Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

CHEMICAL CHARACTERIZATION OF POTATO GENOTYPES OBTAINED THROUGH NON-CONVENTIONAL BREEDING STRATEGIES

STILE R.*, CARDI T.**, ESPOSITO F.***, IOVENE M.*, FOGLIANO V.***, FILIPPONE E.*

* Department of Agronomy and Plant Genetics, University of Naples “Federico II”

** Research Institute for Vegetable and Ornamental Plant Breeding IMOF-CNR, Portici

*** Department of Food Science, University of Naples “Federico II”

potato, transgenic plants, interspecific hybrids, quality

Potato (Solanum tuberosum) represents a staple food in many parts of the World, since its versatility in cooking and its full complement of nutrients (Woolfe, Potato in the human diet, University Press, Cambridge-UK, pp. 7-78). However, many traits have still to be submitted to breeding, like resistance to biotic and abiotic stresses, tuber quality for processing, etc. Conventional breeding schemes are difficult to apply to this species, since both potato genetic basis is rather restrict and its tetraploid genetic structure make difficult to gain results in a very short time. Several strategies have been suggested to improve potatoes, including non-conventional one such as interspecific hybridisation at different ploidy level and genetic transformation; both techniques have been successfully used to transfer resistance traits (Ortiz et al., 1994, J. Genet. Breed. 48:89-98; Lorito et al., 1998, Proc. Natl. Acad. Sci. 95:1-6), to improve tuber quality (Edwards et al., 1999, Plant J. 17:251-261; Greiner et al., 1999, Nature Biotech. 17:708-711), to increase allelic diversity (Carputo et al., 2000, Theor. Appl. Genet. 101:805-813). However, like other breeding techniques, the appareance of indesiderable traits and/or changes in the tuber chemical composition may occur.

In order to figure out the level of changes induced into potatoes coming from non-conventional breeding schemes, chemical analyses were performed on two distinct groups of potato genotypes. The first group contained 5 potato cv. Désirée clones deriving from different transformation events, each clone bearing the endochitinase gene ech42 from the antagonistic fungus Trichoderma harzianum. All clones were previously characterized at molecular level and for their resistance to several potato pathogenic fungi, such as Alternaria spp., Botrytis cinerea and Rhizoctonia solani (Lorito et al., 1998, Proc. Natl. Acad. Sci. 95:1-6). They were analysed in order to verify their substancial equivalence with the non-transformed original clone. The second group contained interspecific hybrids between the cultivated potato and the wild species S. commersonii, that bears a wealth of useful traits (resistance to biotic and abiotic stresses, high dry matter content of tubers, etc.). To this group, hybrids coming from two different origins were analysed: (1) hybrids coming from somatic fusion, represented by 13 progenies obtained after a backcrossing of one somatic hybrid with the cultivated parents; (2) hybrids coming from sexual hydridization, represented by 8 progenies derived from crosses between a pentaloid S. commersonii x S. tuberosum hybrid and cultivated varieties, following a breeding scheme already reported (Carputo et al., 1997, Proc. Natl. Acad. Sci. 94:12013-12017). All plants were grown in the same environmental conditions as their controls, to minimize any environmental effects on the tubers chemical composition.

Biochemical analyses were performed to determine the soluble antioxidative ability and the sugars, proteins, chlorogenic acid, and GA content. In the case of transgenic plants, the analyses showed that there was a negligible difference in the chemical composition between transgenic clones and the control Désirée, confirming their substancial equivalence with the cultivated one for the considered traits. As interspecific hybrids are concerned, each group showed an expected broad variability in all analysed parameters. In this case, this result is felt very important, since the success of plant breeding depends on the variability available. Among the analysed traits, soluble solids and proteins content were better in some hybrid clones than both the S. tuberosum controls and the S. commersonii parental line. Some clones showed a low level of both chlorogenic acid and GA content, thus being ready for further breeding efforts; however, some others showed a level of GA too high to be used for human consuption. Interestingly, results showed that among parameters considered, the GA content is by far the most sensitive to variation in hybrid clones: therefore, its determination should be used for routine control of genotypes coming from various breeding approaches.