OPTIMALIZATION OF THE IN VITRO SELECTION TECHNIQUE FOR ENHANCED TOLERANCE TO ERWINIA CAROTOVORA

The search for genes of resistance to Erwinia carotovora among carrot cultivars, conducted for many years at our Department, was not entirely successful.
The research was broadened to include some wild Daucus carota L. subspecies and several crosses between wild and cultivated forms were made.
Callus lines were developed from a number of roots originating from the crosses tolerant to Erwinia carotovora in the laboratory slice test.
These callus lines were used to develop the technique for in vitro selection.

Three ways of media preparation were used:

1. crude filtered medium after bacterial culture added to the MS growth medium (pectolytic enzymes active)(F)

2. autoclaved filtered medium after bacterial culture added to the MS growth medium (sectolytic enzymes inactivated)(A)

3. pure bacterial medium without prior bacterial culture added to the MS growth medium (no pectolytic enzymes)(P)

The reaction of different callus lines to increasing concentrations of bacterial filtrate was examined.
Callus growth coefficient for each treatment was computed using the formula:

callus growth coef. = (final weight – initial weight)/initial weight

Callus growth was most intensive on the P medium.
A certain decrease of callus growth potential was observed when the A medium was used [figure 1]. Medium with active pectolytic enzymes (F) very clearly limited the growth of all genotypes.
The decrease of the callus growth rate on this medium was in some cases as high as 97 % in comparison to the A medium [figure 2]. The concentrations of 15 or 20% of the filtrate in the growth medium proved to be the most appropriate for selection.
Callus lines used for selection were 3 or 4 times transferred on the F medium.

The genotypes differed in the growth potential of callus in vitro cultures on the A medium.
The callus line from the cross D.c. ssp. gummifer x D.c. ssp. sativus showed the highest growth rate.
Other examined genotypes showed similar growth potential. [figure 2]. However, the growth of some genotypes (i.e. 4890 and 4919) was strongly limited when the F medium was applied instead of the A medium, while genotype 104 retained its high growth potential even in the presence of active enzymes [figure 2]. Plant regeneration from callus lines after selection was initiated in February 1996, and the plants obtained have not yet been evaluated in terms of their reaction to infection with Erwinia carotovora.

III International Symposium on In Vitro Culture and Horticultural Breeding

B. Michalik, R. Baranski, D. Grzebelus, M. Szklarczyk

carrot, Daucus carota, subspecies

https://doi.org/10.17660/ActaHortic.1997.447.92