Browsing by Subject "Broccoli"

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    Evaluation of new open pollinating broccoli genotypes (Brassica oleracea convar. botrytis var. italica) specifically bred for organic farming conditions focusing on agronomic performance and glucosinolate content
    (2018) Sahamishirazi, Samira; Graeff-Hönninger, Simone
    Currently, a considerable share of varieties being used in the organic vegetable production are developed for conventional high-input production systems, and broccoli is no exception. In addition, F1 hybrids are cultivated in organic broccoli production to a great extent because of high quality and yield. Two main restrictions of cultivating the mentioned categories of varieties in organic farming are; 1) ban of using cytoplasmic male sterility (CMS) in organic agriculture for reproduction of F1 hybrids of broccoli and limitations of farmers to produce their own seeds, 2) absence of special traits of these varieties which result in weaker performance when being cultivated under organically low-input conditions. In contrast to hybrids, cultivation of open pollinating broccoli varieties gives the opportunity of reproducing seeds to organic farmers. Therefore, developing new open pollinating broccoli varieties, which have the same quality (agronomical, chemical and sensorial) as F1 hybrids, through organic breeding programs (on-farm breeding) would allow the organic broccoli farmers to replace the hybrids with varieties adapted to organic production conditions. With this in mind, the German Federal office for Agriculture and Food (BLE) initiated a project on “Breeding development of open pollinating cultivars of broccoli for organic farming in terms of agronomic characteristics, secondary and bioactive ingredients and sensory properties”. This was a joint project which was done through the cooperation of University of Hohenheim and Kultursaat e. V. (NGO of on-farm breeders) in two parts during six years (2011-2016). The present doctoral thesis, which was a part of the mentioned project, aims at 1) investigating the agronomic performance of the newly bred open pollinating genotypes of broccoli, 2) developing a Near-Infrared Spectroscopy (NIRS) method for fast analysis of total, indole, aliphatic and individual glucosinolates content of broccoli samples; and 3) determining the total and individual glucosinolate content of the newly bred open pollinating genotypes of broccoli. For investigations on agronomic performance, two field experiments were carried out by cultivating eleven newly bred open pollinating genotypes, two F1 hybrids and an open pollinating variety of broccoli over two growing seasons of fall 2015 and spring 2016. Evaluation of the effect of genotype, growing season and their interactions on agronomic parameters were targeted in this study. According to our findings, assessment of agronomic variables indicated that although there were distinctions in different parameters such as head firmness, head shape and total biomass fresh weight among the newly bred open pollinating genotypes, some genotypes performed similar to hybrid varieties in organic farming. However, most of the open pollinating genotypes had 16 % to 73 % lower yields compared to the hybrid varieties depending on growing season. Generally, the “marketable yield” of the genotypes was under the significant effect of “genotype × growing season interaction”. Head weight was significantly affected by growing season which resulted in significantly lower head weight of some genotypes in the spring compared to the fall season. Overall, cultivation of the genotypes in fall season led to significantly higher marketable yields, head weight and total biomass weight, as well as firmer heads in contrast to the spring season. Considering the performance of different agronomic parameters, we recommend genotypes “TH-CAN-SPB”, “Calinaro”, “CHE-GRE-G” for both fall and spring growing season. Other genotypes such as “CHE-GRE-A”, “CHE-BAL-A” and “CHE-MIC” and “Line 701” are also recommended for cultivation in spring growing season specifically due to the high marketable yield and share of marketable heads. In addition, this thesis aimed at testing a fast analytical technique for determination of glucosinolates content in order to help breeders to quickly test their most favorable genotypes during breeding procedures based on glucosinolates content. For this purpose, the accuracy of NIRS technic was tested, regardless of type of genotype, for fast analysis of the individual and total glucosinolates content of broccoli samples. NIRS calibration was developed by reference method of High Performance Liquid Chromatography (HPLC) based on modified partial least squares regression, to measure individual and total glucosinolates content of open pollinating genotypes of broccoli regardless of the type of genotype. The calibration was analyzed using coefficient of determination in prediction (R2) and ratio of preference of determination (RPD). Large variation occurred in the calibrations, R2 and RPD due to the variability of the samples. Derived calibrations for total glucosinolates (RPD = 1.36), aliphatic glucosinolates (RPD = 1.65), glucoraphanin (RPD = 1.63) and 4-methoxyglucobrassicin (RPD = 1.11) were quantitative with a high accuracy, while for indole glucosinolates (RPD = 0.95), glucosinigrin (RPD = 0.62), glucoiberin (RPD = 0.67), glucobrassicin (RPD = 0.81) and neoglucobrassicin (RPD = 0.56) they were more qualitative. Overall, the results showed a good potential of NIRS in determination of different glucosinolates in a large sample pool of broccoli quantitatively and qualitatively. The achieved calibration equations were used to measure glucosinolates content of the broccoli samples of following years. To evaluate the health beneficial value of the open pollinating genotypes, the glucosinolates content of them were determined. The determination was done by the tested NIRS technic. Six individual glucosinolates were detected in the broccoli samples similar to findings of the previous chapter. Glucoraphanin (1.44-1.69 µmol g-1 DW), glucobrassicin (0.63-0.77 µmol g-1 DW) and neoglucobrassicin (0.38-0.74 µmol g-1 DW) had the highest share and were the main individual glucosinolates. Total glucosinolates content ranged from 3.46 to 3.60 µmol g-1 DW across both growing season. Significant effect of genotype and growing season existed on the total glucosinolates content of broccoli samples. All individual glucosinolates were affected by genotype. The effect of growing season was significant on all individual glucosinolates, except for glucobrassicin. The interaction of genotype × growing season was significant on all indole glucosinolates, glucoraphanin and glucoiberin. Generally, the glucosinolates content of the samples were higher when broccoli genotypes were cultivated in the fall growing season, however the difference in the level of glucosinolates contents across seasons was significant only for glucoraphanin, neoglucobrassicin, 4-methoxyglucobrassicin and glucoiberin. The open pollinating genotypes showed a similar range of glucosinolates compared to the tested hybrids and performed as good as the hybrids. Since total glucosinolates were nearly similar in all open pollinating genotypes across seasons, all are recommended for cultivation in both growing seasons. It is important to note that this study only focused on a single health beneficial compound (glucosinolate) in broccoli heads. To provide a full insight into the nutritive and health benefiting compounds of broccoli such as vitamins and polyphenols, supplementary studies will have to be conducted. All in all, releasing new open pollinating broccoli varieties out of this pool of genotypes and replacing the present varieties with them seemed beneficial due to the well adapted agronomic performance and high health value with regard to glucosinolates content under organic farming conditions.