0.3 (2) 0.0 (0) 0.6 (9) 0.0 (0) 6.4 (22) 7.3 (20) 0.7 (37) 0.8 (16) 1.5 (15) σGCA(Male) 4.4 (37) 177 (32) 0.0 (0) 0.0 (0) 4.6 (16) 0.0 (0) 0.1 (5) 0.4 (8) 1.0 (10) σSCA 0.0 (0) 0.0 (0) 0.7 (12) 3.1 (18) 0.0 (0) 7.6 (21) 0.0 (0) 0.1 (1) 0.0 (0) σError

A morphometric comparison was done in the greenhouse of 220 genotypes representing all the American taxa of octoploid strawberries. Only two groups of Fragaria virginiana Miller (Staudt) and Fragaria chiloensis (L.) Miller were well separated in both principle component and cluster analyses: a group composed primarily of F. chiloensis subspecies plus some F. virginiana ssp. glauca (Wats.) Staudt and F. virginiana ssp. platypetala (Rydberg) Staudt and another group composed primarily of F. virginiana ssp. virginiana Duchesne; and F. virginiana ssp. grayana (E. Vilmorin ex Gay) with some F. virginiana ssp. glauca and F. virginiana ssp. platypetala. Among the individual traits examined, only hair orientation reliably distinguished F. chiloensis ssp. lucida (E. Vilmorin ex Gay) from F. chiloensis ssp. pacifica Staudt, and F. virginiana ssp. grayana from F. virginiana ssp. virginiana. Little separation was observed between North and South American F. chiloensis in our principle component and cluster analyses, although these groups did show significant individual discontinuities for a number of traits. Individuals representing the cultivated race of F. chiloensis were in a relatively tight cluster within the scatter of native F. chiloensis. Taken together, these data indicate that F. virginiana and F. chiloensis may be extreme forms of the same biological species and that many of the subspecies designations currently employed in F. virginiana and F. chiloensis should not be recognized. We suggest, however, that there is sufficient morphological and geographical separation to warrant the species designations F. chiloensis and F. virginiana. Fragaria chiloensis ssp. pacifica and Fragaria chiloensis ssp. lucida do not appear to deserve distinct subspecies rank, nor do F. virginiana ssp. virginiana and F. virginiana ssp. grayana. North and South American F. chiloensis are morphologically quite similar, but probably deserve subspecies rank, based on their isolation from each other and the fact that they are evolving separately. Fragaria virginiana ssp. glauca and F. virginiana ssp. platypetala should probably be joined as a single subspecies and retained within F. virginiana until further investigations more definitively determine affinity to other F. virginiana and F. chiloensis subspecies.Key words: Rosaceae, interspecies hybridization, polyploidy.

Variation in 14 horticultural traits of native octoploid Fragaria L. from North and South America was examined in a greenhouse. Significant levels of variation were found for all but a few of the traits at the species, subspecies, regional and genotypic level, with the highest amount of variation generally being partitioned among genotypes. Fragaria chiloensis (L.) Miller was superior to F. virginiana Miller for crown number, fruit weight, soluble solids and seed set, while Fragaria virginiana was superior for runner production, peduncle length, fruit number, fruit color and winter hardiness. Fragaria chiloensis ssp. pacifica Staudt had the highest soluble solids and among the earliest bloom dates, highest crown numbers and highest seed set. Fragaria chiloensis ssp. chiloensis f. chiloensis (L.) Duch. produced the largest fruit and among the earliest bloom dates and longest peduncles. Fragaria chiloensis ssp. chiloensis f. patagonica (L.) Duch. had among the highest crown numbers and the highest percentage seed set. Fragaria virginiana ssp. platypetala (Rydb.) Staudt produced the most crowns and its fruit ripened earliest. Fragaria virginiana ssp. glauca (Wats.) Staudt were the latest flowering, had the darkest fruit color and the most flowering cycles. Fragaria virginiana ssp. virginiana Duch. displayed the most winter dieback, the longest peduncles, and the highest flower and runner numbers. No significant differences were observed in any of the examined traits between F. chiloensis ssp. pacifica and F. chiloensis ssp. lucida, or F. virginiana ssp. grayana and F. virginiana ssp. virginiana. A number of individual genotypes were superior for more than one trait. CFRA 0024 possessed unusually high crown numbers, was extremely early blooming and displayed multiple fruiting cycles. CFRA 1121 had unusually long peduncles and much higher than average values for fruit weight, soluble solids, fruit color and seed set. CFRA 0094 was extremely early flowering and had much darker fruit color than most other F. chiloensis genotypes. CFRA 0368 flowered unusually early and had among the largest fruit. CFRA 0366 possessed unusually long peduncles and the largest fruit of any North American genotype. CFRA 0560 and CFRA 1369 had an unusual combination of multiple flowering cycles and high runner production. CFRA 1170 and 1171 were unusually late fruiting and had high numbers of large fruit on long peduncles. CFRA 1385 and JP 95-3-1 had extremely high flower numbers, long peduncles and large fruit.

CO2 assimilation rates (A) in two Fragaria xananassa cultivars, ten native F. chiloensis genotypes, and nine native F. virginiana genotypes were compared in growth chambers held at two day/night temperature regimes: 20/15degreesC and 30/25degreesC. Light intensity (PAR) was maintained at 500 mumol m(-2) s(-1) and day lengths were held at 14 hours. At 20/15degreesC, F. virginiana had significantly lower A (10.4 mumol CO2 m(-2) s(-1)) than either F xananassa (11.6 mumol CO2 m(-2)s(-1)) or F. chiloensis (11.7 mumol CO2 m(-2) s(-1)). All species showed a significant reduction in A at 30/25degreesC; however, F. virginiana dropped the least at 24%, while F. xananassa fell 42% and F. chiloensis dropped 54%. 'Seascape' and 'Tribute' had intermediate levels of A under cool temperatures (12.8 mumol CO2 m(-2) s(-1) and 10.4 mumol CO2 m(-2) s(-1)) and their CO2 assimilation rates were reduced by 39-44% by high temperatures. Several E chiloensis genotypes had higher A than the E xananassa genotypes under cool temperatures, but they were more negatively effected by high temperatures. In E virginiana, LH 50-4 and RH 18 had A values comparable to 'Seascape' and 'Tribute', and they showed more modest reduction in A at high temperatures (<5%). These two genotypes may be good parents to improve heat tolerance in cultivated day-neutral germplasm.

The genetics of photoperiod sensitivity, flowering date, fruit size, gender, female fertility, and disease resistance were investigated in progeny between sets of elite F. virginiana selections and F. × ananassa cultivars and selections planted at sites in Michigan, Minnesota and Ontario. Progeny means varied considerably for all the production traits. Most notable were the large fruit and high fertility observed in crosses with High Falls 22 at all three sites, and Montreal River 10 in Ontario and Michigan. Fragaria virginiana ssp. virginiana parents yielded progeny with much larger fruit than F. virginianassp. glauca parents. General combining ability was significant for all traits at all locations, while specific combining ability was significant for only fruit diameter, ovule set and fruit set in Michigan. Overall, the highest number of day-neutral genotypes were detected in Ontario (mean =44%) compared to Minnesota (31%) and Michigan (26%). In progeny populations of day-neutral F. × ananassa × short-day F. virginiana almost all fit the 1:1 ratio expected if day-neutrality is regulated by a single dominant gene; however, only a few families of short-day F. × ananassa ×day-neutral F. virginianacrosses fit a 1:1 ratio. Likewise, in progeny of day-neutral F. virginiana ×day-neutral F × ananassa crosses, only a few of them fit the 3:1 ratio expected if day-neutrality is regulated by a single dominant gene. These data suggest that it should be relatively easy to useF. virginiana germplasm in strawberry cultivar improvement, and that several different sources of day-neutrality may exist in natural populations.

An elite group of 38 strawberry accessions representing all subspecies of the beach strawberry [ Fragaria chiloensis (L.) Miller] and the scarlet strawberry ( F. virginiana Miller) was planted in a replicated design at five locations across the United States, and evaluated for plant vigor, flowering date, runner density, fruit set, fruit appearance, and foliar disease resistance. Considerable genotyp× location interaction was observed for many of these traits. However, a few genotypes were impressive at all locations including PI 551735 (FRA 368) with its unusually large, early fruit, and PIs 612486 (NC 95-19-1), 612493 (Frederick 9), and 612499 (RH 30), which were very vigorous and had unusually good fruit color. Genotypes that were superior at individual locations included PIs 551527 (FRA 110) and 551728 (Pigeon Pt.) in Maryland for their large fruit, and PI 612490 (Scotts Creek) in Oregon which had extremely large fruit, superior color, firmness, and flavor. The PIs 612495 (LH 50-4), 612498 (RH 23), and 612499 (RH 30) performed well as day neutrals at multiple sites.

Received for publication 22 May 2000. Accepted for publication 13 June 2000. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. To whom reprint requests should be addressed. E-mail address: hancock@ pilot.msu.edu The commercial strawberry, Fragaria ×ananassa Duchesne in Lamarck (Staudt, 1999), has a narrow germplasm base, even though its progenitor species have an extensive geographical range (Hancock, 1999; Luby et al., 1991). It originated about 250 years ago when a few New World clones of F. chiloensis (L.) Miller and F. virginiana Miller accidentally hybridized in European gardens (Wilhelm and Sagen, 1972). Thomas A. Knight began the systematic breeding of strawberries in England in 1817, but had at his disposal only a small number of native and cultivated clones. Likewise, North American genetic improvement began in the mid-1800s with a restricted group of European F. ×ananassa cultivars, South American F. chiloensis, and North American F. virginiana (Darrow, 1966). The cultivars originating from this background played the predominant role in most public and private breeding programs for the next 100 years. The majority of the genes in modern North American cultivars still comes from only seven nuclear (Hancock and Luby, 1995; Sjulin and Dale, 1987) and 10 cytoplasmic sources (Dale and Sjulin, 1990), even though at least eight native clones have been incorporated into cultivars in the last half century. These include: 1) two unnamed clones of F. chiloensis from the Pacific Northwest, 2) two unnamed clones of F. virginiana from Oregon and Alaska, 3) two selections of F. virginiana from the Rocky Mountains (Sjulin and Dale, 1987), 4) the Huachi Grande clone of F. chiloensis from Ecuador (Finn et al., 1998), and 5) the Del Norte clone of F. chiloensis from northern California (Moore et al., 1995). Since the germplasm base of strawberries remains narrow, native germplasm can be injected into the lineage of cultivars relatively easily. However, identification of more wild clones and their use in strawberry improvement would be beneficial. We have spent the last decade cataloging horticulturally useful traits in native populations (Cameron et al., 1993; Hancock, 1999; Hancock et al., 1990; Luby et al., 1991) and utilizing that variability (Dale et al., 1993; Hancock et al., 1993). Our primary goals have been to: 1) expand the germplasm base of F. ×ananassa by hybridizing it with elite native octoploid clones, 2) reconstruct F. ×ananassa using these clones, and 3) develop pure F. chiloensis cultivars. We would also like to construct a “supercore” group of native F. virginiana and F. chiloensis clones that can be used by other breeders to expand their germplasm base and serve as a reference point for future collections.

The performance of four California and 11 eastern cultivars of Fragaria × ananassa Duchesne in Lamarck, and 12 elite F 1 hybrids of Fragaria × ananassa with F. virginiana Miller in their immediate background was evaluated in a producer's field with and without methyl bromide-chloropicrin fumigation. Averaged across all genotypes, plants in nonfumigated soils had 43% fewer runners, 18% smaller fruit, and 46% lower yields than did plants on fumigated soil. They also had an average of 27% fewer crowns, 49% more root discoloration, significantly fewer fine roots, and showed symptoms of the black root rot syndrome. The most commonly isolated pathogens from discolored roots were Pythium sp., Rhizoctonia sp., Idriella lunata P.E. Nelson & K. Wilh., and the root-knot nematode ( Meloidogyne hapla Chitwood). The performance of all genotypes was enhanced by fumigation, although the F. virginiana hybrids performed comparatively better than the other cultivars on nonfumigated soils.

Flower bud and leaf samples collected from a wide range of native North American Vaccinium populations were tested for the presence of blueberry shoestring virus (BBSSV) using the enzyme-linked immunosorbant assay. The highest disease incidence was found in Michigan (14%), although a few positive samples also were found in Virginia, New Jersey, Maine, Ontario, and Quebec. Of seven species tested, only V. corymbosum L. and V. angustifolium Ait. were infected with BBSSV.

Twenty-one western and 13 eastern strawberry [Fragaria × ananassa (Duch.)] cultivars were grown in a polyethylene-covered greenhouse (polyhouse) in deep beds at either 10 × 10 or 25 × 25 cm spacing. Runners were removed weekly from the closest-spaced plants (hills), and the more open-spaced plants were allowed to set four runners on each side of the mother plant before the runners were removed (matted rows). Temperatures were allowed to fluctuate normally in the polyhouse, except that winter temperatures were maintained above 0C. The average yield of eastern and western cultivars did not differ significantly in most comparisons, but the average fruit weight of the Californian cultivars was significantly higher than the eastern ones, and Californian cultivars allocated a higher proportion of their biomass to reproduction. Nonbearing plants of eastern and western cultivars produced similar numbers of runners per plant and daughters per runner. There was no significant relationship between CO 2 assimilation rate and yield. Interbreeding eastern cultivars with the most productive western genotypes might result in increased yields, but only if the higher reproductive efforts of the western types can be captured and transferred.

Flower bud injury was assessed in 18 cultivars of highbush blueberry ( Vaccinium corymbosum L.) after two spring frosts. Bud position on shoots was significantly correlated ( P < 0.05) with percent brown ovaries. Significant differences in proportion of brown ovaries were noted among cultivars, but most of the variation was associated with stage of bud development. The least-developed buds were the most hardy. Bloom date was significantly correlated with harvest date across cultivars, although ‘Spartan’ flowered much later than other early ripening cultivars.

Protoplasts isolated from suspension cultures of atrazine resistant black nightshade (Solanum nigrum L.) a weed biotype, were enucleated by centrifugation through a stepwise mannitol/sucrose gradient. Two cytoplast, enucleated subprotoplast, bands were routinely formed: one, a minor band at the 6.4%/18.2% mannitol border containing highly vacuolate cytoplasts with 95%+ enucleation; secondly a major cytoplast band at the 18.2% mannitol/33% sucrose border containing 90%+ enucleated protoplasts in quantities up to 4 million per 50 ml gradient tube. Efficient production of cytoplasts depended on the subculture procedures used for the cell suspensions. Optimal cytoplast yield (44%) occurred for protoplasts isolated three days after subculture. The vigor of the donor suspension cultures as visually monitored had to be controlled in order to obtain consistently high enucleation percentages.

The present research presents a metholodogy for the bulk production of cytoplasts from suspension-culture-derived protoplasts of Solanurn nigrum (L.) containing cytoplasmically carried resistance to the herbicide atrazine. The ultimate purpose of this research is to use such cytoplasts in somatic fusion with protoplasts of atrazine—sensitive crop plants in an effort to transfer the herbicide resistance without concommitant transferance of nuclear genes of the weed species. Such a method is in contrast to those with similar aims such as the use of iodoacetate or irradiation inactivation of the donor nuclei.