An assessment of genetic stability of potato in vitro by molecular and phenotypic analysis

Abstract

It has generally been assumed that plants micropropagated by multiplication of organised meristems or by serial subculture of stem nodes are genetically stable. This assumption has been tested for potato plants, all of which originated from one shoot culture of cv Desiree, that have been propagated or stored under different regimes in vitro, by two methods. The first is by developing DNA restriction fragment analysis and using it to study changes in DNA banding patterns of regenerated plants, and the second is morphological analysis of the same plants grown in the field. Potato plants regenerated via callus can exhibit somaclonal variation, and so plants regenerated via a brief callus phase from the same stock plant of Desiree were also analysed. Molecular analysis involved combinations of 4 single or low copy DNA probes and 4 restriction enzymes. Variation in DNA fragment patterns was not found in any of the 128 plants micropropagated through 6 rounds of nodal subculture, nor in 18 plants that had been stored at low temperature or in 21 plants stored by osmotic reduction of growth. In contrast, 6 of 46 plants regenerated from leaf callus exhibited variations in banding pattern. In the morphological analysis, variants were also only identified in the population of plants regenerated via leaf callus. These results support the concensus view that the plants obtained from micropropagation of meristems are stable genetically, in contrast to those regenerated via callus. However, with the combinations of DNA probes and restriction enzymes used in the analysis, it is not possible to state that variation was not present. Restriction fragment analysis is a suitable approach for analysis of genetic stability of stock plants in vitro, but more plants can be screened for stability by morphological analysis in the field if time delays of 1–2 years are acceptable.