Development of an empirical model to predict losses in eggplant (Solanum melongena L.) production caused by Verticillium wilt

A model relating Verticillium wilt assessment in early stages of eggplant growth to total crop losses is proposed, based on the results of 3 years experimentation. The model resulted from the integration of the area below the yield versus disease regression curve and the ordinates axis, represented losses, on axis Y from Y-0 to Y-100 which are the limits of % yield losses and leaf symptom index (LSI) on X-axis from X-0 to X-5 which are the limits of LST. According to mathematical functions the following model is proposed: integral(5)(0) f(x) dx = A = (0.5/n)(0 * n(0) + 2 * n(1) + 4 * n(3) + 6 * n(3) + 8 * n(4) + 5 * n(5)), where n is the total number of plants counted, n = n(0) + n(1) + n(2) + n(3) + n(4) + n(5), where n(0), n(1), n(2), n(3), n(4) and n(5) are the numbers of plants belonging in each rank of the LSI, and the area A has limits 0-5. The algorithm obtained by the model is interpolated in the data of yield losses of each rank of the symptom index found in the experimental work, and the resultant number is the final estimation for future losses. The model has been validated with several results from other experiments and gave high accuracy (R-2 = 0.961) at least for the cultivars used in the experiments. (c) 2006 Elsevier Ltd. All rights reserved.