PATHOLOGICAL ASPECTS OF WILT AND ROOT ROT COMPLEX IN CHICKPEA (Cicer arietinum L.) AND THEIR MANAGEMENT 3653
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Date
2023-02
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JAU JUNAGADH
Abstract
Globally, pulses are considered as the second most common food source after
cereal crops with high protein, vitamins and minerals content. The significance of pulses
is much more in countries like India, where the majority of the people are vegetarians.
Among the pulses, chickpea (Cicer arietinum L.) popularly known as bengal gram or
chana is one of the important pulse crop grown in temperate, sub-tropical and tropical
climate throughout the world. The several biotic and abiotic stresses become the prime
reason for its low productivity. Among the different biotic stresses, wilt and root rot
complex is considered the most important, devastating and challenging disease that
becomes major limiting factor in successful cultivation of chickpea crop in Saurashtra
region of Gujarat state.
The management of chickpea wilt and root rot complex is quite difficult to
achieve, as pathogens are soil borne in nature and survive in the soil for many years even
in the absence of host by producing resistant structures i.e. chlamydospores and sclerotia.
The effective control measures against this disease are not available till date. Considering
the importance of this disease, the present investigation was performed to develop the
most effective and eco-friendly management strategies to manage this soil borne
complex disease.
The pathogens can infect the crop at any stage of its growth. The disease
characterized by shrinking of the collar region, drooping and chlorosis of petioles and
leaves, internal discolouration of xylem vessels followed by rotting of tap roots with
shredding of bark and lateral roots. The isolations were made from infected chickpea
plant roots showing characteristic symptoms, revealed the association of Fusarium
oxysporum f. sp. ciceri, Fusarium solani and Macrophomina phaseolina.
Based on cultural and morphological characters, chickpea wilt and root rot
complex pathogens were identified as F. oxysporum f. sp. ciceri, F. solani and
M. phaseolina and further confirmed with molecular identification based on 18s rDNA
ITS sequencing with NCBI accession number OP107270.1 (F. oxysporum f. sp. ciceri),
OP102548.1 (F. solani) and OP094831.1 (M. phaseolina). The ITS rDNA region-based
sequencing of M. phaseolina proved accurate for species-level identification of the
pathogen, whereas Fusarium spp. were identified based on the multilocus analysis of the
ITS region, TEF1-α and β-TUB gene. The phylogenetic trees were also constructed and
compared with other similar worldwide fungal isolates available in the NCBI database.
Out of sixty-five fungal isolates collected, thirty isolates of F. oxysporum f. sp.
ciceri, twenty-five isolates of F. solani and ten isolates of M. phaseolina were observed
that were designated as Foc, Fs and Mp, respectively. The frequency of occurrence of
F. oxysporum f. sp. ciceri was high (46.15%) among all the samples collected followed
by F. solani (38.46%) and M. phaseolina (15.39%). All the representative fungal
pathogens isolated from infected plants were found pathogenic in pathogenicity test
employed by soil and seed inoculation method.
Abstract
The survey was conducted to identify wilt and root rot complex hot spots and
disease free areas in major chickpea growing tracts of Anand, Amreli, Bhavnagar,
Jamnagar, Junagadh, Porbandar and Rajkot districts of Gujarat state. Out of ninety fields
surveyed, eighteen fields were noted free from disease or near about negligible disease
incidence (less than 5 per cent) whereas, seventy two fields were recorded as infected
with the disease in a range of 1.25-52.78 per cent.The villages of Porbandar district viz,
Madhavpur (52.78%), Kadegi (47.50%), Amipur (45.93%) and Ratia (40.65%) were
identified as highly prone areas to wilt and root rot complex.
The Fusarium spp. produce dense to sparse, fluffy to flat, white to pale yellow,
pale violet, orange or pink colour colony with regular to irregular margin. It also
produced hyaline, septate or aseptate, oval/ellipsoid to reniform/oblong, slightly
curved/straight microconidia and 2-5 septate, sickle shape with pointed or blunt end
macroconidia as well as globose/spherical to oval/pear, terminal or intercalary
chlamydospores. M. phaseolina produced aerial, fluffy, compact, partial submerged,
greyish white to blackish/brownish grey mycelium with spherical/circular to oval/oblong
black microsclerotia.
All the isolates of F. oxysporum f. sp. ciceri, F. solani and M. phaseolina
exhibited tremendous variability in their cultural and morphological characters. The
colonies of different isolates differed considerably with regard to their colony colour,
texture, pigmentation and sporulation. The glaring differences in the size and shape of
conidia/chlamydospore/sclerotia were also noticed among the isolates. The twelve
isolates of F. solani and fifteen isolates of F. oxysporum f. sp. ciceri demonstrated the
fast growth rate.
Among 105 varieties/germplasm screened, none showed immune response
against the wilt and root rot complex disease, whereas nine varieties/germplasm viz.,
WR-315 (6.26%), Phule G-08108 (6.33%), AKG-1303 (7.49%), JG 315 (7.89%), GJG
1713 (9.17%), GJG 2002 (9.44%), GJG 2015 (9.49%), GJG 1820 (9.69%), PUSA-256
(9.88%) were found as resistant, thirty seven were moderately resistant, thirty six were
moderately susceptible, seventeen were susceptible and six were highly susceptible.
The biochemical alteration in infected roots as compared to healthy roots
revealed that sugar and protein content were maximum in healthy root of chickpea,
while phenol content was maximum in infected root. The minimum decreased in protein
(32.48%) and sugar (24.48%) content and maximum increase in phenol content
(30.69%) was recorded in resistant germplasm (WR 315).
Out of nine antagonists evaluated in vitro against wilt and root rot complex
causing pathogens by dual culture technique, T. harzianum showed strongest
antagonistic activity against F. oxysporum f. sp. ciceri (87.28%), while B. subtilis found
to be the best antagonist against F. solani (84.62%). With respect to M. phaseolina, the
maximum per cent growth inhibition was observed in T. virens (70.98%).
In field condition, seed biopriming treatment for 10 hrs with the suspension of
talc-based formulation of B. subtilis (1x108 CFU/g) @ 50 g in 250 ml of water/kg of seed
remained the best treatment with minimum disease incidence (4.79%), maximum seed
yield (2339 kg/ha), seed germination (97.10%), root (12.62 cm) and shoot (25.05 cm)
length as well as vigour index (3021).
The chickpea wilt and root rot complex disease was effectively managed under
irrigated field conditions by soil application of B. subtilis (1x108 CFU/g) @ 5 kg/ha
enriched in 500 kg FYM/ha as it recorded minimum disease incidence (15.24%) and
highest seed germination (96.55%) and seed yield (2228 kg/ha). While, soil application
of T. harzianum (2x106 cfu/g) @ 5 kg/ha enriched in 500 kg FYM/ha was found most
effective under unirrigated field condition with 96.87 per cent seed germination, 7.60 per
cent disease incidence and 1383 kg/ha seed yield.