STUDIES ON VARIABILITY AND INTEGRATED DISEASE MANAGEMENT OF WILT OF SAFFLOWER (Carthamus tinctorius L.) CAUSED BY Fusarium oxysporum f. sp. carthami
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Date
2022-07-02
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PROFFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
Safflower (Carthamus tinctorius L.) is one of the major Rabi oilseed crop
cultivated in the Deccan Plateau region of India. Wilt of safflower caused by Fusarium
oxysporum f. sp. carthami Klisiewicz and Houston (Foc) results in yield loss up to 93
per cent in susceptible varieties.
Wilt samples of safflower were collected from different locations of Telangana
and Andhra Pradesh and fifteen isolates of Fusarium oxysporum f. sp. carthami were
isolated from the collected diseased samples and they designated as FOC 1 to FOC 15.
Morphological variations among collected isolates were studied. Based on the
observed length of microconidia the isolates could be divided into 5 distinct groups i.e.
Group I to V, based on macroconidia length the isolates could be divided into 3 distinct
groups i.e. Group I to III. Based on chlamydospore diameter, the isolates could be
divided into four distinct groups (Group I to IV), based on the cultural characters they
were categorized into eight distinct groups (Group I to VIII) and based on colony
diameter the isolates grouped into seven distinct groups (Group I to Group VII).
The variation was present among the isolates at molecular level and the isolates
were grouped into different clusters. The results of molecular variability revealed that
There was a relationship exists between clustering of isolates based on molecular
variability with the location.
Pathogenic variability of the fifteen isolates of Fusarium oxysporum f. sp.
carthami was tested using susceptible safflower cultivar PBNS-12 under high inoculum
pressure in glasshouse conditions. Wilt incidence was recorded in the range of 53.3 %
(FOC-11) to 93.3 % (FOC-I).
Forty one germplasm lines were collected from ARS, Tandur and were screened
against Fusarium oxysporum f. sp. carthami. Based on the disease scale (0-9), they were
categorized from highly resistant to highly susceptible.
Seed mycoflora detected from the seeds of 41 germplasm lines by using standard
blotter method and agar plate methods. In both the methods, eight fungal genera viz.,
Alternaria spp., Aspergillus flavus, Aspergillus niger, Chaetomium spp., Rhizopus spp.,
Curvularia spp., Macrophomina phaseolina and Fusarium spp. were recorded. Among
the observed fungi A. niger was found predominant (40.28 % and 42.52 %), while M.
phaseolina was least (2.39 % and 2.02 %).
Effect of fungicides and biocontrol agents on seed germination, seedling vigour
index and seed mycoflora was evaluated on four popular verities of safflower viz., Nira,
ISF-764, PBNS-12 and Manjira by standard blotter method and paper towel method.
Seed treatment with captan (0.25 %) was found superior followed by seed treatment
with Trichoderma harzianum (1 %), in all the four popular varieties tested in the testes
parameters.
Susceptible variety PBNS-12 was used to find the effect of seed treatment with
bioagents, organic amendments and carbendazim and their combinations on per cent
seedling emergence, pre emergence and post emergence mortality in glass house
conditions. Among all the treatments tested, T11-combination treatment of (T1 + T2 + T3
+ T4 (seed inoculation with test pathogen followed by seed treatment with Trichoderma
harzianum (10 g kg-1
seed) + T2 (seed treatment with Pseudomonas fluorescens (10 g kg 1
seed) + T3 (seed treatment with carbendazim (1 g kg-1
seed) + T4 (soil application with
neem cake (10 g kg-1
soil) was found superior in all the parameters discussed. When
tested for growth parameters, shoot length was recorded highest in T11 (59.2 cm), root
length was recorded highest in T6 (10 cm) and Total length was recorded highest in T11
(68.2 cm). Highest fresh weight (272.10 g) and dry weight (105.35 g) was also recorded
from the same combination treatment.
In integrated disease management experiment, when the cost benefit ratio is
compared, T16 (Seed treatment with carbendazim) was found effective with C:B ratio of
1:67 followed by T14 Seed treatment with Trichoderma harzianum + Seed treatment
with Pseudomonas fluorescens (1:52) and T3 Seed treatment with Trichoderma
harzianum (1:50). Among the above treatments, T16 recorded highest yield (1681 kg ha 1
) highest germination (88.42 %) and lowest wilt incidence (15.12 %) followed by T14
(Seed treatment with Trichoderma harzianum + Seed treatment with Pseudomonas
fluorescens) recorded yield of 1580 kg ha-1
, germination of 82.33 per cent and wilt
incidence of 22.10 per cent respectively.