Aerial high-throughput phenotyping of peanut leaf area index and lateral growth

Abstract

Leaf area index (LAI) is the ratio of the total one-sided leaf area to the ground area, whereas lateral growth (LG) is the measure of canopy expansion. They are indicators for light capture, plant growth, and yield. Although LAI and LG can be directly measured, this is time consuming. Healthy leaves absorb in the blue and red, and reflect in the green regions of the electromagnetic spectrum. Aerial high-throughput phenotyping (HTP) may enable rapid acquisition of LAI and LG from leaf reflectance in these regions. In this paper, we report novel models to estimate peanut (Arachis hypogaea L.) LAI and LG from vegetation indices (VIs) derived relatively fast and inexpensively from the red, green, and blue (RGB) leaf reflectance collected with an unmanned aerial vehicle (UAV). In addition, we evaluate the models’ suitability to identify phenotypic variation for LAI and LG and predict pod yield from early season estimated LAI and LG. The study included 18 peanut genotypes for model training in 2017, and 8 genotypes for model validation in 2019. The VIs included the blue green index (BGI), red-green ratio (RGR), normalized plant pigment ratio (NPPR), normalized green red difference index (NGRDI), normalized chlorophyll pigment index (NCPI), and plant pigment ratio (PPR). The models used multiple linear and artificial neural network (ANN) regression, and their predictive accuracy ranged from 84 to 97%, depending on the VIs combinations used in the models. The results concluded that the new models were time- and cost-effective for estimation of LAI and LG, and accessible for use in phenotypic selection of peanuts with desirable LAI, LG and pod yield.

Accelerating leaf area measurement using a volumetric approach

“…In summary, although nowadays leaf area is estimated largely based on the indirect techniques of ground-based [ 45 – 52 ] or airborne [ 53 – 57 ] remote sensing, the precise methods of destructive measurements have been still utilized considerably (e.g., see [ 16 , 26 , 58 ]) and remained as a reference for validating the indirect approaches. Therefore, parallel to the progress in the remote sensing procedures, removing the obstacles of the conventional destructive methods, or development of new techniques for direct measurement of leaf area, seems to be necessary for eco-physiological studies.…”

Utility of unmanned aerial systems for measuring plant height and plant vigor among several Georgia runner peanut cultivars

“…The objective of our study was to evaluate the use of a simple and inexpensive UAS equipped with an RGB camera to make detailed measurements of plant height and plant vigor at different time points in the growing season. We were interested to see if these inexpensive tools could be more narrowly used than Sarkar et al (2020Sarkar et al ( , 2021 to differentiate among a less diverse set of genotypes, such as runner-type cultivars from the Georgia peanut breeding program. Comparisons among this closely related group would more closely reflect the types of comparisons seen within breeding nurseries and replicated breeding trials.…”

“…Values within columns followed by the same letter are not different at k-ratio = 100 according to Waller-Duncan least significant difference (LSD). (Sarkar et al, 2021). In their canopy height study, Sarkar et al (2020) used genotypes from the peanut mini-core germplasm collection, which is highly diverse (Holbrook & Dong, 2005).…”

“…In their canopy height study, Sarkar et al (2020) used genotypes from the peanut mini-core germplasm collection, which is highly diverse (Holbrook & Dong, 2005). Evaluating leaf area and lateral growth, Sarkar et al (2021) used a diverse group of cultivars and breeding lines with a wide range of growth habits and market types.…”

“…We were interested to see if these inexpensive tools could be more narrowly used than Sarkar et al. (2020, 2021) to differentiate among a less diverse set of genotypes, such as runner‐type cultivars from the Georgia peanut breeding program. Comparisons among this closely related group would more closely reflect the types of comparisons seen within breeding nurseries and replicated breeding trials.…”