Citrus Tristeza Virus - Hosts and Symptoms

Hosts and Symptoms

CTV infects several species of the plant genus, Citrus, including sour orange (Citrus aurantium), and any Citrus species grafted onto sour orange root stock, sweet orange (C. sinensis), grapefruit (C. paradisi), lime and Seville orange (C. aurantifolia), and mandarin (C. reticulata). CTV is also known to infect Aeglopsis chevalieri, Afraegle paniculata, Pamburus missionis, and Passiflora gracilis. CTV is distributed worldwide and can be found wherever citrus trees grow. Symptoms of CTV infection are highly variable and depend on several factors including host, virulence of the particular virus strain, and environmental conditions. The three most common groupings of symptoms are decline (quick and slow), stem-pitting, and seedling yellows. Decline is generally exhibited with sweet orange, mandarin, or grapefruit when they are grafted on infected sour orange rootstock. This decline includes chlorotic leaves and general dieback of the infected tree. Decline may be slow, lasting several months to years after the first symptoms are noticed. In this case the infected tree will also show a bulge above the bud union and honeycombing on the inner face of the original sour orange root stock bark. The decline may also be quick, resulting in host death just days after the first symptoms are noticed. Stem-pitting is another symptom of CTV that manifests in most host types under the proper conditions, and especially in Citrus trees grafted onto sour orange rootstock. The host will develop pits in the trunk and stem. This results is decreased tree vigor and reduced fruit yield. This is typically caused by the more virulent strains of CTV. The third major symptom of CTV infection is seedling yellows. This tends to occur on sour orange, Natsudaidai, lemon and buntan. Symptoms include yellowing of foliage and general dieback.