Plant Protection Quarterly Vol.13(4) 1998 157 The Moriferi Relationships between weedy and commercially The Moriferi includes those species as- cribed to R. fruticosus L. agg. All the Aus- grown Rubus species tralian weedy blackberries are included in this aggregate species, and all belong to G. McGregor, Institute for Horticultural Development, Knoxfield, Private Bag the European sections of the Moriferi. Se- 15, South-Eastern Mail Centre, Victoria 3176, Australia. lections of wild Moriferi species have been introduced to cultivation over thousands of years, sometimes for food, but also as Summary medicinal plants and as hedges to impede The cultivated blackberries grown in R. macropetalus is duodecaploid (each nu- marauders. Only three introductions to Australia are all complex hybrids, mostly cleus contains twelve copies of each chro- commerce are still either grown or repre- derived from successive generations of mosome, as six pairs), the two species sented in modern cultivars: these are controlled crosses. They may be grouped freely hybridize where their distributions R. laciniatus Willd. (Moriferi, Section according to derivation as (i) mainly Ru- overlap. These species are unusual in the Sylvatici), R. procerus P.J.Müll. (Section bus ursinus germplasm; (ii) derivatives of sub-genus Eubatus in being dioecious. Discolores) and R. rusticanus (Section R. ulmifolius crossed with R. argutus and They are thought to have evolved from a Discolores). R. alleghaniensis, and (iii) derivatives of species similar to R. argutus Link or R. Oregon thornless is a periclinal chi- R. alleghaniensis. Cultivated blackber- alleghaniensis Porter, both of which are meric form of R. laciniatus; it is not culti- ries do not manifest weedy behaviour or erect plants of north-eastern North vated in Australia, and commercially is represent a threat to Australian ecosys- America (Moriferi, Section Suberecti). confined to northern Oregon. tems, either through naturalization or Derivatives of R. ursinus have contrib- Rubus procerus gave rise to the cultivar hybridization. Hybridization between uted to cultivated blackberries through Theodor Reimers, from which Himalaya crop Rubus and weedy Rubus is slight, the varieties Boysen, Young, Marion, and Giant was selected, neither of which and produces hybrids less adapted to Silvan blackberries and loganberry, all cultivar is grown in Australia. survival as weeds than seedlings of of which are of economic importance in Rubus rusticanus var. inermis E.Merc. is weedy Rubus. south-eastern Australia. None, however, a spine-free variant of R. ulmifolius, a is exclusively R. ursinus germplasm (Fig- weedy species extending from southern Introduction ure 1) (McGregor and Kroon 1984). England to the Mediterranean. It has been The purpose of this paper is to examine The youngberry and boysenberry both used for breeding since the early 1800s the relationships between cultivated derive from similar crosses involving Phe- and is the major source of genetic spine- blackberries and the blackberries that nomenal or Logan × Mayes, and are there- lessness currently used in blackberry have become weedy, and to indicate areas fore in species terms (R. ursinus × R. idaeus) breeding. where the disciplines of weed manage- × (R. baileyanus × R. argutus); they combine Rubus rusticanus var. inermis is diploid, ment and blackberry fruit cultivation may the south-western trailing form of R. although an unreduced germ-cell of this interact. ursinus with the north-eastern trailing R. diploid species functioned in a cross with baileyanus, and a north-eastern erect form the tetraploid R. thyrsiger, a rare British Taxonomy in R. argutus. The youngberry is an occa- species, to produce a tetraploid spiny Cultivated blackberries, also known as sional garden escape, which has achieved cultivar released as John Inness (Figure 2). cane fruits or brambles, are closely related weed status in isolated areas of south Further selection from John Inness selfed to their weedy relatives. All belong to the Gippsland ,Victoria, and at Black Moun- produced Merton Thornless, a spineless family Rosaceae, genus Rubus, sub-genus tain, ACT (E. Bruzzese personal commu- tetraploid form. Merton Thornless has Eubatus. Within the sub-genus Eubatus, nication). been the basis for a very successful breed- taxonomists recognize eight Sections, and The marionberry has achieved the least ing program conducted by the USDA at several thousand species or sub-species commercial success of this group and is Beltsville, MD. The recessive thornless- or microspecies. The precise classification noteworthy mainly as a parent of Silvan ness of Merton Thornless has been used of forms of Eubatus into species and sub- blackberry, the most successful derivative in crosses and backcrosses including species is controversial, and made com- of R. ursinus in Australia. Marion contrib- Brainerd and Eldorado as parents. plex by the ability of species to freely hy- utes germplasm derived from R. ulmifolius Brainerd is a cross between Himalaya Gi- bridize, not only within Eubatus but also Schott to Silvan, which may contribute to ant and the erect-growing Georgia Mam- with species of other sub-genera. Silvan’s superior hardiness compared to moth, and Eldorado is thought to be de- For the purposes of understanding the other R. ursinus derivatives. rived from R. alleghaniensis × R. argutus, relationships between cultivated and The loganberry is an interesting case; it similar to Lawton (Figure 2). From this weedy blackberries in Australia, the im- occurred by chance in Judge Logan’s gar- breeding program the varieties Thornfree, portant Sections within the sub-genus are den, and is a product of an unreduced pol- Smoothstem, Dirksen Thornless, Black the Moriferi from Europe and eastern len grain of diploid R. idaeus (red Antwerp Satin and more recently Chester have been North America, and the Ursini, from west- raspberry) fertilizing a pistillate selection obtained. All have semi-erect, arching ern North America (Jennings 1988). of Aughinbaugh blackberry, a selection of canes, and fruit is harvested in summer octoploid R. ursinus (Jennings 1988). (January–February). Agronomically, they The western North American species, The Lawton berry represents a small demand good deep soil and abundant Section Ursini eastern US group within the Moriferi, water to grow and yield well. They are fa- The Ursini are found from California to characterized by very erect stems. It is voured by growers as their skin is tougher British Columbia. In the south, the Califor- thought to be a hybrid between R. frond- than the R. ursinus derivatives, and their nian dewberry, R. ursinus Cham. & osus Bigel. and R. alleghaniensis. Its com- fruits are less prone to bleeding in the Schltdl., is most common, and in the mercial success is declining, because of the punnet. north, R. macropetalus Dough., is more availability of thornless blackberries Australian growers can produce black- common. Although R. ursinus is octoploid which produce fruit at the same time as berries continuously from November, (each cell nucleus contains eight copies Lawton. starting with Boysen and Young, through of each chromosome, as four pairs) and Silvan in December, Murrindindi and 158 Plant Protection Quarterly Vol.13(4) 1998 Zielinski R. macropetalus Dougl. Pacific Aughinbaugh blackberry R. ursinus Cham. & Schltdl. Logan Red Antwerp raspberry R. idaeus L. US-Oregon 742 Aughinbaugh R. ursinus Phenomenal Boysen Cuthbert raspberry R. idaeus R. baileyanus Britt. Mayes Silvan R. argutus Link Santiam R. macropetalus Chehalem Himalaya Giant R. procerus P.J.Müll. US-Oregon 928 Aughinbaugh R. ursinus Marion Black Logan R. alleghaniensis Porter Texas Early Ollallie R. frondosus Bigel. R. ursinus Phenomenal OR Logan Young R. idaeus R. baileyanus Mayes R. argutus

Figure 1. Pedigree of Silvan blackberry. Cultivars represented in Australia are shown in bold.

Himalaya Giant R. procerus P.J.Müll. Brainerd Georgia Mammoth R. alleghaniensis Porter OR R. argutus Link

R. ulmifolius Schott Merton Thornless Thornfree R. thyrsiger Banning & Focke Merton Thornless R. alleghaniensis Eldorado R. argutus Figure 2. Pedigree of Thornfree blackberry, an example of USDA – Maryland late season, erect, thornless blackberries. The broken line indicates more than one species.

Loch Ness in January, and the Maryland Maryland program continues to develop The weed risk associated with cultivars from January to May. The vari- forms similar to Thornfree, with im- commercial blackberry cultivars ety Loch Ness was bred at Scottish Crops proved flavour, and the Arkansas pro- Escape of cultivated forms Research Institute, and combines the ge- gram aims at erect plants suitable for me- None of the cultivars currently used in netic thornlessness of Thornfree with chanical management (Moore 1997). The commerce has established as weeds, be- erectness and early flowering of Darrow Scottish program focuses on early ripen- yond small areas of youngberry in south (R. argutus × R. alleghaniensis) with rapid ing, winter-hardy, erect, thornless forms. Gippsland. In preliminary weediness as- fruit maturation of either Chehalem or Australian access to overseas cultivars is sessment trials established at the Institute Ashton Cross. impeded by privatization, plus importa- for Horticultural Development (IHD), tion costs. Knoxfield in 1981, only wild forms of R. Future breeding directions In summary, the blackberries grown in fruticosus were able to establish when No blackberry breeding is currently con- Australia may be grouped into three planted into an ungrazed pasture and left ducted in Australia. There are breeding classes according to derivation: to fend for themselves. Plants of Silvan, programs in New Zealand, Scotland, and • derivatives of R. ursinus, such as Boysen, Young, Ollalie, Thornfree and the USA (Oregon, Maryland and Arkan- Boysen and Silvan; Bedford Thornless (another R. rusticanus sas) which produce hybrids of interest to • derivatives of R. ulmifolius modified by derivative) all died out (McGregor unpub- Australian growers. The New Zealand crossing with R. argutus × R. lished). breeding program aims at producing alleghaniensis forms, such as Thornfree Another form of investigation of thornless hybrids similar to Boysen (Hall and Loch Ness; and weediness consists of surveying berry and Brewer 1993). The Oregon program • derivatives of R. argutus and R. farms and surrounding bushland for Ru- aims at replacing Marion with a higher- alleghaniensis, such as Lawton. bus seedlings. To date, the only seedlings yielding, more winter-hardy form. The bearing any resemblance to crop plants Plant Protection Quarterly Vol.13(4) 1998 159 have been found in the cropping rows; weeds. It does, however, allow those seed- Jennings, D.L. (1988). ‘Raspberries and none has been reported from surrounding lings too poorly adapted to survive as blackberries: Their breeding, diseases bush. This result is consistent with obser- weeds, to continue as cultivars, and and growth’. (Academic Press, New vations from the weediness assessment weediness may become attenuated York). trial conducted at IHD Knoxfield. Grow- through successive crosses and selections. McGregor, G.R. and Kroon, K.H. (1984). ers have an interest in finding chance Even at the first (F1) generation derived Silvan blackberry. HortScience 19, seedlings as they may potentially be new from crossing wild species (e.g. 732-3. cultivars. Chehalem), the R. ulmifolius derivatives Moore, J.N. (1997). Blackberries and rasp- The lack of weediness of commercial have been shown through field trials and berries in the southern United States: cultivars can be considered from several countless grower observations not to pos- Yesterday, today and tomorrow. Fruit points of view. Firstly, the commercial sess the phenotypic character of establish- Varieties Journal 51, 148-57. cultivars all require managed soil in order ment under adversity. Selection has also to thrive. They lack the hardiness of R. favoured erect plants which cannot bend fruticosus and only under good conditions to the ground to tip-layer in autumn, and and management can they achieve the has favoured plants which sucker less vegetative growth displayed by R. frut- than wild progenitors. Cultivated forms icosus. Secondly, their seedlings represent related to R. ulmifolius are therefore likely the range of genotypes achieved by selfing to confer poorer thicket-forming charac- and through apomixis. Only rarely will ters to progeny than their weedy rela- they cross with wild blackberries. Bees are tives. their main pollinators, and honey bees Biological control of weedy blackberry usually work only one species on each can present a threat to commercial black- flight. Bee-mediated crosses between cul- berry production through the introduc- tivated plants and weeds can therefore oc- tion of pests or diseases which cannot dis- cur only when a bee either mistakes a spe- criminate between weeds and commercial cies, or fails to shed all its pollen in the crops. Given the close genetic relationship hive; both mistakes occur, but the rate of between weeds and crops outlined above, bee-mediated genetic drift will be slow. finding appropriate organisms presents a challenge. The release of Phragmidium Hybridization between weeds and violaceum was seen to present only a mi- cultivated Rubus nor threat to commercial blackberry grow- The potential combination of R. fruticosus ers, on the basis that the Ursini derivatives germplasm with cultivated Rubus germ- are not susceptible, and that the suscepti- plasm would in most instances give rise to ble cultivars (Moriferi derivatives) were hybrids less well adapted to Australian likely to be protected by fungicides ap- conditions than are weed hybrids, weeds plied as a routine protectant against fruit selfed, or weed apomicts. This arises be- spoilage fungi (Bruzzese and Hasan 1987). cause the cultivated forms represent the The current trend towards minimization results of years and generations of cross- of pesticide usage would strongly discour- ing and selection for characters which ei- age blackberry fruit growers from sup- ther negate weediness or at least reflect porting the importation of any biological criteria other than fitness as a weed. This weed control organisms which would re- argument may be broken down into those quire them to maintain routine pesticide characteristics which determine or facili- use, or increase their use of chemical pesti- tate weediness; they are: cides. • seed germination; To summarize, crosses between the • seedling establishment; weed species R. fruticosus and cultivated • thicket formation via tipping or derivatives of R. ulmifolius will tend to suckering; have lower weed potential than the R. • survival of grazing, browsing or preda- fruticosus parent. They therefore do not tion; and represent a threat to commerce beyond • seed production and dispersal. berry production, nor to natural ecosys- Of these characteristics, seedling estab- tems. Their only contribution, rarely lishment would appear both from experi- made, is to weaken F1’s derived from ence and genetic considerations to be the weed × crop Rubus crosses through point of failure as a weed of both culti- introgression of genes derived from plants vated Rubus seedlings and weed Rubus × selected either naturally or commercially crop Rubus hybrid seedlings. for environments not found naturally in The introgression of genes from the Australia. north-eastern USA erect blackberries in- troduces the results of selection pressure References for a wetter environment than suits R. Bruzzese, E. and Hasan, S. (1987). Infec- fruticosus (which is a weed in south-west- tion of blackberry cultivars by the Eu- ern USA) and conversely is not suited to ropean blackberry rust fungus, most of Australia. Seedling establishment Phragmidium violaceum. Journal of Horti- is either selection-neutral or is dis- cultural Science 62, 475-9. favoured by breeding; that is, artificial se- Hall, H.K. and Brewer, L.R. (1993). Breed- lection under commercial conditions nei- ing Rubus cultivars for quality and di- ther favours nor disfavours potential versity. Acta Horticultura 352, 329-38.