A Review on Haploid and Double Haploids in Ornamental Plants

Sporophyte plants with many gametophytic chromosomes are called haploid plants. These plants can be produced naturally or through in vitro or in vivo induction techniques. Double haploid (DH) can be obtained by doubling the number of haploid chromosomes spontaneously or artificially. They are homozygous, and this homozygosity will be realized in the life cycle of a generation using the DH production system. This production system is used to correct heterosis. Easy to interact with the DH population. DH can be used as parental inbreds of new varieties or self-pollinated plants or cross-pollinated plants. Haploids can be used to isolate mutants, especially if the mutant allele is not diploid. If the haploid is transformed immediately after the chromosome is copied, the plant can be obtained step by step. By combining biotechnological means with conventional methods, the important goal of improving cultivated plants can be achieved in a short time. This article analyzes the various developments in the field of haploid species related to economically important ornamental species.

Komagataella phaffii YPS1-5 encodes the alpha-factor degrading protease Bar1

ABSTRACT Yeast mating pheromones are small secreted peptides required for efficient mating between cells of opposite mating type. Pheromone gradients allow the cells to detect potential mating partners. Secreted pheromone degrading proteases steepen local gradients and allow fast recovery from the pheromone signal. The methylotrophic yeast Komagataella phaffii is a preferentially haploid species. Only under nitrogen starvation, mating genes are activated and the cells are able to undergo a full sexual cycle of mating and sporulation. It has been shown that, similar to other yeasts, K. phaffii requires the mating pheromone and pheromone surface receptor genes for efficient mating. The analysis of so far uncharacterized mating-type-specific genes allowed us to identify the K. phaffii α-factor protease gene YPS1–5. It encodes an aspartic protease of the yapsin family and is upregulated only in a-type cells under mating conditions. The phenotype of K. phaffiia-type strains with a deletion in the protease gene was found to be highly similar to the phenotype of Saccharomyces cerevisiae α-factor protease BAR1 deletion strains. They are highly sensitive to α-factor pheromone in pheromone sensitivity assays and were found to mate with reduced efficiency. Based on our results, we propose to rename the gene into K. phaffii BAR1.

Testing for Epistasis Between Deleterious Mutations

Determining the way in which deleterious mutations interact in their effects on fitness is crucial to numerous areas in population genetics and evolutionary biology. For example, if each additional mutation leads to a greater decrease in log fitness than the last (synergistic epistasis), then the evolution of sex and recombination may be favored to facilitate the elimination of deleterious mutations. However, there is a severe shortage of relevant data. Three relatively simple experimental methods to test for epistasis between deleterious mutations in haploid species have recently been proposed. These methods involve crossing individuals and examining the mean and/or skew in log fitness of the offspring and parents. The main aim of this paper is to formalize these methods, and determine the most effective way in which tests for epistasis could be carried out. We show that only one of these methods is likely to give useful results: crossing individuals that have very different numbers of deleterious mutations, and comparing the mean log fitness of the parents with that of their offspring. We also reconsider experimental data collected on Chlamydomonas moewussi using two of the three methods. Finally, we suggest how the test could be applied to diploid species.

Occurrence and mechanisms of 2n egg formation in 2x potato

The occurrence of 2n eggs in 381 haploids from six tetraploid parents and in 127 plants representing five diploid wild species was detected using 2x × 4x crosses. Sixty-two percent of the haploids and 24% of the wild-species plants produced 2n eggs. Twenty-six haploids and 17 species plants that gave high seed set in 2x × 4x crosses were examined cytologically to determine the frequency and mechanisms of 2n egg formation. There was significant variation in the frequency of 2n eggs among haploids (7–57%) and among species plants (4.9–57.3%). Five mechanisms of 2n egg formation were identified: synaptic variant (genetically first division restitution); delayed meiotic division (first division restitution and second division restitution); omission of the second division (the prevalent mechanism, second division restitution); irregular anaphase II (second division restitution); and failure of second cytokinesis (second division restitution). 2n eggs can be formed by more than one mechanism within a clone. The occurrence of 2n eggs in wild species and the higher frequency of 2n eggs in haploids than in wild species indicate that sexual polyploidization has been involved in the origin and evolution of polyploid series in potato. The high frequency of 2n eggs in both haploids and diploid wild species allows generation of haploid-species hybrids that produce 2n eggs. These hybrids can then be used in the 2x × 4x and 2x × 2x breeding schemes.Key words: haploids, wild species, 2n gametes, first division restitution, second division restitution.