DIVERSITY ANALYSIS OF Drechslera maydis, THE INCITANT OF MAYDIS LEAF BLIGHT OF MAIZE AND ITS MANAGEMENT
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Date
2022
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Punjab Agricultural University, Ludhiana
Abstract
The investigation entitled “Diversity analysis of Drechslera maydis, the incitant of maydis leaf blight of maize and its management” was carried out at PAU Ludhiana and ICAR-IIMR, Ludhiana during 2019-2021. The sixty-nine isolates of D. maydis were collected from Punjab and other states showed significant variation in terms of cultural, morphological, and pathological characteristics. The majority of isolates (31) were having greyish black growth of the mycelium on the PDA medium, while 10, 11 and 17 isolates were black, grey and whitish grey, respectively. Most of the isolates (37) showed rough appressed type growth pattern, whereas sectoring and irregular margins were present in 36 isolates. The twenty isolates recorded slow growth (6.0 mm/day). The isolates Dm_8, Dm_46, Dm_58, and Dm_69 showed minimum number septa (3-5 septa/conidium) whereas maximum number of septa (8-12) were observed in isolate Dm_22. Similarly, maximum and minimum spore count (×104/ml) were recorded in isolates, Dm_29 (58) and Dm_51 (11), respectively. Isolate Dm_25 (Ladhowal) recorded minimum incubation (2 days), maximum average lesion numbers (15.03), and highest PDI (94.07%) on susceptible genotype, CM 600, while Dm_26 (Gujarat), the least aggressive isolate, showed maximum incubation period of 4 days with minimum average lesions (11.73) and minimum PDI (61.85%). The isolates were clustered into four groups based on the PDI and representative isolates, viz., Dm_25, Dm_27, Dm_44, Dm_49, and Dm_61 were selected from these groups which were further tested on 10 maize genotypes. The isolate Dm_25 showed maximum average PDI (63.9%), number of lesions (11.1) and AUDPC (846.6), while Dm_27 exhibited minimum average PDI (50.7%), number of lesions (9.1) and AUDPC (668.8). Forty-eight unique polymorphic SSRs were obtained through in-silico analysis of D. maydis strains and filtered to 15 SSRs for further amplification and validation. Six markers (SSR1, SSR4, SSR5, SSR10, SSR13, and SSR15) exhibited high polymorphism with PIC values ranging from 0.81-0.92. Among the 69 isolates, maximum melanin production at 25ºC was recorded in the isolate Dm_25 (2.62 μg/g) while minimum production of melanin (0.37 μg/g) was recorded in Dm_62 isolate. The majority of isolates showed maximum melanin production at temperature range of 25-30°C. Out of 234 maize inbred lines screened under artificial epiphytotic conditions, thirteen genotypes (HKI 42050, V-373, IML66-1, HKI 484-5, LM 13, HKI 163, UMI 112, DQL- 2017, DQL- 2030, DQL- 2231, DQL- 2300-1-1, DQL-2294, and DQL-2105) were found resistant to MLB pathogen. The evaluation of SAR chemicals revealed that maximum disease control (36.72%) and highest yield (29.59 q/ha) were recorded in foliar application of BABA at 200 mg/L followed by ASM (28.66% and 28.34 q/ha) and SA (25.73% and 28.06 q/ha) at 200 mg/L, respectively, as compared to the inoculated control (24.62 q/ha). An overall trend of an upsurge in defensive enzymes (PAL, β-1,3 glucanase and chitinase), antioxidative enzymes (POX and PPO), total phenols and flavonoids was found in inoculated plants of Punjab Sweet Corn 1 treated with SAR chemicals up to 6 days after treatment. Thus, these resistant genotypes may serve as an important source in resistance breeding program against maydis leaf blight and SAR chemicals could be applied for disease management in maize.
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Bagaria, Pravin Kumar (2022). DIVERSITY ANALYSIS OF Drechslera maydis, THE INCITANT OF MAYDIS LEAF BLIGHT OF MAIZE AND ITS MANAGEMENT (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.