Gametic and somatic embryogenesis through in vitro anther culture of different Citrus genotypes

Abstract: In vitro tissue culture represents a useful technique for advancing Citrus breeding and propagation. Among in vitro regeneration systems, anther culture is commonly used to produce haploids and doubled haploids for a fast-track producing homozygous lines, in comparison with the traditional self-pollination approach, which involves several generations of selfing. In addition, anthers culture can produce somatic embryos that can also be used for clonal propagation. In this study, two thermal shocks were applied to the anthers of six Citrus genotypes (two clementine and four sweet oranges), just after they were put in culture. The response obtained was different depending on the genotype: both clementines, namely Hernandina and Corsica, produced homozygous and triploid regenerants (microspore-derived embryos), whereas all of the analyzed regenerants from sweet oranges, three cultivars of Tarocco and Moro, produced heterozygous and diploid regenerants similar to the parental genotypes (somatic embryos)

Mothers’ command: phenotypes changes resulting from reciprocal interploidy crosses

Polyploidy is considered a valuable tool in plant breeding because can increase the size of flowers, leaves, and fruits or generate seedless plants, such as infertile triploids. Triploid plants can be obtained by reciprocal interploidy crosses (4x × 2x or 2x × 4x), but the influence of parent-of-origin effects in the plants’ phenotype caused by these interploidy crosses, as well as the interactions between cytoplasm and nucleus in these crosses are not clearly defined. Therefore, this work aimed to characterize the morphology and physiology of triploid tomato plants leaves by parent-of-origin 2x and 4x. For this purpose, we induct the tetraploidy with colchicine from diploid plants to performed the reciprocal interploidy crosses and obtained the triploid hybrids by differents parents-of-origin (2x or 4x). Histological slides from the leaves of all plant genotypes were assembled to analyze the anatomy, morphology and to measure the chlorophyll a, b, and the total index. Tetraploid tomato plants showed greater adaxial and total epidermis leaf thickness. Triploid plants by parent-of-origin 4x presented higher leaf thickness and spongy parenchyma than the triploid plants by parent-of-origin 2x, as well as higher rates of chlorophyll a and b, and an inbalance in the ratio of chlorophyll index a/b. We conclude that changes in cytoplasmatic organelles, caused by tetraploidization, can be transferred from parent-of-origin 4x to triploid plants. However, further studies are necessary, aiming to understand the genetic interaction between the cytoplasmatic genome (and consequently organelles) and the nucleus genome of triploid plants by differents parents-of-origin.216CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQSem informaçã