Effect of fungal biocontrol agents on enhancement of drought stress tolerance in rice (Oryza sativa L.)

Rice is the staple food crop for about half of the population of the world. Drought is a major stress limiting factor of this crop. In the recent years, biocontrol agents like Trichoderma spp. have become popular as plant growth promoter and shown to enhance drought tolerance in plants. Therefore, present investigation investigation was undertaken to evaluate the different biocontrol agents i.e. Trichoderma harzinum 1, Trichoderma harzianum 2, Chaetomium globosum and Talaromyces flavus against the drought in resistant (DRR 42 and Sahbhagi Dhan) and susceptible (IR 64) varieties of rice. Prior to sowing seeds were bioprimed separately with each isolates of Trichoderma harzianum @ 10g/kg and were sown in pots. Drought treatment of 4 days, 7 days, 10 days and 13 days were given as per the standard protocol. Biocontrol agent Trichoderma harzianum (T2) was observed most effective for drought tolerance followed by Chaetomium globosum. After 13 days of drought treatment minimum wilting (20%) was observed in Sahbhagi Dhan treated with Trichoderma harzianum 2. Four and 10 days drought stressed plants were subjected to different biochemical analysis. Significantly positive correlation (r = 0.91) was observed between wilting and Malondialdehyde (MDA) content. While negative correlation (r = −0.67) was observed between wilting and average plant weight. Study suggested that Trichoderma harzianum 2 treatment during drought stress in rice plants can delay the drought upto 3-5 days

Expression analysis of maize genes during Bipolaris maydis infection and assessing their role in disease resistance and symptom development

82-93Bipolaris maydis causing maydis leaf blight (MLB) is an aggressive fungal pathogen of maize. The present study focused on the responses of certain defence genes in the resistant and susceptible maize inbred lines viz., SC-7 and CM 119, respectively, against MLB and symptom development in the host. Biochemical activity of the PR protein β-1, 3-glucanase and phenylalanine ammonia lyase (PAL) assay, with total chlorophyll content was recorded for both the inbred lines before and after pathogen inoculation. Gene expression was studied by quantitative polymerase chain reaction (qPCR) at different time intervals post inoculation. Differential expression pattern was observed even at the same time point in both the inbred lines. Enhanced expression of the pathogenesis related (PR) protein and phenylalanine ammonia lyase (PAL) enzyme at different time points in resistant lines indicated their association with infection stages of B. maydis and response of the resistant line against disease establishment. Down regulated gene expression of pheophytinase suggests reduced enzyme activity linked with less chlorophyll degradation in the resistant line compared to the susceptible line. This fact directly correlates with symptom development of MLB disease. The present study thus revealed that the expression of defence related genes is aligned with developmental stages of the pathogen to restrict its growth and gene expression of constitutive genes also changes differentially during the disease development in resistant and susceptible lines

Genetic diversity and population structure of Fusarium fujikuroi causing Bakanae, an emerging disease of rice in India

45-52Bakanae caused by Fusarium fujikuroi (Nirenberg), is emerging as a serious threat for rice (Oryza sativa. L.) cultivation in India. In this study, 63 isolates of Fusarium fujikuroi isolated from symptomatic diseased plants were characterized for their morphology, pathogenicity and molecular variability using universal rice primers (URP). Of the 12 URPs used in the study, 6 primers could produce polymorphic fragments in all the isolates. The URP 17R primer was highly polymorphic (100%), whereas, the URP 1F primer produced 75% polymorphic fragments. A dendrogram obtained from the combined analysis of 6 URP primers categorized the isolates into four clusters, where most of the isolates from Punjab and Haryana were clustered separately. Mating type of the population was identified based on MAT-1 and MAT-2 region universal primers for Gibberella fujikuroi. Among the 63 isolates, 18 (28.57%) were identified as MAT-1 and 45 (71.42%) as MAT-2. The effective population number for mating type was 89% of the total population. Since the distribution frequencies of both mating types were not equal in the Indian population of F. fujikuroi, it could conclude that majority of the multiplication of isolates under field conditions was through asexual reproduction. However, the presence of both mating types in F. fujikuroi indicates that the population is also capable of sexual reproduction. Therefore, it is important to develop cultivars with inbuilt resistance to bakanae disease, taking into consideration the factors such as environmental conditions and variability of the pathogen in the area of intended cultivation

Utilization of fungal biocontrol agents against rice sheath blight disease provides insight into their role in plant defense responses

Biotic and abiotic factors have an effect on rice production all around the world. Diseases are regarded as major restrictions among the biotic stressors, and rice sheath blight (Rhizoctonia solani Kühn) is one of the most calamitous diseases that significantly damage the crop. Lately, biocontrol of fungal plant pathogens has appeared as an appealing approach. The present investigation was undertaken to evaluate different biocontrol agents like Talaromyces flavus, Chaetomium globosum, Pseudomonas fluorescens and Aspergillus niger against sheath blight disease. Prior to sowing, seeds were bioprimed with each isolate and sown in the nursery. After 21 days, seedlings were transplanted in-vivo and were inoculated with a virulent isolate of Rhizoctonia solani at maximum tillering stage. Observations on biochemical parameters and gene expression studies were carried out at 24, 48, 72, and 96 hpi. Enzymatic activity viz., chitinase, β-1,3-glucanase, catalase, and PAL was observed  maximum in Chaetomium globosum. PR-genes viz., IPT, BrD, HmPr, AMP, AldD, NIC and LisH showed up-regulation at 96 hpi. Chaetomium globosum had the highest yield, maximum number of tillers with least RLH% as compared to other treatments. However, results indicated biocontrol agents are helpful and they induce multitude of defence responses against R. solani in rice

Genetic diversity and population structure of Fusarium fujikuroi causing Bakanae, an emerging disease of rice in India

Bakanae caused by Fusarium fujikuroi (Nirenberg), is emerging as a serious threat for rice (Oryza sativa. L.) cultivation in India. In this study, 63 isolates of Fusarium fujikuroi isolated from symptomatic diseased plants were characterized for their morphology, pathogenicity and molecular variability using universal rice primers (URP). Of the 12 URPs used in the study, 6 primers could produce polymorphic fragments in all the isolates. The URP 17R primer was highly polymorphic (100%), whereas, the URP 1F primer produced 75% polymorphic fragments. A dendrogram obtained from the combined analysis of 6 URP primers categorized the isolates into four clusters, where most of the isolates from Punjab and Haryana were clustered separately. Mating type of the population was identified based on MAT-1 and MAT-2 region universal primers for Gibberella fujikuroi. Among the 63 isolates, 18 (28.57%) were identified as MAT-1 and 45 (71.42%) as MAT-2. The effective population number for mating type was 89% of the total population. Since the distribution frequencies of both mating types were not equal in the Indian population of F. fujikuroi, it could conclude that majority of the multiplication of isolates under field conditions was through asexual reproduction. However, the presence of both mating types in F. fujikuroi indicates that the population is also capable of sexual reproduction. Therefore, it is important to develop cultivars with inbuilt resistance to bakanae disease, taking into consideration the factors such as environmental conditions and variability of the pathogen in the area of intended cultivation

Temporal transcriptome of tomato elucidates the signaling pathways of induced systemic resistance and systemic acquired resistance activated by Chaetomium globosum

C. globosum is an endophytic fungus, which is recorded effective against several fungal and bacterial diseases in plants. The exclusively induce defense as mechanism of biocontrol for C. globosum against phyto-pathogens is reported. Our pervious study states the effectiveness of induced defense by C. globosum (Cg), in tomato against Alternaria solani. In this study the temporal transcriptome analysis of tomato plants after treatment with C. globosum was performed for time points at 0 hpCi, 12 hpCi, 24 hpCi and 96 phCi. The temporal expression analysis of genes belonging to defense signaling pathways indicates the maximum expression of genes at 12 h post Cg inoculation. The sequential progression in JA signaling pathway is marked by upregulation of downstream genes (Solyc10g011660, Solyc01g005440) of JA signaling at 24 hpCi and continued to express at same level upto 96 hpCi. However, the NPR1 (Solyc07g040690), the key regulator of SA signaling is activated at 12 h and repressed in later stages. The sequential expression of phenylpropanoid pathway genes (Solyc09g007920, Solyc12g011330, Solyc05g047530) marks the activation of pathway with course of time after Cg treatment that results in lignin formation. The plant defense signaling progresses in sequential manner with time course after Cg treatment. The results revealed the involvement of signaling pathways of ISR and SAR in systemic resistance induced by Cg in tomato, but with temporal variation

Fine mapping of qBK1.2, a major QTL governing resistance to bakanae disease in rice

Bakanae disease caused by Fusarium fujikuroi is an emerging disease of rice causing losses in all rice-growing regions around the world. A BC2F2 population was developed by backcrossing the recurrent parent Pusa Basmati 1121 (PB1121) with the recombinant inbred line RIL28, which harbors a major quantitative trait locus (QTL) governing resistance to bakanae, qBK1.2. MassARRAY-based single-nucleotide polymorphism (SNP) assays targeting the genomic region of qBK1.2 helped in fine mapping the QTL to a region of 130 kb between the SNP markers rs3164311 and rs3295562 using 24 recombinants. In-silico mining of the fine-mapped region identified 11 putative candidate genes with functions related to defense. The expression analysis identified two significantly differentially expressed genes, that is, LOC_Os01g06750 and LOC_Os01g06870, between the susceptible genotype PB1121 and the resistant genotypes Pusa1342 and R-NIL4. Furthermore, the SNPs identified in LOC_Os01g06750 produced minor substitutions of amino acids with no major effect on the resistance-related functional motifs. However, LOC_Os01g06870 had 21 amino acid substitutions, which led to the creation of the leucine-rich repeat (LRR) domain in the resistant genotype Pusa1342, thereby making it a potential candidate underlying the major bakanae-resistant QTL qBK1.2. The markers used in the fine mapping program are of immense utility in marker-assisted breeding for bakanae resistance in rice

<span style="font-size:10.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-US">Synthesis of Schiff bases of 4-amino-3-mercapto-5-pyridin-4yl-4<i style="mso-bidi-font-style:normal">H</i>-1,2,4-triazole and their evaluation as SAR inducers</span>

1260-1274A series of twenty five Schiff bases 6a-y of 4-amino-3-mercapto-5-pyridin-4yl-4H-1,2,4-triazole having different substitution in the aryl ring attached to imine group designed incorporating the isonicotinic acid moiety present in INA, a known SAR inducer have been synthesized and characterized using 1H and 13C NMR, FT–IR spectroscopy and elemental analysis. All twenty five Schiff bases, 4-arylideneamino-3-mercapto-5-pyridin-4-yl-4H-1,2,4-triazoles have been screened for systemic acquired resistance (SAR) inducing activity against sheath blight of rice and five potential compounds viz. <b style="mso-bidi-font-weight: normal">6f, 6g, 6r, 6t and 6u analogues have been further evaluated. All the five compounds have considerably decreased the relative lesion height (RLH) as compared to control with maximum reduction in RLH shown by compound 6u (47.15%). These five potential compounds have been further studied for their effect on phenol content, PAL and peroxidase activity. The compound 6u has been identified as the most potent SAR inducer both based on phenotypic and biochemical study and also does not show direct fungicidal activity against R. solani. Its RI activity is found better than 2,6-dichloroisonicotinic acid (INA), a resistance inducing chemical used as standard. </span

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