Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen

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.

Molecular evidence for the natural production of homozygous Cupressus sempervirens L. lines by Cupressus dupreziana seed trees

“…Most progeny (57) came from open-pollinated C. dupreziana seed trees planted in five ex situ collections (South Eastern France) as described by Pichot et al (2008). In three of these five cypress collections (Avignon, Carpentras and Montpellier), C. dupreziana seed trees were very close to numerous C. sempervirens pollen trees (more than 30).…”

“…All progeny produced by controlled pollination of the Mediterranean cypress (Cupressus sempervirens) using C. dupreziana pollen were pure C. dupreziana seedlings (Pichot et al, 2001). Reciprocally, the ability of C. dupreziana to act as a surrogate mother for the development of all-paternal C. sempervirens progeny was more recently demonstrated (Pichot et al, 2008). Indeed two-thirds of the seedlings produced by open pollinated C. dupreziana trees planted in a South Eastern France collection were pure C. sempervirens individuals.…”

“…It is represented by only one natural population in the Tassili N'Ajjer desert, Algeria, and the number of surviving individuals is limited to 233 (Abdoun and Beddiaf, 2002). This species can easily be distinguished from C. sempervirens L. (common cypress or Mediterranean cypress) on the basis of a multi-locus profile obtained using AFLP (Pichot et al, 2008) and nuclear microsatellites (transferred from Sebastiani et al, 2005). The precarious state of the species results from a combination of extreme climatic conditions, long-term human pressure and extremely scarce regeneration.…”

“…Most of these seedlings were haploid, which was consistent with the fact that they would derive from haploid C. sempervirens pollen grains without fecundation. On the other hand, the remaining seedlings were diploid and their ontogenic origin remained unknown (Pichot et al, 2008).…”

“…In addition to the progeny included in the study by Pichot et al (2008), new progeny originating from either open or controlled pollinations were analyzed. The observed genetic profiles allowed inference of the ontogenic origin of seedlings.…”