i ii iii iv SUMMARY............................................................................................................................................... VII ZUSAMMENFASSUNG ............................................................................................................................ IX LIST OF ABBREVIATIONS AND ACRONYMS ........................................................................................ XI PREFACE ............................................................................................................................................... XIII 1 INTRODUCTION .................................................................................................................................. 3 1.1 Increasing demand on exotic tropical fruits .......................................................................... 3 1.2 Klein-Eden: Sustainable production and local marketing of (exotic) tropical fruits ....... 9 1.3 The lulo (Solanum quitoense) as model species for exotic tropical fruits ............................ 12 1.4 Aims and structure of this thesis ........................................................................................... 14 2 SOLANUM QUITOENSE: BACKGROUND TO MY MODEL SPECIES ................................................ 21 2.1 Lulo is an underutilized Solanaceae crop ............................................................................. 21 2.2 Description, origin, distribution and varieties of lulo ........................................................ 23 2.3 Growing conditions, fruit production and use of lulo ....................................................... 25 3 SYNOPSIS ........................................................................................................................................... 31 3.1 Key results and discussion ...................................................................................................... 31 3.1.1 Focus 1: Consumer acceptance of fresh lulo fruits in Germany ............................ ..31 3.1.2 Focus 2: Lulo´s suitability for greenhouse cropping in Central Europe ................. 34 3.2 Outlook: Potential of lulo, implications of the findings and future research ................. 38 4 REFERENCES ..................................................................................................................................... 43 5 LIST OF INCLUDED MANUSCRIPTS AND PERSONAL CONTRIBUTION ......................................... 55 v 6 MANUSCRIPTS ................................................................................................................................... 61 6.1 Manuscript I: Liked or disliked? Consumer sensory acceptance of the exotic lulo fruit in Germany ...................................................................................................................... 61 6.2 Manuscript II: Reife und gesundheitlicher Wert: Redoxpotenzial-Messungen an der exotischen Lulo-Frucht ........................................................................................................... 83 6.3 Manuscript III: Solanum quitoense, a new greenhouse crop for Central Europe: Flowering and fruiting respond to photoperiod ................................................................. 93 6.4 Manuscript IV: Physico-chemical and sensory quality of the lulo fruit is high but varies seasonally under greenhouse conditions ................................................................. 117 6.5 Manuscript V: Successful pollination of the Neotropical crop Solanum quitoense by Bombus terrestris: behaviour, efficiency and yield ................................................................ 145 7 LIST OF FURTHER, NOT INCLUDED PUBLICATIONS ................................................................... 169 8 APPENDIX ....................................................................................................................................... 173 8.1 Appendix A1: Study of impact of ripeness/storage on sensory profile ........................ 173 8.2 Appendix A2: Fusarium-infestation of lulo plants ............................................................. 178 8.3 Appendix A3: Preliminary growing trial of different lulo varieties ................................ 179 ACKNOWLEDGEMENTS ...................................................................................................................... 181 DECLARATIONS ................................................................................................................................... 183 vi Fruit consumption and fruit trade is expected to increase rapidly in Europe; today’s interest is especially rising for the exotic, lesser-known, tropical fruits which are up to now niche products in Europe. Against this background, the concept of the innovative project “Klein- Eden” in Germany to cultivate and market such tropical crops is promising for the future. By using industrial waste heat as energy source for greenhouse cropping, Klein-Eden makes it possible and environmentally acceptable to introduce novel fruits to the Central European market. One of these is the lulo (Solanum quitoense Lam.), as yet cultivated and consumed mainly locally and regionally in Latin America. The lulo seems to unify several promising attributes for successful marketing and cultivation, e.g. special aroma and good nutritional value of the fruits. Thus the lulo was used in this thesis as model species. This thesis aims to assess the prospect of the lulo as an exotic tropical fruit for marketers and growers in Central Europe, with particular application in Klein-Eden, by evaluating lulo’s acceptance among consumers (Focus 1) and suitability for local greenhouse cropping (Focus 2). More specifically, five major research objectives were investigated on lulo, including five manuscripts: 1) degree of familiarity among consumers and consumer sensory acceptance, 2) antioxidative capacity of the fruits, 3) influence of photoperiod on fruit supply, 4) seasonal variation in quality of fruits, and 5) pollination success by Bombus terrestris. The consumer survey revealed that the lulo fruit was widely unfamiliar confirming that it is a novel, exotic fruit in Germany. The sensory acceptance among consumers was assessed to be overall high and lulo fruits are likely to be repeatedly consumed and (re)purchased. Firmness, colour, odour, juiciness, taste, sourness und sweetness were detected to be relevant attributes for consumer. Apart from sweetness, which was frequently assessed as being too low, all these attributes were liked by the majority of consumers. Furthermore, an important antioxidative capacity could be proven for lulo fruits. Taking all these findings into account, the lulo appears to be very attractive to consumers and have high commercial promise for German market.This assumption should be tested in follow-up studies. One critical factor challenging marketing could be the short shelf life of ripe lulo fruits. The sensory properties and antioxidant capacity were most favourable at fully ripeness, determined in this study to occur at fruit fall, but decreased already after four days of storage. This (currently) favours lulo as a niche product for direct marketing, as handled in Klein-Eden. vii Lulo fruits for direct marketing can be gainfully produced in greenhouses in Central Europe under natural light conditions and existent cultivation practices as demonstrated for the first time in these cultivation trials. Flower initiation and fruit set occurred throughout the year under seasonal variations in day length, though harvest begin was accelerated at long-days, and only two sowing dates provided near year-round fruit supply. Furthermore, greenhouse production provided fruits with an intense fruit aroma and a similar physico-chemical quality as reported in lulo fruits harvested in Latin America, even under short-day conditions in winter. However, this study showed that seasonal effects in fruit quality, particularly a decline in dry matter, firmness and sugar level during winter season, occurred under year-round fruit production in Germany. For fruit set in lulo pollination was crucial but pollination experiments gave clear evidence that the lulo can be successfully pollinated by the Eurasian Bombus terrestris in greenhouse cropping. B. terresitris adopted lulo flowers as pollen source, visited single flowers frequently, and as long as multiple visits were ensured, fruit set and seed set were as high as those resulting from cross-pollination by hand. The thesis gives first invaluable insights of lulo’s performance in Germany, Central Europe, and indicates that lulo is overall highly attractive for marketing and cultivation in greenhouses like Klein-Eden. The obtained results can be directly implemented in Klein- Eden, transferred to similar regional projects or give motivations and implications for many other actors in the (tropical) fruit sector in future. New research issues arose from this work assumed to be relevant for contributing towards promotion and commercialization of lulo, particularly phytomedicinal issues, extending shelf life and selecting an appropriate variety or cultivar for (greenhouse) cropping. The results of this thesis and possible follow- up studies will help, in long-term, to extend knowledge of lulo in general and to promote public awareness, familiarity, scientific attention and research investment also outside the homeland of lulo. This could drive research efforts, improvements and innovations in