V. P. Gupta

Bio: V. P. Gupta is an academic researcher from Government Medical College, Thiruvananthapuram. The author has contributed to research in topics: Mental health & ICD-10. The author has an hindex of 3, co-authored 9 publications receiving 42 citations.

Surface Ultrastructural Studies on Penetration and Infection Process of Colletotrichum gloeosporioides on Mulberry Leaf Causing Black Spot Disease

Abstract: Unicelled conidia of Colletotrichum gloeosporioides germinated 3 h after inoculation producing single germ tubes. The orientation of the germ tubes and their lateral branches as they grew was towards the open stomata and away from closed stomata. By 24 h post-inoculation, the lateral branches had developed specialized infection vesicles either over the stomata or within the stomatal cavities. The infection vesicles produced primary infection hyphae which entered the leaves through stomatal openings. The disease symptoms became apparent by 6 days post-inoculation when clusters of abundant conidiophores emerged by rupturing the leaf epidermal layer, forming acervuli mostly near the base of idioblasts. The pressure exerted by the emerging conidiophores caused stretching of epidermal layer leading to the widening of the acervuli. The conidia are borne on the tips of the erect conidiophores.

Scanning electron microscopy on the perithecial development of Phyllactinia corylea on Mulberry-II. Sexual stage

Abstract: Development of perithecia of Phyllactinia corylea (Pers.) Karst. on mulberry (Morus spp.) leaves was examined by scanning electron microscopy. Two short specialized structures, antheridium and ascogonium, emerged from two separate hyphae, were fused with each other and developed into an egg-shaped perithecial primordia. These primordia later developed into globose immature perithecia, which covered with protruded wall cells with clear margins. A large number of hyphae emerged from near the base of globose perithecia, which radiated on the leaf surface and thus helped the perithecia to fix to the surface. Specific characteristic penicillate cells and acicular appendages originated from the immature perithecia. The penicillate cells developed with apical sterigma-like projections from the wall cells of the upper part of immature perithecia, whereas the acicular appendages originated from the shrunken wall cells at the perithecial equatorial planes. On maturation of perithecia, the acicular appendages bent down and pushed the perithecia above the substrate and thus helped them to liberate out. The sterigma-like projections were covered with paste-like granular substance, which help the dispersed perithecia to attach to mulberry leaves and branches.

Puccinia romagnoliana Marie & Sacc. – a Potential Bioherbicide Agent for Biocontrol of Purple Nutsedge (Cyperus rotundus L.) in Mulberry

Abstract: The ingress, infection process and disease development of Puccinia romagnoliana Marie & Sacc. on purple nutsedge (Cyperus rotundas L.) and its cross-infectivity to an economically important sericultural crop, mulberry (Mores alba L.) were investigated under a scanning electron microscope. The potential of P. romagnoliana as a biocontrol agent was also evaluated for the control of purple nutsedge under greenhouse conditions. Uredinia of P. romagnoliana were paraphysate that bore numerous pedicellate urediniospores, having echinulate spore wall. Urediniospores had 2-3 subequatorial germpores, which gave rise to germtubes. Germtubes were observed to orientate toward stomata and terminated in appressoria, through which infection pegs were formed that penetrated the leaf. Symptoms developed on leaves 10 days after inoculation. P. romagnoliana was highly pathogenic to purple nutsedge, which, when disease was severe, caused death of the shoots and reduced both number and vigour of the tubers. P. romagnoliana did not infect the main commercial crop, mulberry. Thus, the present study demonstrated the potential of P. romagnoliana as a bioherbicide to control the purple nutsedge in mulberry fields.

Mulberry Shoot Blight: Axenic Culture, Pathogenicity and Plant-Pathogen Interaction

Abstract: Occurrence of a new disease, shoot blight was observed afflicting mulberry (Morus spp.) in the southern peninsula of India. The disease initiated as marginal burning or blackening of leaf lamina which later spread across the whole lamina and then to the stems of affected shoots, resulting in the drooping of the entire shoot and complete death of the affected plants. On isolation of the causal organism, a bacterial isolate was found to be associated with the disease symptoms, which was identified as Xanthomonas campestris pv. mori. Scanning electron microscopic (SEM) examination of cross sections of stems revealed the presence of rod-shaped bacteria inside xylem vessels of affected plants. This indicates the vascular translocation and colonization of X. campestris pv. mori which resulted in shoot blight in mulberry.

Pathogenicity and Polyhedra Morphology of Spilarctia obliqua Nucleopolyhedrosis Virus

Abstract: Spilarctia obliqua(Wlk.) is a serious pest of mulberry which is naturally affected by its nucleopolyhedrosis virus (SoNPV) in field conditions. The polyhedral occlusion bodies (POB's) were hexahedron under scanning and transmission electron microscope and measured 0.42 to 0.67 in diameter. The symptoms of NPV infected S. obliqua larvae resembled with that of other NPVs' infected lepidopterous larvae. The pathogenicity and potentiality of this virus against S. obliqua was tested in the laboratory conditions and the results showed 100% mortality in larvae inoculated with SoNPV at 6.23 POBs/ml. Therefore, SoNPV appears to have a high potential as a microbial biocontrol agent against S. obliqua larvae.

Elevated CO2 reduces disease incidence and severity of a red maple fungal pathogen via changes in host physiology and leaf chemistry

Abstract: Atmospheric CO2 concentrations are predicted to double within the next century Despite this trend, the extent and mechanisms through which elevated CO2 affects plant diseases remain uncertain In this study, we assessed how elevated CO2 affects a foliar fungal pathogen, Phyllosticta minima ,o fAcer rubrum growing in the understory at the Duke Forest free-air CO2 enrichment experiment in Durham, North Carolina Surveys of A rubrum saplings in the 6th, 7th, and 8th years of the CO2 exposure revealed that elevated CO2 significantly reduced disease incidence, with 22%, 27%, and 8% fewer saplings and 14%, 4%, and 5% fewer leaves infected per plant in the three consecutive years, respectively Elevated CO2 also significantly reduced disease severity in infected plants in all years (eg mean lesion area reduced 35%, 50%, and 10% in 2002, 2003, and 2004, respectively) To assess the mechanisms underlying these changes, we combined leaf structural, physiological and chemical analyses with growth chamber studies of P minima growth and host infection In vitro exponential growth rates of P minima were enhanced by 17% under elevated CO2, discounting the possibility that disease reductions were because of direct negative effects of elevated CO2 on fungal performance Scanning electron micrographs (SEM) verified that conidia germ tubes of P minima infect A rubrum leaves by entering through the stomata While stomatal size and density were unchanged, stomatal conductance was reduced by 21‐36% under elevated CO2, providing smaller openings for infecting germ tubes Reduced disease severity under elevated CO2 was likely due to altered leaf chemistry and reduced nutritive quality; elevated CO2 reduced leaf N by 20% and increased the C:N ratio by 20%, total phenolics by 15%, and tannins by 14% (Po005 for each factor) The potential dual mechanism we describe here of reduced stomatal opening and altered leaf chemistry that results in reduced disease incidence and severity under elevated CO2 may be prevalent in many plant pathosystems where the pathogen targets the stomata

Comparative proteomic analysis provides new insights into mulberry dwarf responses in mulberry (Morus alba L.).

Abstract: Mulberry dwarf (MD) is a serious infectious disease of mulberry caused by phytoplasma. Infection with MD phytoplasma results in stress phenotypes of yellowing, phyllody, stunting, proliferation, and witches' broom. Physiological and biochemical analysis has shown that infection with MD phytoplasma causes an increase in soluble carbohydrate and starch content, and a decrease in the net photosynthesis rate, carboxylation efficiency, and pigment content of leaves. Furthermore, damage to the chloroplast ultrastructure was detected in infected leaves. To better understand the pathogen-stress response of mulberry (Morus alba L.) to MD phytoplasma, we conducted a comparative proteomic analysis using 2-DE of infected and healthy leaves. Among 500 protein spots that were reproducibly detected, 20 were down-regulated and 17 were up-regulated. MS identified 16 differentially expressed proteins. The photosynthetic proteins rubisco large subunit, rubisco activase, and sedoheptulose-1,7-bisphosphatase showed enhanced degradation in infected leaves. Based these results, a model for the occurrence mechanism of MD is proposed. In conclusion, this study provides new insights into the mulberry response to MD phytoplasma infection.