LED for faster and better propagation (LED4FaB Roots)

UK lettuce and celery crops are produced commercially from transplants - young plants which are propagated in greenhouses before being planted out in the field. A significant proportion of transplants are produced in winter and spring when day lengths are short and greenhouse heating requirements are high. Low ambient light levels in heated greenhouses can lead to reduced quality, stretching and slow growth, taking 6 - 8 weeks from sowing to planting out.

G's require 5 - 6 million lettuce and 3 - 4 million celery transplants each year, producing harvested crops worth >£2.5 million. The challenge for salad producers is producing vegetable transplants using reduced energy inputs and having increased quality and resilience to abiotic stress during the post transplanting stage of establishment.

This 2-year project would optimise supplementary LED lighting irradiance and spectra for a) improving quality b) shortening production cycles, and c) manipulating root system architecture (RSA) in transplants.

During the winter, with low levels of ambient light, plant growth and quality is directly linked to supplementary irradiance across the spectrum that supports photosynthesis (400 - 700 nm). A previous KTP between HAU and G's has manipulated RSA in transplants by varying the ratio between red and blue LED illumination (data not published). This response is not well understood but has the potential to improve efficiency of transplant production across a wide range of crops.

A recent PhD at HAU has also suggested that transplants with a greater 'root potential' recover more quickly from shock associated with planting out and may have improved resilience to abiotic stress, such as drought, during establishment and growth in the field.1 This project would study plant growth and RSA development in the greenhouse in response to LED light treatments (spectrum, irradiance, timing and duration) and subsequent plant performance in the field.

Genes associated with rooting responses to light have been identified in model organisms.2 We will quantify expression of key rooting genes linked to light-responsive rooting traits under key lighting treatments to better understand the molecular basis of the trait in these crops.

The work would enable the selection of light recipes for propagation periods but the response may vary with genotype, limiting efficacy. The project will utilise germplasm from three partner breeders to a) optimise genotype x lighting responses, and b) identify breeding material for future development towards optimised propagation of novel varieties.

Potential impacts Shortened transplant production cycle Reduced heating costs Improved transplant quality Improved crop quality Increased understanding of the molecular basis of root responses to light in crop species Identification of lines and genes of interest for PACE-targeted breeding for improved propagation