Lily hybrids vary in their ability to produce
virus-free (VF) bulblets when grown from virus-infected
scales in tissue culture. Asiatic hybrids typically
produce a higher percentage of in vitro VF scale bulblets
than do Lilium longiflorum cultivars. Three hypotheses
concerning the cause of this variation are tested on five
lily hybrids: an Asiatic hybrid, two L. longiflorum
cultivars, an Oriental hybrid and L. candidum.
The first hypothesis states that VF scale bulblets
originate from wound tissue that is naturally low in virus
concentration and blocks the passage of virus particles
from one cell to the next. The second hypothesis says that
scale-to-bulblet vascular connections, which serve as virus
pathways, occur in hybrids showing high percentages of
virus-infected scale bulblets, while connections are absent
in those hybrids with low numbers of virus-infected
bulblets. The third hypothesis concerns the virus
concentration in the scale at the site of bulblet origin:
bulblets of hybrids producing large numbers of VF bulblets
originate from scale tissues low in virus concentration;
bulblets of low percentage VF bulblet hybrids originate
from scale tissues high in virus concentration.
The first two hypotheses are not supported by the
results of this study. First, lily bulblets do not
originate from wound tissue. Second, scale-to-bulblet
vascular connections consistently occur in 'Enchantment,'
an Asiatic hybrid, and occasionally occur in L. candidum.
Vascular connections are not detected in the low VF bulblet
producers, L. longiflorum cultivars 'Ace' and 'Nellie
White,' nor are they seen in the Oriental hybrid
'Stargazer.'
Speculative support exists for the third hypothesis
concerning uneven virus concentration in the scale.
Distinct virus particles are observed with the electron
microscope in the double virus-infected L. longiflorum
cultivars and not in the other singly-infected lilies. The
doubly-infected lilies produce a continuous layer of
divided cells in the adaxial subepidermis of the scale
where bulblets originate, whereas the singly-infected
lilies produce cell division masses in the same area but
only beneath forming bulblets.
This study suggests that virus particles in
L. longiflorum cultivars are more uniformly distributed
than particles in the other lilies examined. This occurs
not only at the site of bulblet origin but also throughout
the scale mesophyll. Whether this is due to concurrent
viral infection or to hybrid variation is unknown. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36587 |
| Date | 27 June 1991 |
| Creators | Ruttum, Joanne C. |
| Contributors | Allen, Thomas C. Jr |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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