Studies on Penicillium fruit rot (Penicillium citrinum) of citrus (Citrus aurantifolia Swingle) and its management
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Date
2012
Authors
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Publisher
AAU, Anand
Abstract
Citrus (Citrus aurantifolia Swingle) is the most
important fruit crop, belongs to the family Rutaceae and subfamily
Aurantioidea. The important commercial citrus fruits
cultivated in India are the Mandarin orange (Citrus reticulata
Blanco) followed by Sweet orange (Citrus sinensis Osbeck.), Acid
lime (Citrus aurantifolia Swingle) and Lemon (Citrus limon Burn.).
In India, mandarin constitutes about 41, sweet oranges 23 and
acid lime and lemon about 23 per cent of total citrus produced.
Lime is a potential source of vitamin-C and it also extensively
used for medicine and culinary purposes. In India, citrus fruits
rank third in area and production after mango and banana with
an estimated production of 96,38,000 MT with an area of 9.87
lakh hectares contributing 13.5 per cent of total fruit production.
Gujarat state at present has 37,100 ha. area under citrus (Citrus
aurantifolia Swingle) crop producing 3.85 lakh tonns fruits with
productivity of 10.4 tonns/h
Diseased citrus fruits showing typical symptoms of
Penicillium rot were collected from Sardar Patel vegetable market,
Anand and brought to the laboratory for isolation of the pathogen.
The infected fruit exhibit water soaked, light brown, soft areas
with olive green spore mass. The Koch’s postulates of isolated
pathogen were proved on healthy matured citrus fruits following
wound inoculation method. The pathogen was reisolated from the
artificially inoculated fruits on PDA. The pure culture obtained
was sent for identification to Indian Type Culture Collection
(I.T.C.C.), I.A.R.I., New Delhi – 110 012 and was identified as
Penicillium citrinum (ID. No: 8298.11).
The morphological studies revealed that the pathogen
(Penicillium citrinum) produced bluish green mycelial growth with
abundant sporulation on PDA. The conidiophores are branched
twice or thrice, elongate, bearing long tangled chains of conidia.
The weekly survey carried out from first week of
October to fourth week of March, 2010-11 revealed that the
incidence of Penicillium rot was predominant (6.48 & 5.95 %) at
both the markets, respectively.
The activities of polygalaturonase and polyme
thylgalacturonase enzymes were studied on fruits inoculated with
P. citrinum along with healthy fruit. The PG activity was higher in
fruits inoculated with P. citrinum than healthy fruits, while no
significant difference was observed in PMG activity between
inoculated and healthy fruit peel.
DNA analysis of five isolates with 15 primers showed
amplification of total 160 bands, with a range of 16 to 7 bands
per primer. Overall, Penicillium isolates exhibited a moderate level
of genetic diversity. The maximum 16 bands were generated by a
primer 0PA- 12.
Clustering pattern of dendrogram generated by using
the pooled molecular data of 14 RAPD loci indicated that two
clusters namely 1 and 2 were formed. Cluster 1 includes four
isolates viz., isolate AND, ABD, DKR and NAV. While cluster 2
includes single isolate i.e. VAD. The similarity coefficient ranged
from 0.42 to 0.53 with all 15 primers. Among the 15 primers the
primer viz., OPA-13, OPA-10, OPE-17 and OPE-18 showed 100
per cent polymorphism. These primers can be utilized further to
ascertain the variability among the isolates of P. citrinum.
Among the fungicides screened in vitro, complete
mycelial growth inhibition of P. citrinum was observed in
azoxystrobin and azoxystrobin 18.2% + difenconazole. (250 and
500 ppm), mancozeb (1000 and 2000 ppm), hexaconazole (5%) +
captan (70%), carbendazim (12%) + mancozeb (63%), cymoxanil
(8%) + mancozeb (64%), carbendazim at both the concentrations
(500 & 1000 ppm). The lowest Penicillium rot severity was
recorded in fruits treated with mancozeb at 2000 ppm followed by
carbendazim (1000 ppm) both in pre (4.16 %) and postinoculation
(4.99 %) treatments, respectively at 8 days after
inocubation.
Complete mycelial growth inhibition was recorded in
tulsi, garlic, and henna extract. Further tulsi leaf extract (10%)
found most effective in reducing the Penicillium fruit rot severity
both in pre- (3.00 %) and post-inoculation (4.00 %) treatments at
8 days after inoculation.
Trichoderma harzianum found most efficient
antagonist in inhibiting the mycelial growth of P. citrinum (77.41
%) in vitro. It was also found most effective in reducing the
Penicillium rot severity in pre inoculation (10.00 %) treatment at
8 days after inoculation.
The fruits exposed to hot water treatment at all five
treatments showed 100 per cent reduction in Penicillium rot
incidence over control up to ten days of storage at 25±1ºC without
any changes in natural fruit colour. The protein pattern of citrus
fruit peels treated with HWT showed the presence of 103 KDa of
molecular weight of proteins but these bands were absent in
healthy and untreated and inoculated protein samples. The
profile results showed the bands ranging from 30-35 number with
protein molecular weight ranging from 15 KDa to 195 KDa.
Description
Keywords
agriculture, plant pathology, study