Mohammad Mehdi Faghihi

Citrus huanglongbing (HLB) associated with Candidatus Liberibacter spp. is the most destructive bacterial disease of citrus crops worldwide. In this study, the response of three-year-old seedlings of 14 commercial citrus cultivars and rootstocks to the Asian form of HLB disease ( Ca . L. asiaticus) was investigated through graft-inoculation. The seedlings' reactions to the HLB disease were evaluated based on the PCR detection of CLas after grafting, the disease incubation period (time between graft-inoculation and appearance of the first disease symptoms), and disease severity. Depending on the time of the positive PCR detection of CLas and appearance of disease symptoms, Mexican lime, Persian lime and Volkamer lemon were ranked at the highest level of tolerance (lowest susceptibility), and Rough lemon and Local orange were at the next level, i.e., semi-tolerance (intermediate susceptibility). Alemow, Bakraei, Rangpur lime, Cleopatra, Clementine mandarin, Local mandarin, Blood orange, and Washington navel orange were classified as susceptible to the disease, followed by Valencia orange, which was the most susceptible. In conclusion, all citrus genotypes studied, were affected by HLB. However, symptoms varied by cultivar, with the most severe observed on Valencia sweet orange and Local mandarin, while less severe symptoms were observed on Mexican lime, Persian lime and Volkamer lemon.

Root‐knot nematodes ( Meloidogyne ), with their broad host range and ability to challenge plant resistance, represent a significant obstacle to the development of crop production, including eggplant cultivation. In this greenhouse study, the resistance of 26 eggplant varieties to M. javanica was evaluated. The plant seeds were sown in two‐kilogram plastic pots and kept under greenhouse conditions at a temperature of 27°C ± 2°C. The seedlings were inoculated at the four‐leaf stage with 6000 nematode eggs. After 60 days, the plants were harvested, and the indices of plant growth and nematode populations were evaluated. In addition, catalase, peroxidase, and superoxide dismutase activity were measured. For this purpose, the varieties Noorabad and Black Beauty, which are highly sensitive and less sensitive varieties, respectively, were planted in one‐kilogram pots and kept in the greenhouse. The seedlings were inoculated with 3000 nematode eggs at the four‐leaf stage. Root tissue extraction was performed at six time points (0, 5, 9, 13, 17 and 21 days) after inoculation. The results showed that the growth indices of the varieties Faselis and Black Beauty were better compared to the other varieties. The significant changes in enzyme activity observed in the Black Beauty variety in response to infection were considered to be the reason for the lower nematode damage. However, according to the Canto‐Saenz classification, all varieties analyzed were classified as susceptible, as they had a gall index > 2 and a reproduction factor > 1.