Field and In Vitro Evaluation of Mandarin Cultivars Resistance to Alternaria alternata

Alternaria brown spot (ABS) of tangerines, caused by the necrotrophic fungus Alternaria alternata (Fr.) Keissl, is one of the most destructive diseases affecting mandarins worldwide, especially under the Mediterranean climate. The present study aimed to assess the susceptibility of mandarins to the A. alternata, through in vivo and in vitro inoculation for 10 mandarins varieties from a Moroccan collection at INRA-Kénitra including Ananas, Bergamota, Dancy, Murcott Honey, Carvhalal, Satsuma Wase, Vohanisahy Ifranica, Temple, Nadorcott and Lée. Field inoculation trials were performed in parallel with the laboratory experiments by inoculation of fungal spores in fruits and young detached leaves. In vitro leaves inoculations were conducted in two successive years to confirm results and ABS-resistant hybrids were selected. The severity of disease in fruits and leaves was determined by following a specific diagrammatic scale of ABS and calculating the disease progress curve (AUDPC). The results indicated that all the cultivars showed disease symptoms on fruits and leaves either in the field or in the laboratory. The AUDPC values of the ABS of fruits and leaves inoculated in the field ranged from 87.63 to 201.2 and 32.88 to 74.04, respectively. For the in vitro inoculations, the minimum values of AUDPC were essentially obtained by the Temple and Nadorcott varieties. Temple, Nadorcott, Lée and Vohanisahy Ifranica have low AUDPC values and seem to be resistant to the disease, whereas others namely Dancy, Carvhalal, Ananas, Murcott Honey, Satsuma Wase exhibited a greater disease susceptibility. © 2022 Friends Science Publishers