A Beta Regression Model for Himalayan Medicinal Plant Disease Prediction

Radhika Sharma

doi:10.17485/ijst/2014/v7i6.16

Abstract

Picrorhiza kurrooa plants were grown in greenhouse and was tested for powdery mildew disease. The result of temperature and wetness duration on P.kurrooa was studied under controlled-environment to develop a disease prediction model for controlling infection.Plants were kept at a temperature ranging from 31°C to 37°C with Relative Humidity (RH) more than 90% was maintained in greenhouse and it is measured in the terms of wetness duration (in hours) from 5 to 40hr.To determine the relationship between infection index, temperature and wetness duration data for P. kurrooa were analyzed by nonlinear regression model. Beta model was used to provide the best fit to the data for modeling. Infection index on plant increased with increasing wetness duration at optimum temperature. Minimum and maximum temperatures for infection were around 31 and 37°C, respectively. At 35.5°C maximum infection was recorded, and a minimum duration of wetness that is required for germination of the fungus was 5hr. Highest infection index 0.95 was noticed at 35.5°C. Temperature and duration of wetness were recorded for each event and used in the model equation to calculate disease infection index. Regression coefficient (R 2 ) between observed infection index and predicted infection index was 0.8103 and coefficient of determination (R) was 0.9. It indicates that the model could reliably predict the disease infection index over a wide range of temperatures and wetness durations.

Highlights

Picrorhiza kurrooa Royle ex Benth generally known as P. kurrooa is a perennial herb of medicinal value usually found at high altitude ranging from 3000-5000m amsl
P. kurrooa is dominant in Western Himalayan regions of Northern part of India while Picrorhiza scrophulariiflora Pennel second species of Picrorhiza (Scrophulariaceae) is generally found in Eastern Himalayan regions of Sikkim, Nepal[2,3]
The infection index declined with further increase in temperature

Summary

Introduction

Picrorhiza kurrooa Royle ex Benth generally known as P. kurrooa is a perennial herb of medicinal value usually found at high altitude ranging from 3000-5000m amsl. P. kurrooa is dominant in Western Himalayan regions of Northern part of India while Picrorhiza scrophulariiflora Pennel second species of Picrorhiza (Scrophulariaceae) is generally found in Eastern Himalayan regions of Sikkim, Nepal[2,3]. Aerial as well as underground parts (roots and rhizomes) contain picrosides, the medicinally important constituents of P. kurrooa[10,11]. Picroside-I, Picroside-II and Kutkoside are important constituents of the species which have many medicinal uses. P. kurrooa is traditionally used for the intervention of liver disorders, fever, asthma and jaun-

Methods

Results

Conclusion