When tobacco,
Nicotiana tabacum variety Xanthi (scion) grafted on
Nicotiana glutinosa (stock) was inoculated with TMV on its t6bacco leaf several weeks after grafting, systemic necrosis of lateral shoot of
N. glutinosa was observed 9 to 16 days after inoculation, in 13 out of 18 tests. Similarly, when
N. glutinosa (scion) grafted on tobacco (stock) was inoculated with TMV on its tobacco leaf, systemic necrosis was observed on the apical portion of
N. glutinosa 15 to 24 days after inoculation, in 4 out of 11 tests. From these necrotized portions TMV was recovered in high concentration.
When any of the leaves of
N. glutinosa grafted with tobacco were inoculated with TMV, necrotic lesions appeared only on the inoculated leaves. However, no systemic infection was observed in the tobacco part.
When doubly cleft-grafted plant-
N. glutinosa (scion), tobacco (middle part), and
N. glutinosa (stock)-was inoculated with TMV on its tobacco leaf, systemic necrosis began to appear on the lateral shoots of the stock
N. glutinosa 10 to 14 days after inoculation.
Contrary to this, when doubly cleft-grafted plant-tobacco (scion),
N. glutinosa (middle part), and tobacco (stock)-was inoculated with TMV on the leaves of either of the two tobacco shoots, mosaic symptoms appeared on the young leaves of the opposite tobacco shoot 15 to 24 days after inoculation. This fact indicates that TMV is able to move from one tobacco shoot to another without hindrance from the middle part,
N. glutinosa.
Immediately and 5 days after the appearance of systemic necrosis due to TMV infection, the affected lateral shoots of
N. glutinosa were fixed with FAA and serial sections from these materials were examined for the distribution of the necrotized portions caused by the TMV which had been moved.
The first appearanance of necrosis was observed within young phloem tissues next to the apical meristem. Then the necrotic portion extended gradually to the surrounding tissues. No necrotic portions were found at the growing point and its peripheral meristematic cells. And no necrosis was observed in the mature phloem at least for 2 weeks after inoculation.
It is concluded that TMV moved through enucleate mature sieve tubes of
N. glutinosa plant into the young phloem and multiplies there to form necrotic lesion, and that TMV is incapable to multiply within the meristematic tissues.
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