Reduction In Plant Growth Parameters Research Articles

Salicylic acid and iron-oxide nanoparticles improved the growth and productivity of ajowan under salt stress

Two factorial experiments with randomized complete block design in three replicates were conducted in a greenhouse at the University of Tabriz to investigate the individual and combined effects of SA and Fe2O3-NPs spray (1 mM and 3 mM, respectively) on cations contents, root and shoot growth, seed filling and yield parameters of salt-stressed ajowan plants (0, 4, 8 and 12 dS m-1 NaCl; as non-saline and low, moderate and high salinities, respectively). Salt stress enhanced Na+ contents and reduced K+ and Ca2+ contents, and K+/Na+ and Ca2+/Na+ ratios, leading to a reduction in root and shoot growth, particularly under high salinity. Reduction in plant growth parameters under salt stress had a negative impact on yield components and seed yield of ajowan. These deleterious impacts of salinity on plants were largely overcome by foliar treatments, particularly by SA + Fe2O3-NPs. The improvement of seed yield by these treatments was highly correlated with enhanced root and shoot growth, seeds per plant, and 1000-seed weight, especially under moderate and high salinities. Thus, the simultaneous application of SA and Fe2O3-NPs was the best foliar treatment for enhancing the growth and productivity of ajowan plants under normal and saline conditions.

Synthesis and Characterization of a Quercetin-Based Nanocomposite and Its Ameliorating Impacts on the Growth, Physiological, and Biochemical Parameters of Ocimum basilicum L. under Salinity Stress

Quercetin (Qu), as an essential flavonoid in plants with antioxidant properties, scavenges environmental stress-induced ROS. Quercetin-based nanocomposites (QNCs) with the same and adequate properties were designed and synthesized for effective Qu delivery in Ocimum basilicum. QNCs were synthesized using the coacervation method, and their effect on the growth, physiological, biochemical, and phytochemical traits of O. basilicum under salinity stress was investigated. Various treatments, including selected concentrations of Qu (0.01 mg/mL) and QNCs (0.01 mg/mL), and four concentrations of NaCl (0, 50, 100, 150 mM) at the vegetative stages, were applied. Results showed that stress markers (Electrolyte leakage, malondialdehyde, hydrogen peroxide) increased with increasing salinity levels. Conversely, salinized plants showed a reduction in plant growth parameters (seed germination, root and shoot length, fresh and dry weight of shoot and root, and plant height) and physiological and photosynthetic parameters (Relative water content, photosynthesis rate, stomatal conductance, photosynthetic pigments, and chlorophyll fluorescence), while application of Qu and QNCs increased these critical parameters. Furthermore, Qu and QNCs enhanced O. basilicum’s tolerance to salinity by increasing compatible solutes content such as glycine betaine, proline, total free amino acids, and soluble carbohydrates; increasing antioxidant enzyme activity; increasing antioxidants content like anthocyanins, tannins, phenols, and flavonoids; and decreasing proteins content and stress markers in plant tissues. Our study suggests that treatment with Qu and QNCs is an effective strategy that can be used to enhance the salt tolerance of O. basilicum plants, and QNCs treatment had a better effect than treatment with Qu.

RNA sequencing in Artemisia annua L explored the genetic and metabolic responses to hardly soluble aluminum phosphate treatment.

Artemisia annua L. is a medicinal plant valued for its ability to produce artemisinin, a molecule used to treat malaria. Plant nutrients, especially phosphorus (P), can potentially influence plant biomass and secondary metabolite production. Our work aimed to explore the genetic and metabolic response of A. annua to hardly soluble aluminum phosphate (AlPO4, AlP), using soluble monopotassium phosphate (KH2PO4, KP) as a control. Liquid chromatography-mass spectrometry (LC-MS) was used to analyze artemisinin. RNA sequencing, gene ontology (GO), and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were applied to analyze the differentially expressed genes (DEGs) under poor P conditions. Results showed a significant reduction in plant growth parameters, such as plant height, stem diameter, number of leaves, leaf areas, and total biomass of A. annua. Conversely, LC-MS analysis revealed a significant increase in artemisinin concentration under the AlP compared to the KP. Transcriptome analysis revealed 762 differentially expressed genes (DEGs) between the AlP and the KP. GH3, SAUR, CRE1, and PYL, all involved in plant hormone signal transduction, showed differential expression. Furthermore, despite the downregulation of HMGR in the artemisinin biosynthesis pathway, the majority of genes (ACAT, FPS, CYP71AV1, and ALDH1) were upregulated, resulting in increased artemisinin accumulation in the AlP. In addition, 12 transcription factors, including GATA and MYB, were upregulated in response to AlP, confirming their importance in regulating artemisinin biosynthesis. Overall, our findings could contribute to a better understanding the parallel transcriptional regulation of plant hormone transduction and artemisinin biosynthesis in A. annua L. in response to hardly soluble phosphorus fertilizer.

Screening for resistance and susceptibility in some beetroot cultivars to root-knot nematode, Meloidogyne javanica

Aim: The present study was conducted to identify the resistance and susceptibility of beetroot cultivars against root-knot nematode, Meloidogyne javanica. Methodology: In this study, seven beetroot cultivars were screened against the root-knot nematode, Meloidogyne javanica, at the inoculum level of 1500 second-stage juveniles (J2s) per pot. Five replications of each cultivar of beetroot were used for screening and kept in a completely randomized design (CRD) at 25 ± 2 °C under greenhouse conditions. The data were subjected to ANOVA using SPSS-17 statistical software (SPSS Inc., Chicago, IL, USA). According to Duncan’s Multiple Range Test, the mean values were statistically compared and separated at P ≤ 0.05. Results: The results revealed that all seven cultivars of beetroot showed varying degrees of resistance and susceptibility to M. javanica. Among all the cultivars, three were moderately resistant, i.e., CG, DDR and Red Ace with the minimum number of galls (4.0, 8.0 and 7.0), and two were moderately susceptible, i.e., Atlas and Red Queen (28 and 22). Red Ruby (84) was found susceptible and Red Express was highly susceptible with the maximum galls (126). None of the cultivars were found to be highly resistant or immune. Interpretation: A positive and significant correlation was found between the number of galls and per cent reduction in plant growth parameters. From the results, it can be recommended that the use of resistant cultivars is an environment-friendly approach that can be used to manage the nematode density below the economic threshold level.

Influence of root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood infection on different plant growth parameters in Mungbean, Vigna radiata (L.) Wilczek

Root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, is a major threat to mungbean cultivation. The pest causes a significant reduction in plant growth parameters that ultimately results in loss of grain yield. The present study was carried out under glass house condition to study the effect of different inoculum load of root-knot nematode M. incognita on plant growth, nodulation and nematode development and nutrients status of Mungbean. The results revealed a progressive decline in plant growth parameters viz., fresh and dry shoot weight and shoot length with respect to increase in inoculum level. However, fresh and dry root weight showed the opposite trend. The fresh and dry shoot weight was decreased by 44% and 66%, respectively at 4 J2s/g soil. The chlorophyll content in the leaves also decreased with the increase of inoculum level from 100-6000 J2s/pot. Nutrients contents of the plant viz. N, P, K, Ca and Mg were significantly reduced in shoots while in roots these was increased with an increase of inoculum levels. Nodulation was affected by 80% at the highest inoculum level i.e. 6000 J2s/pot. Also leghaemoglobin, bacteroid content and nitrogenase activity was reduced progressively with increased levels of nematode inoculum. Thus, the root-knot nematode, M. incognita interferes with the process of symbiotic nitrogen fixation between mungbean host and rhizobium and that can affect the quality of produce.

Host status of Bambara groundnut accessions to Meloidogyne incognita using conventional screenhouse and novel seedling pouch methods

Summary Bambara groundnut (Vigna subterranea) is an underexploited legume indigenous to sub-Saharan Africa with high protein content. Production constraints of Bambara groundnut include the root-knot nematodes (Meloidogyne spp.), which causes substantial losses that present an additional burden that growers need to manage. In this study we: i) assessed genetic resistance against Meloidogyne incognita in Bambara groundnut; and ii) evaluated an improved, more efficient screening method for Bambara. Fifty accessions were evaluated in two screenhouse trials. Following this, the use of seedling pouches was assessed for a high throughput screening method, using two accessions identified from each of three host status categories (resistant, tolerant and susceptible). Variability in host response was observed between the trials but five accessions demonstrated good resistance to M. incognita. A general reduction in plant growth parameters was observed on inoculated plants, especially for chlorophyll content at 11 weeks after planting. The pouch screening system confirmed the screenhouse pot results but appears to be more sensitive. From a range of inocula no differences in gall index were observed over the 28 days of assessment in pouches but the number of egg masses proved a useful parameter and differed between inoculum levels, with 500 juveniles/eggs determined as the optimum inoculum level. The use of seedling pouches reduced time, space and cost to screen Bambara groundnuts for resistance against M. incognita. Consequently, it is recommended as an efficient, high throughput, rapid screening protocol for Bambara groundnut compared to conventional pot screening methods.

Interactive effect of Meloidogyne javanica and Fusarium solani in causing root rot of fennel

Fennel (Foeniculum vulgare Mill.) popularly known as “Saunf” is one of the important and highly valued spice crops grown in India. Fusarium solani is the most common pathogen in causing root rot of fennel with qualitatively and quantitatively losses. Development of disease in cultivated crops depends on the complex interaction between host, pathogen and prevailing environmental conditions. The significant role of nematodes in aggravating fungal diseases is well known in many crops throughout the world. In lieu of this, present study was planned to know the interactive effect of Meloidogyne javanica in enhancing the incidence of root rot by Fusarium solani. The experiment was laid out in a completely randomized design with four replications in pot conditions. The results of the experiments showed that inoculation of nematode at the time of sowing and fungus one week after caused maximum reduction in plant growth parameters and increased disease incidence followed by simultaneous inoculation of nematode and fungus in comparison to check. Whereas, maximum nematode reproduction was recorded in nematode alone followed by N+F. Conclusively, presence of root damaging nematodes in rhizosphere zone of plants plays an important role in enhancing incidence of root rot diseases.

Accumulation of compatible solutes in rice (Oryza sativa L.) cultivars by inoculation of endophytic plant growth promoting bacteria to alleviate salt stress

Salinization of agricultural lands, particularly rice paddies, results in the drastic decline of crop yields. Soil salinization impacts the plant physiology by inducing salt stress which may leads to osmotic stress, ionic stress and water-related nutrient imbalance. These imbalances necessitate the need for plants to produce osmolytes including proline and glycine betaine. This study aimed to elucidate the dynamic changes in proline and glycine betaine accumulation modulated by the inoculation of Brevibacterium linens RS16 in salt-sensitive and moderately salt-tolerant rice plants under salt stress conditions. This study showed the interaction of four major factors including rice genotypes with differing tolerance to salt stress, length of exposure to salt stress, level of salt stress and effects of inoculation. Salt stress resulted in significant reduction in plant growth parameters with the salt-sensitive rice genotype (IR29) having a more significant growth reduction. Both the salt-sensitive and salt-tolerant rice genotypes increased in total proline and glycine betaine accumulation at 3 days and 10 days after subjecting under 50 mM and 150 mM salt stress conditions. A significant increase in proline and glycine betaine was observed in the salt-sensitive genotype after 10 days under 50 mM and 150 mM salt stress conditions. Inoculation of the rice genotypes with B. linens RS16 resulted in the improvement of plant growth parameters in both rice genotypes, and total proline and glycine betaine accumulation, especially in IR29. This study showed that proline and glycine betaine are compatible osmolytes of rice under salt stress, and that inoculation of rice genotypes with B. linens RS16 mediated salt tolerance through improvement of plant growth parameters and proline and glycine betaine accumulation in rice plants.

Evaluation of Indian Musa Germplasm for Resistance to Radopholus similis in Greenhouse

Fifty nine wild and cultivated banana genotypes (Musa spp.) including 10 diploids (AA, AB and BB genome) and 49 triploids (AAA, AAB, ABB) belonging to the Eumusa section, were evaluated for their host reaction against the burrowing nematode (Radopholus similis) under greenhouse conditions. Reduction in plant growth parameters was comparatively higher in susceptible genotypes when inoculated with nematodes. Root studies indicated higher number of roots, root fresh and dry weight in resistant and tolerant accessions even after nematode inoculation. Based on the corm grade, root necrosis percentage and the reproduction rate of nematode, the level of resistance to R. similis was assessed. The experiment revealed that the diploid accessions, Kanai Bansi (AA), Elakkiebale (AB), M. balbisiana (BB), Bhimkol (BB), Athiakol (BB) and Aittakola (BB) were resistant. Among triploids, Kothia (ABB) and Ankur II (ABB) were resistant to R. similis.

Effect of Fusarium oxysporum f. sp. lycopersici and Meloidogyne incognita interaction on wilt disease incidence in tomato

Development of diseases in cultivated crops depends on the complex inter-relationship between host, pathogen and prevailing environmental conditions. The significant role of nematodes in the development of nematode–fungus interaction is demonstrated in many crops throughout the world. Therefore, the main objectives of this study were to evaluate the interaction between Fusarium oxysporum f. sp. lycopersici and Meloidogyne incognita. The experiment was laid out in a completely randomized design (CRD) with three replications in pot conditions. The results show that inoculation of nematode at 7th day prior to inoculation of fungus caused maximum reduction in plant growth parameters and increase per cent disease incidence followed by simultaneous inoculation of nematode and fungus as compared to control.

Effect of different inoculum levels of Meloidogyne incognita, Alternaria dauci and Rhizoctonia solani on the growth, chlorophyll and carotenoid content and disease progression of carrot (Daucus carota L.)

The economic threshold level of Meloidogyne incognita, Alternaria dauci and Rhizoctonia solani were determined on carrot (Daucus carota L.) under greenhouse conditions. The results revealed that plant length, plant fresh weight, shoot and root dry weight, chlorophyll and carotenoid decreased progressively with the corresponding increase in the inoculum levels of each pathogen. The significant reduction in plant growth parameters, chlorophyll and carotenoid occurred when 2000 or more second stage juveniles (J2s) of M. incognita, 1.0 g or more inoculum of A. dauci or R. solani per kg soil were inoculated. Maximum reduction in plant growth attributes, chlorophyll and carotenoid occurred at the highest inoculum level of the test pathogens. Increase in the inoculum level of M. incognita caused an increase in the number of root galls, while the multiplication of nematode was found inversely related to the inoculum density. The increase in the inoculum levels of A. dauci and R. solani resulted in a progressive increase in leaf blight and crown rot indices and caused a higher reduction in plant growth parameters. The damaging threshold level of M. incognita was 2000 J2 per kg soil while 1.0 g per kg soil of A. dauci or R. solani was threshold level on carrot. The assessment of infestation levels of test pathogens will enable growers to cost-effectively select and implement the management tactics.

Environmental condition of saline compact soils of the Central Pre-Caucasian region and its sanitation

The main factors determining the change of the ecological situation in the zone of salinized compact chernozems distribution are the hydrological state, waterlogging, water erosion and the use of chemical crop products. In order to prevent further progress in the degradation of these lands, a number of activities are required. The most important task is to ensure the expanded reproduction of soil fertility. Its solution suggests the systematic application of fertilizers. A great advantage on saline soils should be given to organic fertilizers in order to maintain stocks of humus. The value of humus in their composition increases even more due to the fact that it reduces the possible negative impact on plants of some components of the mineral part of the soil, improves its water-physical properties. Humus limits the leaching of nitrogen caused by uncontrolled mineralization, increases the filtering and buffering effect of the soil and groundwater. In the intensive farming system, a deficit-free humus balance can be observed by combining the use of organic and mineral fertilizers. At the same time, the use of higher doses of them leads to pollution of the soil, plants and the environment. Therefore, the use of fertilizers should be carried out taking into account the biological needs of plants and specific soil conditions. On saline soils, due to a significant reduction in plant growth parameters and the biomass formed by them, the removal of nutrients in the composition of the primary and secondary crop significantly decreases. In addition, they are characterized by relatively high osmotic potential, which may further increase due to the application of higher doses of fertilizers. Therefore, in these conditions, moderate and small doses of mineral fertilizers are effective, and they meet the needs of plants and the interests of the soil ecology.

Comparative orchestrating response of four oilseed rape (Brassica napus) cultivars against the selenium stress as revealed by physio-chemical, ultrastructural and molecular profiling

Selenium (Se) is an essential micro-element for human and animals. In higher plants, Se essentiality or phyto-toxicity is less explored. Therefore, we aimed to examine the effects of Se (0, 25, 50, and 100 µM) as sodium selenite on the physio-chemical, cell ultra-structural and genomic alterations in hydroponically grown seedlings of four cultivars of B. napus (cvs. Zheda 619, Zheda 622, ZS 758, and ZY 50). Results showed that excessive (100 µM) Se (IV) exhibited significant reduction in plant growth parameters, declined pigment contents, lower water-soluble protein levels, and overproduction of H2O2 and MDA contents. A significant increase in antioxidant enzyme activities and transcript levels of superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR), except catalase (CAT) were noticed in the leaves and roots. Non-enzymatic antioxidants including glutathione (GSH) and oxidized glutathione (GSSG), except GSSG in roots were enhanced under higher Se (IV) levels. Transmission electron microscopy analysis revealed the ultrastructural damages in leaf mesophyll and root tip cells induced by excessive Se (IV). Less-significant phytotoxic effects were observed in above-mentioned parameters at 50 µM Se (IV). Overall, Se (IV) supplementation at 25 µM displayed marginal beneficial effect by enhancing plant growth, pigment contents, protein levels and restrict H2O2 and MDA overproduction. A marginal increase/decrease in ROS-detoxifying enzymes (except CAT activity) and elevated GSH and GSSG levels were noticed. The accumulation of Se (IV) was much higher in roots as compared to leaves. This accumulation was maximum in Zheda 622 and minimum in ZS 758, followed by Zheda 619 and ZY 50. Overall findings showed that Zheda 622 was the most sensitive and ZS 758 as most tolerant to Se (IV) phyto-toxicity. In addition, Se (IV) was found beneficial until 25 µM Se (IV) but phytotoxic at higher Se levels especially at 100 µM Se (IV).

Morpho-anatomical changes in gladiolus due to infection by Meloidogyne incognita

Meloidogyne incognita is emerging as a major problem in the successful cultivation of gladiolus. The present study was aimed to study the effect of M. incognita on some plant growth parameters of gladiolus cv. ‘Sylvia’ and to demonstrate the histopathological changes in gladioli due to M. incognita infestation. During the experiment, gladiolus crop was found severely infested with M. incognita and showed significant reduction in plant growth parameters and flower production. In severe infestation, no flower was produced. The histopathology of plant roots revealed that 2ndstage juveniles penetrated into root cortex and moved along the cortical layer of cells and started feeding. During feeding process, they produced some hypertrophied cells in vascular cylinder and hyperplasia in pericycle regions. The hypertrophied cells were metabolically highly active, multinucleate and contained dense cytoplasm. In gladiolus, 4–6 such hypertrophied cells were observed in vascular tissues and stellar region of roots. Though the site of infection was vascular tissue but due to the nematode development and giant cell formation, the entire nematode complex and giant cells appeared irregular in root section. The nematodes damaged complete thickness of roots and this condition lead to the destruction of feeder roots which ultimately affected plant growth by reducing water and nutrient absorption from soil.

The Possible Roles of Priming with ZnO Nanoparticles in Mitigation of Salinity Stress in Lupine (Lupinus termis) Plants

To our knowledge, little attention has been paid to evaluating ZnO nanoparticles (ZNPs) roles in plants grown under salinity stress. In this study, seeds of lupine (Lupinus termis) plants were grown in plastic pots and exposed to 0 (control) and 150 (S) mM NaCl with or without priming with different concentrations of ZnO [20 mg L−1 (ZNPs1), 40 mg L−1 (ZNPs2), and 60 mg L−1 (ZNPs3)] for 20 days. Salinized plants showed a reduction in plant growth parameters (root length, shoot length, fresh weight, and dry weight) and in the contents of photosynthetic pigments (chlorophyll a and b, and carotenoids) and Zn, as well as in the activity of catalase (CAT) against control plants. On the other side, salinity stress boosted the contents of organic solutes (soluble sugar, soluble protein, total free amino acids, and proline), total phenols, malondialdehyde (MDA), ascorbic acid and Na, as well as the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in stressed plants over control plants. However, seed-priming with ZNPs mostly stimulated growth of stressed plants, which was accompanied by reinforcement in the levels of photosynthetic pigments, organic solutes, total phenols, ascorbic acid and Zn, as well as in the activities of SOD, CAT, POD, and APX enzymes over stressed plants alone. On the contrary, priming with ZNPs caused a decrement in the contents of MDA and Na in stressed plants relative to salinized plants alone. It is worthy to mention that, this improvement in salt tolerance of plants primed with ZNPs was more obvious in plants primed with ZNPs3 and grown both in unstressed and stressed regimes. Thus, our findings suggest that seed-priming with ZNPs, especially 60 mg L−1 ZnO is an effective strategy that can be used to enhance salt tolerance of lupine plants.

Response of selected okra cultivars to Meloidogyne incognita

Root–knot nematodes (Meloidogyne spp.) are major pests of vegetables especially in the tropics and subtropics. All commercial okra varieties are susceptible to root knot nematodes and cause substantial losses. The objective of this study is to find out resistant germplasm in order to facilitate our breeders for gene manipulation. A greenhouse study was conducted to evaluate 28 okra cultivars against Meloidogyne incognita inoculated with 5000 eggs. Five cultivars (Bamya Yalova, 19,232, 19,236, 1,922,121, and Green Wonder) had significantly fewer root galls and eggs and less reduction in plant growth (shoot weight and root length), than most of the other entries. A positive relationship was demonstrated between root galls and reduction in plant growth parameters measured. These cultivars may improve okra production in fields infested with M. incognita. During our study, none of the cultivars tested were observed to be immune or resistant to nematode infection according to a scale where: good host [susceptible] when Pf/Pi (Pf = Final population of nematodes after harvest and Pi = Initial population of nematodes which was used as inoculum during experiment) > 5.0, fair, better [moderately resistant] if 5.0 ≥ Pf/Pi > 1, poor if 1 > Pf/Pi > 0, and non-host [resistant] when Pf/Pi = 0. The cultivars, including 19,224, 19,235, Pusa Sawami, Ikra-1, Ikra-2 and Sabzperi China Red, were found to be susceptible with Pf/Pi > 5.0, and they were declared as good hosts of M. incognita. While all the other cultivars were moderately resistant, with 0 ≥ Pf/Pi > 1 but still a significant penetration of nematodes was found. The regression studies showed positive and significant relationships between the number of galls and the reduction in shoot weight (r2 = 0.95), number of galls and reduction in shoot length (r2 = 0.81), and number of galls and decrease in root length (r2 = 0.89).

Exogenous application of thiamin promotes growth and antioxidative defense system at initial phases of development in salt-stressed plants of two maize cultivars differing in salinity tolerance

The effects of thiamin (Thi) applied as seed soaking or foliar spray on some key physiological parameters were investigated in two differentially salt-responsive maize (Zea mays L.) cultivars, DK 5783 and Apex 836 F1, exposed to saline stress in two different experiments. An initial experiment (germination experiment) was designed to identify appropriate doses of Thi which could lessen the deleterious effects of salt on plants and screen all available maize cultivars for their differential tolerance to salt stress (100 mM NaCl). The seeds of nine maize cultivars were soaked for 24 h in solutions containing six levels of Thi (25, 50, 75, 100, 125 and 150 mg l−1). Based on the results obtained from the germination experiment, maize cultivar DK 5783 was found to be the most salt tolerant and Apex 836 as the most sensitive cultivar. Also, of six Thi levels used, two levels (100 and 125 mg l−1) were chosen for subsequent studies. In the second experiment (glasshouse experiment), two maize cultivars, DK 5783 (salt tolerant) and Apex 836 (salt sensitive) were subjected to saline regime (100 mM NaCl) and two levels of Thi (100 and 125 mg l−1) applied as foliar spray. Salt stress markedly suppressed shoot and root dry mass, total chlorophylls (“a” + “b”), leaf water potential and maximum fluorescence yield (Fv/Fm) in the plants of both maize cultivars, but it increased proline accumulation, leaf osmotic pressure, malondialdehyde (MDA) and hydrogen peroxide (H2O2) concentrations, electrolyte leakage (EL) as well as activities of some key antioxidant enzymes, superoxide dismutase (SOD; EC. 1.15.1.1), peroxidase (POD; EC. 1.11.1.7) and catalase (CAT; EC. 1.11.1.6). Salt-induced reduction in plant growth parameters was higher in the salt-sensitive cultivar, Apex 836, which was found to be associated with relatively increased EL, and MDA and H2O2 levels, and decreased activities of the key antioxidant enzymes. Application of Thi as seed soaking or foliar spray partly mitigated the deleterious effects of salinity on plants of both maize cultivars. The most promising effect of Thi on alleviation of adverse effects of salt stress on maize plants was found when it was applied as foliar spray at 100 mg l−1. Thiamin application considerably reduced tissue Na+ concentration, but improved those of N, P, Ca2+ and K+ in the salt-stressed maize plants. Exogenously applied thiamin-induced growth improvement in maize plants was found to be associated with reduced membrane permeability, MDA and H2O2 levels, and altered activities of some key antioxidant enzymes such as CAT, SOD and POD as well as increased photosynthetic pigment concentration under saline regime.

Pathogenic potential of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on chilli (Capsicum annuum L.)

Damaging threshold levels of root-knot nematode Meloidogyne incognita and root-rot fungus Fusarium solani on plant growth parameters, viz., plant length, fresh and dry weight of chilli were determined by conducting their pathogenicity trials in pot experiments. The results revealed a significant reduction in the plant growth parameters at and above the inoculum level of about 1000 J2 per plant of M. incognita and the highest reduction was recorded at 8000 J2 per plant. Significant reduction in plant growth parameters was recorded at 1.00 g mycelial mat of F. solani per plant, while the highest reduction was observed at 8.00 g mycelial mat per plant. The damaging threshold level was 1000 J2 per plant of M. incognita and 1.00 g mycelial mat of F. solani.

Interactive effect of root-knot nematode, Meloidogyne incognita and root-rot fungus, Rhizoctonia solani, on okra [Abelmoschus esculentus L.

The individual, concomitant and sequential inoculation of second stage juveniles (at 2000 J2/kg soil) of Meloidogyne incognita and Rhizoctonia solani (at 2 g mycelial mat/kg soil) showed significant reduction in plant growth parameters viz. plant length, fresh weight and dry weight as compared to control. The greatest reduction in plant growth parameters was recorded in the plants simultaneously inoculated with M. incognita and R. solani followed by sequential and individual inoculation. In sequential inoculation, plant inoculated with M. incognita 15 days prior to R. solani shows more reduction in comparison to plant inoculated with R. solani 15 days prior to M. incognita. Moreover, the multiplication of nematode and number of galls/root system were significantly reduced in concomitant and sequential inoculation as compared to individual inoculation, whereas the intensity of root-rot/root system caused by R. solani was increased in the presence of root-knot nematode M. incognita as compared to when R. solani was inoculated individually.

Comparative study of <i>Fusarium oxysporum</i> f sp. <i>lycopersici</i> and <i>Meloidogyne incognita</i> race-2 on plant growth parameters of tomato

Many species of soil-inhabiting fungus Fusarium, cause severe yield loss in many crops. Experiments were conducted in net house condition with complete randomized block design to determine the individual effect of different in-oculum levels of root-knot nematode, Meloidogyne incognita, Race-2 and Fusarium oxysporum f sp. lycopersici on plant growth parameters viz., Plant length, fresh and dry weight and number of fruits of tomato var. P21. The experimental results showed that both the pathogens cause significant reduction in plant growth parameters. However, the fungus was not much effective on plant growth parameters in comparison to root-knot nematode. Greatest reduction in plant growth parameters was recorded in plants inoculated with 8000 J2/Kg soil of Meloidogyne in-cognita race 2. The threshold level of root-knot nematode was 1000 J2/kg soil while threshold level of Fusarium was @ 1 g/Kg soil. Inoculum level of Fusarium oxysporum f sp. lycopersici and Meloidogyne in-cognita race-2 was pathogenic and caused significant reduction at and above 1 g/kg soil and 1000 J2/Kg soil respectively.