Symptom Differences in Lime Trees Infected with Various Tristeza Virus Isolotes

Abstract

During the period 1980 - 85, 137 isolates of citrus tristeza virus (CTV) were collected from various citrus growing areas in Thailand; they comprised six from Leech lime (Citrus hystrix DC.,), 48 from acid lime (C. aurantifolia Swingle) , 36 from mandarin (C. reticulata B1.), 20 from sweet orange (C. sinensis Obs.), 12 from pummelo (C. grandis Osb.) and 15 from other citrus species. Acid lime seedlings were used as indicator plants for CTV detection. The infected citrus tissue was grafted to the seedlings and any expression of symptoms subsequently observed. T1-NRRB, a CTV isolate from Romphiboon District of Nakhon Sri Thammarat Province with mild symptoms, was subsequently further examined in cross protection studies under greenhouse conditions. Acid lime plants carrying the T1-NRRB isolate and then infected with a severe isolate, grew significantly better and showed fewer symptoms than those which were not pre-immunized with T1-NRRB. The cross protection studies using T1-NRRB are being further pursued munder field conditions.