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, 178 (1), 379-83

Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen

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Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen

Christian Pichot et al. Genetics.

Abstract

Although most living organisms reproduce sexually, some have developed a uniparental reproduction where the embryo usually derives from the female parent. A unique case of paternal apomixis in plants has been recently reported in Cupressus dupreziana, an endangered Mediterranean conifer. This species produces unreduced pollen that develop into all-paternal embryos within the seed tissues. We analyzed seedlings produced by open-pollinated C. dupreziana seed trees using morphological descriptors, ploidy levels assessed through flow cytometry, and AFLP genetic diversity. In situ C. dupreziana seed trees (from Algeria) produced only diploid C. dupreziana progeny. In contrast, only one-third of the progeny produced by ex situ C. dupreziana seed trees planted in French collections were similar to C. dupreziana seedlings; the other progeny were haploid or diploid C. sempervirens seedlings. These results demonstrate that C. dupreziana ovules allow for the development of all-paternal embryos from pollen produced by another species, C. sempervirens. Thus, the in planta androgenesis is achieved through the combination of the embryogenic behavior of pollen grains and the ability of seed tree ovules to act as a surrogate mother. This phenomenon offers a unique opportunity to produce, by natural means, highly valuable material for genetic studies and selection of sterile cultivars.

Figures

F<sc>igure</sc> 1.—
Figure 1.—
Morphology and ploidy of the progeny produced by open-pollinated C. dupreziana seed trees. (A) Diploid C. dupreziana phenotype from in situ and ex situ seed trees. (B) Diploid C. sempervirens phenotype from ex situ seed trees. (C) Haploid C. sempervirens phenotype from ex situ seed trees.
F<sc>igure</sc> 2.—
Figure 2.—
Investigation of the genetic origin of progeny using AFLP markers. Only progeny produced by C. dupreziana seed trees planted in ex situ collections were studied. The individual genetic profiles were plotted as supplemental points on the plane defined by the first two axes of a discriminant analysis of cypress species used as a control (the three Mediterranean species C. sempervirens, C. atlantica, and C. dupreziana; one American cypress group; and one Asian cypress group). All haploid progeny (A) were assigned to C. sempervirens. For diploid progeny (B), the genetic assignment either to C. dupreziana or to C. sempervirens was fully consistent with the classification based on the morphological type (Table 1, Figure 1).

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