Читать книгу Biotechnology of Fruit and Nut Crops - Группа авторов - Страница 145

The development of elite lines for oil palm has thus far been prevented by difficulties in generating homozygous parental types for F1 generation. Henderson (2005) reported the regeneration of haploid embryos from oil palm microspores. A range of factors leading to the induction and regeneration of haploids via anther culture were investigated. Oil palm anthers incubated at 5°C for 96 h or treated with 0.4 M mannitol for 24 h produced multicellular structures from the microspores. While high temperature (30, 35 or 40°C) induced extensive morphological changes in microspores, it did not lead to androgenesis. Low temperature was adopted as the standard protocol to avoid any possible interference by mannitol in the biochemical or biophysical pathways leading to androgenesis. The greatest number of multicellular structures was obtained when six anthers were cultured per 2 ml of medium. Henderson (2005) found that medium containing 250 M maltose and 25 mM inorganic nitrogen (NO3:NH4 ratio of 80:20) produced higher numbers of multicellular structures than did oil-palm specific callogenic (U2) or embryogenic (E97 A) media. Anthers produced significantly higher numbers of multicellular structures when cultured under continuous light. Microspore responses to white (0.85%), blue (0.72%) or red (0.57%) wavelengths were significantly greater than from continuous darkness (0.36%). While the production of multicellular structures varied between individual palms (0–7.9%), no significant genotypic effect was found with any treatment. Plants have not been regenerated from these microspore-derived multicellular structures.

Dunwell et al. (2010) designed the first high-throughput screen to identify spontaneously formed haploid and doubled haploid palms. The authors secured over 1000 haploids and one doubled haploid from genetically diverse material and derived further doubled haploid/mixoploid palms from haploids using colchicine. The viability of pollen from haploid plants was demonstrated and it is thus expected to generate 100% homogeneous F1 seed from intercrosses between doubled haploid/mixoploids once they develop female inflorescences. Such genetically diverse haploid/doubled haploid palms can provide parental clones in sufficient numbers to enable the commercial-scale breeding of F1 varieties.

Iswandar et al. (2010) utilized haploid cultures of oil palm to investigate and exploit spontaneous chromosome doubling during embryogenesis. Flow cytometry of embryogenic tissue showed the presence of both haploid and doubled haploid cells, indicating spontaneous doubling. Completely doubled haploid ramets were regenerated suggesting that doubling occurred during the first mitosis during embryogenesis. The method provided a means for producing a range of doubled haploids in oil palm from a collection of >1000 haploids. Iswandar et al. (2010) also produced doubled haploid (and haploid) clones.