FruitBreeding - Blackcurrant breeding at The James Hutton Institute

Blackcurrant breeding at The James Hutton Institute

Historical perspective on blackcurrants at The James Hutton Institute

The blackcurrant breeding programme at The James Hutton Institute (formerly the Scottish Crops Research Institute and the Scottish Horticultural Research Institute) was established in the 1950s, to provide varieties suitable for cultivation in northern parts of the UK. Initially, the work covered only the establishment in 1952 of variety trials for both black- and redcurrants, under the aegis of Malcolm Anderson, but results from the trials showed scope for considerable improvement within the existing genetic base, and breeding of blackcurrants was inaugurated in 1956. The initial objectives of the programme were to produce improved germplasm with cold tolerance, especially in the spring, even and earlier ripening and fungal disease resistance. Initial hybridisations were made between established UK varieties and varieties from Canada, Scandinavia and northern Europe, together with a small interspecific programme, and the first commercialised product of the continuing breeding effort, 'Ben Lomond', was released in 1972. Since then, further varieties have been released for commercial cultivation, with 'Ben Hope' now the most popular cultivar in the UK.

Current breeding programme

Breeding of new commercially useful varieties is based on recurrent selection and backcrossing from seedling populations at The James Hutton Institute, with initial selections in the first (non-fruiting) year based on vegetative characters, followed by selection on fruiting characters and longer term agronomic traits. Trialling of the most promising seedlings is carried out at sites in Norfolk and Gloucestershire where commercial large-scale fruit assessments are made. Recommendations for release are made after 3 years' trialling. The Breeding programme is commercially funded, and 95% of UK blackcurrant production is used for the production of Ribena.

Breeding objectives

Breeding objectives in blackcurrant have altered significantly in recent years, with fruit quality attributes now regarded as equally important as agronomic traits due to end-user requirements. The main agronomic goals are consistency of yield and resistance to pests and diseases. The latter is driven by the loss of many chemical controls and a widespread move towards Integrated Crop Management systems.

Frost tolerance

The objectives of the programme were initially to improve the frost tolerance of the available varieties and thereby to produce consistency of cropping. This was achieved by the introduction of a late-flowering character into many of the The James Hutton Institute varieties, reaching its highest expression in 'Ben Tirran' released in 1990. Beyond this point, further delays in flowering are likely to compromise eventual yield. However, recent years have been characterised by warm winters and a lack of frost events, probably due to a changing climate (Atkinson et al 2004) so the breeding programme is now aimed at the introduction of low-chill germplasm for the production of new varieties in the longer term which are better-adapted to warmer conditions.

Disease resistance

Other agronomic objectives within the programme are resistance to gall mite (Cecidophyopsis ribis) and to Blackcurrant Reversion Disease (BRD). Resistance to gall mite has been a breeding objective in most blackcurrant programmes for many years (Brennan 1996). The most effective source of resistance used so far in western Europe is the Ce gene from gooseberry, and the introgression of this gene into R. nigrum is described by Knight et al (1974). A long-term backcrossing programme to restore acceptable fruiting characters was undertaken, latterly at the Scottish Crop Research Institute, and potential new varieties with resistance to C. ribis are now approaching commercialization. Work to develop molecular markers linked to mite resistance is also in progress. For reversion disease, resistance is derived from a Russian cultivar, 'Golubka', itself a derivative from the species R. dikuscha. This resistance has proved durable in the cultivar 'Ben Gairn' in a range of environments throughout Europe, and the development of new PCR tests for the viral agent causing BRD will facilitate the selection of further resistant material within the programme.

Fruit quality and nutritional aspects

The main fruit quality objectives in blackcurrant breeding have traditionally focused on ascorbic acid (AsA) content. The range of AsA in commercially available varieties varies from 130 - 200 mg/100 ml juice, but this increases to over 350 mg/100 in some breeding lines and even higher in wild accessions of R. nigrum var. sibiricum. Some reports suggest that the AsA contained in blackcurrant fruit is more stable than most other sources, possibly due to the protective effects of anthocyanins and other flavonoids within the berries. The main period of AsA accumulation coincides with the berry expansion phase, soon after fertilization, and genotypic rankings of AsA content established in this early stage remained constant thereafter (Viola et al 2000).

Blackcurrants and other Ribes species are outstanding sources of antioxidants, both in the form of high ascorbate levels but also in the high concentrations of polyphenolic compounds that are contained within the fruit. The latter include flavonoids, such as anthocyanins and flavonols. The amounts of these compounds present in the berries varies with cultivar, environment and agronomic practices. The main anthocyanins in blackcurrant are cyanidin-3-rutinoside, delphinidin-3-rutinoside, delphinidin-3-glucoside and cyanidin-3-glucoside, and the relative proportions vary between genotypes. For example, a survey of available germplasm has shown that western European varieties contain more cyanidin derivatives, whilst Scandinavian varieties contain a higher proportion of delphinidin derivatives. Since the latter are generally more stable, many breeding programmes including the The James Hutton Institute programme have preferentially selected for a high delphinidin:cyanidin ratio (Brennan 1996) and varieties such as 'Ben Alder' are particularly high in delphinidins. There are also within blackcurrant fruit minor compounds, such as cyanidin-3-sophoroside, delphinidin-3-sophoroside and pelargonidin-3-rutinoside, which collectively amount to ca. 5% of the total anthocyanins.

The stability of these nutritionally important compounds in blackcurrant during processing has been assessed, and whilst juice processing can cause considerable losses of ascorbate, the phenolic compounds are relatively stable during processing and antioxidant activity is retained in the juice. However, there may potentially be changes caused within the phenolic compounds by the processing, which may affect bioavailability. There are at present various studies worldwide, involving clinical trials, to ascertain how much of the ingested blackcurrant phenolics are actually taken up by the body and thereby play a role in proposed health benefits from berry consumption.

Fruit flavour

Sensory components, such as flavour, aroma and mouthfeel, are also part of the selection process within the The James Hutton Institute programme. Advanced material is assessed by trained panels and the most suitable selections from the end-users' perspective are progressed in the breeding process. Flavour appears to be the most important sensory attribute, and initial studies have suggested that some flavour characteristics are dominant in their inheritance. Overall, however, sensory attributes show highly complex patterns of inheritance and further work is in progress to examine this so that specific breeding strategies can be used.

References and further reading

Atkinson CJ, Sunley RJ, Jones HG, Brennan RM & Darby P (2004) Desk study on winter chill in fruit. Defra Report CTC 0206.
Barney DL & Hummer KE (2005) Currants, gooseberries and jostaberries: a guide for growers, marketers and researchers in North America. Haworth Press: Binghampton, NY.
Brennan RM (1996) Currants and gooseberries. In: Janick, J. and Moore, J.N. (Eds.) Fruit Breeding, Vol. II: Vine and Small Fruits Crops. John Wiley and Sons, Inc. New York, pp. 191-295.
Brennan RM (2005) Currants and gooseberries (Ribes L.). In: The Encyclopedia of Fruit and Nut Crops, ed. J. Janick. CABI (in press). Inc. New York, pp. 191-295.
Knight RL, Keep E, Briggs JB & Parker JH (1974) Transference of resistance to blackcurrant gall mite, Cecidophyopsis ribis, from gooseberry to blackcurrant. Annals of Applied Biology 76:123-130.
Viola R, Brennan RM, Davies HV & Sommerville L (2000) L-ascorbic acid accumulation in berries of Ribes nigrum L. Journal of Horticultural Science and Biotechnology 75:409-412.