BIOLOGICAL CONTROL AND UNDERSTANDING THE DEFENCE BIOLOGY ASSOCIATED WITH RESISTANCE AGAINST FUSARIUM WILT (Fusarium oxysporum f. sp. cubense) IN BANANA ECOTYPE NANJANGUD RASABALE
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Date
2021-02
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University of Horticultural Sciences Bagalkot. (College of Horticulture, Bagalkot).
Abstract
Banana (Musa spp.) is seriously threatened by the soil-borne fungus Fusarium
oxysporum f. sp. cubense, also known as panama disease. Cultivar Nanjangud
Rasabale is top ranked due to their inviting aroma and pulp. The cultivar is highly
susceptible to Fusarium wilt and area under this variety is declining every year, which
has necessitated the detail study on survey for the incidence of wilt, biological
management of Fusarium wilt, Understanding the defense mechanism of cultivar
Nanjangud rasabale upon application of bioagents, and the role of silicon in control of
Fusarium wilt. A survey was carried out in major banana growing districts of
Karnataka to know the incidence of wilt during 2016-17 and 2018-19, which revealed
that the highest average disease incidence was recorded in Mysuru district (25.47 %)
and least incidence in Mandya district (6.54 %). While, the severe form of disease
was observed in the cultivar Nanjanagudu Rasabale (60.57 %) and no incidence of
Fusarium wilt was recorded in the Cultivar Grand Nine. In biological management
studies, a total of 33 Trichoderma isolates, six Pseudomonas species and six Bacillus
species were collected from the soil samples. The isolates were identified as
Trichoderma harzianum, Trichoderma asperellum and Trichoderma longibrachiatum
through microscopic and colony characters. Bacillus spp. and Pseudomonas spp. were
confirmed through 16S rDNA test. In vitro evaluation of antagonistic bioagents
showed that all the isolates significantly inhibited the growth of Fusarium, the isolate
MNF-3 showed highest inhibition (71.55 %) followed by isolates CKF- 4 (68.28 %),
The lowest per cent inhibition recorded by isolate MNF – 4 (43.30 %). Further, the
potential bioagents screened under pot condition, rhizospheric Trichoderma spp.
(CRT) and T. asperellum (MNF-3) showed least wilting and internal discolouration
respectively. In addition to suppressing panama wilt, isolates also showed significant
in plant height, number of leaves and pseudostem girth compared to control plants.
The effect of silicon at concentrations of 700 mg 1-1wk-1 to 2000 mg 1-1wk-1 was very
effective in enhancing the root parameters, minimizing the root damage and disease
severity of panama diseases. Similarly, identification of expression pattern of
pathogenesis associated genes helped to enable the understanding of different defense
response mechanism and plant-fungus communication at gene level in banana plants.