A Light Recipe including Far-Red Wavelength during Healing of Grafted Watermelon Seedlings Enhances the Floral Development and Yield Earliness

Abstract

Watermelon is widely propagated through grafting, after which seedlings are subjected to healing under controlled conditions including artificial lighting. Light wavelengths, such as blue, red, and far-red, impose considerable effects on seedlings, which possibly carry on to the mature plants. The aim of the present study is to examine whether different light wavelengths during healing of grafted watermelon seedlings impose variable effects during field cultivation. After grafting, seedlings were healed in an environmentally controlled healing chamber under fluorescent (FL) lamps and light-emitting diodes, providing 100% red (R), 100% blue (B), 88/12% R/B (12B), and 12B including 5% far-red (12B + FR). After acclimatization, seedlings were transplanted in the field. Vegetative growth until floral initiation was enhanced by 12B and 12B + FR, as shown by stem diameter and leaf number measurements. Flowering was mainly accelerated by 12B + FR and considerably decelerated by FL and B. The same pattern was followed by fruit yield, which was similar for all treatments at the end of the experiment. Nevertheless, fruit quality was not affected by any of the light treatments. It is concluded that a light recipe, including red, blue and far-red, wavelengths during healing of grafted seedlings enhances the overall growth, and flowering and yield earliness of watermelon crops.

The Use of High-Quality Watermelon Seedlings Is Prerequisite to Limit the Transplanting Shock and Achieve Yield Earliness

“…In another experiment [27], watermelon fruits in Greece, in 2018, which had milder summer temperatures, showed lower total phenolic content and antioxidant activity compared those in the present study. This was also observed in another study of our group which resulted in greater fruit quality in 2021 crops compared with that of 2018 crops [28]. The potentially enhanced fruit quality may lead to increased market value when yield is not negatively affected.…”

“…In this experiment, male flowers started to bloom on DAT 21, while female flowers started to bloom on DAT 24. Therefore, on DAT 24, we started to measure and tag the female flowers with plastic labels every two days until after peak flowering on DAT 36 (i.e., on DAT 24,26,28,30,32,24,and 36). The labels were placed with the purpose of identifying the flowering dates and quality categories of the produced fruits at the end of the experiment.…”

Ascophyllum nodosum and Silicon-Based Biostimulants Differentially Affect the Physiology and Growth of Watermelon Transplants under Abiotic Stress Factors: The Case of Salinity

“…Nevertheless, this region still offers the best microclimatic conditions for fruitful watermelon growth; thus, it is imperative that such soils continue to be cultivated, which will further deteriorate the salinity conditions in the upcoming years. Greece is among the highest watermelon producers reaching 12% of the total export value in Europe (FAOSTAT, 2022), with over 60 million euros [ 18 ]. The crop is mainly established using seedlings produced in nurseries and afterwards transplanted in the field.…”

Impact of Light on Horticultural Crops

“…All contributions are original research articles dealing with a wide range of subjects. These subjects include seed treatment with light and laser to enhance caper germination [1], light quantity and quality effects on the production of grafted and ungrafted vegetable seedlings [2][3][4][5], application of light in a greenhouse or a PFAL system to enhance the yield and nutritional value of lettuce varieties [6][7][8] and watercress [9], light colour impact on Chrysanthemum cuttings' rooting and growth [10], as well as a study of the potential of LEDs in combination with adaptive lighting control protocols and greenhouse-integrated photovoltaics to enable year-round crop cultivation in the Nordics [11].…”

“…Throughout the world, watermelon (Citrullus lanatus L.) is propagated in high percentages through grafting, and seedlings are then subjected to a healing stage where conditions such as light are controlled. Bantis et al [3] examined the impact of different light qualities (applied at the healing stage) for the field cultivation of grafted watermelon (cv. Celine F1 scion grafted onto Cucurbita maxima × C. moschata cv.…”