Browsing by Author "Lakshmi B"

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    Characterization of diseases and potential antagonistic endophytes of moringa (Moringa oleifera Lam.)
    (Department of Plant Pathology, College of Agriculture,Vellanikkara, 2024-09-05) Lakshmi B; Anju, C.
    Moringa (Moringa oleifera), commonly known as ‘drumstick tree’ or ‘horseradish tree’ belonging to the family Moringaceace is an indigenous crop widely cultivated in the tropical and subtropical regions. It is a versatile crop with high nutritional value and tolerance to environmental conditions. Despite the antimicrobial properties of the plant, it is affected by several diseases. However, not much information is available in Kerala about the diseases affecting moringa. Hence, this study was aimed to document the diseases affecting moringa and to exploit endophytes for the development of management strategies against the selected pathogens. Sampling surveys were carried out in moringa growing homesteads and nurseries of Thrissur (AEU 2, AEU 6, AEU 10, AEU 14 and AEU 15), Palakkad (AEU 22 and AEU 23) and Wayanad (AEU 20) districts of Kerala. The diseases observed were stem canker, stem blight, stem gall, wilt, dieback, leaf spot, leaf blight and pod rot. Highest PDI and PDS was recorded for stem canker in the surveyed districts. However, stem canker along with leaf spot disease showed highest disease incidence and severity in Thrissur distric t. The highest PDI (100 %) was recorded for stem canker (Chalakudy/ AEU 10, Valapad/ AEU 2 and Ambalavayal/ AEU 20), stem gall (Chalakudy/ AEU 10) and leaf spot (Polukkara/ AEU 10) whereas the highest PDS (75 %) was recorded for stem canker (Chalakudy/ AEU 10). A total of forty-four fungal isolates were obtained from thirty-five diseased samples. The major pathogens isolated from diseased samples were Fusarium, Lasiodiplodia and Colletotrichum. Fusarium spp. (16) was isolated from stem canker, stem gall, wilt, pod rot and leaf spot. Colletotrichum spp. (7) was obtained from stem gall, stem canker and leaf spot. Lasiodiplodia sp. (10) was isolated from stem canker, dieback and leaf spot. Choanephora sp. (1) and Pseudopithomyces sp. (1) were isolated from stem blight, and Curvularia sp. (3) was isolated from stem canker and leaf blight. Molecular characterization of selected ten pathogens through sequencing of ITS region confirmed the identity of isolates. Stem canker pathogen isolates ABLSCF4, VLK2SC2F1, and MDKSC were identified as Fusarium proliferatum, Lasiodiplodia theobromae, and Curvularia lunata respectively. Stem gall pathogen isolates were identified as Colletotrichum gloeosporioides (CKYSGh), Nectria sp. (VLK2SGF1), and Colletotrichum gigasporum (VLK2SGF2). The stem blight pathogen isolate VLK1SB was identified as Pseudopithomyces sacchari, wilt isolate CKYWF2 as Trametes menziesii, leaf spot pathogen isolate PLKLS1 as Colletotrichum fructicola, and the pod rot pathogen isolate CHRPRF2 as Fusarium equiseti. Twelve endophytes (EM 1 to EM 12) were isolated from healthy shoots of moringa from AEU 10 (Thrissur district). The endophytes were tested against eight major pathogens in vitro by dual culture assay. The endophyte isolate EM 6 showed highest inhibition of stem canker pathogens Fusarium sp. (63.33 %), C. lunata (66.97 %) and leaf spot pathogen C. fructicola (65.50 %). EM 2 showed highest inhibition of stem gall pathogen C. gigasporum (68.47 %), and comparable inhibition of leaf spot pathogen C. fructicola (64.77 %). EM 4 recorded highest inhibition of wilt pathogen isolate T. menziesii (67 %) and stem blight pathogen P. sacchari (65.87 %). EM 9 showed highest inhibition of stem canker pathogen L. theobromae (66.23 %) and stem blight pathogen P. sacchari (65.87 %). EM 12 recorded highest inhibition of wilt pathogen Fusarium sp. (60.73 %) and comparable inhibition of stem blight pathogen P. sacchari (65.50 %). The promising three endophyte isolates EM 2, EM 4 and EM 6 were identified as Cerrena sp., Diaporthe sp. and Xylaria feejeensis respectively. Pot culture experiments were carried out to evaluate the effectiveness of endophytes Cerrena sp. (EM 2) and X. feejeensis (EM 6) in managing stem canker caused by Fusarium sp. (ABLSCF1) and leaf spot disease caused by C. fructicola (PLKLS1) in one-month-old moringa seedlings. Treatment with X. feejeensis (EM 6) resulted in the lowest stem canker disease severity (23.63 %). However, the endophytic fungi, Cerrena sp. (EM 2) and X. feejeensis (EM 6) and the biocontrol agents viz., Trichoderma asperellum and Pseudomonas fluorescens proved ineffective in managing leaf spot disease. The treatments with P. fluorescens (67.93 %) and the endophyte isolate X. feejeensis (EM 6) (69.85 %) exhibited the lowest severity of leaf spot disease compared to other treatments.