Light plays an essential role in plant growth and development together with host defensive mechanisms.
Subjecting plants to specific wavelengths of light such as ultraviolet (UV) and red light can induce plants to develop higher levels of disease resistance against pathogens.
UV-C irradiation leads to accumulation of phytoalexin hydroxyphaseollin, which helps soybean plants develop resistance against P. megasperma var. sojae [12].
UV irradiation also facilitates accumulation of the phytoalexins sakuranetin and oryzalexin F in rice leaves, which might help increase resistance against microbial pathogens [13,14].
Red light treatment of pepper, pumpkin, and tomato seedlings led to development of resistance against P. capsici [15]. Furthermore, systemic disease resistance against root-knot nematode Meloidogyne javanica and a bacterial disease, P. syringae pv.
Tomato DC 3000, was induced by pretreatment of Arabidopsis with red light [16].