Radiometeric Spectral Reflectance As A Tool To Monitor Ascochyta Blight Development In Chickpea Fields

Roula Shamsi⁽¹⁾, Ahmed El-Ahmed ⁽¹⁾ Younis Idrees ⁽²⁾ Rajinder Malhotra ⁽¹⁾ and Siham Asaad ⁽¹⁾.
⁽¹⁾International Center for Agricultural Research in the Dry Areas (ICARDA), P.O. Box 5466, Aleppo, Syria.
⁽²⁾ General Organizationo of Remote Sensing (GORS), Damascus, Syria.

Abstract

Chickpea is one of the most important cool season food legumes grown in West Asia and North Africa. The production of chickpea is seriously constrained by a devastating disease, Ascochyta blight, caused by Ascochyta rabiei (Pass) lab. Occasionally, severe epidemic occurs when the environmental conditions favor the spread of the disease, it causes heavy yield losses, or even crop failures. The present study was done to see whether radiometric spectral reflectance (RSR) could be used as a tool to monitor ascochyta blight development in chickpea. The material for the present study comprised five different artificially created inoculation levels. The RSR measurements were recorded during the incubation period (IP) before the development of the disease. Results revealed clear differences between the NIR (TM₄ channel 0.76-0.90) as well as Normalized Difference Vegetative Index (NDVI) values for infected and non-infected plants. The NIR and NDVI values decreased at all inoculation concentrations (10⁵, 10⁴, 10³, 10² spores/ml and water as a check) starting from the first day after inoculation. There was a significant correlation between IP and TM₄ (0.89, 0.75, 0.88, 0.85 and 0.22) and NDVI values (0.99, 0.82, 0.75, 0.86 and 0.30), respectively. Whether a low or high inoculum levels were used to induce the disease, RSR was instrumental in detecting the disease. The present findings, therefore, may contribute to early detection of the disease and consequently lead to the development of more efficient control measures.