Potato Journal
Year : 2005, Volume : 32, Issue : 1 and 2
Print ISSN : 0970-8235.
Title of paper: Genetic divergence in tetraploid potatoes (Solanum tuberosum subsp. tuberosum) as revealed by RAPD vis-à-vis morphological markers
Authors: Kujal Sheetal(1), Chakrabarti S.K., Pandey S.K.(2), Khurana S.M. Paul(3), Former Director
1)Department of Biotechnology, Ch. Charan Singh University, Meerut 250 110, Uttar Pradesh, India
2)Division of Crop Improvement, Central Potato Research Institute, Shimla 171 001, Himachal Pradesh, India
3)Central Potato Research Institute, Shimla 171001, Himachal Pradesh, India
Since potato is an out-breeder, maintaining the maximum genetic divergence between the parents would be ideal for obtaining heterosis (23) or increased characteristics like size or yield. Traditionally, morphological characters are used to study the genetic divergence between parents through biometrical techniques, such as principal component analysis, cluster analysis or Mahalanobis D2 statistics (19, 21).
However, estimation of genetic divergence based on morphological characters may sometimes be misleading particularly when non-additive gene action is significant for the trait of interest (12). Moreover, since morphology reflects a complex interaction of the genotype with its environment, traits solely based on morphology are unreliable indicators of plant genotype.
As a result, satisfactory measure of genetic divergence in cultivated potato could not be achieved using the above estimates and several studies have concluded that the various measures of genetic divergence are not correlated (17). This situation changed dramatically with the advent of molecular markers, which provide the best estimates of the genetic diversity since they are independent of the environmental effects.
Powell et al. (24) suggested that molecular markers could be employed to estimate genetic distance for selecting diverse parents capable of producing high-performing progeny. The present study aims at evaluating genetic divergence within a population of tetraploid potato using RAPD markers as well as their morphological attributes. Promising parents have been identified on the basis of such divergence data.
Genotypic divergence within a group of 31 genotypes, preferentially used as parents for potato breeding in India, has been estimated from both random amplified polymorphic DNA (RAPD) and morphological data. RAPD data revealed a broader genetic divergence (similarity values 0.52-0.80, ca 0.65) than that of morphological data (0.60-0.98, ca 0.86).
A weak positive correlation between the similarity values derived from RAPD and morphological data was observed. Both the types of analyses separated tuberosum from andigena genotypes, and indicated andigena accessions as the most distantly related genotypes within the group thus suggesting better value as parents. However, no significant correlation between the similarity matrices obtained from RAPD and morphological data was observed as indicated by a very low (0.3) matrix correlation value.
It may be concluded that divergence analysis using RAPD markers would be a cheaper and feasible technique for parent selection in tetraploid potatoes. Apparently no such comparison has so far been made for the divergence data derived from RAPD markers with that of morphological diversity in potato. Average pair-wise dissimilarity of any particular genotype, calculated on the basis of all possible combinations in the group, may give an idea about its usefulness in breeding programme.
