{'fraction_non_alphanumeric': 0.026729857819905212, 'fraction_numerical': 0.024360189573459715, 'mean_word_length': 5.105902777777778, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Studies on Aerobiology and Epidemiology of Late Blight Disease of Potato

Potato (Solanum tuberosum L.) is the world’s largest grown vegetable crop followed by sweet potato and tomato and ranks fourth in the worldwide production after maize, rice and wheat. In India, the potato covers an area of 21.79 lakh ha with yearly production of 53,027.21tonnes. Karnataka stands 11 th among potato producing states in India, which accounts for 1.23 per cent of overall potato production (Annon, 2019).

temperature, favours the development of various fungal and bacterial diseases. Poor agricultural practices can also lead to increase in disease incidences, reduction in yield and also quality of the produce.
Among the diseases, late blight of potato caused by Phytophthora infestans (Mont.) de Bary is the most destructive disease affecting leaves, stem, petioles and tuber. It has been documented that under unfavourable environmental conditions, late blight can cause considerable yield losses and can lead up to 100 per cent yield losses.
However, the onset of infection and the severity vary considerably from year to year as the disease epidemic depends on weatherparameters and aerial spore quantity which accounts for the spread of disease. Sporangia of P. infestans are thought to be dispersed by wind. Monitoring the pathogen's airborne inoculum along with the weather parameter could therefore help to forecast blight epidemic and need for fungicidal sprays.
Hence, scheduling timely application of fungicides based on the spore concentrations in plant canopy by obtaining reliable predictive models that allow us to know beforehand the atmosphere spore content in a particular area and the suitable meteorological conditions for occurrence of aerial sporangia, can lead to forecasting the emergence of fungal blight. These allows the utilization of forecasting tools for deliberating the need based and timely application of fungicides and to reduce the cost of cultivation.

Materials and Methods
Field experiment was carried out in both Kharif and Rabi, 2019 season at Agricultural Research Station. Gunjevu, Hassan is located in the Southern transition zone (Zone-7) of Karnataka state at 12.874°N latitude, 76.379° E longitude with an altitude of 874m above the mean sea level. Seed tubers of cultivar Kufri Jyothi were sown into the field with 60cm inter 20cm intra row spacing in plots measuring 25 x 20 m. All the agronomical practices and pest control measures were followed as per the recommended package of practices.
Aerobiological studies were carried out to trap the sporangia present in the air current during 2019. For this, aeroscope exposure of stationary slide was done by mounting it on a wind vane and placed inside potato field at two different heights (at plant canopy and 1mt above ground level) (Plate1).
A slide, which was thinly smeared with vaseline was used for trapping spores, by keeping smeared slide in the slot inside the box. The slide was removed every day at 8.00am. Average number of sporangia per microscopic field was recorded under low power objective taking count of ten microscopic fields on a slide (Plate 2).
Further, to understand the influence of environmental factors on aerial spore load and development of the disease the weather parameters viz., temperature, relative humidity, evapo-transpiration and rain fall data were recorded during cropping period and they were correlated with spore load and disease development by simple correlation and multiple regression analysis (Table 1 and 2). Ten plants were randomly selected and tagged for regular observations. Observation on disease severity of foliage was recorded by using 1-9 scale as given by CIP and per cent disease index (PDI) was worked out using formula of wheeler1969. The fruit yield in each plot was also recorded.
CIP scale for recording the field observation on potato late blight:

Results and Discussion
Studies on aerobiology of Phytophthora infestans revealed that the sporangia were trapped throughout the crop season, initially sporangia was trapped on 11 th July (Kharif), 3 rd October (Rabi) which was about one week before first disease symptoms appeared (July 18 th Kharif, October 11 th Rabi) noticed that onset of infection begun one week after the appearance of first aerial spore of P. infestans.

Concentration profiles
The aerial concentration of sporangia decreased rapidly with height above the canopy ( Fig. 1 and 2). Spore concentrations measured by the sampler just above the top of the canopy ranged from 3.26 to 48.84 sporangia/week in Kharif and from1.5 to 21.56 sporangia /week in Rabi.
Similarly, Spore concentrations measured by the sampler at 1m above the ground level ranged from 3.24 to 22.36 sporangia/week in Kharif and from1.52 to 9.23 sporangia /week in Rabi. These findings are in agree with Aylor et al., (2001)who conducted an experiment to determine the rate of release of sporangial spores per square meter per second for quantifying their further dispersal and the potential spread of disease. Values of Q (spores) were obtained for Phytophthora infestans sporangia released from an area source of diseased plants in a potato canopy recorded highest when compared with the concentrations of airborne sporangia measured at several heights above the source.

Simple correlation and multiple linear regressions with spore load of Phytophthora infestans in relation to weather parameters
The relationship was established between weather parameters viz., maximum and minimum temperature, relative humidity, rainfall and evapotranspiration with spore load of Phytophthora infestans through correlation and multiple linear regression analysis. The correlation coefficients are presented in Table 3.
The relationship between spore load of P. infestans and weather factors during both season in 2019 indicated that minimum temperature, relative humidity and rainfall was positively correlated with weekly spore load. Whereas maximum temperature and evapotranspiration was negatively correlated. The data are again subjected to multiple linear regression analysis.
The coefficient of multiple correlation (R 2 ) was calculated to measure the contribution of linear function of independent variables such as maximum temperature(X 1 ), minimum temperature(X 2 ), relative humidity (X 3 ), rainfall (X 4 ) and evapotranspiration (X 5 ) on dependent variable i.e. average spore load (Y) and is presented in the Table 4.
The multiple regression equation was found highly significant for the data with the spore load, revealed that spore load recorded in microclimate of potato field was governed up to 86.80 per cent in Kharif and 83.30 per cent in Rabi by the cumulative effects of independent environmental factors (relative humidity, maximum temperature, minimum temperature, rainfall and evapotranspiration).     -0.578* -0.132 **Significant at 1% probability(Two-tailed) * Significant at 1% probability(Two-tailed)  Plate.1 View of Spore trap installed in potato field at plant canopy and at one meter above ground level to quantify spore number One meter above ground level At the plant canopy Plate.2 Microscopic view of sporangia obtained from spore trap installed in Potato field These findings are in line with Roopa (2012) who conducted aerobiology study on early blight of tomato. She developed the relationship between spore load of A. solani and weather factors during 2011 indicated that maximum temperature and rainfall found significantly positively correlated with spore load, whereas minimum temperature,. morning relative humidity and evening relative humidity were significantly negatively correlated with weekly spore load, multiple linear regression equation was developed for 2011 was Y= -17.116 +0.092X 1 -0.333 X 2 + 1.211X 3 -1.485 X 4 +0.363X 5 With R 2 =0.86 i.e., the weather factors put together influence spore load to the extent of 86 per cent.

Simple correlation and multiple linear regression with percent disease severity of Phytophthora infestans in relation to weather parameters
The perusal of simple correlation studied (Table 5) revealed that the metrological parameters including minimum temperature, relative humidity and rainfall were positively correlated with percent disease severity of Phytophthora infestans indicating simultaneous increase in the disease development with increase in minimum temperature, RH and rainfall during both season of 2019. Whereas maximum temperature and evapotranspiration was found to be negatively correlated indicating that late blight severity decreased gradually with increase of maximum temperature. These findings are in agree with Koushal (2019)who reported the positive correlation of tomato late blight with minimum temperature, relative humidity, mean air temperature and rainfall, negative correlation with maximum temperature.
The coefficient of multiple correlation (R 2 ) was calculated to measure the contribution of linear function of independent variables such as maximum temperature(X 1 ), minimum temperature(X 2 ), relative humidity (X 3 ), rainfall (X 4 ) and evapotranspiration (X 5 ) on dependent variable i.e. percent disease severity (Y).
The multiple regression equation was found highly significant for the data with the spore load, revealed that progression of late blight disease was governed up to 90.30 per cent in Kharif and 87.70per cent in Rabi by the cumulative effects of independent environmental factors (relative humidity, maximum temperature, minimum temperature, rainfall and evapotranspiration). The significance of the coefficients is presented in Table 6.
Thus, the study revealed that there will be a significant increase of late blight severity and spore load concentration when the maximum temperature less than 24℃, relative humidity more than 90 Per cent, minimum temperature from 12-16℃ and rainfall ranged from1.5-4.2mm.The findings are in agreement with the studies of Iglesias et al., (2009) reported the studies on seasonal variation of Phytophthora infestans concentrations in atmosphere and the highest concentrations of spores were registered during June and July from 82-145 spores/m 3 as a result of the maximum temperature around 16-23ᵒC. Ahmed et al., (2015) studied the effect various environmental factors on late blight severity and they found that high relative humidity of 63-71 Per cent coupled with rainfall ranged from 1.5-3.75mm, temperature range from 16-20ᵒC and wind speed in the range of 1-5.5Km/h were significantly favoured the disease development.