Lentil Roots Research Articles

Transcriptomic analysis of salt-stress-responsive genes in lentil roots and leaves

Transcriptomic analysis of salt-stress-responsive genes in lentil roots and leaves

Molecular identification and characterizations of rhizobacterial isolates collected from lentil rhizosphere of Indo-gangetic plains.

Plant growth promoting rhizobacteria (PGPR) are also known to colonize in the soil rhizosphere and prevent the development of other soil borne pathogens residing in the root surface. These microorganisms play a vital role in growth and development of the plant and also enhances the soil fertility by enriching the soil with different beneficial nutrients. This study was aimed at isolation of different rhizobacteria and their molecular characterization in search of efficient bacterial strains with multiple growth regulating activities. A total 36 bacteria were isolated from lentil root nodule as well as soil from different lentil growing fields with a view to screen/evaluate their plant growth promoting potential. Morphological characterization of isolated rhizobacterial candidates were done by observing the colonies on YEMA and nutrient agar media. Determination of CFU, Congo red test and gram staining tests were done to further screen them according to their morphology. All the isolates were then undergone molecular phylogenetic analysis using the partial sequences of the 16S rDNA. Based upon the Gram staining test, all the isolates were negative in gram reaction except six Bacillus isolates, PSB2 and AB3. Results of Ribosomal Database Project (RDP) and Basic Local Alignment Search Tool for Nucleotide Sequences (BLASTn) from 16S rDNA gene sequences showed that these isolates are genetically diverse. A total of 15 isolates of Rhizobium, 6 isolates of Bacillus, 3 isolates of Pseudomonas, 2 isolates of Phosphate Solubilizing Bacteria, 4 isolates of actinomycetes were identified by molecular sequencing of their 16S rDNA region and comparing them with the other isolates enlisted in the database of NCBI for the similarity percentage, query coverage. The purpose of the present study was to select native rhizosphere bacteria from the lentil nodule and soil of Lentil field and to evaluate their plant growth promoting potential as an alternative of chemical fertilizer for sustainable, environment friendly agriculture and assessment of their phylogenetic characterization.

Genome wide identification and expression profiling of ATP binding cassette (ABC) transporters gene family in lentil (Lens culinaris Medikus) under aluminium stress condition

Adenosine triphosphate-binding cassette transporters (ABC transporters) are involved in regulating plant growth, development and tolerance to environmental stresses. In this study, a total of 138 ABC transporter genes were identified in the lentil genome that were classified into eight subfamilies. Four lentil ABC transporters from subfamily B and I were clustered together with the previously characterized ABC transporter proteins related to aluminium (Al) detoxification. Lentil ABC transporter genes were distributed across the chromosomes. Tandem duplication was the main driving force for expansion of the ABC gene family. Collinearity of lentil with soybean indicated that ABC gene family is closely linked to Glycine max. ABC genes in the same subfamily showed similar gene structure and conserved motifs. The ABC promoter regions harboured a large number of plant hormones and multiple stress responsive cis-regulatory elements. The qRT-PCR showed that ABC genes had varied expression in roots of lentil at different time points under Al stress. This is the first report on genome wide identification and expression analyses of genes encoding ABC transporter genes in lentil which has provided in-depth insight for future research on evolution and elucidation of molecular mechanisms for aluminium tolerance.

Increasing diversity gradient in lentil mixtures for intercropping with wheat reveals an increase in lentil biomass with minimal impact on mycorrhizal activity

The management of arbuscular mycorrhizal fungi (AMF) is crucial for sustainable agricultural systems, given its beneficial impacts on soil health and crop productivity. This study aimed to assess the effect of lentil (Lens culinaris Medik.) mixtures for intercropping with durum wheat (Triticum durum Desf.) on mycorrhiza and investigate the role of legume intraspecific diversity in mycorrhizal development and crop biomass production. Since both intraspecific and interspecific diversity (i.e., cultivar mixtures and intercropping) have an effect in shaping soil microbiota in the rhizosphere, we hypothesised that increasing the level of diversification in the system enhances the provision of services (e.g., aboveground biomass accumulation), due to enhanced microbial activity and diversity. Specifically, increasing diversity within lentil cultivar mixtures strengthens the affinity of wheat for mycorrhiza, thereby influencing wheat mycorrhization in wheat-lentil intercrops. To test our hypothesis, we designed three lentil cultivar mixtures with increasing diversity levels using a trait-based approach, drawing from a pool of Italian lentil landraces characterised in a previous study. As an additional factor, we intercropped lentil mixtures with wheat and compared it with sole wheat and sole lentil commercial cultivar. In both experimental years, intercropping lentil mixtures with wheat consistently yielded higher soil mycorrhization levels (46% in 2021 and 52% in 2022) compared to sole wheat cultivation (23% in 2021 and 34 % in 2022). Nevertheless, AMF colonisation in lentil roots was significantly higher in sole crops (55% in 2021 and 70% in 2022, except for the commercial cultivar) compared to intercrops (35% in 2021 and 60% in 2022). This difference could be attributed to the presence of wheat, which might have suppressed the capacity of lentils to establish successful symbiosis with mycorrhiza. On the other hand, AMF colonisation of wheat roots in 2022 was significantly higher (52%) when intercropped with lentils than when cultivated as sole wheat (40%). Concerning biomass production in lentil mixtures in 2022, we observed a positive correlation between lentil biomass and the number of functional groups in the mixtures, both as pure stands (R2 = 0.19, p = 0.06) and intercrops (R2 = 0.29, p = 0.01). Additionally, in 2022, the total biomass of the intercropped system increased with the increase in diversity. Further experiments, incorporating microbial genetic analysis, are necessary to uncover potential associations between functional mixtures and AMF composition.

Lentil Landrace Seed Origin and Genotype Affects Rhizosphere Microbiome

Lentil (Lens culinaris Medik.) is an essential legume crop providing healthy and nutritious food for people in low- to middle-income countries, worldwide. Lentil roots support symbiotic interactions with soil rhizobia species fostering nitrogen fixation; however, assemblage and diversity of the complete microbial rhizosphere community and the effect of seed genotype and origin remain largely unexplored. In this study we examined, via metagenomic analysis, the effects of seed origin on the rhizosphere’s communities in samples of the famous Greek lentil landrace, Eglouvis, derived from different local farmers and farming systems (including a Gene Bank sample), in comparison to a commercial variety. The landrace exhibited higher rhizosphere microbiome diversity compared to the commercial variety for all indexes. A core microbiome comprised of 158 taxa was present in all samples, while a greater number of unique bacterial taxa was recorded in the landrace samples compared to the commercial cultivar. Notably, landrace samples originated from organic farming had more than double the number of unique taxa compared to conventional counterparts. The study revealed a higher diversity of N2 fixers and archaea, Crenarchaeota and Thaumarchaeota, in landrace samples and particularly in those derived from organic farming, underpinning the distinct recruiting efficiency of beneficial soil microbes by the landrace.

Characterization of plant growth-promoting bacteria isolated from rhizosphere of lentil (Lens culinaris L.) grown in two different soil orders of eastern India.

Lentil, which is an important grain legume, can be co-inoculated with plant growth-promoting rhizobia and rhizobacteria to boost nitrogen fixation, increase biomass, and a possibility for early nodulation. The goal of the ongoing study was to identify plant growth-promoting rhizobacteria (PGPR) in the rhizosphere of lentil growing soils in eastern India. Sixteen rhizosphere bacteria were isolated from two different soil orders, and their capacity to solubilize phosphate and generate hydrogen cyanide (HCN), siderophore, and indole acetic acid (IAA) was assessed. The three best strains were selected for compatibility study with twenty Rhizobium isolated from lentil root nodules. The isolated rhizobacteria were able to produce ammonia and different mycolytic enzymes. Isolate B3 produced the highest amount of IAA and siderophore; the highest amount of phosphate solubilized by PSB1 strain; and isolates AB1, AB2, B3, PS2, and PSB2 produced considerable amount of HCN gas. Among all the isolates, B3, PSB1, and PS2 performed better based on different plant growth-promoting abilities. These three bacterial isolates showed compatible reaction with most of the Rhizobium strains. Isolates B3, PS2, and PSB1 were identified as Bacillus subtilis (MT729775), Pseudomonas palmensis (MT729782), and Paraburkholderia caribenis (MZ956803), respectively. Lentil shoot weight, root length, nodule number, N uptake, and P uptake were increased in the pot culture experiment when inoculated with these strains. PGPR strain B3 performed best among the three strains in the pot culture experiment. Strain B3 can be used as potential biofertilizer along with compatible Rhizobium species for better production of lentil.

Durum wheat-lentil relay intercropping enhances soil mycorrhizal activity but does not alter structure of arbuscular mycorrhizal fungal community within roots

In intercropping systems, crop species select host-adapted microorganisms and influence the associated plant-microbial interactions like in the case of arbuscular mycorrhizal fungi (AMF). Attempts to assess the impact of intercropping on the activity, diversity, and community composition of AMF remain inconclusive, more so in intercropping systems involving traditional Mediterranean crops such as durum wheat and lentils. We carried out field experiments in Central Italy to assess the impact of relay intercropping durum wheat (Triticum durum Desf. cv. Minosse) and lentil (Lens culinaris Medik. cv. Elsa) on soil mycorrhizal inoculum potential (MIP) (2019 and 2020), AMF root colonization (2019, 2020, and 2021), and root AMF diversity and community composition (2020 and 2021), compared to the respective sole crops. Results showed that relay intercropping enhanced lentil grain yield and durum wheat grain protein concentration but marginally reduced durum wheat grain yield and lentil grain protein concentration. In addition, relay intercropping enhanced soil mycorrhizal activity but differentially influenced mycorrhizal root colonization compared to sole cropping. Sequencing analyses generated a total of 234 amplicon sequence variants belonging to Glomeromycota, which were assigned to 31 virtual taxa using the MaarjAM reference database. Glomeraceae and Claroideoglomeraceae were the most abundant taxa but had contrasting abundances in 2020 and 2021. The overall changes in AMF species diversity and community structure were affected by the interaction between crop species and year, and not by intercropping. Claroideoglomus and Septoglomus showed a strong association with lentil roots while Rhizophagus and Paraglomus were associated with durum wheat roots in 2020, affirming host genotype-AMF preferences. The principal component analysis showed that grain protein concentration was associated with selected mycorrhizal parameters such as community richness and AMF root colonization. Further studies on the functional analysis of the different AMF communities selected by the crop genotype and year may reveal the importance of intercropping in maintaining soil functionality and productivity under low-input systems.

Inoculum dose-disease response relationships for the pea root rot pathogen, Aphanomyces euteiches, are dependent on soil type and other pathogens.

The oomycete pathogen, Aphanomyces euteiches, was implicated for the first time in pea and lentil root rot in Saskatchewan and Alberta in 2012 and 2013. Subsequent surveys from 2014 to 2017 revealed that Aphanomyces root rot (ARR) was widespread across the Canadian prairies. The absence of effective chemical, biological, and cultural controls and lack of genetic resistance leave only one management option: avoidance. The objectives of this study were to relate oospore levels in autoclaved and non-autoclaved soils to ARR severity across soil types from the vast prairie landscape and to determine the relationship of measured DNA quantity of A. euteiches using droplet digital PCR or quantitative PCR to the initial oospore inoculum dose in soils. These objectives support a future end goal of creating a rapid assessment method capable of categorizing root rot risk in field soil samples to aid producers with pulse crop field selection decisions. The ARR severity to oospore dose relationship was statistically significantly affected by the soil type and location from which soils were collected and did not show a linear relationship. For most soil types, ARR did not develop at oospore levels below 100/g soil, but severity rose above this level, confirming a threshold level of 100 oospores/g soil for disease development. For most soil types, ARR severity was significantly higher in non-autoclaved compared to autoclaved treatments, demonstrating the role that other pathogens play in increasing disease severity. There was a significant linear relationship between DNA concentrations measured in soil and oospore inoculum concentration, although the strength of the relationship was better for some soil types, and in some soil types, DNA measurement results underestimated the number of oospores. This research is important for developing a root rot risk assessment system for the Canadian prairies based on soil inoculum quantification, following field validation of soil quantification and relationship to root rot disease severity.

Nitric Oxide and Strigolactone Alleviate Mercury-Induced Oxidative Stress in Lens culinaris L. by Modulating Glyoxalase and Antioxidant Defense System.

Developmental activities have escalated mercury (Hg) content in the environment and caused food security problems. The present investigation describes mercury-incited stress in Lens culinaris (lentil) and its mitigation by supplementation of sodium nitroprusside (SNP) and strigolactone (GR24). Lentil exposure to Hg decreased root and shoot length, relative water content and biochemical variables. Exogenous application of SNP and GR24 alone or in combination enhanced all of the aforementioned growth parameters. Hg treatment increased electrolyte leakage and malondialdehyde content, but this significantly decreased with combined application (Hg + SNP + GR24). SNP and GR24 boosted mineral uptake and reduced Hg accumulation, thus minimizing the adverse impacts of Hg. An increase in mineral accretion was recorded in lentil roots and shoots in the presence of SNP and GR24, which might support the growth of lentil plants under Hg stress. Hg accumulation was decreased in lentil roots and shoots by supplementation of SNP and GR24. The methylglyoxal level was reduced in lentil plants with increase in glyoxalase enzymes. Antioxidant and glyoxylase enzyme activities were increased by the presence of SNP and GR24. Therefore, synergistic application of nitric oxide and strigolactone protected lentil plants against Hg-incited oxidative pressure by boosting antioxidant defense and the glyoxalase system, which assisted in biochemical processes regulation.

Impact on plant productivity under low-fertility sandy soil in arid environment by revitalization of lentil roots.

Lentil is one of the essential legume crops, which provides protein for humans and animals. This legume can improve soil fertility through nitrogen fixation, which is imperative in low-fertility soils. The growth and productivity of lentil could be enhanced through improving nutrition and root revitalization. Therefore, the objective of this study was to assess the impact of root activator (RA) and phosphorus (P) application on morphological, physiological, agronomic, and quality traits of lentil under newly reclaimed low-fertility sandy soil in an arid environment. The RA was applied at four levels of 0 (RA0-untreated control), 1.25 (RA1), 2.5 (RA2), and 3.75 (RA3) l ha–1. RA contained 9% potassium humate, 1,600 ppm indole butyric acid, 200 ppm gibberellic acid, and 200 ppm naphthalene acetic acid. The recommended rate of phosphorus (P) fertilization in the newly reclaimed low-fertility sandy soil (75 kg P2O5 ha–1) was applied, and its amount was increased and decreased by 25 kg P2O5 ha–1 vs. non-added control. Thus, P rates were applied at four rates 0 (P0; control), 50 (P1), 75 (P2), and 100 (P3) kg phosphorus pentoxide (P2O5) ha–1. Our results revealed that treated lentil plants with the high levels of both treatments (RA3 and P3) exhibited superiority in root measurements (root length, total number of nodules plant−1, number of active nodules plant−1, dry weights of active nodules, and total root), nitrogenase activity, chlorophyll a and b, carotenoids, yield traits, and seed proteins and carbohydrates. However, the recommended P level (75 kg P2O5 ha–1, P2) under the high level of RA (3.75 l ha–1, RA3) displayed non-significant differences in yield traits (plant height, 1,000-seed weight, seed yield ha–1) and quality traits (protein and carbohydrate) with the high P level (100 kg P2O5 ha–1, P3). Accordingly, its recommended economically and environmentally to use this coapplication of RA3 and P3 in low-fertility soil for better lentil growth, and seed yield and quality.

First Report of Wilt on Lentil (Lens culinaris) Caused by Fusarium redolens in Tunisia.

Lentil (Lens culinaris Medik.) is widely grown in arid and semi-arid regions of Tunisia. Low yields are often attributed to it being grown on marginal growing land. Since 2016, symptoms of wilt including yellowing and discoloration of the stem and root tissues were observed in lentils in several region of Tunisia. The annual mean incidence of infected plants ranged from 10% to 15%. In 2019-2020 growing seasons, symptomatic adult plants were randomly sampled from two fields located in south Tunisia (33°37’N; 11°4’E; N and 33°33’N; 11°2’E), and one field located in north west Tunisia (36°7’N; 8°43’E). Pieces were cut from roots and stem, surface sterilized, then plated on ¼ strength Potato Dextrose Agar (PDA) + 100 mg L-1 streptomycin sulfate (Burgess et al., 1994). Cultures were incubated for 5-6 days. Nine colonies with floccose mycelia, spare or abundant and white to violet color, morphologically similar to Fusarium redolens according to Leslie & Summerell (2006) were isolated from both roots and stems. They were single-spored (Burgess et al., 1994). Microconidia were formed in false heads on short monophialides. They were oval to elliptical or reniform and were 0-1 septate. Three-septate macroconidia with short apical cells were also observed. The strains were also deposited in the microbial ITEM Collection of Institute of Sciences of Food Production. Extraction of genomic DNA of Fusarium sp. strains was carried out according to Wizard® Magnetic DNA Purification System (Promega, Fitchburg, WI, USA). Molecular identification was carried out based on translation elongation factor (TEF) gene sequencing, as described in Fallahi et al. (2019). The TEF sequences were searched on GenBank database by using the Basic Local Alignment Tool (BLAST). The sequences of four strains (Z2P6, Z2P7, Z3P2 and Z3P5) on a total of nine, recovered from lentil roots from the two fields of south Tunisia showed 100% homology with TEF sequences of the epitype culture of F. redolens NRRL25600 (accession number MT409453) (Balmas et al. 2010; Gargouri et al. 2020). Sequences of the strains were submitted to GenBank with accession numbers MW393853, MW393854, MW393856 and MW393857. Pathogenicity of the four strains of F. redolens was evaluated on Kef lentil variety (Kharrat et al. 2007). Inoculum was produced on sterilized oat colonized with each strain. The colonized grains were air-dried on filter paper, ground in a laboratory mill, mixed at 10 % to soil (10 g of each isolate inoculum for 100 g of disinfected soil substrate) and potted. Three germinated lentil seeds were placed in each pot and irrigated periodically. The test was replicated four times. After 21 days, 60% (33-100%) of the plants inoculated with the four F. redolens strains showed symptoms of wilting, yellowing and rotting of roots and 17% died when inoculated by Z2P6 and Z2P7 strains. Non-inoculated plants showed no symptoms. F. redolens was isolated from 100% of the inoculated plants roots. This is the first report of F. redolens as a pathogen on lentil in Tunisia. This species has also been associated with lentil wilting in other regions of the world including Italy (Riccioni et al. 2008), Canada (Taheri et al. 2011) and Pakistan (Rafique et al. 2020). F. redolens was previously reported from wilted chickpea crops in Tunisia (Bouhadida et al. 2017). These findings are important for the Tunisian national legumes program and call for larger surveys to better understand the biology and ecology of this species and to prevent from disease spreading.

FORMATION OF A SYMBIOTIC APPARATUS OF LENTIL DEPENDING ON INOCULATION AND PROCESSING OF SEEDS WITH MICROELEMENTS

The article presents the results of a long-term study of the features of the formation of the symbiotic potential of lentil plants, taking into account both the hydrothermal features of the vegetation period of plants, and from the standpoint of using various options for pre-sowing seed treatment with inoculant and complex micronutrient fertilizers. Aspects of the formation of the symbiotic potential of lentils in the context of different years according to the hydrothermal regime were determined, which made it possible to determine the optimal SCC interval for the realization of the effective potential of the formation of nodule bacteria and their vital activity. The features of the use of one of the modern lentil seed inoculants Anderiz-r and complex chelated micronutrient fertilizer for presowing seed treatment - Oracle in the format of single and combined use against the background of the recommended background of mineral nutrition at the level of 30 kg / ha of the active substance nitrogen, phosphorus and potassium from the standpoint of the formation of a symbiotic apparatus in the dynamics of the phenological development of lentils. The effect of these preparations on the formation of the number and mass of nodule bacteria on the root system of lentil plants was studied for the period from the branching of the stem to the beginning of the formation of fruit elements. It has been proven that the combined use of an inoculant and microfertilizer provides a general increase in the number of nodule bacteria on a plant by at least 80% for an increase in their mass by 2.4 times. The features of the formation of the ratio between the number and mass of nodule bacteria in lentil plants have been established both from the standpoint of hydrothermal vegetation regimes and from the standpoint of using options for pre-sowing seed inoculation and the use of complex micronutrients for the same pre-sowing seed treatment. It is noted that from the standpoint of a positive influence on the general indicators of the formation of the symbiotic potential of lentil plants, an obligatory technological element is the pre-sowing inoculation of seeds with a species-specific strain of bacteria, which makes it possible to significantly increase the total number of nodule bacteria on lentil roots from 5-7 to 30-31, depending on the phenological phase. plants and years of research

Fusarium spp. Associated With Root Rot of Pulse Crops and Their Cross-Pathogenicity to Cereal Crops in Montana.

Root rot caused by Fusarium species is a major problem in the pulse growing regions of Montana. Fusarium isolates (n = 112) were obtained from seeds and roots of chickpea, dry pea, and lentil. Isolates were identified by comparing the sequences of the internal transcribed spacer region and the translation elongation factor 1-α in Fusarium-ID database. Fusarium avenaceum was the most abundant species (28%), followed by F. acuminatum (21%), F. poae (13%), F. oxysporum (8%), F. culmorum (6%), F. redolens (6%), F. sporotrichioides (6%), F. solani (4%), F. graminearum (2%), F. torulosum (2%), and F. tricinctum (0.9%). The aggressiveness of a subset of 50 isolates that represent various sources of isolation was tested on three pulse crops and two cereal crops. Nonparametric analysis of variance conducted on ranks of disease severity indicated that F. avenaceum and F. solani isolates were highly aggressive on pea and chickpea. In lentil, F. avenaceum and F. culmorum were highly aggressive. In barley, F. avenaceum, F. solani, F. culmorum, and F. graminearum were highly aggressive. In wheat, F. avenaceum, F. graminearum, and F. culmorum were highly aggressive. Two F. avenaceum isolates were highly aggressive across all the crops tested and found to be cross-pathogenic. One isolate of F. culmorum and an isolate of F. graminearum obtained from chickpea and lentil seed were highly aggressive on barley and wheat. The results indicate that multiple Fusarium spp. from seeds and roots can cause root rot on both pulse and cereal crops. Rotating these crops may still lead to an increase in inoculum levels, making crop rotation limited in efficacy as a disease management strategy.

Animal Biomedicine Controls Root Knot Disease in Lentil Callus Culture: Enriched Advanced Clinical Toxicology Socio Economy Science Technology Communication by Preventing 21st Century COVID-19 Like Pandemic Diseases

The economic pulse seeds, Lens esculentum L. Cv. ‘Asha’ root callus develop on Murashige and Skoog (MS)-media supplemented with 2 mg/1, 2,4-D (2,4-dichloro phenoxy acetic acid) and inoculated with Meloidogyne incognita larvae (65 ± 2 J2) in the culture tube to study their multiplication rate under sterilized condition in the tissue culture laboratory, and biomedicine-nematode extract (NE) prepared from M. incognita females, when applied at 1.3mg/culture tube to root callus of lentil, reduced nematode infestation of callus and improved callus growth. This animal biomedicine-NE is thought to induce defense-resistance in lentil root callus and may prevent 21st –century pandemics like virus diseases by boosting immunity, resisting toxic effects, and improved biomedicine, advanced in clinical toxicology, green-socio-economy, science technology, and communication application. The biomedicine-NE not only increase agriculture and crop production but also enable the development of a new-generation of nanotechnology-agrochemicals reducing negative-environmental-impacts and maintaining-crop-yields. And both; biomedicine-NE and pulses may itself focus on nanoformulation of agrochemicals and other nanotechnological interdisciplinary future nanotoxicology research and applications in agriculture, and interaction nanomaterials-NE with plants, their environment, and other organisms also.

Fusarium Species Associated with Root Rot of Lentil (Lens culinaris) in North Dakota

Root rot of lentils is caused by a pathogen complex that includes several Fusarium species as well as Aphanomyces euteiches, Rhizoctonia solani, and Pythium species. Surveys of lentil fields were conducted in 2016 and 2018 in North Dakota to identify Fusarium species associated with root rot. Isolations were performed from lentil roots exhibiting disease, and isolates were identified via morphology and sequencing. In total, 114 fields were surveyed, and 391 Fusarium isolates were collected. A diversity of Fusarium species was recovered, as 10 different species were represented; however, F. oxysporum was the most frequently isolated species, present in 71% of fields. Based on correlation with disease severity data, it is likely that some of these isolates are pathogenic. F. avenaceum was relatively uncommon, unlike previous survey efforts on field pea in North Dakota. Further research is needed to determine how the Fusarium population responsible for root rot of lentil may be affected by cropping practices or seasonal climatic variation. Assessment of the virulence and host range of Fusarium species associated with root rot of lentil will further enhance our understanding of the root rot complex in lentil and the development and integration of effective management practices.

Effects of Lentil Genotype on the Colonization of Beneficial Trichoderma Species and Biocontrol of Aphanomyces Root Rot.

Trichoderma species are opportunistic plant symbionts that are common in the root and rhizosphere ecosystems. Many Trichoderma species may enhance plant growth, nutrient acquisition, and disease resistance, and for these reasons, they are widely used in agriculture as biofertilizers or biocontrol agents. Host plant genotype and other microorganisms, such as root pathogens, may influence the efficacy of Trichoderma inoculants. Aphanomyces euteiches is an important soil-borne oomycete in western Canada that causes root rot in legume crops such as lentil and pea, and there is not yet any significantly resistant varieties or effective treatments available to control the disease. In this study, the composition of root-associated fungal communities and the abundance of Trichoderma species, T. harzianum strain T-22 and T. virens strain G41, was determined in the roots of eight Lens genotypes based on internal transcribed spacer (ITS) Illumina MiSeq paired-end sequencing, both in the presence and the absence of the root rot pathogen Aphanomyces euteiches. Biocontrol effects of T. harzianum on A. euteiches was also examined. Significant genotypic variations were observed in the composition of root-associated fungal communities and the abundance of the different Trichoderma species in the lentil roots. The presence of A. euteiches altered the composition of Trichoderma found associated to the lentil genotypes. Biocontrol of A. euteiches by T. harzianum T22 species was observed in vitro and positive correlations between the abundance of Trichoderma and plant root and shoot biomass were observed in vivo. These findings revealed that lentil genotype and infection by the phytopathogen A. euteiches greatly influenced the colonization of root-associated fungi and the abundance of the Trichoderma species, as well as the effect on plant growth promotion. The multipartite interactions observed among lentil genotypes, Trichoderma species and A. euteiches suggest possibilities to select compatible host-beneficial microbe combinations in lentil breeding programs and to develop application strategies to harness the beneficial effects of Trichoderma inoculants in sustainable crop production systems.

In-Vitro Plant Growth Promotion of Rhizobium Strains Isolated from Lentil Root Nodules under Abiotic Stresses

Plant growth-promoting rhizobia are known to improve crop performance by multiple mechanisms. However, the interaction between host plants and Rhizobium strains is highly influenced by growing conditions, e.g., heat, cold, drought, soil salinity, nutrient scarcity, etc. The present study was undertaken to assess the use of Rhizobium as plant growth promoters under abiotic stress conditions. Fifteen Rhizobium strains isolated from lentil root nodules were tested for phosphate solubilization activity (PSA) and phytohormones production under salt and drought conditions. The results showed that 15 Rhizobium strains were significant phosphate solubilizers, and indole acedic acid (IAA) and gibberellic acid (GA3) producers based on least significant difference (LSD) analysis (p ≤ 0.05). The highest rate of PSA was attributed to three strains namely, 1145N5, 1159N11, and 1159N32 with a range of 144.6 to 205.6 P2O5 (µg/mL). The highest IAA production was recorded in the strain 686N5 with 57.68 ± 4.25 µg/mL as compared to 50.8667 ± 1.41 µg/mL and 37.32 ± 12.59 µg/mL for Rhizobium tropici CIAT 899 and Azospirillum brasilense DSM-1690, respectively. Strain 318N2111 produced 329.24 ± 7.84 µg/mL of GA3 as against 259.84 ± 25.55 µg/mL for A. brasilense DSM-1690. R. tropici CIAT 899 showed tolerance to salt (5% NaCl) and drought (ψ = −2.6 MPa) stress, whereas strain 686N5 showed an extremely high level of salt-tolerance (5% NaCl) and moderate level of drought tolerance (ψ = −0.75 MPa). These results indicate different pathways for drought and salt tolerance mechanisms. The assessment of plant growth promoting (PGP) activities of Rhizobium showed differences between bacterial viability and bacterial PGP activity in terms of abiotic stress tolerance where bacterial PGP activity is interrupted before reaching the bacterial tolerance threshold. These results integrate a new concept of PGPR screening based on PGP activity under abiotic stress.

Insights into acetate-mediated copper homeostasis and antioxidant defense in lentil under excessive copper stress

Gradual contamination of agricultural land with copper (Cu), due to the indiscriminate uses of fungicides and pesticides, and the discharge of industrial waste to the environment, poses a high threat for soil degradation and consequently food crop production. In this study, we combined morphological, physiological and biochemical assays to investigate the mechanisms underlying acetate-mediated Cu toxicity tolerance in lentil. Results demonstrated that high dose of Cu (3.0 mM CuSO4. 5H2O) reduced seedling growth and chlorophyll content, while augmenting Cu contents in both roots and shoots, and increasing oxidative damage in lentil plants through disruption of the antioxidant defense. Principle component analysis clearly indicated that Cu accumulation and increased oxidative damage were the key factors for Cu toxicity in lentil seedlings. However, acetate pretreatment reduced Cu accumulation in roots and shoots, increased proline content and improved the responses of antioxidant defense (e.g. increased catalase and glutathione-S-transferase activities, and improved action of glutathione-ascorbate metabolic pathway). As a result, excess Cu-induced oxidative damage was reduced, and seedling growth was improved under Cu stress conditions, indicating the role of acetate in alleviating Cu toxicity in lentil seedlings. Taken together, exogenous acetate application reduced Cu accumulation in lentil roots and shoots and mitigated oxidative damage by activating the antioxidant defense, which were the major determinants for alleviating Cu toxicity in lentil seedlings. Our findings provide mechanistic insights into the protective roles of acetate in mitigating Cu toxicity in lentil, and suggest that application of acetate could be a novel and economical strategy for the management of heavy metal toxicity and accumulation in crops.

Effects of tillage and rice residue management practices on lentil root architecture, productivity and soil properties in India’s Lower Himalayas

Large areas in North Eastern Region (NER) of India remain fallow (approx. 2.50 million hectare) after the rainy season (June-October) rice (Oryza sativa L.) could be cultivated in succession with winter pulses like lentil (Lens esculentum L.) on residual soil moisture. Growing short-duration lentil cultivars under no-till (NT) and mulch rice may limit the pulse drought stress. A 2-year study (2011–2013) was conducted in terraced land of Meghalaya, India (950 m ASL), involving rice-lentil cropping system to evaluate on soil and legume parameters short-term impacts of three tillage management prior lentil crop i.e. no tillage (NT), minimum tillage (MT), conventional tillage (CT) and four residue management i.e. residue removal (RM), 20 cm standing rice stubble (20SS), 40 cm standing rice stubble (40SS) and mulch @ 5 Mg ha−1] and two lentil plant types [early and medium duration varieties: DPL 62 (Sheri) and DPL 15 (Priya), respectively]. Soil moisture content, water holding capacity and infiltration rate (IR) were higher in soil under mulch followed by 40 SS compared to 20SS and RM. The IR was significantly higher at lentil harvest for both in soil under NT in rice followed by NT in lentil (NT-NT) as compared to MT in rice followed by NT in lentil (MT-NT), and CT in rice followed by NT in lentil (CT-NT). The soil organic carbon (SOC) concentration, soil microbial biomass carbon (SMBC) and dehydrogenase activities (DHA) were significantly higher in 0–15 cm soil depth under NT-NT and MT-NT as compared to CT-NT. On an average, significantly higher SOC (17.3 g kg−1), DHA (2.32 μg g−1 hr−1) and SMBC (79.5 μg g−1 dry soil) in 0–15 cm soil layer at harvest of lentil were obtained under mulch followed by 40 SS as compared to RM. Lentil leaves chlorophyll and relative water contents were significantly higher under mulch followed by that under 40SS than 20SS and RM. Total root length, surface area and root volume increased significantly under mulch compared with those under RM. Lentil grown with mulch and 40SS recorded significantly higher seeds per pod, pods per plant, 1000 seed weight and lentil seed yield than RM and 20SS. Lentil seed yield recorded under mulch was 66.6 and 36.5% higher than that under RM. We concluded that reduced tillage (MT/NT) and residue retention through mulch or 40SS could be adopted to reduce drought stress lentil constraints in rice successions while physical improving soil properties.

Comparative RNA-seq analysis of the drought-sensitive lentil (Lens culinaris) root and leaf under short- and long-term water deficits.

Drought stress is one of the main environmental factors that affects growth and productivity of crop plants, including lentil. To gain insights into the genome-wide transcriptional regulation in lentil root and leaf under short- and long-term drought conditions, we performed RNA-seq on a drought-sensitive lentil cultivar (Lens culinaris Medik. cv. Sultan). After establishing drought conditions, lentil samples were subjected to de novo RNA-seq-based transcriptome analysis. The 207,076 gene transcripts were successfully constructed by de novo assembly from the sequences obtained from root, leaf, and stems. Differentially expressed gene (DEG) analysis on these transcripts indicated that period of drought stress had a greater impact on the transcriptional regulation in lentil root. The numbers of DEGs were 2915 under short-term drought stress while the numbers of DEGs were increased to 18,327 under long-term drought stress condition in the root. Further, Gene Ontology analysis revealed that the following biological processes were differentially regulated in response to long-term drought stress: protein phosphorylation, embryo development seed dormancy, DNA replication, and maintenance of root meristem identity. Additionally, DEGs, which play a role in circadian rhythm and photoreception, were downregulated suggesting that drought stress has a negative effect on the internal oscillators which may have detrimental consequences on plant growth and survival. Collectively, this study provides a detailed comparative transcriptome response of drought-sensitive lentil strain under short- and long-term drought conditions in root and leaf. Our finding suggests that not only the regulation of genes in leaves is important but also genes regulated in roots are important and need to be considered for improving drought tolerance in lentil.