Abstract
Abstract. Bacterial wilt disease (pathogen: Pseudomonas solancearum) is a major problem affecting brinjal crop. Infected leaves show yellowing, loss in turgidity, drying and ultimately the entire plant collapses. The study aims to examine the potential of hyperspectral remote sensing for detection of biotic stress caused due to bacterial wilt disease and identify best spectral band widths and hyperspectral indices indicative of disease infestation. This study was conducted in a farmer’s plot at Alampur in Baruipur block, South 24 Pargana district, West Bengal. Canopy spectra (using ASD Fieldspec 2 Spectroradiometer), chlorophyll content (by Chlorophyll meter) and Leaf Area Index (LAI) (by plant canopy imager) were collected. The healthy plants had green and fully turgid leaves whereas diseased plants had lower chlorophyll content and LAI. The reduction in chlorophyll content lowered reflectance in green region and internal leaf damage in near-infrared region. A correlation analysis was carried out between reflectance at specific bandwidths and hyperspectral indices with chlorophyll content and LAI of healthy and stressed plants. Bandwidths of 528–531 nm, 550–570 nm, 710–760 nm, and single bands such as 800 nm and 920 nm and indices viz. Greenness index, Modified Chlorophyll Absorption in Reflectance Index (MCARI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Triangular Vegetation Index (TVI), Simple Ratio Pigment Index (SRPI), Photochemical Reflectance Index (PRI 2), Lichtenthaler Indices (LIC1, LIC2), Structure Intensive Pigment Index (SIPI) etc. were found to have strong positive correlation (R2 > 0.9) with plant parameters. These specific bandwidths and indices can be helpful in biophysical parameter estimation and early detection of crop stress, crop growth and disease monitoring.
Highlights
Brinjal (Solanum melongena) or eggplant is considered as one of the important vegetable crops after potato,onion and tomato
This study aims to examine the potential of hyperspectral remote sensing for detection of biotic stress caused due to bacterial wilt disease and identify the best spectral band widths and hyperspectral indices indicative of disease infestation
In diseased and severly diseased brinjal there is a decrease in reflectance in the green region due to reduction in chlorophyll content and in near-infrared reflectance due to internal leaf damage
Summary
Brinjal (Solanum melongena) or eggplant is considered as one of the important vegetable crops after potato,onion and tomato. West Bengal state of India has the highest area (about 160 thousand hectares) under Brinjal cultivation in India with a production of approximately 3000 thousand tonnes. Bacterial wilt disease (pathogen: Pseudomonas solancearum) has been widely reported for causing severe problems in brinjal cultivation in the tropical, sub tropical and warm temperate regions of the world. Several researchers have reported the occurrence of this devastating disease from India, and especially, West Bengal (Das et al, 1955; Chatterjee et al, 1997; Samaddar et al, 1998; Mondal el al., 2004b). It has been reported that brinjal crops transplanted during summer months are more prone to get infected with this disease (Mondal et al, 2014). Wilting is generally observed in the reproductive stage of the crop growth, caused by infection in the vascular system of the plant. Loss in turgidity, drying and the entire plant collapses
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