VEGETOS: An International Journal of Plant ResearchOnline ISSN: 2229-4473
Print ISSN: 0970-4078

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Research Article, Vegetos Vol: 29 Issue: 3

Survey and Status of Rice Blast Caused by Magnaporthe Oryzae B.C. Couch in Commercial Rice Growing Areas of Kashmir

Farahanaz Rasool1, Mushtaq Ahmed2, Mehraj-ul-din Shah2 and Sandeep Sahni1*
1Division of Plant Pathology, SKUAST-K Shalimar, Srinagar, Jammu and Kashmir, India
2Division of Soil Sciences, SKUAST-K Shalimar, Srinagar, Jammu and Kashmir, India
Corresponding author : Sandeep Sahni
Division of Plant Pathology, SKUAST-K Shalimar, Srinagar, India, Jammu and Kashmir
E-mail: [email protected]
Received: May 07, 2016 Accepted: July 12, 2016 Published: July 18, 2016
Citation: Rasool F, Ahmed M, Shah M, Sahni S, (2016) Survey and Status of Rice Blast Caused by Magnaporthe Oryzae B.C. Couch in Commercial Rice Growing Areas of Kashmir. Vegetos 29:3. doi: 10.5958/2229-4473.2016.00065.3

Abstract

Survey and Status of Rice Blast Caused by Magnaporthe Oryzae B.C. Couch in Commercial Rice Growing Areas of Kashmir

Four commercial rice growing districts of Kashmir valley viz.,Bandipora, Kulgam, Anantnag and Pulwama were surveyed for incidence and intensity of leaf and neck blast of rice. The survey was carried out at tillering and around flowering stages. The highest leaf and neck blast incidence of 80.67 and 19.36 per cent was observed in Anantnag, whereas it was the lowest (18.33 and 1.03 per cent) in Kakapora in district Pulwama. The leaf blast intensity ranged from 10.82 per cent in district Bandipora to 29.59 per cent in district Kulgam. The highest neck blast intensity (4.83%) was recorded at Duroo Shahabad, whereas the lowest (0.77%) was observed at Ajus in district Bandipora. The rice blast showed the highest occurrence in south Kashmir as it is the hot spot for the disease having the ideal predisposing conditions for the disease..

Keywords: Magnaporthe oryzae; Kashmir; Rice blast; Neck blast; Leaf blast; Incidence; Intensity

Keywords

Magnaporthe oryzae; Kashmir; Rice blast; Neck blast; Leaf blast; Incidence; Intensity

Introduction

Among the major constraints in boosting the production and productivity of rice in the state, the onslaught of blast disease is believed to be a major bottleneck, and takes a heavy toll of the produce [1]. Rice blast caused by Magnaporthe oryzae is endemic to most rice-growing areas of Kashmir valley due to prevailing blast-conducive environments during the crop season [2].The pathogen manifests itself at the seedling, tillering and flowering stages of crop growth causing losses on account of leaf-, node- and neck-blast in the state [3]. Frequent epiphytotics of the disease in the state for the last about fifteen years have been inflicting heavy qualitative and quantitative losses to the growers. The disease emerged as a major problem in the Jammu and Kashmir state prior to 1950’s [4]. With the evolution and wide spread cultivation of blast tolerant varieties, the blast incidence in Kashmir remained under check till suddenly the disease surfaced in late 1990’s . In order to provide a baseline information on the status of the disease in the major rice growing areas in the valley and its relation with edaphic factors and effect on productivity, the present investigation was taken up to analyse the status of incidence and intensity of rice blast.

Materials and Methods

Three random rice growing blocks/locations in each district and five fields representing each block/location were selected to record the incidence and intensity of rice blast at, tillering and around flowering stages.
The leaf blast incidence was recorded by assessing upper three leaves of each random tiller from each of the ten random hills from each field and expressed as per cent for each location [5].
image
The following 0 to 9 scale [6] was adopted for recording the blast intensity of leaves in each field (Figure 1 ; Table 1).
Figure 1: Grading of infected rice leaves on 0-9 scale.
Table 1: Leaf blast disease score for rice [6].
The leaf blast disease intensity was calculated using the following formula:-
image
Where
PDI = Per cent disease intensity
Σ = Summation
V = Disease score
n = Number of leaves showing a particular score
N = Total number of leaves examined/assessed
Neck blast incidence
One random tiller from each of the ten hills in each field was assessed for the neck blast and expressed as per cent. Neck blast incidence was calculated using the following formula:-
image
Neck blast intensity
The extent of neck blast was further quantified by scoring it using the following scale (Table 2).
Table 2: Neck blast disease score for rice [6].
Neck blast intensity was calculated using the following formula:-
image
Where
NBI = Per cent neck blast basnity
Σ = Summation
V = Disease score
n = Number of panicles showing a particular score
N = Total number of panicles examined

Results and Discussion

An intensive stratified survey of paddy growing areas of four rice growing districts viz., Anantnag, Bandipora, Kulgam and Pulwama, of Kashmir valley, revealed that the disease occurred in all the surveyed areas of Kashmir in varying proportions during all the cropping seasons with maximum leaf and neck blast intensity recorded in district Anantnag (36.89 and 4.83%, respectively) and Kulgam (29.58 and 3.54%,respectively) known as the rice bowl of Kashmir; the leaf blast intensity in Pulwama and Bandipora being lower (12.18 and 10.82%, respectively). Anwar et al. [1] also confirmed high incidence and intensity of leaf and neck blast in these areas. The results (Table 3) revealed that the overall mean leaf blast incidence in all the four districts during 2011, 2012 and 2013 varied from 21.78 per cent in district Bandipora to 61.45 per cent in district Kulgam. The highest mean leaf blast incidence of 80.67 per cent was observed in Anantnag followed by 74.76 per cent in Duroo Shahabad in district Anantnag, whereas it was the lowest (18.33%) in Kakapora in district Pulwama during 2011-13. The pooled leaf blast incidence during 2011, 2012 and 2013 was 45.50, 31.75 and 48.69 per cent, respectively, with a pooled mean of 41.98 per cent.
Table 3: Incidence of leaf and neck blast (Magnaporthe oryzae) disease of rice at different locations in Kashmir during 2011-2013.
The average leaf blast intensity ranged from 10.82 per cent in district Bandipora to 29.59 per cent in district Kulgam (Table 4) during 2011, 2012 and 2013. The highest leaf blast intensity (36.89%) was observed at Anantnag followed by Duroo Shahabad (34.04%) in district Anantnag and Khudwani (33.41%) in district Kulgam during 2011, 2012 and 2013. The pooled leaf blast intensity during the years 2011, 2012 and 2013 was 21.12, 15.30 and 23.67 per cent, respectively, with a pooled mean of 20.03 per cent. The average neck blast intensity ranged from 0.97 per cent in district Bandipora to 4.14 per cent in district Anantnag (Table 4) during 2011, 2012 and 2013. The highest neck blast intensity (4.83%) was recorded at Duroo Shahabad.
Table 4: Intensity of leaf and neck blast (Magnaporthe oryzae) disease of rice at different locations in Kashmir during 2011-13.
The average neck blast incidence ranged from 1.83 per cent in district Pulwama to 12.57 per cent in district Anantnag during 2011, 2012 and 2013 (Table 3). The highest neck blast incidence (19.36%) was observed in Anantnag followed by Duroo Shahabad (16.53%) in district Anantnag, whereas the lowest neck blast incidence (1.03%) was recorded in Kakapora in district Pulwama. The pooled neck blast incidence during 2011, 2012 and 2013 was 5.88, 4.32 and 7.68 per cent, respectively, with a pooled mean of 5.96 per cent followed by Anantnag (4.50%) in district Anantnag, whereas the lowest neck blast intensity (0.77 %) was observed at Ajus in district Bandipora. The pooled neck blast intensity during the years 2011, 2012 and 2013 was 2.32, 2.64 and 2.32 per cent, respectively, with a pooled mean of 2.43 per cent.
The widespread occurrence of the disease and the introduction and cultivation of different rice genotypes together with their distribution in time and space predispose the pathogen population for co-evolution and emergence of variable isolates and pathotypes/ races. Ascertaining the prevalence, frequency of occurrence and the ultimate status of the disease in length and breadth of rice growing areas of the valley was, therefore, imperative before taking up studies on pathogen variability. The disease has been found occurring with different dimensions in other parts of the globe. Several studies have been made to estimate the incidence and intensity of leaf and neck blast [1,7,8,2,9].Variations in disease intensity observed in different years and different places during the present studies were mostly due to variations in fertilizer dosage, field and seed insanitation and the tolerance levels of rice genotypes cultivated. The rice growing regions which showed higher levels of blast intensity were the hot spots of the disease where the predisposing factors for the disease development and spread were prevalent. High plant density with high relative humidity in the micro-environment, and high inoculum load in fields/areas with history of blast occurrence serve as the main factors for the pathogen proliferation and establishment of infection in the surveyed areas as have also been argued by Rathour et al. [10] and Singh et al. [11].

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