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

Tackling banded leaf and sheath blight disease of maize through activation of host defense

Maize or corn (Zea mays L.) is the third most important cereal crop in the economy of agriculture. Banded leaf and sheath blight (BLSB) caused by Rhizoctonia solani (= R. solani f. sp. sasakii) is one of the highly devastating soil-borne diseases of maize in South and Southeast Asia. Although the use of resistant varieties is preferred as an eco-friendly and cheapest approach to disease management, unfortunately, no true genetic sources of BLSB resistance are available in maize. Hence, chemically induced resistance in the host plant is considered an alternative strategy against many crop diseases. The present study investigated the basis of BLSB resistance in maize hybrid variety Vivek QPM-9 by seed priming with two plant defense inducers, viz., salicylic acid (SA) and jasmonic acid (JA). Higher concentrations (100 ppm) of SA and JA were significantly more effective against R. solani than the lower concentrations (75 and 50 ppm) in vitro. The study found that the application of SA and JA as exogenous pretreatment resulted in improved seed germination, increased seedling weight, and enhanced overall plant growth. During the Kharif season (June–October) in both 2020 and 2021, under in vivo conditions in a net house, the application of SA at 100 and 75 ppm and JA at 100 ppm resulted in a significant decrease in the percent disease index (PDI) of 46.79%, 47.05%, and 48.85%, respectively. Both plant defense inducers elevated the activity of the enzymes superoxide dismutase (SOD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) in maize at higher concentrations of 100 ppm. Seed priming with a high concentration of the inducers was more effective in suppressing the disease and increasing grain yield under the controlled condition of the net house. The study shows the scope of using need-based fungicides with a reduced amount in the management of fungal diseases of maize by adopting a plant defense inducer-mediated host resistance approach

Structured Framework and Genome Analysis of Magnaporthe grisea Inciting Pearl Millet Blast Disease Reveals Versatile Metabolic Pathways, Protein Families, and Virulence Factors

Magnaporthe grisea (T.T. Herbert) M.E. Barr is a major fungal phytopathogen that causes blast disease in cereals, resulting in economic losses worldwide. An in-depth understanding of the basis of virulence and ecological adaptation of M. grisea is vital for devising effective disease management strategies. Here, we aimed to determine the genomic basis of the pathogenicity and underlying biochemical pathways in Magnaporthe using the genome sequence of a pearl millet-infecting M. grisea PMg_Dl generated by dual NGS techniques, Illumina NextSeq 500 and PacBio RS II. The short and long nucleotide reads could be draft assembled in 341 contigs and showed a genome size of 47.89 Mb with the N50 value of 765.4 Kb. Magnaporthe grisea PMg_Dl showed an average nucleotide identity (ANI) of 86% and 98% with M. oryzae and Pyricularia pennisetigena, respectively. The gene-calling method revealed a total of 10,218 genes and 10,184 protein-coding sequences in the genome of PMg_Dl. InterProScan of predicted protein showed a distinct 3637 protein families and 695 superfamilies in the PMg_Dl genome. In silico virulence analysis revealed the presence of 51VFs and 539 CAZymes in the genome. The genomic regions for the biosynthesis of cellulolytic endo-glucanase and beta-glucosidase, as well as pectinolytic endo-polygalacturonase, pectin-esterase, and pectate-lyases (pectinolytic) were detected. Signaling pathways modulated by MAPK, PI3K-Akt, AMPK, and mTOR were also deciphered. Multicopy sequences suggestive of transposable elements such as Type LTR, LTR/Copia, LTR/Gypsy, DNA/TcMar-Fot1, and Type LINE were recorded. The genomic resource presented here will be of use in the development of molecular marker and diagnosis, population genetics, disease management, and molecular taxonomy, and also provide a genomic reference for ascomycetous genome investigations in the future

Hybrid de novo genome-reassembly reveals new insights on pathways and pathogenicity determinants in rice blast pathogen Magnaporthe oryzae RMg_Dl

AbstractBlast disease incited by Magnaporthe oryzae is a major threat to sustain rice production in all rice growing nations. The pathogen is widely distributed in all rice paddies and displays rapid aerial transmissions, and seed-borne latent infection. In order to understand the genetic variability, host specificity, and molecular basis of the pathogenicity-associated traits, the whole genome of rice infecting Magnaporthe oryzae (Strain RMg_Dl) was sequenced using the Illumina and PacBio (RSII compatible) platforms. The high-throughput hybrid assembly of short and long reads resulted in a total of 375 scaffolds with a genome size of 42.43 Mb. Furthermore, comparative genome analysis revealed 99% average nucleotide identity (ANI) with other oryzae genomes and 83% against M. grisea, and 73% against M. poe genomes. The gene calling identified 10,553 genes with 10,539 protein-coding sequences. Among the detected transposable elements, the LTR/Gypsy and Type LINE showed high occurrence. The InterProScan of predicted protein sequences revealed that 97% protein family (PFAM), 98% superfamily, and 95% CDD were shared among RMg_Dl and reference 70-15 genome, respectively. Additionally, 550 CAZymes with high GH family content/distribution and cell wall degrading enzymes (CWDE) such endoglucanase, beta-glucosidase, and pectate lyase were also deciphered in RMg_Dl. The prevalence of virulence factors determination revealed that 51 different VFs were found in the genome. The biochemical pathway such as starch and sucrose metabolism, mTOR signaling, cAMP signaling, MAPK signaling pathways related genes were identified in the genome. The 49,065 SNPs, 3267 insertions and 3611 deletions were detected, and majority of these varinats were located on downstream and upstream region. Taken together, the generated information will be useful to develop a specific marker for diagnosis, pathogen surveillance and tracking, molecular taxonomy, and species delineation which ultimately leads to device improved management strategies for blast disease.</jats:p