Eco-Friendly Management of Leaf Spot of Spinach (Spinacia oleracea L.) Caused by Alternaria alternata (Fr.) Keissler
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Date
2024
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MPUAT, Udaipur
Abstract
The present study was undertaken on “Eco-friendly management of leaf spot
of spinach caused by Alternaria alternata”. The investigations have various aspects
viz., isolation of pathogen, identification, pathogenicity test, cultural and
morphological characteristics of pathogen in laboratory and evaluation of host plant
resistance, fungicides, bio-agents and botanicals in vitro and field condition for the
management of alternaria leaf spot of spinach.
The pathogen was isolated and purified by single spore isolation technique
from diseased leaves of spinach. The pathogencity of Alternaria alternata was proved
on susceptible spinach cultivar “All Green” in cage-house.
The growth of culture studied in in vitro, showed olive green with regular
margin and on later turned grey to dark brown and black colour. Conidiophore were
simple cylindrical branched to un-branched and thick walled with 1–4 septate and
dark brown in colour. Conidia were pale brown to dark brown in colour and obclavate
to obpyriform (muriform) with four to five transverse and zero to two longitudinal
septa. The size of conidia was measured within the range of 22-34 μm long × 12-16
μm wide (Average size of conidia 27.40 μm long × 13.90 μm wide).
Five spinach cultivars viz., “Swarna”, “Green Star”, “Ever Green”, “Desi
palak” and “All Green” were tested against alternaria leaf spot. Cultivar “Swarna”
showed minimum per cent disease index 22.53% followed by “Desi Palak” with
24.33% disease index under inoculated condition.
Seven fungicides were tested for mycelial growth inhibition of Alternaria
alternata in the laboratory. Among these tebuconazole 50% + trifloxystrobin 25%
(75WG) was found most effective with complete inhibition (100%) of mycelial
growth followed by tebuconazole 25.9% EC was found effective at all tested
concentration against the pathogen while, among four bio-agents Trichoderma viride
was found most effective with 70.00% growth inhibition. Similarly, out of five phyto- extracts tested in vitro against A. alternata, garlic clove extract was found most
effective with 63.06%, 75.28%, and 81.94% at 5, 10 and 15 per cent concentration
respectively.
A field experiment was conducted by using promising treatments for
integrated management of alternaria leaf spot of spinach on susceptible cultivar “All
Green” on the basis of in vitro studies. Among different seven treatments “seed
treatment with tebuconazole 50% + trifloxystrobin 25% (75WG) @0.1% + two foliar
spray of garlic clove extract @10% + T. viride @ 2% having 2.5×106 c.f.u.ml-1
showed maximum efficacy of disease control 81.09, 76.13, 76.77 at 30, 45 and 60
days after sowing respectively. This treatment also gave maximum spinach leafy yield
4.10, 4.35 and 4.57 kg per plot at Ist, IInd and IIIrd cuttings respectively
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Citation
Jat S. and Bunker R. N.