Zijlstra Zaadhoudende karwij and Botanical Research

"Zaadhoudende Karwij" was the name of a non-shattering (NS) variety the initial plants of which had been found in the vicinity of Wageningen in 1915 (Zijlstra 1916, p. 337/8). An unspecified process of selfing and observing segregation in selfed progenies, selecting and selfing homozygous NS plants eventually yielded a 'pure' variety.

In the mean time it had become clear that the NS character showed a dominant and simple inheritance. Goedewaagen and Zijlstra (1925) describe the NS character in detail and visualise it in the anatomical drawing as in Figure 1. Yields of 2t/ha and over are reported, and Zijlstra (1940) confirms the same yield level in 1939.

The variety appeared in the first Dutch list of recommended varieties in 1924 classified as variety worth of further testing (Broekema 1924) commenting that the crop plants are somewhat slender. The variety disappears from the list in 1927 unfortunately without comment. The agronomic characters of the variety were apparently not up to standard. As the underlying cause inbreeding depression is suggested in reports concerning the 'Bleija' breeding programme summarised below. Zijlstra's extensive treatise of 1916 contains detailed descriptions and drawings of morphological and anatomical features of plant parts with particular attention to flower and mating system, fruit and vittae. He was particularly concerned with the carvone component of the oil which he believed to be by far the most valuable substance of the caraway fruit. The analytical method used is outlined in the former chapter.

With the purpose to get a better understanding of the environmental effects on oil and carvone content, two interesting studies were conducted which results are summarised here.

(1) Caraway seed samples obtained from different parts of Europe were analysed for oil and carvone content. Two years later samples were analysed of the respective progenies grown in replicated plots inside a commercial field in The Netherlands (Zijlstra 1916). Table 1 shows the data. Contents of the original samples vary a great deal, from 3.4 to 7.2%. However, contents of the progeny samples produced in The Netherlands converge to around the average content obtained in this country, i.e. between 4.0 and 4.5%. This seems to indicate that most of the variation obtained in the original samples was due to environmental factors including seed processing. Nevertheless, the sample from Wuertemberg Germany was also the highest when grown in The Netherlands and may well express a heritable character. The samples from Kolozsvar are very nearly equal and consistently high, also showing possibly a heritable trait.

(2) Some 25 years later, Zijlstra (1940) presents data of nine years of field experiments to study the effect of the date of cutting the crop in windrows on yield and seed values of the variety "Noord-Hollandsche". At each date of cutting, duplicate plots were cut out of a large field at the Groningen Experimental Farm on Oldambt clay, for treatment and analysis. In the first 5 years three harvesting dates were used: 'early', 'timely' and 'late' with 3-4 day intervals. It should be kept in mind that due to the shattering nature of the fruit, cutting could not be delayed much without loosing a lot of seed. In the last three years two earlier dates of cutting were added. At each date of harvesting: seed yield, 1000-seed weight (except for the first two years), oil contents of air-dry as well as oven-dry seed, and carvone content of the oil were determined.

The oil content data enabled the computation of seed moisture content (MC). In Table 2 the seed values are shown, recalculated to a standard 11% MC. The volume of oil in 1000 seeds, '1000-s volume' was computed using 0.9 as the standard density of the oil to convert weight to volume.

Table 1 Essential oil and carvone content of oil in samples of commercial caraway seed and of their progeny grown in The Netherlands. (Modified after Zijlstra 1916)

Origin of the seed

EssentiaI oil


Essential oil Carvone




>/f progeny

Moscow, Russia, wild

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