ASSESSMENTS OF YIELD LOSSES DUE TO DOUBLE INFECTION OF RICE RAGGED STUNT VIRUS AND RICE GRASSY STUNT VIRUS AT DIFFERENT SEVERITY IN THE FIELD, YOGYAKARTA, INDONESIA

Abstract

Rice is the most important commodity in Indonesia. Double infection of Rice ragged stunt virus and Rice grassy stunt virus cause a large decrease in production. The information about yield loss is very necessary for the efforts of policy action, control, and decision making. This research aims to describe a yield losses assessments caused by the attack of double infection at different severity levels in Yogyakarta, Indonesia. Rice fields were observed during the three growing seasons and then observed attacks of double infection of virus based on differences in severity. Rice plant samples were taken to be analyzed using regression. The validity of the regression model was confirmed using residual analysis through the Histogram Standardized Regression Residual and Normal Probability Plots on standard residuals. The result showed that there was a relationship between crop damage to rice growth as indicated by linear regression. Similarly, the relationship between the severity of the disease and the loss of result was shown by linear regression with the equation y = 2.866x - 0.3004. Based on residual analysis of regression models indicated that the regression model used in this research was a ‘good fit' to predict loss results caused by double infection of RRSV and RGSV. Regression analysis showed that there is a very strong relationship between the parameters observed to yield loss where the higher the severity of the disease that occurred in rice plants, the higher the yield loss obtained.