The contents of the chemical constituents of twenty-nine recently bred (hereafter refers to as "recent") and old varieties of Japanese green tea were compared at different harvest times and growth stages. The contents of total nitrogen (T-N), total-free amino acid (T-A), theanine (γ-glutamylmethylamine), tannin, caffeine and vitamin C were analyzed by the near infrared spectroscopic method. At the first flushes, the contents of T-N, T-A and theanine, which affect the quality of tea, were high in the recent varieties of tea. However, the content of caffeine, which is a major nitrogen compound and which contributes to the characteristic bitter taste of tea, did not differ between the recent and old varieties of tea. The amount of tannin, which contributes to the astringent taste of tea, was lower in the recent varieties. In the mature leaves, the contents of T-N, T-A and theanine were high in the recent varieties of tea. However, no significant correlation was observed in tannin content between recent and old varieties of tea. In addition, there were positive correlations in the amounts of T-A between the first flushes and mature leaves both in the recent and old varieties of tea. Subsequently, the shoots with three leaves and one bud of ten of the 29 varieties were harvested at the first flushes at the fifth stage on May 4, 14 and 17 and analyzed by standard chemical methods. Higher contents of T-N and soluble nitrogen (corresponding to T-A) were observed in these recent varieties. The results showed that the recent varieties of tea contained higher nitrogen and lower tannin levels, suggesting that the recent varieties had been selected according to the changes in the breeding objectives from high yield to quality due to the changes in the consumers' demand. Modern cultivation methods, such as the use of frost-protecting fan, pest control and rate of fertilizer application, etc., have contributed to raising tender clones with higher quality in the experimental fields of many tea breeders in Japan. Furthermore, it was suggested that it might be possible to estimate the contents of the chemical constituents of tea flushes by analysing the overwintering leaves before the first cropping season or three leaves and one bud harvested at anytime in the first cropping season.

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Plug nursery systems are being introduced into Japanese bunching onion (Allium fistulosum L.) production in Japan, to promote the mechanization of transplanting. Transplants raised in plugs, however, are so young and small that their rooting is not always satisfactory or they cannot grow into a uniform stand under unfavorable conditions. It is considered that the use of cultivars with vigorous seedling growth can expand the application of plug nursery systems. In order to gain information about the mode of inheritance of the seedling growth rate in bunching onion, we conducted a diallel analysis using a 9 × 9 half diallel cross involving various types of inbred lines. Fresh weight at the transplanting stage (seven weeks after seeding) showed a high heritability in the broad sense (h_B²) and a low heritability in the narrow sense (h_N²). Average degree of dominance was 1.50, suggesting that the fresh weight at the transplanting stage is controlled by overdominant genes. The correlation between Vr + Wr and Pr showed that dominant genes induced heavier weight. Fresh weight at four weeks after transplantation also showed a high h_B², a low h_N², and a very high average degree of dominance (3.10), indicating the presence of a higher grade of overdominance. Plant height at both growth stages also showed overdominance. Dominant genes induced an increase in plant height. Since the value of h_N² was higher for plant height than for fresh weight, it is considered that the contribution of additive effects was larger for plant height than for fresh weight. Furthermore, it was suggested that frequency of the dominant alleles which induced an increase in fresh weight was high in the parental lines derived from the 'Senju' group, while the frequency of the alleles which induced an increase in plant height was high in the lines derived from the 'Kujyo' group. The present study revealed that the characters related to the initial growth rate showed an overdominant inheritance. This indicates that the F₁ hybrid breeding method could be applied to bunching onion to develop cultivars with vigorous seedling growth, suitable for plug nursery systems.

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