abbreviations BM basal medium [MS (Murashige & Skoog 1962) salts+B₅ (Gamborg et al. 1968) vitamins] - BA 6-benzyladenine - AdS adenine sulphate - IAA indole-3-acetic acid - NAA-1 naphthaleneacetic acid - IBA indolebutyric acid     

Micropropagation of the endangered aromatic varieties of Vigna radiata (L.) Wilczek in West Bengal, India

Summary Vigna radiata (L.) Wilczek, popularly known as mungdaal in India, is an important source of protein for supplementing the vegetarian diet in all the states of India. There are various varieties of mungbean. Depending upon the flavor and aroma, these are classified into two groups: (a) the good aromatic variety or Sonamung, and (b) the other, without any significant aroma, the Tilmung. In the present investigation, we attempted to propagate a good aromatic variety of mungbean (which is becoming nearly extinct) by in vitro shoot-tip multiplication. The best hormone combination in B5 medium was 0.2 mg of α-naphthalene acetic acid per 1 (1.074 μM) and 5 mg of N⁶-benzyladenine per 1 (22.192 μM). The plantlets were then rooted in hormone-free B5 medium and finally transferred to soil. This method of shoot-tip multiplication was found to be a reproducible and effective method for germplasm preservation of mungbean.     

Comparative efficacy of pedigree selection and selective intermating in greengram (Vigna radiata (L.) Wilczek)

Summary Selective intermating and pedigree selection methods were applied simultaneously to highly heterogeneous and heterozygous base populations of greengram in order to compare their relative efficacy in terms of evolving the number of productive lines as well as their production potential. Selection after two cycles of selective intermating was found to be a better method than traditional pedigree selection. The demerits of pedigree selection and merits of selective intermating are discussed. It is suggested that selective intermating replace the widely adopted but less effective pedigree selection for generating promising new material in such autogamous crops as greengram.Part of Ph.D. Thesis submitted by the senior author to the Haryana Agricultural University, Hisar, India     

Yield, growth and physiological responses of mung bean [Vigna radiata (L.) Wilczek] genotypes to waterlogging at vegetative stage

A study was conducted to examine the physiological response of contrasting mung bean (Vigna radiata) genotypes viz., T 44 & MH–96–1 (tolerant) and Pusa Baisakhi & MH–1K–24 (sensitive) under waterlogging conditions. Plants were waterlogged at vegetative stage (30 days after sowing) for 3, 6 and 9 days. Waterlogging resulted in decreased leaf area, crop growth rate, root growth and nodules number, membrane stability index, photosynthesis rate, chlorophyll and carotenoid contents, flowering rate, pod setting, yield and altered dry matter partitioning. Sensitive genotypes showed large reductions in aforementioned physiological traits and slow recovery in photosynthesis rate. On the other hand, tolerant genotypes maintained higher photosynthetic rate, chlorophylls and carotenoids, growth rate, membrane stability and fast photosynthetic recovery under waterlogging. After 9 days of exposure to waterlogging, photosynthetic rate and yield losses in most sensitive genotype (MH-1K-24) were 83 and 85 %, respectively. On an average, photosynthetic loss at 3, 6 and 9 days of waterlogging was 43, 51, and 63 %, respectively, while grain yield loss was 20, 34 and 52 % respectively.     

Anthocyanin Synthesis in Seedlings of Vigna radiata (L.) Wilczek: Interaction between Hypocotyl and Cotyledons

During the development of mung bean seedlings, cotyledons graduallyacquired the capacity to synthesize anthocyanins after red lightirradiation. When isolated from 36 hr old seedlings, cotyledonsaccumulated anthocyanins with a time-course similar to the oneobserved with cotyledons of intact seedlings (Dumortier andVendrig 1982). In both cases, there were two periods of rapidpigment accumulation separated by a stagnation phase. Experimentsin which the hypocotyl hook or the cotyledons had been shieldedduring irradiation led to the conclusion that cotyledons containphotoreceptors for anthocyanin accumulation in the hypocotylhook (which also had to be irradiated). The reverse was alsotrue: irradiation of the hypocotyl hook influenced pigment accumulationin the cotyledons in a positive way. A hypothesis is presentedconcerning the level at which P_FR exerts its influence. (Received January 18, 1982; Accepted April 30, 1982)     

Genetic basis of variation of yield, and yield components in mungbean (Vigna radiata (L.) Wilczek)

Additive, dominance, and epistasis genetic basis of seed yield per plant, number of pods per plant, number of seeds per pod, and 1000 seed weight in mungbean (Vigna radiata (L.) Wilczek) have been examined, using Triple Test Cross (TTC) analysis. The material for TTC test was evaluated in two seasons i.e., kharif (July-October) and spring/summer (March-June), at the research station of the Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad, Pakistan. Epistasis was present significantly for number of pods per plant and number of seeds per pod when grown in the spring/summer season (March to June). Partition of epistasis showed that additive x additive ('i' type) interaction was an important component of number of pods per plant, and number of seeds per pod was found to be of both types 'i' type, and additive x dominance, and dominance x dominance ('j' and 'l' type) interactions. This indicated that epistasis might be a non-trivial factor in the inheritance of pods per plant, and seeds per pod in mungbean. The expression of epistasis was influenced differentially by particular genotypes, indicating that a limited number of genotypes may not be sufficient to detect non-allelic interactions for a trait in mungbean. Additive and dominance genetic components were significant for all four traits in kharif season (July to October) but only for seed yield and 1000 seed weight in spring/summer season. This suggests that the genes controlling seed yield per plant, and 1000 seed weight are equally sensitive to the environment. The predominance additive gene action in those traits is not significantly influenced by epistasis, suggesting that improvement of the traits can be achieved through standard selection procedures.     

The wild ancestors of urid and mung beans (Vigna mungo (L.) Hepper and V. radiata (L.) Wilczek)

The crop plants Vigna mungo (urid, urd or black gram) and V. radiata (mung bean or green gram: and related taxa have been studied by seed protein electrophoresis, leaf phenolics chromatography, vegetative morphology, and seed testa patterns. The results disprove the theory that these species are very closely related and have evolved from a single wild taxon. The present evidence shows that V. mungo var. mungo and I. radiata var. radiata have independent lineages and were domesticated from two very distinct taxa. namely V. mungo var. silvestris and V. radoata var. sublobata respectively.     

Genetic basis of plant height and its degree of indetermination in mungbean (Vigna radiata (L.) Wilczek)

The genetic basis of plant height at various growth stages and the degree of indetermination of plant height in six mungbean genotypes (NM 92, 6601, NM 89, VC 1560D and VC 3902A) were assessed through half diallel cross. Cultivars, 6601 and NM 92, were the best general combiner for pre-flowering dry matter accumulation and minimum increase in plant height from first flower to 90% pods maturity, respectively. For these traits, the combination NM 92 x NM 89 was the best specific combiner of all the crosses. Both additive and dominant gene effects controlled the inheritance of plant height at first pod and to 90% pods maturity, degree of indetermination of plant height (DDh) from first flower to first pod maturity (DDh1), DDh from first flower to 90% pods maturity (DDh2) and DDh from first pod maturity to 90% pods maturity (DDh3). Plant height at first flower was additively inherited. The additive gene action was predominant as compared to dominant gene action for all the traits examined. High narrow and broad sense heritability estimates for DDh2 showed that better response to selection is possible for the development of mungbean genotypes with minimum increase in plant height during post-flowering development.     

Diversity in greengram (Vigna radiata (L.) Wilczek) germplasm collection and its potential use in crop improvement

Greengram or mungbean (Vigna radiata (L.) Wilczek), which originated in the Indian sub-continent, is an important pulse crop in India. Genetic diversity and patterns of variation among 111 accessions representing the better agronomic types from the entire collection of the National Bureau of Plant Genetic Resources were studied. Wide variation in morphological and agronomic traits viz. number of pods per plant, yield per plant, 100-seed weight, fruit setting capacity, flowering period, maturity, number of pod bearing peduncles, plant height, number of primary branches, length of branch, nodulation and leafiness was observed. Grain yield was found to be significantly correlated with 100-seed weight and pod length. The data were subjected to cluster and principal components analysis. The accessions were grouped into six discrete and well-defined clusters. The study demonstrated the patterns of variation at the population level. The multivariate analysis was useful in identifying a group of accessions with yield enhancing traits within a highly diverse group of accessions and their potential value in greengram improvement is suggested.     

Alleviation of fungicide-induced phytotoxicity in greengram [Vigna radiata (L.) Wilczek] using fungicide-tolerant and plant growth promoting Pseudomonas strain

This study was designed to explore beneficial plant-associated rhizobacteria exhibiting substantial tolerance against fungicide tebuconazole vis-à-vis synthesizing plant growth regulators under fungicide stressed soils and to evaluate further these multifaceted rhizobacteria for protection and growth promotion of greengram [Vigna radiata (L.) Wilczek] plants against phytotoxicity of tebuconazole. Tebuconazole-tolerant and plant growth promoting bacterial strain PS1 was isolated from mustard (Brassica compestris) rhizosphere and identified as Pseudomonas aeruginosa following 16S rRNA gene sequencing. The P. aeruginosa strain PS1 solubilized phosphate significantly and produced indole acetic acid, siderophores, exo-polysaccharides, hydrogen cyanide and ammonia even under tebuconazole stress. Generally, tebuconazole at the recommended, two and three times the recommended field rate adversely affected the growth, symbiosis, grain yield and nutrient uptake in greengram in a concentration dependent manner. In contrast, the P. aeruginosa strain PS1 along with tebuconazole significantly, increased the growth parameters of the greengram plants. The inoculant strain PS1 increased appreciably root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, and seed yield of greengram plants at all tested concentrations of tebuconazole when compared to the uninoculated plants treated with tebuconazole. The results suggested that the P. aeruginosa strain PS1, exhibiting novel plant growth regulating physiological features, can be applied as an eco-friendly and plant growth catalyzing bio-inoculant to ameliorate the performance of greengram in fungicide stressed soils.