Breeding and regulatory opportunities and constraints for developing broccoli cultivars adapted to organic agriculture

This thesis is about the regulatory and technical challenges to the organic seed and breeding sector. This study specifically explored the mutual influence of the regulatory environment for organic seed sector development in the United States (US), Europe Union (EU) and Mexico, and the extent to which cultivars performed differently under organic conditions compared to conventional conditions, measured by selected horticultural and phytochemical traits. Organic farming practices often differ substantially from conventional practices and in the diversity of their crop rotations and market outlets. Currently, organic farmers depend largely on cultivars bred for conventional farming systems. We investigated the requirements of organic growers for seed that allowed optimization of their production system, and fulfilled consumer expectations for high nutritional value. In addition, we discuss the implications for seed production and crop improvement. Broccoli is one of the most important horticultural crops in the world’s fastest growing organic product market, the US. The field research was based on stakeholder interviews, participant observation, documentary analyses, laboratory analyses and paired field trials (organic/conventional) conducted in two contrasting regions in the US, Northeast US (Maine) and Pacific Northwest (Oregon), over two seasons (spring, fall) and two years for a total of 16 trials with 23 cultivars. The main findings of the regulatory component were: (1) New organizations, procedural arrangements and activities have emerged in the US, EU and Mexico to support organic seed regulatory development, with both positive and negative results; (2) Official guidance on the interpretation of the regulation in the US has not been sufficiently decisive to prevent divergent interpretation and practice, and in consequence the needs of a rapidly growing economic sector are not being met; and (3) Growth of the organic seed sector is hindered by regulatory imbalances and trade incompatibilities within and between global markets. For the field studies the main findings were: (1) In the partitioning of variance, location and season had the largest effect on broccoli head weight. For glucoraphanin and lutein, genotype was the major source of total variation; for glucobrassicin, region and the interaction of location and season; and for neoglucobrassicin, both genotype and its interactions with season were important. For δ- and γ- tocopherols, season played the largest role in the total variation followed by location and genotype; for total carotenoids, genotype was the largest source of variation and its interactions with location and season. For both horticultural and phytochemical concentrations, Management main effect and G × M interactions were often small but G × M × E (location and season) were large; (2) Cultivars with both greater head weight and stability under conventional conditions generally had high head weight and stability under organic growing conditions, although there were exceptions in cultivar rank between management systems. Cultivars highest in tocopherols and carotenoids were open pollinated or early maturing F1hybrids. Distinct locations and seasons were identified where phytochemical performance was higher for each compound; (3) Larger genotypic variances and somewhat increased error variances were observed in organic compared to conventional management systems led to repeatabilities for several horticultural and phytochemical traits that were similar or even higher in organic compared to conventional conditions; (4) The ratio of correlated response (predicting performance under organic conditions when evaluated in conventional conditions) to direct response (predicted performance in organic when evaluated under organic conditions) for all traits was close to but less than 1.0 with the exception of bead uniformity. This would imply that in most cases, direct selection in an organic environment could result in a more rapid genetic gain than indirect selection in a conventional environment; (5) Correlations among phytochemical traits demonstrated that glucoraphanin was negatively correlated with the carotenoids and the carotenoids were highly correlated with one another; and (6) There was little or no association between phytochemical concentration and date of cultivar release, suggesting that modern breeding has not negatively influenced the level of tested compounds and there were no significant differences among cultivars from different seed companies. Based on the findings strategies for breeding and seed models are discussed.