Agriculture: ENEA and CREA UV treatment increases kiwifruit plants resistance to pathogens

An ENEA and CREA research team has demonstrated that kiwifruit plants^[1] treated with UV rays are more resistant to pathogens. In particular, over 60% of the plants treated showed reduced sensitivity to the main kiwi disease, the so-called "bacterial canker".

"The UV rays induced the production of particular molecules^[2], such as carotenoids and phenols, which strengthened the natural defenses of the plant", explained Paolo Di Lazzaro at the ENEA Laboratory of Plasma Applications and interdisciplinary Experiments, which conducted the study with Daniele Murra and Sarah Bollanti, Antonia Lai at the ENEA Diagnostics and Metrology Laboratory and Loretta Bacchetta at the ENEA Bioproducts and Bioprocesses Laboratory.

"This effect is known as 'hormesis' and could be a promising alternative to limit the use of pesticides in agriculture, with significant benefits for the environment and the health of consumers and operators", pointed out Simona Lucioli, researcher at the Olive, Fruit and Citrus Growing Center (CREA-OFA), which conducted the study with Emilia Caboni and Marco Scortichini (CREA-OFA Rome Office).

To irradiate the plants, researchers from the Eccimeri Laboratory of the ENEA Frascati Research Center (Rome) have developed a portable device as big as a smartphone (9×3 cm²), made of 20 LEDs, which provide irradiation of variable power and duration and a cooling system, essential to ensure stability of the irradiated intensity especially in long-term treatments. "Compared to traditional mercury lamps used in this type of treatment, the LEDs of our device have better features in terms of robustness, lightness, rapid switching on/off and, above all, transportability^[3] for field applications" , pointe out Di Lazzaro.

In detail, the kiwi leaves infected and not treated with UV-C rays, already after a week, showed browning and leaf wilting, which were almost absent in the groups irradiated with a dose of 1.3 kJ/m2 and infected. After 10 days, also the irradiated groups began to show symptoms of infection but, after three weeks the infection remained limited to 36% of the irradiated and inoculated leaves while it affected over 90% of the infected and UV untreated leaves. These results are in line with those already obtained against pathogens such as gray mold (Botrytis spp) and green mold (Pennicillum) on basil, apples and citrus fruits.

"A comparison among the kiwi samples showed an increase in the production of chlorophylls, carotenoids, polyphenols and antioxidant activity in the irradiated leaves. The results confirm the importance of a specific study to identify the optimal UV-C dose range", the researchers said.

The FAO estimates the global area planted with kiwifruit at over 270 thousand hectares, with Italy (25 thousand hectares) second only to China (185 thousand hectares); the most productive Italian region is Lazio with around 9,500 hectares (Istat data 2022). Climate change, kiwi death and bacterial canker are among the main issues facing farmers. The bacterial canker of kiwifruit, caused by the bacterium Pseudomonas syringae pv. actinidiae (Psa), has spread to a pandemic scale since 2008, causing devastating effects; currently the control of this pathology relies on agronomic and chemical approaches, which have however an impact on the environment.