In this study, (Myrtus communis L.) was explored in vitro and in vivo for controlling blight disease using two chickpea genotypes ILC 3279, INRA 199 and a local cultivar Bouazza. Blight caused by Ascochyta rabiei Pass. Lab. is major disease affecting chickpea production. To control this disease, chemical harmful fungicides are used hence, developing natural plant protection products as an alternative has become important regarding the environmental impact. The effect of essential oil (EO) extracted from myrtle leaves by hydrodistillation was evaluated on the growth of Ascochyta rabiei Pass. Lab. mycelium, by dilution method using chickpea culture medium added with 0, 200, 300, 500 and 1000 ppm. The radial growth of A. rabiei Pass.Lab. was inhibited at 40.9, 68.18 and 96.69% with 200, 300 and 500 ppm respectively. Myrtle essential oil used at 1000 ppm inhibited the fungus growth completely (100%). In vitro EO efficacy was investigated using detached leaflets method inoculated with 5 µl pathogen spore solution of 106 spores / ml concentration. Efficacy was investigated using 750 ppm EO solution. Disease (DS) Severity and disease incidence (DI) on detached leaflets were determined.

Highest disease incidence was observed on Bouazza (100%) followed by ILC 3279 (84.28%) and INRA 199 (17.5%). Myrtle essential oil showed an efficacy in all cases and decreased significantly disease incidence for Bouazza, ILC 3279 and INRA 199 to 63.33, 56.66 and 16% respectively. Disease severity showed the same profile, Bouazza noted the highest rate followed by ILC 3279 and INRA 199 with 60, 40 and 21% respectively and EO showed a significant efficacy and reduced these disease severity rates to 52 32 and 18 %. The bioassay conducted in vivo under greenhouse conditions with plants including a negative control with any treatment and two other batches inoculated by hand held sprayer, a spore solution with a concentration of 106 spores/ ml and treated or not with myrtle EO. Disease incidence percentage (DIP) decreased significantly under common myrtle EO compared to control in INRA 199 and ILC 3279 for severity percent index (SPI) no significant difference was observed for all genotypes under Myrtus communis L. essential oil treatment effect. This study showed Myrtus communis L. essential oil efficacy on chickpea blight disease in vitro on fungal radial growth and in vivo either on deatached leaflets or whole plants under greenhouse condition. This natural product reduced significantly blight disease incidence and severity. And to control disease, myrtle essential oil extraction as fungicide is a promising alternative against this disease.