MSc

The study entitled “Schizophyllum commune for the management of
Colletotrichum leaf blight of turmeric’’ was carried out at College of Agriculture,
Vellayani during 2021-2023, with the objective of characterization and utilization of
antimicrobial compounds from S. commune for the management of Colletotrichum leaf
blight of turmeric.
Survey was conducted during October 2022-February 2023 in three districts of
Kerala, viz., Thiruvananthapuram, Kollam and Alappuzha to study about the disease
incidence (DI) and disease severity (PDI) of leaf blight of turmeric. The disease incidence
ranged between 31.12 – 55.11% and disease severity between 24.32 – 62.00 %. The
highest DI and PDI was observed at Neyyattinkara location of Thiruvananthapuram. The
common symptom observed in surveyed area was brownish necrotic blighting from tip or
margin with prominent yellow halo. Ten fungal isolates were obtained, sub-cultured and
purified. Pathogenicity of these fungal isolates were proved. The pathogen was identified
as Colletotrichum sp.
The morphological studies of Colletotrichum sp. revealed that mycelial width,
septal distance and conidial size ranged from 1.01- 1.85 µm, 13.41-7.98 µm and 9.10 ×
3.70 - 18.54 × 4.50 µm2 respectively. The conidial shape was either dumbbell or oblong.
Colony colour was either off white, ash grey or dark grey. Colletotrichum isolate C6 was
identified as the most virulent (Sadanandapuram from Thiruvanathapuram) after
virulence rating. The molecular characterization of isolate C6 was done using ITS primers
where it had the maximum identity with Colletotrichum gloeosporioides. Morphological,
cultural and molecular characterization is done and identified C6 isolate as C.
gloeosporioides.
The mycelial growth of Schizophyllum commune was either fluffy, cottony or
sparse. The mycelial growth rate was maximum in SC5 (S. commune 5; DMRX-2160)
followed by SC3 (S. commune 3; DMRX-2158) (1.03 and 1.01 cm day-1 respectively).
SC 1 (S. commune 1; DMRX-2156), SC2 (S. commune 2; DMRX-2157), SC4 (S.
commune 4; DMRX-2159) exhibited growth rate of 0.92, 0.81 and 0.69 cm day-1
respectively. Potato dextrose agar (PDA) was identified as the most suited and Czapek
dox agar (CDA) least suited media for S. commune.
In vitro antagonism was done by dual culture assay and poisoned food technique.
All the S. commune strains were effective in managing the pathogen in vitro. The strains
SC1, SC3, and SC5 exhibited lysis where as SC2 and SC4 showed overgrowth as mode
of inhibition in dual culture assay. Highest inhibition was exhibited by SC5 (40.78 %)
followed by SC3 (39.62%). Different concentration viz., 25, 50 and 75% of S. commune
culture filtrate were tested against C. gloeosporioides in poisoned food technique. Among
these, 75% concentration exhibited highest inhibition percentage. SC5 culture filtrate
amended media showed highest inhibition (44.46%) of followed by SC3 (37.03%). Two
most effective strains of S. commune viz., SC5 and SC3 were selected for in vivo studies.
In vivo studies were conducted to evaluate effect of S. commune mycelial extract
and cell free culture filtrate (CF) on leaf blight of turmeric in comparison with biocontrol
agent (Pseudomonas fluorescens) and chemical control (Propiconazole). Among all the
treatments spraying culture filtrate of SC5 at seven days interval showed lowest PDI
(17.76%) at 14 days after inoculation (DAI) followed by propiconazole (T8), P.
fluorescens (T7) and culture filtrate of SC5 (T5) which were statistically on par with each
other. Similar trend was also observed at 21 and 28 DAI. Similarly, lowest lesion size
observed in T5 (CF of SC5) at 14 DAI (1.96 ×1.4 cm2), 21 DAI (2.4×1.6cm2) and 28 DAI
(3.96×2.3cm2). The maximum plant height was observed in T7 (127.66 cm) followed by
absolute control (126.65 cm) and T5 (125 cm). There was no significant difference in the
number of leaves in response to different treatments.
Plant defence enzyme viz., peroxidase, polyphenol oxidase, and phenyl alanine
ammonia lyase showed enhanced activity followed post inoculation the spray of
P. fluorescens and culture filtrate of SC 5. Hot water extraction recovered 0.18g and
0.119g crude polysaccharide from S. commune mushroom mycelial powder and culture
filtrate respectively.
The results of this study revealed wide spread occurrence of Colletotrichum leaf
blight in the turmeric growing areas of Kerala viz., Thiruvananthapuram, Kollam and
Alappuzha. Wide variation in cultural and morphological characters of Colletotrichum
isolates was observed from the surveyed areas. The most virulent isolate (C6) obtained
from Sadanandapuram identified as Colletotrichum gloeosporioides based on cultural,
morphological and molecular characters. PDA was identified as the most suitable media
for the growth of S. commune. Schizophyllum commune strains possessed biocontrol
potential with lysis and overgrowth as mode of action against C. gloeosporioides in dual
culture assay. Culture filtrate of S. commune reduced the disease severity in leaf blight of
turmeric. Crude polysaccharides were present in culture filtrate as well as in mushroom
mycelial powder. The active compound responsible for biocontrol property of S.
commune should be identified, fractionated and structurally elucidated. In vitro and in
vivo activity of purified compound against fungal, bacterial and viral pathogens should
be investigated and more research is needed for field level application.