Eighteen tomato cultivars have been cultured and regenerated from leaf or other tissue types on modified Murishige and Skoog media (1 mg/l thiamine HC1, 0.5 mg/l nicotinic acid, 0.5 mg/l pyridoxine, 3 M IAA-aspartic acid, and 5 M zeatin riboside). This media was selected for optimal tomato regeneration after tests on comparable levels of NAA, IAA,IAA-alanine, IAA-phenylalanine, isopentenyl adenosine, zeatin, and kinetin. Direct explants from stem, leaf, pith, epicotyl and cortex, and hypocotyl tissues that have been cultured for over 18 months were regenerated. This medium produces bigh numbers of shoots on direct explants, and limited numbers of shoots on long term cultures. On long term cultues, all varieties tested have been successfully regenerated; however, passage number and time required on regeneration media differed among varieties.
Observations of long term cultures of UC82 pith and stem callus indicated small explants (2 - 3 mm) were more responsive to regeneration than larger explants. Some differences were observed between tissue types on specific cultivars but this was not true of all cultivars. In general, leaf explants gave the greatest number of plants per explant and root the least.
Table 1 shows the cultivars tested and the percent of direct explants that produced shoots after eight weeks on this modified MS medium. The number of plants that could be transferred to rooting medium at 8 weeks is also indicated. This number of ten increases significantly after an additional transfer. Those varieties that could regenerate shoots after long term culture are also indicated.
Table 1. Regeneration of direct explants and long term callus cultures of tomato.
_______________________________________________________________
% direct explants
Tissue Callus regenerated/number Regenerability
Line/cross source(s) growth plants per explant long-term callus
_________________________________________________________________
UC82 leaf very good 98-100/2.6 good
hypo very good 95-100/NA good
root very good
stem very good good
epi &
cortex good good
SP-l* leaf** good >95/1.35 good
hypo good good
stem good fair
epi &
cortex good fair
SP-2* leaf** good 75-80/1.7 good
SP-4* leaf** good >95/NA
LA13 leaf very good 88-100/1.45-3.17 good
hypo very good
LA14 leaf good 88-100/2.5-3 good
hypo good good
LA154 leaf** good. 62.5/<l
LA159 leaf good >95/NA good
LA274 leaf very good >95/NA good
LA715 leaf excellent
hypo excellent 75-90/2.8 good
LA811 stem poor
leaf poor
hypo poor-fair 56-67/1.2 fair
LA1002 leaf fair 75-80/NA
LA1223 leaf good
hypo** good 95/NA
LA2363 leaf excellent 98-100/4.38 good
Lukullus leaf good
hypo good >95/NA
VFNT
cherry leaf** poor 25/1.9 poor (1/76)
L.
peruvianum stem excellent >95/>6 excellent
L.
chiloensis leaf excellent >95 excellent
hypo excellent >98 excellent
stem excellent >95/>6 excellent
_________________________________________________________________
*SP lines provided courtesy of Dr. R.S. Poethig
(SP-1 chlorophyll mutator;SP-2 e/e,u/u, wf/wf,mc/mc,
SP-4 Xa2/+,a/a,h/h,t/t, and u/u). **Sample size
for regeneration of these direct explants was less than 100.