Search

Stalk rot disease is a major constraint in maize production and till date reported to be caused by two to three species of phytopathogenic fungi but, in our present study, we disclose the first report of stalk rot is caused by complex species of phytopathogens, which belongs to five different genera. Therefore, to substantiate these findings, a total of 105 diseased samples of maize were collected from 21 different locations in six different geographical locations of India from which 48 isolates were used for the research study. Morphological features such as pigmentation, colony color, type of mycelium and pattern of mycelium was examined using macro and microscopic methods. A total of 11 different spp. of pathogens belonging to the five different genera: Fusarium verticillioides (56.25%), F. equiseti (14.5%), F. andiyazi (6.25%), F. solani (2.08%), F. proliferatum (2.08%), F. incarnatum (2.08%), Lasidioplodia theobrame (6.25%), Exserohilum rostrtum (4.16%), Nigrospora spp. (4.16%). and Schizophyllum commune (2.08%) were identified by different housekeeping genes (ITS, TEF-1α, RPB2 and Actin). Fusarium verticillioides, F. equiseti and F. andiyazi were major pathogens involved in stalk rot. This is the first report on F. proliferatum, F. solani, F. incarnatum, Lasidioplodia theobrame, Exserohilum rostrtum, Nigrospora spp. and Schizophyllum commune causing stalk rot of maize and their distribution in the different states of India. Studies on population dynamics of PFSR will enhance the understanding of pathogen behavior, virulence, or its association with different pathogens across India, which will facilitate the development of resistant maize genotypes against the PFSR. [ABSTRACT FROM AUTHOR]

Post flowering stalk rot (PFSR) of maize caused by the Fusarium species complex is a serious threat to maize production worldwide. The identification of Fusarium species causing PFSR based on morphology traditionally relies on a small set of phenomic characteristics with only minor morphological variations among distinct Fusarium species. Seventy-one isolates were collected from 40 sites in five agro-climatic zones of India to assess the diversity of Fusarium spp. associated with maize crops showing symptoms of PFSR in the field. To investigate the pathogenicity of Fusarium spp. causing PFSR sixty isolates were toothpick inoculated between the first and second node at 55 days after sowing during the tassel formation stage of the crop in Kharif (Rainy season), and Rabi (Winter season) season field trials. Ten most virulent Fusarium isolates, based on the highest observed disease index, were identified by homology and phylogenetic analyses of partial sequences of the translation elongation factor 1 α (Tef-1α). Based on morphological traits such as mycelial growth patterns and mycelial pigmentation, Fusarium isolates were divided into nine clusters. The isolates were judged to be virulent based on their ability to decrease seedling vigour in in-vivo situations and high disease severity in field experiments. Pathogenicity test during the Kharif season showed 12 isolates with virulent disease symptoms with a mean severity ranging between 50 to 67 percent disease index (PDI) whereas in Rabi season, only five isolates were considered virulent, and the mean severity ranged between 52 to 67 PDI. Based on pathological characterization and molecular identification, 10 strains of Fusarium species namely, Fusarium acutatum (2/10), Fusarium verticillioides (Syn. Gibberella fujikuroi var. moniliformis) (7/10), Fusarium andiyazi (2/10) recorded the highest diseases index. All these species are part of the Fusarium fujikuroi species complex (FFSC). The distribution of virulent isolates is specific to a geographical location with a hot humid climate. Increased knowledge regarding the variability of Fusarium spp. responsible for PFSR of maize occurring across wide geographical locations of India will enable more informed decisions to be made to support the management of the disease, including screening for resistance in maize-inbred lines. [ABSTRACT FROM AUTHOR]

Fusarium spp. complex, (Fusarium verticillioides, F. subglutinans, F. moniliforme, F. graminearum) causing post flowering stalk rot (PFSR), has been reported as a serious disease in southern Rajasthan, and eastern Gujarat in winter maize. In the present study, emphasis has been laid on the efficacy of twenty seven Trichoderma strains against F. verticillioides which is a major causal organism. Efficacy evaluation of Trichoderma strains was based on the radial growth of the pathogen in the presence of biological control agent (BCA). Based on per cent inhibition three potential native strains of Trichoderma spp (Trichoderma harzianum BThr29, T. asperellum BTas25, and T. erinaceum BTer43) were selected for biological control of PFSR in the field. T. harzianum BThr29, T. asperellum BTas25, and T. erinaceum BTer43 showed per cent inhibition of F. verticillioides by 87.8, 83.9, and 81.1 percent respectively. Maize plants were artificially inoculated with F. verticillioides, and three potential Trichoderma strains were delivered as soil application (Trichoderma enriched FYM 10 tones ha−1), seed treatment (10 g/kg seeds), and drenching (10 g/liter water). Split stem observation at the harvest of crop showed a restricted lesion of T. harzianum BThr29 treated plant at par with fungicidal application with an average mean rating scale of 1–1.3, which showed less than 50% discoloration in inoculated internode. In control, the mean disease rating scale was 3–3.4 which showed 51–75% of the inoculated internode is discolored. Application of Trichoderma strains improved crop stand by reducing lodging from 42.1 to 71.1% in inoculated maize plants, and reduced PFSR disease severity from 17.58 to 62.37%, Fungicidal application reduced lodging of maize plant from 57.91 to 77.78% and PFSR disease by 58.24–64.35% as compared to untreated control. The results obtained suggested that Trichoderma harzianum BThr29 has the potential to be used as a non-chemical alternative for PFSR disease management in maize crops. [Display omitted] • Fusarium verticillioides was a major cause of post flowering stalk rot (PFSR). • Trichoderma spp. BThr29, BTas25, and BTer43 were found highly antagonistic. • F. verticillioides Fuv3 was used for artificial inoculation assess pathogenicity. • Treatments with T. harzianum BThr29 managed PFSR at par with fungicidal treatment. [ABSTRACT FROM AUTHOR]