Temporal and spatial changes of chlorophyll fluorescence as a basis for early and precise detection of leaf rust and powdery mildew infections in wheat leaves

Abstract

Temporal and spatial changes in parameters of fast chlorophyll fluorescence kinetics (ground fluorescence, Fo and maximal fluorescence, Fm) and red/NIR reflectance were assessed with a Pulse-Amplitude-Modulated (PAM)-Imaging system on a daily basis over a period of 2 weeks following inoculation of wheat leaves with powdery mildew and leaf rust. The early detection of these infections by means of fluorescence imaging was possible 2-3 days before visual symptoms or significant changes in normalised-differenced-vegetation index (NDVI) became apparent. The initial infection of both fungi caused an increase in Fo and decrease in photochemical efficiency (Fv/Fm, Fv/Fo). The appearance and development of fungal pustules was accompanied by reduction in Fo and Fm. This resulted mainly from lower absorption of fluorescence exciting light by the leaf mesophyll due to the shielding effect of fungal mycelium, and to lesser extent from the chlorophyll breakdown underneath pustules. Among the evaluated fluorescence parameters, Fv/Fo displayed the most pronounced response to both kinds of infection. Mildew infection influenced chlorophyll fluorescence neither in the direct vicinity of mycelium nor in the apparently healthy leaf regions. Rust infected plants, in contrast, displayed significantly reduced photochemical efficiency Fv/Fm and Fv/Fo in chlorotic tissue around pustules. The same, but less pronounced tendency was found in the apparently healthy regions of rust infected leaves in the last days of the experiment. Dark adaptation of leaves proved to be necessary for accurate detection of both pathogen infections by means of fluorescence imaging. Additional experiments are needed to estimate the potential of this technique for remote sensing under field conditions.

Prompt chlorophyll fluorescence as a tool for crop phenotyping: an example of barley landraces exposed to various abiotic stress factors

“…The measurement of photochemical process at PSII level and photosynthetic pigment contents gives a clear idea of a stress plant is going through (Kautsky andHirsch 1931, Kalaji et al 2016). In recent years, the measurement of Chl fluorescence has become a popular method for assessment of the impact of different stress factors on photosynthesis (Bolhàr-Nordenkampf and Öquist 1993, Schreiber et al 1994, Maxwell and Johnson 2000, Strasser et al 2000, Fracheboud and Leipner 2003, Kuckenberg et al 2009, Dai et al 2009). …”

“…Analysis of Chl fluorescence parameters can be used as a precise tool to test a direct response of adverse environmental conditions on photosynthesis and therefore the indirect assessment of their impact on plants (Kuckenberg et al 2009). Chl fluorescence techniques have been used to study precisely effects of various stress factors, such as high and low temperature (Mathur et al 2011), quality and intensity of radiation, water stress, salinity (Mehta et al 2010), herbicides as inhibitors of photosynthesis, heavy metals (Mathur et al 2016), particulate pollution (Tomar and Jajoo 2014), soil gas, and phytotoxic materials on plants and in atmosphere (Fracheboud andLeipner 2003, Dai et al 2009).…”

“…The test can be performed both on individual plants (including transgenic), or entire ecosystems in order to evaluate a tolerance for individual or various stress factors (Bolhàr-Nordenkampf and Öquist 1993, Schreiber et al 1994, Strasser et al 2000, Maxwell and Johnson 2000. Measurement of Chl fluorescence allows to detect stress response before we notice visible signs (wilting, necrosis, chlorosis) or before it might be detected by other methods, such as measurements of gas exchange or changes in Chl contents (Devi et al 1996, Roschina and Melnikowa 1996, Kalaji and Pietkiewicz 2004, Kalaji and Guo 2008, TsimilliMichael and Strasser 2008, Kuckenberg et al 2009.…”

Hyperspectral and Chlorophyll Fluorescence Imaging for Early Detection of Plant Diseases, with Special Reference to Fusarium spec. Infections on Wheat

“…Chlorophyll fluorescence analysis (CFA; e.g., [13,14] and chlorophyll fluorescence imaging (CFI; e.g., [15,16]) are well-established, effective tools for a comprehensive examination of development and effects of bacterial, fungal and viral infections on leaves of many cultivated plants [17][18][19][20]. It can be used for entire intact plants [21,22], detached leaves and also leaf disks punched out from infected plant material [23][24][25].…”

Fusão sensorial por classificação cognitiva ponderada no mapeamento de cenas naturais agrícolas para análise quali-quantitativa em citricultura

“…São técnicas sob imagens no espectro visível e infravermelho, termografia óptica, foto reflexão e fluorescência. Na fluorescência, a detecção de doenças é feita nos estágios iniciais, mesmo antes de alterações visíveis no tecido da planta, todavia a acurácia é dependente da intensidade luminosa; a foto reflexão identifica o fator de estresse foliar, mas é eficiente somente após o aparecimento visível dos sintomas e sensível a descoloração da folha; a termografia detecta doenças relacionadas com a hidratação foliar, mas é dependente de iluminação, baixa acurácia em climas instáveis e na identificação das espécies (LAMB et al, 2007;KUCKENBERG et al, 2009;NAIDU et al, 2009). …”