Response of different citrus cultivars to citrus root nematode (Tylenchulus semipenetrans Cobb.)

Citrus is the most extensively produced fruit of world. Citrus root nematode (Tylenchulus semipenetrans Cobb.) is the predominant nematode present in citrus orchards of Pakistan. A greenhouse experiment was conducted to identify the accessions of nematodes in various citrus cultivars (Kinnow, Musambi, Shakri, Futrell's early and Blood oranges) for susceptibility, invasion, development and its effects on citrus growth. The results indicated that the maximum leaf losses (31%) were recorded in Kinnow cultivar as compared to control due to infection with nematode. A similar trend was reported in all other cultivars. The results revealed that T. semipenetrans had lethal effects on the plant height. The maximum difference for plant height (25 cm) was noticed in Musambi where T. semipenetrans treated plants showed an average plant height of 60 cm; while in control it was 85 cm. As for as the juveniles were concerned, the maximum number (3593) was noted for Futrell's early; the minimum (2956) juveniles were recorded in Shakri. Likewise, highest value (577) for females of T. semipenetrans was recorded in Futrell's early, while the lowest number (447) was counted in Shakri showing resistant and moderately resistant reaction to the tested nematode. The root weight of all citrus cultivars was statistically at par as compared to control. The maximum reduction (17.8%) in shoot weight was noticed in Blood oranges, while all other cultivars also showed significant reduction in shoot weight as compared to control.