Investigations on foot rot (Fusarium moniliforme Sheld.) of basmati rice with reference to survival and variability of pathogen and host-resistance
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Date
2017
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Punjab Agricultural University, Ludhiana
Abstract
The foot rot (bakanae) disease of rice caused by Fusarium moniliforme (syn. F. verticilloides) has
become a serious bottleneck in the successful cultivation of basmati rice in Punjab and its
adjoining areas. Studies of cultural characteristics of F. moniliforme on Potato dextrose agar
(PDA), Soil Extract Agar (SEA) and Spezieller Nahrstoffarmer Agar (SNA) showed that all the 38
isolates produced whitish to pinkish color on the surface with dense and fluffy growth on both
PDA and SEA, and moderate but not fluffy on SNA. The best growth was observed on PDA,
followed by SEA and SNA. The growth rate of different isolates varied between 12.28-25.86-mm/
48 hrs on PDA, between 9.09-19.59 mm/ 48 hrs on SEA and between 5.97- 16.44 mm/ 48hrs on
SNA media. The size of the spores varied in the range of (6.8-9.8) X (2.9-6.0) µm for microconidia
with no septa and (24.23-62.97) X (2.90-4.27) µm for macro-conidia having 3-5 septa.
Micro-conidia were formed in chains on water agar with KCl and none of the isolates produced
chlamydospores. DNA of 35 out of the 38 isolates was amplified with the set of primers VERT1
and VERT2 specific for F. verticilloides and gave a single amplicon of 800bp. All the isolates
showed variable production of gibberellic and fusaric acid. All 38 isolates produced gibberellic
acid whereas fusaric acid was produced by 30 isolates. Statistical analysis showed that the
production of fusaric acid significantly correlated positively with the number of stunted plants and
gibberellic acid production positively correlated with the number of elongated plants. Molecular
studies using Simple Sequence Repeats (SSR) primers revealed 102 alleles using 27 primers. Out
of 27 markers, all of the markers showed polymorphism with least polymorphism shown by
primer (8H01) and no polymorphism by primer 2H06. Maximum number of alleles was produced
by the primer 5H09. Polymorphic Information Content (PIC) values varied from 0.10-0.89 with an
average of 0.46. Eleven SSR primers revealed PIC values higher than the average. The primers
7H05, 11H01, 5H09, 3H19, 10H09, 10H01, 9H05, 1H02, 2H17, 2H15, 3H02, 11H03 and 10H07
showed PIC values equal to or higher than 0.50. The genetic dissimilarity index ranged from 25 to
75%. The variability in pathogen, its survival and identification of resistant sources will help to
formulate effective strategies for management of foot rot. Investigations on survival of Fusarium
moniliforme in soil revealed that the pathogen doesn’t survive in soil up to next season. Out of
nine weeds evaluated against foot rot under artificial inoculation conditions in field, none of the
weeds was infested. Out of 134 basmati germplasm lines screened under artificial inoculation field
conditions, 24 lines were moderately susceptible, 4 lines were susceptible, 4 were highly
susceptible, 27 were moderately resistant, 7 lines were resistant and 5 lines were highly resistant.
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