Understanding how an amphicarpic species with a mixed mating system responds to fire: a population genetic approach

Amphicarphic species produce both aboveground and belowground seeds; the belowground seeds have been proposed to be an adaptation to disturbed sites because they are protected belowground, enabling them to persist and recolonize a site after disturbance. However, it is unknown whether such seeds indeed serve as the main colonizers after a disturbance. The amphicarpic species Polygala lewtonii is endemic to fire-prone Florida sandhill and scrub and is among only a few species with three flower types (aboveground chasmogamous flowers and both above and belowground cleistogamous flowers). The goal of this study was to understand whether recolonization of sites by P. lewtonii was accomplished primarily through germination of belowground seed. First, we quantified the outcrossing rate in seeds produced by aboveground chasmogamous flowers to determine whether we could detect differences in colonization of between seeds produced aboveground vs. belowground. Approximately 25% of seeds from aboveground chasmogamous flowers showed evidence of cross pollination and the seeds showed greater heterozygosity and lower inbreeding coefficients than pure selfing, indicating that it is possible to differentiate between selfed and non-selfed seed types in postfire colonization. Second, we analyzed genetic diversity, inbreeding, and genetic structure of the populations before and after a prescribed fire. If heterozygosity and admixture increased, and spatial population genetic structure and inbreeding decreased, this would indicate that fire promoted germination of outcrossed seed from aboveground flowers. However, inbreeding increased and spatial genetic structure and admixture decreased after fire, suggesting that selfed seed produced by belowground flowers predominantly recolonized the site after fire. Thus, amphicarpy is a powerful adaptation to fire-maintained environments by producing seeds that are well suited to the range of conditions presented by a highly variable, disturbance prone habitat.

Selffertilization in Campanula rotundifolia L. s. 1. group

Artificial selfpollination of six taxa of <i>C. rotundifolia</i> L. group was perfomed. More than 60% of the tetraploid plants and diploid <i>C. rotundifolia</i> s. str. representatives set seeds which germinated in some 42-76%. The seed setting in <i>C. serrata</i> was a little lower and the germination was very poor (0.07%). Only 18% of <i>C. cochleariifolia</i> plants yielded seeds after selfpollination. These seeds failed to germinate. The selfed offspring was viable only in part. Some developmental distur-bances were observed. A general tendency to reduction of height of stems and of the number of flowers per stem was also noted in successive selfed generations. A gradual decrease of pollen fertility was also observed. No tendency to gradual decrease of selfed seed fertility and germination was demonstrated. The factors preventing selffertilization proved to be efficient in <i>C. cochleariifolia</i> and <i>C. serrata</i>, but it seems that in nature they are strong enough even at a tetraploid level.

Variation in the Breeding System of Prunella vulgaris L.

Prunella vulgaris (Lamiaceae), commonly known as selfheal, is a perennial herb with a long history of use in traditional medicine. Recent studies have found that P. vulgaris possesses anti-inflammatory, antiviral, and antibacterial properties, and it is likely that this will lead to increased commercial demand for this species. To date, research publications on P. vulgaris cultivation and genetics are scarce. Using accessions originally collected from different geographical regions, we investigated the breeding system of this species by observing variation in floral morphology, time of pollen release, and selfed-seed set in bagged flowers and isolated plants. Two types of floral morphology, one with exerted styles, extending past open corollas when viewed from above, and the other with shorter, inserted styles, were found among 30 accessions. Two accessions originally collected from Asia uniformly displayed exerted styles, and 27 accessions had inserted styles. One accession from Oregon displayed variation in this trait among individual plants. Microscopic observation of seven accessions, including ones with both exerted and inserted styles, revealed that they all release pollen to some degree before the flowers open. Using bagged flowers, we found that selfed-seed set varied widely among eight accessions, ranging from 6% to 94%. However, bagging may underestimate seed set for some accessions. The two accessions with the lowest rates when using bagged flowers increased in seed set by 350% and 158%, respectively, when we evaluated single, unbagged plants in isolation cages. The accession with 6% selfed-seed set when bagged also had exerted styles. These findings suggest that mating systems in P. vulgaris may be in the process of evolutionary change and that understanding breeding-system variation should be useful in developing efficient seed-regeneration protocols and breeding and selection strategies for this species.

Using Self-compatible Inbreds of Broccoli as Seed Producers

The discovery that broccoli (Brassicaoleracea L., Italica Group) sprouts contain high levels of sulforaphane, a constituent that may provide chemoprotection against certain carcinogens, has stimulated much interest in seed production of this crop. Studies were undertaken to determine the potential for producing broccoli seed using self-compatible selections from open-pollinated (OP) populations or doubled-haploid (DH) programs. In all outdoor and greenhouse trials, three OP selections and seven DH lines produced selfed seed, but seed weight per plant and number per plant varied significantly among the entries. In all environments there were individuals with relatively high (i.e., >3 g/plant) production that were significantly different from low (i.e., <2 g/plant) producers. The relative productivity of some lines varied greatly between experiments, which indicates that seed production of particular genotypes is affected differently by environmental conditions. This indicates the importance of identifying lines that are high producers of selfed seed across different environments. Two OP cultivar-derived lines (USVL102 and USVL104) and two DH lines (USVL062 and USVL093) were identified that consistently produced relatively high yields in greenhouse and screen cage trials. These lines are good candidates for evaluating seed production in field tests and as possible sources of seed for sprouting.

Selfed-seed production depending on individual size and flowering sequence in Iris gracilipes (Iridaceae)

To examine the influence of individual size and time of pollination on selfed and outcrossed seed production, we conducted hand-pollination experiments in 2000 and 2001 in the perennial herb Iris gracilipes A. Gray (Iridaceae). Small individuals produced outcrossed seeds to a greater extent than selfed seeds, whereas large individuals produced not only outcrossed seeds but also selfed seeds. On the other hand, when half of all flowering shoots of an individual were removed, both selfed and outcrossed seeds were produced independent of individual size. Flowers that opened earlier within the same flowering shoots were likely to produce outcrossed seeds, while those that opened later within the same flowering shoots produced relatively more selfed seeds than did the flowers which opened earlier. Thus, the ratio of the numbers of selfed to outcrossed seeds produced may differ between small and large individuals. These results suggest that plants regulate selfed- and outcrossed-seed production depending on their sizes and flowering sequence.Key words: self-fertilization, individual size, flowering sequence, Iris gracilipes.

THE EFFECT OF ENFORCED SELFING ON RESULTANT SEED AND SEEDLING QUALITY IN THE SELF-INCOMPATIBLE ALMOND VARIETY NONPAREIL

All of the major California almond varieties are self-incompatible necessitating the interplanting of pollinizer varieties. The incorporation of self-compatibility into the dominant variety Nonpareil through mutation or genetic engineering would greatly improve cropping efficiency. Negative effects of inbreeding on resultant seed and seedling quality could negate production advantages. Inbred seed of Nonpareil were obtained by: a) enclosing mature trees in pollination cages containing bees at flowering, and, b) controlled crosses to a Nonpareil mutation (Jeffries) which is unilaterally compatible when used as the seed parent. Selfed seed set from caged trees was less than 0.001% of available flowers. Seed set from crosses to the Jeffries mutation averaged 34.4% which was not significantly different than outcrossed controls. No significant loss in kernel weight and dimensions were observed in any of the inbred material when compared with outcrossed controls though a higher proportion of the inbred seed and seedlings failed to develop fully. Both average tree height and trunk diameter after 1 year of growth was significantly lower in inbred vs. outcrossed material. Results suggest no major penalty to kernel quality following self-pollination, though losses in progeny vigor should be a concern when utilizing selfed seed in variety development programs.

Relationship between Parental Blossom Season and Speed of Seed Germination in Peach

A highly significant correlation was observed between time of bloom of individual peach trees [Prunus persica (L.) Batsch.] and number of days required for resulting selfed seed to reach 80% germination on both local (r = 0.71) and introduced (r = 0.87) genotypes that exhibited a wide range in time of blossom. When genotypes with low chilling requirement (LCR) were pollinated with high chilling requirement (HCR) pollen sources, germination was delayed up to 16 days with respect to seeds that originated from selfing, while LCR pollen sources on late-blossoming genotypes accelerated germination 20 to 24 days.

Proportion of cross-bred and selfed seed obtained from successive generations of winter bean (Vicia faba L.) crops

SummaryThe proportions of cross-bred and selfed seed were estimated in up to four consecutive generations of Throws MS winter beans on three farms where farm-saved seed was regularly used.Within one stock the percentage of cross-breds rose a significant amount from 31 to 46, whilst in another stock no change was detected over four consecutive generations. On the third farm a change of stock mid-way through the period of the survey was associated with a highly significant increase in proportion of cross-breds.In general a rise in outcrossing was not followed by a significant fall as would be expected if cross-breds have a greater tendency than inbreds to self pollinate, but the possible role of a regulatory mechanism is discussed as are implications of the range in outcrossing within stocks for variety trials and commercial production of winter beans.Estimates of outcrossing frequency made in two crops in 1983 were slightly lower than some obtained in 1974–6 but no lower than those reported in 1951 thus providing no evidence of any long-term change in levels of natural cross-breeding in field beans in England.

Theoretical effects of seed orchard roguing on selfing and percent filled seeds

Roguing of seed orchards decreases potential seed yields and increases the percentage of selfed seed produced. Calculations indicate that a potential seed loss per cross of about 10% could be expected by roguing a 15-clone orchard to 5 clones, provided certain assumptions are met. Simultaneously, the theoretical percentage of selfed seed rose from 1 to 3% with the same roguing intensity. Roguing to fewer than five clones resulted in greater losses in potential seed yield.