A field experiment was conducted at two locations to determine the correlation between seedling and mature plant characters in a large potato (Solanum tuberosum) population developed for production from true potato seed. There was no significant correlation between seedling and reproductive characters, including earliness, at the two locations. Number of internodes and yield per plant were significantly correlated at Huancayo, and at San Ramon, root length and hypocotyl length had a significant correlation with the number of tubers per plant and yield per plant. Although significant, the latter correlations are not high enough to be used to predict the final behavior of genotypes by their seedling traits. Thus, it may be assumed that a certain independence between seedling and mature plant growth characters exists.
A. Golmirzaie and F. Serquen
D.P. Zhang, M. Ghislain, A. Golmirzaie and J.C. Cervantes
Detecting inter- and intra-varietal variation is essential for the management of a plant germplasm bank. The sensitivity and efficiency of randomly amplified polymorphic DNA (RAPD) for cultivar identification and somaclonal mutation in sweetpotato were evaluated. RAPD demonstrated a highly significant inter-varietal variation. Every one of the 23 tested cultivars can be identified with a RAPD profile generated by a single primer. Suspected duplicates that are morphologically indistinguishable can be unambiguously verified with a combination of three decamers. No intra-varietal variation was found using RAPD. Clones of `Jewel' and `Beauregard' collected from different sources all have the same RAPD profiles. Moreover, with 150 markers, the transgenic `Chogoku' sweetpotato cannot be differentiated from its untransformed counterparts, even though the transgenic plant shows significant morphological changes. These results demonstrate that RAPD is a sensitive and efficient tool for identifying cultivar duplicates, but it is not efficient for detecting intra-clonal variation or somaclonal mutation in sweetpotato.
A. Golmirzaie, D.P. Zhang, L. Nopo, C.A. Newell, A. Vera and F. Cisneros
Euscepes postfasciatus is one of the most important sweetpotato pests in the South Pacific, Caribbean basin, and some countries of Central and South America. Development of host resistance will greatly improve the effects of integrated pest management (IPM) for this pest. Ten transgenic clones of `Jewel' sweetpotato with cowpea trypsin inhibitors and snowdrop lectin, developed by Axis Agri. Genetics, Ltd., were assayed for weevil resistance using a no-choice bioassay. A replicated experiment was conducted in the screenhouse. Five storage roots from each clone were infested with five pairs of adults. Non-transformed `Jewel' was used as a check. Resistance was assessed 60 days after infestation by estimating the percentage of internal damage and the weevil population in the storage roots. A five-grade damage index was recorded. The experiment was repeated twice. Significant enhancement of resistance was found in the transgenic clones. Clone CTI-13 with cowpea trypsin inhibitor and clone PCG-7 with both cowpea trypsin inhibitor and snowdrop lectin demonstrated moderate resistance to E. postfasciatus, whereas the non-transformed `Jewel' was susceptible. This result shows that resistance to Euscepes postfasciatus can be achieved through genetic transformation.