Abstract

POULSEN HORNUM, A.  and  CAMADRO, E.L.. Morphological phenotypes, pollen viability and pollen-pistil relations in three natural populations of the wild potato Solanum chacoense bitter. BAG, J. basic appl. genet. [online]. 2014, vol.25, n.2, pp.16-31. ISSN 1852-6233.

Argentina is center of diversity of approximately 35 wild taxonomic potato species that have wide geographical distribution. These species, which form polyploid series with 2n=2x=24 up to 2n=6x=72 (x=12), can reproduce both sexually and asexually. Most of them are diploid obligate outcrossers because they possess a one-locus gametophytic self-incompatibility system. In nature, wild potatoes can present both external and internal reproductive isolation barriers, within and between populations, which can be incomplete. Most accessions in germplasm banks have been assigned specific categories based on morphological phenotypes (taxonomic species concept), without taking into account the natural reproductive behavior of the sampled populations. One of these species, Solanum chacoense Bitter (2n=2x=24, 2 EBN 1), spontaneously grows from the NW provinces to SE Buenos Aires province, in very diverse habitats and overlapping with other taxonomic potato species, with which it can spontaneously hybridize. As preliminary activities of an in situ study, individual plants from three populations classified as S. chacoense (APEC-1, APEC-2 and APEC-3) that spontaneously grow in Balcarce, Buenos Aires province, were characterized for morphological phenotypes of leaves, flowers and fruits, pollen viability and pollen-pistil relations. The percentage of pollen viability (determined by staining) varied from 34.5 to 98.8% (=81.3%) in APEC-1 (n=23), 0 to 98.8% (=62.8%) in APEC-2 (n=26) and 63.3 to 95.4% (=85%) in APEC-3 (n=21). Variability was also observed for pollen size (<n, 2n, > 2n and 4n, in addition to normal n) and pollen size frequency. Abnormalities were observed at the tetrad stage of meiosis in eight plants of APEC-2 with heterogeneous-size pollen. According to the site of pollen tube arrest, pollen-pistil relationships within APEC-1 and APEC-2 revealed events of cross-incompatibility and/or self-incompatibility, whereas only cross-incompatibility was detected within APEC-3. No relations were found between morphological phenotypes and pollen-pistil reactions, and between corolla shape and pollen viability. The results are indicative of a likely hybrid origin of the studied populations and the need for revising the current taxonomic approaches in wild potatoes. 1 EBN: Endosperm Balance Number (Johnston et al., 1980

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