Optimal LED Wavelength Composition for the Production of High-Quality Watermelon and Interspecific Squash Seedlings Used for Grafting

Filippos Bantis,Anastasios S Siomos,Athanasios Koukounaras,Kalliopi Radoglou,Christodoulos Dangitsis

doi:10.3390/agronomy9120870

Filippos Bantis, Anastasios S Siomos + Show 3 more

Open Access

https://doi.org/10.3390/agronomy9120870

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Abstract

Watermelon is cultivated worldwide and is mainly grafted onto interspecific squash rootstocks. Light-emitting diodes (LEDs) can be implemented as light sources during indoor production of both species and their spectral quality is of great importance. The objective of the present study was to determine the optimal emission of LEDs with wide wavelength for the production of watermelon and interspecific squash seedlings in a growth chamber. Conditions were set at 22/20 °C temperature (day/night), 16 h photoperiod, and 85 ± 5 μmol m−2 s−1 photosynthetic photon flux density. Illumination was provided by fluorescent (FL, T0) lamps or four LEDs (T1, T2, T3, and T4) emitting varying wide spectra. Watermelon seedlings had greater shoot length, stem diameter, cotyledon area, shoot dry weight-to-length (DW/L) ratio, and Dickson’s quality index (DQI) under T1 and T3, while leaf area and shoot dry weight (DW) had higher values under T1. Interspecific squash seedlings had greater stem diameter, and shoot and root DW under T1 and T3, while leaf and cotyledon areas were favored under T1. In both species, T0 showed inferior development. It could be concluded that a light source with high red emission, relatively low blue emission, and a red:far-red ratio of about 3 units seems ideal for the production of high-quality watermelon (scion) and interspecific squash (rootstock) seedlings.

Highlights

Watermelon (Citrullus lanatus) is an economically important crop worldwide producing over 100 million tons annually (2010–2017, FAOSTAT Database)
TZ-148 is the most commonly used rootstock for watermelon grafting throughout the world
Watermelon (Citrullus lanatus) “Celine F1” (HM.Clause SA, Portes-Les-Valence, France) or interspecific squash rootstock (Cucurbita maxima × C. moschata) “TZ-148” (HM.Clause SA, Portes-Les-Valence, France) seeds were sown in plastic 171 and 128-cell plug trays

Summary

Introduction

Watermelon (Citrullus lanatus) is an economically important crop worldwide producing over 100 million tons annually (2010–2017, FAOSTAT Database). Watermelon crop is mainly established using grafted seedlings consisting of two plant segments: the scion and rootstock. The scion segment is a watermelon hybrid offering a number of desired traits including relatively high yield as well as qualitative characteristics such as pleasant fruit flavor and aroma, and higher antioxidant compound content. The rootstock segment provides the grafted seedling with greater protection against environmental stress factors (heavy metals, salinity, low temperatures, etc.) [1,2] and soil-borne pathogens [3,4]. TZ-148 (interspecific squash, Cucurbita maxima × C. moschata) is the most commonly used rootstock for watermelon grafting throughout the world.

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