Germplasm-regression-combined (GRC) marker-trait association identification in plant breeding: a challenge for plant biotechnological breeding under soil water deficit conditions.

In the past 20 years, the major effort in plant breeding has changed from quantitative to molecular genetics with emphasis on quantitative trait loci (QTL) identification and marker assisted selection (MAS). However, results have been modest. This has been due to several factors including absence of tight linkage QTL, non-availability of mapping populations, and substantial time needed to develop such populations. To overcome these limitations, and as an alternative to planned populations, molecular marker-trait associations have been identified by the combination between germplasm and the regression technique. In the present preview, the authors (1) survey the successful applications of germplasm-regression-combined (GRC) molecular marker-trait association identification in plants; (2) describe how to do the GRC analysis and its differences from mapping QTL based on a linkage map reconstructed from the planned populations; (3) consider the factors that affect the GRC association identification, including selections of optimal germplasm and molecular markers and testing of identification efficiency of markers associated with traits; and (4) finally discuss the future prospects of GRC marker-trait association analysis used in plant MAS/QTL breeding programs, especially in long-juvenile woody plants when no other genetic information such as linkage maps and QTL are available.

Roles of enzymatic and nonenzymatic antioxidants in plants during abiotic stress.

Reactive oxygen species (ROS) are produced in plants as byproducts during many metabolic reactions, such as photosynthesis and respiration. Oxidative stress occurs when there is a serious imbalance between the production of ROS and antioxidant defense. Generation of ROS causes rapid cell damage by triggering a chain reaction. Cells have evolved an elaborate system of enzymatic and nonenzymatic antioxidants which help to scavenge these indigenously generated ROS. Various enzymes involved in ROS-scavenging have been manipulated, over expressed or downregulated to add to the present knowledge and understanding the role of the antioxidant systems. The present article reviews the manipulation of enzymatic and nonenzymatic antioxidants in plants to enhance the environmental stress tolerance and also throws light on ROS and redox signaling, calcium signaling, and ABA signaling.

Chelating efficacy of CaNa(2) EDTA on nickel-induced toxicity in Cirrhinus mrigala (Ham.) through its effects on glutathione peroxidase, reduced glutathione and lipid peroxidation.

In this age of modern biology, aquatic toxicological research has provided potential tools for ecotoxicologic investigations. Heavy metals primarily affect protein structures and induce a stress in the organisms. The present investigation was carried out to assess the effect of nickel chloride on the selected organs of the freshwater fish Cirrhinus mrigala and how CaNa(2) EDTA counters its effects as an antidote. Toxicity experiments were conducted for different exposure periods and also in certain tissues namely gill, liver, kidney and muscle. The total protein content, reduced glutathione, glutathione peroxidase and lipid peroxidation were found to be decreased in the nickel chloride treated tissues and the treatment with CaNa(2) EDTA+nickel chloride returned to near normal levels. Histopathological observations also revealed that after the administration of nickel chloride+CaNa(2) EDTA the chelator induced reduction in nickel toxicity. It has also contributed towards reduction in the pathological damage, thus enabling the organs to attain their near normal histological appearance. The present study shown that CaNa(2) EDTA is an effective chelating agent for the removal of nickel and it has proved efficient in restoring both the biochemical variables and pathological features immediately after a sub lethal exposure of nickel chloride in fish.

Effect of physical desiccation on plant regeneration efficiency in rice (Oryza sativa L.) variety super basmati.

This experiment assessed the effect of partial physical desiccation on plant regeneration efficiency in scutellum-derived embryogenic calluses of rice (Oryza sativa L.) variety Super basmati. A number of callusing cultures were developed, and efficient callus induction was observed on MS (Murashige and Skoog) basal medium supplemented with 2.0mg/L 2,4-dichlorophenoxy acetic acid. The calluses were proliferated on the same medium for 3 weeks and then shifted to dehydration desiccation treatment for 72h. The desiccated calluses were cultured on different media for somatic embryogenesis and plant regeneration. A medium with 2.0mg/L alpha-napthaleneacetic acid, 10.0mg/L abscisic acid , 2.0mg/L kinetin was best for somatic embryogenesis only, but not for further plant development. After 10d, differentiated calluses were sub-cultured on medium with various concentrations and types of carbohydrates (carbon source) in (1)MS(2j) medium. A large number of plantlets (14.51+/-2.81 and 8.56+/-2.90 plants/callus) were regenerated via chemical desiccation, on MS with 3% maltose+3% sorbitol and 6% sucrose, respectively. Under dehydration on only simple MS (3% sucrose), 11.23+/-3.22 plants/callus were developed. Under conditions of dehydration and chemical desiccation, plant regeneration rates were higher than the calluses cultured on simple MS medium in the presence of plant growth regulator. After somatic embryogenesis, >25% plants were sterile. The protocol used here may allow maximum regeneration of normal and fertile plantlets of super basmati rice within 3 months.

Endogenous hormonal and enzymatic responses of Catharanthus roseus with triadimefon application under water deficits.

The effect of triadimefon was investigated in a medicinal plant, Catharanthus roseus subjected to water deficit stress. The abscisic acid (ABA) level, DNA and RNA contents and activities of ATPase and protease were found varying in different parts of the plants under treatment. Drought treatment increased the ABA level more than twofold in all parts of the plants. TDM treatment to the drought stressed plants showed highest contents. In roots, stem and leaves, drought stress caused a decrease in the DNA and RNA contents when compared with control and other treatments. TDM treatment with drought increased the nucleic acid contents to the level of the control roots. The activity of ATPase and protease were increased under drought treatment and lowered due to TDM applications. This information could be useful in the field of soil water deficits reclamation efforts by using plant growth regulators.

Soil applied cobalt alters the nodulation, leg-haemoglobin content and antioxidant status of Glycine max (L.) Merr.

The present investigation has been carried out to estimate the effect of cobalt on the nodulation leg-haemoglobin content and antioxidant enzyme activities of soybean plants. The experiments were conducted in earthen pots containing 3 kg of air dried soil. The inner surface of pots was lined with polythene sheet. Soybean plants were raised in soil amended with different concentration of cobalt (0, 50, 100, 150, 200 and 250 mg/kg). The root nodule formation, leg-haemoglobin contents and antioxidant enzyme activities were analysed at 15 days intervals, namely 15, 30, 45, 60 and 75 days after sowing (DAS). There found a significant increase in the total number of root nodules, leg-haemoglobin content and antioxidant enzyme activities at 50mg/kg cobalt application in the soil in all the sampling days when compared to control. Further increase in the cobalt level (100-250 mg/kg) in the soil decreased root nodules formation as well as leg-haemoglobin content antioxidant enzyme activities of soybean plants in all the sampling days.

Prospectives for applying molecular and genetic methodology to improve wheat cultivars in drought environments.

With the advent of molecular biotechnologies, new opportunities are available for plant physiologists to study the relationships between wheat traits and their genetic control. The functional determinations of all genes that participate in drought adaptation or tolerance reactions are expected to provide an integrated understanding of the biochemical and physiological basis of stress responses in wheat. However, despite all the recent technological breakthroughs, the overall contribution of genomics-assisted breeding to the release of drought-resilient wheat cultivars has so far been marginal. This paper critically analyses how biotechnological, genetic and information tools can contribute to accelerating the release of improved, drought-tolerant wheat cultivars. Armed with such information from established models, it will be possible to elucidate the physiological basis of drought tolerance and to select genotypes with an improved yield under water-limited conditions.

Osmoregulation and antioxidant metabolism in drought-stressed Helianthus annuus under triadimefon drenching.

A pot-culture experiment was conducted to estimate the ameliorating effect of triadimefon (TDM) on drought stress in sunflower (Helianthus annuus L.) plants. The plants were subjected to 3-, 6-, and 9-day-interval drought (DID) stress and drought stress with TDM @ 15 mg l(-1) and 15 mg l(-1) TDM alone from the 30th day after sowing (DAS). One-day-interval irrigation was kept as control. The plant samples were collected on and separated into root, stem and leaf for estimating the amino acid (AA), proline (PRO) and glycine betaine (GB) contents and the activities of antioxidant enzymes. Individual and combined drought stress and TDM treatments increased AA, PRO and GB contents, superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and polyphenol oxidase (PPO) activities when compared to control. From the results of this investigation, it can be concluded that the application of TDM caused a partial amelioration of the adverse effects of drought stress by its influence on quaternary ammonium compounds and antioxidant potentials in H. annuus plants.

Higher plant antioxidants and redox signaling under environmental stresses.

Main antioxidants in higher plants include glutathione, ascorbate, tocopherol, proline, betaine, and others, which are also information-rich redox buffers and important redox signaling components that interact with biomembrane-related compartments. As an evolutionary consequence of aerobic life for higher plants, reactive oxygen species (ROS) are formed by partial reduction of molecular oxygen. The above enzymatic and non-enzymatic antioxidants in higher plants can protect their cells from oxidative damage by scavenging ROS. In addition to crucial roles in defense system and as enzyme cofactors, antioxidants influence higher plant growth and development by modifying processes from mitosis and cell elongation to senescence and death. Most importantly, they provide essential information on cellular redox state, and regulate gene expression associated with biotic and abiotic stress responses to optimize defense and survival. An overview of the literature is presented in terms of main antioxidants and redox signaling in plant cells. Special attention is given to ROS and ROS-antioxidant interaction as a metabolic interface for different types of signals derived from metabolism and from the changing environment, which regulates the appropriate induction of acclimation processes or, execution of cell death programs, which are the two essential directions for higher plants.

A glimpse of lignicolous marine fungi occurring in coastal water bodies of Tamil Nadu (India).

In the present investigation, a total of 51 marine fungi were obtained from wood samples collected from four locations of Tamil Nadu (Tuthukudi, Chennai, Kanyakumari and Pichavaram), India. Out of these 51, 28 were ascomycetes, one was basidiomycete and 22 were mitosporic fungi. Maximum fungal diversity was encountered from Tuthukudi, followed by Chennai, Kanyakumari, and the minimum from Pichavaram. Periconia prolifica was the only species common to all the four locations.

Growth and photosynthetic pigments responses of two varieties of Catharanthus roseus to triadimefon treatment.

Triadimefon, potential fungicide cum plant-growth retardant was used in this study to investigate its effect on the growth and the photosynthetic pigment contents of two varieties of Catharanthus roseus (L.) G. Don. The plants of both varieties were subjected to 15 mg l(-1) triadimefon treatment by soil drenching 30, 45, 60, and 75 days after planting (DAP). Plants were uprooted on 90 DAP, and morphological parameters, like plant height, number of leaves, leaf area, root length and fresh and dry weights were determined. The photosynthetic pigments, like chlorophylls a and b, total chlorophyll, carotenoids, floral pigment, anthocyanin, were extracted and estimated. It was observed that plant height, number of leaves and leaf area were decreased and that root length, fresh and dry weights were increased under triadimefon treatment. The photosynthetic and floral pigments were increased under triadimefon treatment in both varieties. The results suggest that the application of this plant-growth retardant (triadimefon) has favourable effects on the reduction of plant height; it can thus be used for replacing manual hand pruning and for improving floral and vegetation colour in bedding plants like C. roseus.

A comparative account of backwater and brackish water marine mycoflora of North Malabar (Kerala) India.

The backwater system of Kerala is well known. In the present investigation, we have tried to explore the marine fungal diversity of selected backwater and brackish water habitats of the North Malabar region of Kerala, India. A total of 30 marine fungi were isolated, which include 19 Ascomycetes, 1 Basidiomycete, and 10 Mitosporic fungi. Periconia prolifica emerged as the most dominant one in terms of percent frequency of occurrence and percent relative abundance.

Water-deficit stress-induced anatomical changes in higher plants.

Water is vital for plant growth and development. Water-deficit stress, permanent or temporary, limits the growth and the distribution of natural vegetation and the performance of cultivated plants more than any other environmental factors do. Although research and practices aimed at improving water-stress resistance and water-use efficiency have been carried out for many years, the mechanism involved is still not clear. Further understanding and manipulating plant-water relations and water-stress tolerance at the scale of physiology and molecular biology can significantly improve plant productivity and environmental quality. Currently, post-genomics and metabolomics are very important to explore anti-drought gene resource in different life forms, but modern agricultural sustainable development must be combined with plant physiological measures in the field, on the basis of which post-genomics and metabolomics will have further a practical prospect. In this review, we discussed the anatomical changes and drought-tolerance strategies under drought condition in higher plants.

Differential responses in water use efficiency in two varieties of Catharanthus roseus under drought stress.

Two varieties, rosea and alba, of Catharanthus roseus (L.) G. Don. were screened for their water use efficiency under two watering regimes, viz. 60 and 100% filed capacity in the present study. Drought stress was imposed at 60% filed capacity from 30 to 70 days after sowing, while the control pots were maintained at 100% filed capacity throughout the entire growth period. Leaf area duration, cumulative water transpired, water use efficiency, net assimilation rate, mean transpiration rate, harvest index, biomass and yield under the water deficit level were measured from both stressed and well-watered control plants. Water use efficiency significantly increased in both varieties under water stress. Drought stress decreased leaf area duration, cumulative water transpired, net assimilation rate, mean transpiration rate, harvest index, and biomass yield in both varieties studied. Among the varieties, rosea variety showed the best results.

Alterations in lipid peroxidation, electrolyte leakage, and proline metabolism in Catharanthus roseus under treatment with triadimefon, a systemic fungicide.

Triadimefon (TDM), a systemic fungicide with non-traditional plant-growth regulator properties, was administered to Catharanthus roseus (L.) G. Don. plants in order to determine its effects on oxidative injury in terms of H2O2 content, lipid peroxidation (LPO), electrolyte leakage (EL), protein and amino acid contents, as well as proline metabolism. The LPO, estimated as thiobarbituric acid-reactive substances (TBARS), decreased under TDM treatment. It was found that H2O2 and EL were reduced under TDM treatment when compared to control. TDM treatment caused a significant increase in the protein and amino acid contents. Glycine betaine (GB) and proline (PRO) significantly accumulated in C. roseus under stress arisen from fungicide applications. Proline oxidase (PROX) activities reduce the PRO content and gamma-glutamyl kinase (gamma-GK) accelerates the synthesis of PRO. Under TDM treatment, the activity of PROX decreased and the gamma-GK activity increased. From our results, it is suggested that fungicide triadimefon causes activation of metabolic processes in the medicinal plant Catharanthus roseus. These findings are of great significance for the cultivation of this medicinal plant, as it was previously reported that TDM causes an enhancement of antioxidant metabolism and ajmalicine production in C. roseus.

Responses of antioxidant potentials in Dioscorea rotundata Poir. following paclobutrazol drenching.

The effect of paclobutrazol (PBZ) treatments on the antioxidant metabolism of white yam (Dioscorea rotundata Poir.) was investigated in the present study. PBZ @ 15 mg l(-1) plant(-1) was given to plants by soil drenching, 30, 60, and 90 days after planting (DAP). The non-enzymatic antioxidant contents like ascorbic acid (AA), reduced glutathione (GSH) and alpha-tocopherol (alpha-toc), activities of antioxidant enzymes like superoxide dismutase (SOD), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and catalase (CAT) were extracted and assayed on 100 DAP from leaf, stem and tubers of both control and PBZ treated plants. It was found that PBZ has a profound effect on the antioxidant metabolism and caused an enhancement in both non-enzymatic and enzymatic antioxidant potentials under treatments in white yam. Our results have good significance, as this increase the innate antioxidant potential of this food crop, which is helpful to satisfy the needs of antioxidants in diet and thereby make it an economically important food crop.

NaCl as a physiological modulator of proline metabolism and antioxidant potential in Phyllanthus amarus.

Some medicinal plants need to be cultivated commercially in order to meet the ever-increasing demand for medicinal plants for the indigenous systems of medicine as well as for the pharmaceutical industry; in this regard, it seems significant to test the important medicinal plants for their salt-tolerance capacity, with a view to exploiting the saline lands for medicinal plant cultivation. Phyllanthus amarus plants were grown in the presence of NaCl in order to study the effect of NaCl (80 mM NaCl) in the induction of oxidative stress in terms of lipid peroxidation (TBARS content), H2O2 content, osmolyte concentration, proline(PRO)-metabolizing enzymes, and antioxidant enzyme activities. Groundwater was used for irrigation of control plants. Plants were uprooted randomly on 90 days after sowing (DAS). NaCl-stressed plants showed increased TBARS, H2O2, glycine betaine (GB), and PRO contents, whereas NaCl uptake decreased proline oxidase (PROX) activity and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased under salinity.

Changes in antioxidant potential and sink-organ dry matter with pigment accumulation induced by hexaconazole in Plectranthus forskholii Briq.

An investigation was conducted in Plectranthus forskholii by giving it different concentrations (10, 15, 20, 25, and 30 mg L(-1)) of hexaconazole, a fungicide cum plant-growth regulator, in order to find out its effects on growth, pigment composition, and antioxidant potential. The treatments were given as soil drenching on different growth stages. All the concentrations of hexaconazole used significantly decreased the stem length and leaf area, whereas side branches, fresh and dry matter content, photosynthetic pigments, and antioxidant potential were increased. The number of tubers, length and girth of tubers, fresh and dry weight of tubers and tuber pigments were found to be the highest at a 25 mg L(-1) concentration of hexaconazole. Hexaconazole application at 25 mg L(-1) concentration was found to be more effective than 10, 15, 20, 25, and 30 mg L(-1) in promoting fresh and dry weight of root tuber over 165 days after planting. The pigments like chlorophyll, carotenoid; anthocyanins, xanthophylls and antioxidants such as ascorbic acid, reduced glutathione and total phenol were significantly increased under hexaconazole treatment when compared to untreated control plants.

Changes in carbohydrate metabolism by triazole growth regulators in cassava (Manihot esculenta Crantz); effects on tuber production and quality.

We have evaluated the ability of two triazole growth regulators, viz. triadimefon (TDM) and hexaconazole (HEX), in the enhancement of tuber production and quality in cassava (Manihot esculenta Crantz) through their effects on carbohydrate metabolism. One litre of 20 mg(-1) TDM and 15 mg(-1) HEX solution per plant were used for the treatments and groundwater was given to control plants. Triazole treatments reduced plant height and leaf area, but increased fresh and dry weights. Plants treated with TDM showed an increased net assimilation rate, which is followed by HEX and control plants. Triazole compounds increased the relative growth rate of cassava after 200 DAP, i.e. in the phase of tuber enlargement. Triazole compounds increased the starch and other carbohydrate contents and carbohydrate metabolising enzyme activities. From the results of this study, it can be concluded that these triazoles can significantly enhance the tuber production and quality by affecting the starch metabolism, apart from their fungicidal properties.

Calcium chloride effects on salinity-induced oxidative stress, proline metabolism and indole alkaloid accumulation in Catharanthus roseus.

Catharanthus roseus (L.) G. Don. plants were grown with NaCl and CaCl2 in order to study the effect of CaCl2 on NaCl-induced oxidative stress in terms of lipid peroxidation (TBARS content), H2O2 content, osmolyte concentration, proline (PRO)-metabolizing enzymes, antioxidant enzyme activities, and indole alkaloid accumulation. The plants were treated with solutions of 80 mM NaCl, 80 mM NaCl with 5 mM CaCl2 and 5 mM CaCl2 alone. Groundwater was used for irrigation of control plants. Plants were uprooted randomly on 90 days after sowing (DAS). NaCl-stressed plants showed increased TBARS, H2O2, glycine betaine (GB) and PRO contents, decreased proline oxidase (PROX) activity, and increased gamma-glutamyl kinase (gamma-GK) activity when compared to control. Addition of CaCl2 to NaCl-stressed plants lowered the PRO concentration by increasing the level of PROX and decreasing the gamma-GK activities. Calcium ions increased the GB contents. CaCl2 appears to confer greater osmoprotection by the additive role with NaCl in GB accumulation. The antioxidant enzymes superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased under salinity and further enhanced due to CaCl2 treatment. The NaCl-with-CaCl2-treated C. roseus plants showed an increase in total indole alkaloid content in shoots and roots when compared to NaCl-treated and untreated plants.