Assessment of mycoviral diversity in Pakistani fungal isolates revealed infection by 11 novel viruses of a single strain of Fusarium mangiferae isolate SP1

An extensive screening survey was conducted on Pakistani filamentous fungal isolates for the identification of viral infections. A total of 396 fungal samples were screened, of which 36 isolates were found double-stranded (ds) RNA positive with an overall frequency of 9% when analysed by a classical dsRNA isolation method. One of 36 dsRNA-positive strains, strain SP1 of a plant pathogenic fungus Fusarium mangiferae, was subjected to virome analysis. Next-generation sequencing and subsequent completion of the entire genome sequencing by a classical Sanger sequencing method showed the SP1 strain to be co-infected by 11 distinct viruses, at least seven of which should be described as new taxa at the species level according to the ICTV (International Committee on Taxonomy of Viruses) species demarcation criteria. The newly identified F. mangiferae viruses (FmVs) include two partitivirids, one betapartitivirus (FmPV1) and one gammapartitivirus (FmPV2); six mitovirids, three unuamitovirus (FmMV2, FmMV4, FmMV6), one duamitovirus (FmMV5), and two unclassified mitovirids (FmMV1, FmMV3); and three botourmiavirids, two magoulivirus (FmBOV1, FmBOV3) and one scleroulivirus (FmBOV2). The number of coinfecting viruses is among the largest ones of fungal coinfections. Their molecular features are thoroughly described here. This represents the first large virus survey in the Indian sub-continent.

Biosynthesis of Fusapyrone Depends on the H3K9 Methyltransferase, FmKmt1, in Fusarium mangiferae

The phytopathogenic fungus Fusarium mangiferae belongs to the Fusarium fujikuroi species complex (FFSC). Members of this group cause a wide spectrum of devastating diseases on diverse agricultural crops. F. mangiferae is the causal agent of the mango malformation disease (MMD) and as such detrimental for agriculture in the southern hemisphere. During plant infection, the fungus produces a plethora of bioactive secondary metabolites (SMs), which most often lead to severe adverse defects on plants health. Changes in chromatin structure achieved by posttranslational modifications (PTM) of histones play a key role in regulation of fungal SM biosynthesis. Posttranslational tri-methylation of histone 3 lysine 9 (H3K9me3) is considered a hallmark of heterochromatin and established by the SET-domain protein Kmt1. Here, we show that FmKmt1 is involved in H3K9me3 in F. mangiferae. Loss of FmKmt1 only slightly though significantly affected fungal hyphal growth and stress response and is required for wild type-like conidiation. While FmKmt1 is largely dispensable for the biosynthesis of most known SMs, removal of FmKMT1 resulted in an almost complete loss of fusapyrone and deoxyfusapyrone, γ-pyrones previously only known from Fusarium semitectum. Here, we identified the polyketide synthase (PKS) FmPKS40 to be involved in fusapyrone biosynthesis, delineate putative cluster borders by co-expression studies and provide insights into its regulation.

FIELD CASE INVESTIGATIONS OF MANGO MALFORMATION DISEASE IN FIVE DISTRICTS OF SOUTHERN PUNJAB AND ITS BIOLOGICAL MEDIATED MANAGEMENT UNDER CONTROLLED CONDITIONS

Mango is the king of fruits and keeps the status of national tree in some countries. Pakistani Mangoes are considered to the best in the world due to its shape, taste, flavor and deliciousness. Mango malformation is said to be the hundred century old disease consistently a source of losses for the mango industry. Extensive mango orchard’s survey showed a dynamic presence of the disease in the orchards. On the basis of visual systems the trees were evaluated and hence maximum disease severity (41.44) was recorded in District Layyah where the soils were observed more clayey as compared to the other districts of the South Punjab. Similarly, Multan ranked second in the infestation of Mango Malformation disease severity in the orchards while (30.11) was calculated in Lodhran followed by Muzaffar-Garh with (27.11) and Khanewal with (23.33). The fungus was identified as Fusarium mangiferae under the microscope and for the biological mediated management of the pathogen as hypothesized that if successful may be the best possible solution for the management of the disease in the orchards by utilizing the various Trichoderma spp. T. harzianum gave best control against F.mangiferae by depicting 71% inhibition against the pathogenic fungi. The use of Trichoderma spp against the pathogenic fungi will open new avenues in the biological control tactics of the plant diseases.

IMPACT OF ENVIRONMENTAL VARIABLES ON SPORE DISPERSAL TREND OF FUSARIUM MANGIFERAE CAUSING MANGO MALFORMATION DISEASE IN PAKISTAN

Malformation is one of the most destructive mango diseases. Although trees are not killed, the vegetative phase of the disease impedes canopy development during vegetative phase of the host plant and floral phase dramatically reduces fruit yield with overwintering inoculums during dormant phase of the host plant. Environmental conditions and trend of spore liberation of its pathogenic fungus “Fusarium mangiferae” were recorded during flowering phase (Feb-April, 2014), fruit development phase (May-July, 2014), vegetative phase (Aug-Oct, 2014), and dormant phase (Nov-Jan, 2014-15), of the mango plants. Through installation of spore traps of various distance levels containing Nash-Synder media in petri plates. During these phases, different environmental variables including temperature (T), relative humidity (R.H) and wind speed (W.S) were observed. Maximum number of colonies were observed through the spores trapped from the centre of the experimental block (0m) while minimum numbers of colonies were developed from the spores trapped at 150 m distance. Amongst different phenological phases of mango, fruit development remained very much contaminated with spores of the fungus while minimum spore liberation was noted during flowering phase of mango indicating very rare infection during this phase. This study also reflected that maximum number of airborne macro conidia of F. mangiferae were recorded when R.H was below 55%. Low R.H appeared to be a major factor associated with the diurnal conidial dispersal of airborne pathogen. Hence primary infection of F. mangiferae starts from vegetative and floral buds differentiation and control strategy including spray of systemic fungicides should start at this stage of development.