Over summering behaviour of Puccinia striiformis f. sp. tritici Erikss., the incitant of yellow rust of wheat and its management
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Date
2019
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Punjab Agricultural University, Ludhiana
Abstract
Yellow rust of wheat was found to survive in off season on main crop, self grown plants, ratooned plants and abandoned un-harvested plants/ fields in nine regions viz. Janjehli and Rohanda (Mandi), Bhalyani and Pulga (Kullu), Galu (Shimla), Haripurdhar (Sirmaur), Keylong in H.P. and Kargil and Leh in J&K from April to October. Aeciospores of rust from barberry caused chlorotic specks on susceptible wheat cultivar PBW 343, but no further sporulation was observed even after one month. Average minimum temperature influenced incubation period, latent period and disease severity. Incubation period increased to 19 days and 14 days with minimum average temperature above 12˚C and below 6˚C, respectively even when RH was around 90%. Minimum temperature in the range of 7-13˚C, relative humidity ≥ 90%, frequent rains during Feb-March along with winds are congenial for development and spread of yellow rust. No infection developed on barberry under in situ conditions when inoculated with teliospores from wheat. Twenty nine polymorphic SSR primers revealed polyphyletic origin of the races of Pst. Bhutti and Bhalyani (Kullu) isolates grouped together with Pst 46S119 isolate from Santokhgarh adjoining Punjab. Isolates from Sundarnagar (H.P.) grouped with Pst isolate from Fatehgarh Sahib (Punjab). Primer pair Scaffold233-153774 and Scaffold904-62635 were found to differentiate Pst 46S119 and 110S119, respectively. Barberry rust isolates were not amplified by any SSR primers specific to Pst, indicating them to be different from Pst. Early sowing (October) of wheat resulted in highest disease severity and highest area under disease progress curve as compared to November sowings. Out of four wheat varieties tested, PBW 343 was found to give highest AUDPC of upto 2041.7. Fungicides viz. Amistar top 325SC, Amistar xtra 280SC, Custodia 320SC, Opera 175SE and Tilt 25EC @ 0.1%, Nativo 75WG @ 0.6% and Taqat 75WP @ 0.3% were found to give almost complete control of yellow rust along with significant increase in thousand grain weight (26.0 to 30.3 %) and increase in yield varying from 33.3 to 40.2 per cent. Amistar top 325SC reduced the average plant height, but recorded maximum tillers in both the years without any adverse effect on yield. Maximum activity of PAL, PPO and POX was observed in resistant variety PBW 725 as compared to susceptible cultivar HD 2967. Enzyme expression under challenged conditions was more than un-challenged. Highest PAL activity was observed in Nativo, PPO in fermented butter milk and POX activity in Opera, where elevation of 10.8, 1.8 and 5.6 fold, respectively was observed as compared to unchallenged conditions. Timely sowing, varietal diversity, cultivation of resistant/ tolerant varieties, monitoring of crop during December – January, management of initial foci of infection in disease prone areas and timely advisories based on weather forecasting has been found the best strategy for management of yellow rust in Punjab.
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