Maternal Clones Research Articles

Isolation of Doubled-Haploid Plants Through Anther Culture in Arabidopsis thaliana

Summary Calluses of Arabidopsis thaliana (L.) Heynh. induced from cultured anthers and shoots regenerated from such callus were analyzed genetically and cytologically. Chromosome counts suggested that all anther calluses giving rise to shoots were haploid but that the derived shoots could be either haploid or diploid. Simultaneous genetic analysis employing an acid phosphatase marker locus revealed that regenerant diploid shoots were of two types - doubled-haploids and maternal clones. Some regenerants from anther callus set seed. However, analysis of marker segregation in the resultant progeny families indicated that the shoots producing seeds were maternal clones rather than doubled-haploids.

Disappearance of the heteroplasmic state for chloroplast markers in zygospores of Chlamydomonas reinhardtii

In the investigations reported here, the length of zygospore incubation or “maturation” prior to the induction of meiosis was found to affect the inheritance pattern of chloroplast genes. The frequency of zygospores transmitting chloroplast alleles from both parents drops with increasing zygospore age following mating, while the frequencies of zygospores homoplasmic for maternal or paternal chloroplast alleles increase correspondingly. Since there is a negligible reduction in viability, zygospores which are initially biparental appear to become pure for the chloroplast genes from one or the other parent prior to the occurrence of cell division. These results are amplified in crosses of mt + cells which have been irradiated with ultraviolet (uv) light or grown in the presence of the base analog, 5-fluorodeoxyuridine, which also perturbs maternal inheritance. Low doses of uv irradiation, applied to zygospores derived from crosses in which the maternal parent was also irradiated prior to mating, increase the biparental zygospore frequency while reducing the proportion of maternal zygospores. This indicates that at least some maternal zygospore clones are actually derived from zygospores which still contain both parental chloroplast genomes prior to the induction of germination. Thus, a subclass of zygospores must contain paternal chloroplast genomes which are either eliminated upon germination or are not expressed in the resulting zygospore clone. Tetrad analysis of biparental zygospores derived from uv-irradiated mt + gametes demonstrates that the frequency of maternal chloroplast alleles in biparental zygospores decreases as they age. One result is an increase in the proportion of meiotic products homoplasmic for all paternal markers. The increased segregation of homoplasmic daughter cells during the meiotic divisions may result from a reduction in chloroplast ploidy by elimination of maternal genomes. Alternatively, it may reflect an altered ratio of maternal:paternal genomes due to continuous rounds of pairing and gene conversion between heterologous chloroplast DNAs leading to genetic drift within the DNA population of the organelle.

Multivariate methods as an aid in identifying Poa ampla × P. Pratensis hybrids from maternal-type offspring

An objective screening procedure was needed which would enable separation of F1 hybrids between Poa ampla and P. pratensis for use in a plant breeding programme from maternal-type offspring. Data from a cloned plant field trial were used in canonical analysis of discriminance, principal components analysis and principal co-ordinate analysis; a measure of Euclidean distance was also computed. The relationship between hybrid, maternal and parent biotypes appeared remarkably consistent from the three forms of analysis over the first two axes of variation and to a lesser extent on the third axis. Euclidean distances were very highly correlated with the positions of clones on the first axis of variation in each of the analyses. Maternal clones were clearly separated from hybrids by each of these four methods and this distinction was supported by a more subjective visual assessment made in the field.

Fertility of Eight Bermudagrass Clones and Open‐Pollinated Progeny from Them1

We determined the percent of open‐pollinated (OP) seed set for eight bermudagtass (Cynodon dactylon (L.) Pers.) clones and for 420 of their OP progeny in 1969 and 1970, respectively. After selecting 30 of the most fertile of the 420 progeny, we determined their percent of OP and self‐pollinated (SP) seed set for 3 and 2 years, respectively. Objectives of the studies were to characterize the seed‐set potential of the clones and their progeny, thereby estimating the variation that exists among bermudagrass genotypes for cross and self‐fertility, and to provide information pertinent to the genetic improvement of bermudagrass seed production.The OP seed set was significantly different (P < 0.01) among the eight clones, ranging from 2.8 to 43.2%. Seed set of the 420 OP progeny ranged from 0 to 78.8%. Mean OP seed set of progeny families paralleled rather closely that of the maternal parent. Standard deviations for OP fertility of progeny clones increased as the OP fertility of the maternal clone increased.The 30 selected clones differed significantly in both OP and SP seed set each test year and for the combined averages. The seed set percentages averaged over clones differed significantly between years for OP but not SP seed set. The year ✕ clone interaction was not significant for either OP or SP seed set. The OP seed set of the 30 progeny clones averaged over 3 years ranged from 15 to 57%, most values being considerably lower than the initial ones used as indices for their selection. The 2‐year averages for SP seed set ranged from 0.10 to 8.09%. The selffertility of 24 of the clones was, however, less than 1%.

Estimates of the Percentage of Self‐ and Cross‐Pollination in Sainfoin (Onobrychis viciaefozia Scop.)1

Percent cross‐pollination in sainfoin (Onobrychis viciaefolia Scop.) was estimated under three planting arrangements by using flower color and growth characteristics as genetic markers. The amount of cross‐pollination was dependent upon the planting arrangement. A substantial amount of crossing occurred when one row of a maternal multicut line was seeded between two rows of a sinplecut pollen parent. More than 90% of progeny produced by three white‐flowered maternal clones surrounded by rows of pink‐flowered pollen parents resulted from crosspollination. Eight to 28% cross‐pollination occurred between white‐flowered maternal clones and pink‐flowered male clones in two clone crosses under isolation with honey bees as pollinators.