| Citrus tatter leaf disease caused by Citrus tatter leaf virus (CTLV) is an economically important systemic disease of citrus, and it was first discovered in 1962 in California by Wallace and Drake. CTLV is transmitted by mechanical rubbing, grafting inoculation and seed. CTLV-infected cultivars on trifoliate orange or its hybrids showed virus-induced bud-union incompatibility, leaf yellowing and even plant death. Up to now, there have been no effective methods to cure the disease, but a combination of thermotherapy and shoot-tip grafting was used to get virus-free cultivate seedlings in order to control this disease in citrus production.Many articles have reported about thermotherapy, shoot-tip-grafting and combination of both methods to eliminate CTLV as well as a combination of variable temperature alternating conditions, but there is still the lack of data about influence of CTLV relative expressions in citrus plants under different temperature treatments. This study was designed to know the influence of different alternating temperatures on relative CTLV expressions in young leaves of sweet orange plants by Real-time RT-PCR and their effects on CTLV elimination by shoot-tip grafting. The results are as follows:(1) Influences of constant temperature condition on CTLV relative expression in mature leaves of sweet orange plantsunder three treatmens of 25℃,30℃ and 35℃ with light lOh/dark 14h for 30 days, The relative expressions of CTLV in old leaves of sweet orange were found to slightly increase, then decrease and significantly decrease, respectively, suggesting that some this virus were killed or transferred to some where else under high temperature conditions.(2) Influences of constant temperature condition on CTLV relative expression and extrusion in buds of sweet orangeCTLV relative expressions of buds and corresponding mature leaves were detected. CTLV amount of the first leaf of the top five leaves was the lowest, under 25℃ for 10 days and 24 days, the latter slightly lower. Under 3O℃ treatment for 24 days, CTLV relative expression in the first leaf was lower than the rest four-leaves. Under 35℃ treatment for 10 days, CTLV in all the top five leaves were not detected. In comparing between 25℃,30℃and 35℃ treatments, CTLV relative expression of the top five leaves under 25℃ treatment was highest. Under 30℃ treatment CTLV relative expression of the top five leaves was slightly lower than 25℃treatment. Under 35℃ treatment, no CTLV was dectected. For three treatments, grafted shoot-tip survival rate was higher under 25℃and 30℃ treatments, but elimination rate of CTLV was much lower. Under 35℃ treatment gafted shoot-tip survival rate was lower, but elimination rate I was much higher.(3) Influences of different alternating temperature treatments on CTLV relative expression of sweet orange buds and extrusion in buds of sweet orange.CTLV in the top two leaves were not detected under conventional heat treatment (40℃ 10h/30℃14h) for 30 days. CTLV in the first leaf was detected under 40℃ 4h/25℃ 4h for 30 days and 50 days, neither. CTLV in the other leaves including their corresponding mature leaves were detected. CTLV in the top two leaves were not detected under 40℃ 4h/30℃ 4h for both 30 days and 40 days, while no CTLV detection in the three leaves for 50 days. The germinational rate of shoots and grafted shoot-tip survival rate was lowest under conventional heat treatment and its CTLV was not eliminated. However, the germinational rate of shoots and grafted shoot-tip survival rate was much higher under both 40℃ 4h/25℃ 4h and 40℃ 4h/30℃ 4h with much more CTLV elimination than conventional heat treatment。... |
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