Role of agronomic manipulations in modification of wheat microclimate under central Punjab

Wheat crop is influenced by different microclimatic parameters like solar radiation, canopy temperature etc. Agronomic manipulation like change in row spacing and row direction can be used as a strategy to modify the microclimate of crop. Keeping these facts in view, field trials were conducted during rabi 2012-13 and 2013-14 under two experiments in first experiment wheat varieties HD 2967, PBW 550 and PBW 343 were sown under three row spacing viz. 15 cm, 22.5 cm and 30 cm. In second experiment, wheat varieties HD 2967, PBW 550 and PBW 343 were sown under two row direction viz. North-South (N-S) and East-West (E-W). Short wave radiation interception and canopy temperature was recorded under different treatments at 15 days interval. Among different row spacing, short wave radiation interception and canopy temperature was maximum at 30 cm row spacing (77.7% and 25.1oC) followed by 22.5 cm (75.7% and 24.2oC) and 15 cm row spacing (73.9% and 23.2oC), whereas under row directions short wave radiation interception and canopy temperature was more (76.5% and 23.9oC) in E-W row direction as compared to N-S row direction (75% and 23.2oC). Relationships were developed between dry matter accumulation and canopy temperature. Polynomial relationships gave significant R2 value (0.66 & 0.69) under different treatments. This two year study indicated that agronomic manipulations play an important role in microclimate modification and canopy temperature significantly influence dry matter accumulation under different crop geometry

Effect of meteorological parameters on incidence of brown leaf spot in rice crop under different planting methods

The field experiments were conducted during three kharif seasons 2012, 2013 and 2014 to study the effect of meteorological parameters on brown leaf spot of rice under different transplanting dates, methods and plant population. The experiment was laid out in split-split plot design with two transplanting dates (15th June and 30th June) in main plots, three methods of planting (conventional, SRI and furrow) in sub plots and two plant population (625 and 300 plants per m2) in sub-sub plots with three replications. The brown leaf spot incidence was recorded at weekly interval from the start of its incidence. The incidence of disease (percentage) was higher under conventional planting (58.6 %) followed by SRI (52.3 %) than furrow planting (49.9 %). The disease incidence was 5 per cent higher in high plant population (625 plants m-2) as compared to lower plant population (300 plants m-2) mainly due 4.1 per cent higher relative humidity within canopy. The correlation analysis revealed that minimum temperature and evening relative humidity significantly affected the disease incidence. The regression model developed with 2012 and 2013 data had highly significant R2 values which was validated with 2014 data.

Effect of abiotic factors on pathotypes causing yellow and brown rust in wheat

An attempt was made to determine the most favourable abiotic factors influencing germination of urediniospores of different pathotypes of Puccinia species. The causal organism of rusts in wheat is Puccinia spp. Five pathotypes of Puccinia striiformis (46S119, 78S84, 110S84, 110S119, 238S119) causal organism of yellow rust and two pathotypes of Puccinia triticina (77-5 and 77-9) causal organism of brown rust in wheat were obtained from Department of Plant Pathology, Punjab Agricultural University, Ludhiana. The data related to spore germination on agar slides was analysed and the levels of urediniospores germination at different temperatures (5,10,15 and 20oC) and pH (5,6,7 and 8) for each pathotype was compared using analysis of variance. The most appropriate temperature and pH were later used to conduct an experiment to study effect of different light intensities (500, 750,1000 and 1250 lux) on spore germination of all the pathotypes under study. The data showed that on agar, 15°C was proved as most suitable for urediniospore germination for Puccinia striiformis. Mean per cent spore germination was highest over the temperature range 15°C (43.55%) for Pst pathoypes and dropped significantly at 10°C (37.97%), 20°C (29.66%) and 5°C (21.04%). Mean urediniospore germination for Puccinia triticina was highest at 20°C (43.89%) followed by 15°C (39.44%), 10°C (30.43) and 5°C (27.39% ). Experimental results revealed that per cent spore germination was better under pH 7 followed by 6, 5 and 8 for all the pathotypes considered for study. The highest urediniospore germination was observed for 1250 lux (46.54%) followed by 1000 lux (41.29%), 750 lux (38.42%) and 500 lux (27.60%)

Forewarning of stripe rust (Puccinia striiformis) of wheat in central zone of Punjab

Wheat crop is attacked by number of diseases some of which cause yield losses and deteriorates quality. Rust pathogens are most important pathogens of wheat which can cause considerable economic losses if uncontrolled. Stripe rust, caused by Puccinia striiformis f. sp. tritici, is an important wheat disease common in wheat growing areas experiencing cold and humid weather conditions during the crop season. Different meteorological parameters influence occurrence and development of stripe rust in northern India including Punjab. Based on investigations on relationship of stripe rust with weather parameters, weather based prediction model for stripe rust was developed using disease severity and weather data (2007-08 to 2018-19) recorded at Ludhiana. The data of 2009-10 and 2019-20 was used for validation of model. Regression model based on maximum and minimum temperature, morning relative humidity and sunshine hours gave good results. Validation of model indicated that relationship between observed values of disease and predicted values was very close.