Search

In order to investigate further the interest of using the Chilean gene pool in potato breeding programmes, the genetic diversity and population structure of a collection of Solanum tuberosum L. genotypes including 350 worldwide varieties or breeders' lines (referred to as the modern group) and 30 Chiloé Island landraces were examined using simple sequence repeat markers. The close genetic proximity of the Chiloé Island landraces to the modern group was confirmed using several structure analysis methods: principal coordinate analysis; hierarchical clustering analysis; analysis of molecular variance; Bayesian model-based clustering analysis. The latter analysis, in particular, revealed no clear genetic structure between the modern group and the Chiloé Island landraces. The Chiloé Island germplasm appears to represent an interesting gene pool that could be exploited in potato breeding programmes using an association mapping approach. [ABSTRACT FROM AUTHOR]

Most current tulip cultivars are diploid (2n = 24), some are triploid (Darwin Hybrids) and there are some rare tetraploid cultivars. Crosses between diploids are generally successful, but crosses between diploid cultivars and tetraploid selected species often fail, which constitutes a major obstacle to broadening of the genetic base. Our objective was thus to develop a method to obtain tetraploid material from diploid genotypes using a stem-disc regeneration process and the chromosome-doubling agent oryzalin, applied in different ways. Tetraploid clones were obtained from all treatments and from all cultivars tested. The final yield of tetraploids was low (0 – 3.75 tetraploids for one treated flower stem), but was sufficient to initiate crossing experiments between diploid and tetraploid progenitors to obtain triploid offspring. A genotypic effect was observed during the regeneration process. The cultivars ‘Lucky Strike’ and ‘Gander’ were more responsive in vitro than cvs. ‘Lustige Witwe’ and ‘Don Quichotte’. However, the percentage of tetraploid clones finally obtained was not influenced by genotype or by the way in which oryzalin was applied. [ABSTRACT FROM AUTHOR]

Bulbing was studied in shallot plants cultured in vitro. Bulbing occurred under a 16 h photoperiod with fluorescent + incandescent light and 30–50 g l–1 sucrose in the culture medium. Exogenous gibberellin (10 µm GA3) inhibited leaf and root growth and bulbing. When added to the medium at a concentration of 10 µm, three inhibitors of gibberellin biosynthesis (ancymidol, flurprimidol and paclobutrazol) promoted bulb formation and the percentage of bulbing. When ancymidol was used in combination with GA3, it did not reverse the effect of GA3 applied alone. Under treatments with 30–70 g l–1 sucrose, bulbing ratios greater than those found in control plants were achieved by addition of ancymidol, and bulb fresh weight was increased in the same way. Ancymidol caused a 66 % decrease in sucrose content in leaf bases but greatly increased the glucose, fructose and fructan contents. The increase in fructan content by ancymidol could result from the three‐fold rise in total [14C]sucrose uptake per plant from the culture medium associated with a marked increase in leaf base labelling at the expense of root labelling. The possible role of ancymidol is discussed and evidence supports a major regulatory role for gibberellins in bulbing. [ABSTRACT FROM PUBLISHER]