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Variation in the virulence of Magnaporthe grisea isolates adapted to finger millet
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Variation in the virulence of Magnaporthe grisea isolates adapted to finger millet

  1.  This work is part of National Post Doctoral Fellowship funded by DST SERB, undertaken as part of CGIAR Research Program – Genetic Gains.  Financial support from DST-SERB is greatly acknowledged. 63 82 92 16 46 48 0 20 40 60 80 100 Leaf Neck Finger Nuberofisolates/samples Blast infected tissue Total samples collected Single spore Isolates established Isolates Finger millet Host Differentials IE2911 IE2957 IE3392 IE4497 IE5091 IE6240 IE6337 IE7079 GPU28 VR708 Fm.Pg165 S S S S S S S S S S Fm.Pg166 R S S R S S S S S S Fm.Pg168 S S S R S S S S S S Fm.Pg169 S S S S S S S S S S Fm.Pg179 S S S S S S S S S S Fm.Pg180 S S S S S S S S S S Fm.Pg22 S S S S S S S S S S Fm.Pg43 S S S S S S S S S S Fm.Pg107 S S S S S S S S S S Fm.Pg207 R S S R S S S S S S Fm.Pg213 R S S R S S S S S S Fm.Pg236 R S S S S S S S S S Fm.Pg32 S R S R S S S S S S Fm.Pg44 S S S S S S S S S S Fm.Pg95 R R S S S S S S S S Fm.Pg210 R S S S S S S S S S Fm.Pg216 R S S S S S S S S S Fm.Pg237 S R S S S S R S S S Figure 1: Single spore cultures established and their cultural variability. Figure 2: Single spore isolates established from the samples collected from finger millet growing areas. Figure 3: Pathogenicity of 110 isolates screened on susceptible check VR 708. Table 1. Reaction of host differential lines to isolates of M. grisea adapted to finger millet Coefficient 0.85 0.90 0.95 1.00 Fm.Pg165 Fm.Pg169 Fm.Pg179 Fm.Pg180 Fm.Pg22 Fm.Pg43 Fm.Pg107 Fm.Pg44 Fm.Pg168 Fm.Pg166 Fm.Pg207 Fm.Pg213 Fm.Pg236 Fm.Pg210 Fm.Pg216 Fm.Pg95 Fm.Pg32 Fm.Pg237 Cluster I Cluster II Cluster III Cluster IV Cluster V Cluster VI Cluster VII Figure 4 . Pathogenic groups/pathotypes of finger millet infecting populations of M. grisea. Nov 2019 * Email: s.deshpande@cgiar.org Acknowledgement Conclusion  Profiling of virulence pattern of finger millet blast isolates will establish a platform for the screening of finger millet germplasm and breeding lines.  These isolates will be promising to develop blast resistant finger millet cultivars. Results  Pathogenicity of 110 isolates was proved on susceptible line VR 708 and the disease scores ranged from 4 – 8 across the isolates (Figure 3).  Based on pathogenic variation on host differentials, 18 isolates were distributed into seven clusters; cluster I was represented by eight isolates which were highly virulent on all the host differentials Fm.Pg 180 from Bengaluru was the most aggressive isolate with a disease score of 7.1 followed by other isolates in cluster I (Figure 4 and Table 1).  Isolates Fm.Pg 166, Fm.Pg 207, Fm.Pg 213 representing cluster III were avirulent on IE 2911 and IE 4497 whereas isolates Fm.Pg 236, Fm.Pg 210 and Fm.Pg 216 representing cluster IV were avirulent only on IE 2911 (Figure 4 and Table 1).  Clusters II, V, VI and VII were independently represented by Fm.Pg 168 (avirulent on IE 4497), Fm.Pg 95 (avirulent on IE 2911 and IE 2957), Fm.Pg 32 (avirulent on IE 2957 and IE 4497) and Fm.Pg 237 (avirulent on IE 2957 and IE 6337), respectively (Figure 4 and Table 1). Materials and Method  A total of 237 disease samples were collected from southern parts of Karnataka and Vizianagaram in Andhra Pradesh.  Off the 237 disease samples, 110 single spore isolates of M. grisea were established, of which 16 isolates were from leaf, 46 from neck and 48 from finger tissues (Figure 1 and 2).  VR 708, a susceptible check was used to asses the pathogenicity of 110 isolates  Ten Host differential lines (IE 2911, IE 2957, IE 3392, IE 4497, IE 5091, IE 6240, IE 6337, IE 7079, GPU 28 and VR 708) of finger millet were used to assess the pathogenic variability of randomly selected eighteen isolates.  The experiment was conducted under greenhouse condition in a completely randomized design (CRD) with three replicates; 1 pot/replicate with ten seedlings.  Fifteen days old seedlings were inoculated and blast severity was recorded seven days after inoculation using a 1-to-9 disease progressive scale.  Based on the reaction type (avirulent reaction = score ≤ 3.0 and virulent reaction = score ≥ 4.0 on 1-to-9 scale), isolates were grouped into different pathogenic groups. Objective To assess the pathogenic variability in M. grisea isolates adapted to finger millet. V Sujay, Rajan Sharma and Santosh Deshpande* International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Hyderabad, India Variation in the virulence of Magnaporthe grisea isolates adapted to finger millet Introduction Finger millet (E. corocana L. Gaertn.) is the fourth most important millet covering 10 % of the global millet area in over 25 countries in Asia and Africa. Though India is the leading producer of the crop with an area of 1.4 million ha and 2.0 million tons grain production. Its production is severely hampered by blast fungus Magnaporthe grisea (anamorph- Pyricularia grisea(Cooke) Sacc.) which affects leaves, fingers, neck and discolors the seed; thus, significantly reducing the grain yield and quality. The average loss due to blast has been reported to be around 20-30% and could be as high as 80-90% in endemic areas. Recognizing the importance of finger millet and constraints posed by blast disease, present study was planned to characterize populations of M. grisea adapted to finger millet from diverse geographical locations with reference to pathogenicity of the isolates.
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