Changes in phenylalanine and glucosinolate concentrations in the leaves of kimchi cabbage colonized by Heteroconium chaetospira

Kimchi cabbage is the main ingredient in kimchi, and improvements in yield and quality are therefore meaningful for the health of the consumer and the kimchi industry. In light of this, the present study investigated whether the gluconasturtiin (GNT) content of kimchi cabbage can be increased by applying the endophytic fungus Heteroconium chaetospira (HC). We observed that the composition of amino acids in kimchi cabbage leaves differed depending on the type of fertilizer applied during cultivation. Kimchi cabbage seedlings grew well in glutamine medium supplied with nitrate nitrogen regardless of HC inoculation. However, unfertilized kimchi cabbage seedlings that were not inoculated with HC grew poorly while those inoculated with HC grew well, suggesting HC has a beneficial effect on phenylalanine absorption by the root. When kimchi cabbage was grown with endophytic fungi inoculation and oil cake application, phenylaniline content in the leaves increased. Furthermore, when the 'Suho' cultivar inoculated with HC was grown in oil cake-supplemented soil, the gluconapin and glucobrassicanapin contents were slightly lowered and the GNT content was 8.36 μmole/g, or 74% of the total glucosinolate (GSL) content (11.3 μmole/g). When the 'Asiaipssam' cultivar was grown under the same conditions, its GNT content increased to 6.7 μmole/g, or 81% of the total GSL content (8.3 μmole/g). This cultivar difference was due an increase in GNT content without any change in the content of other GSLs. In conclusion, we propose the use of endophytic root fungi is an effective means to increase kimchi cabbage growth by improving the absorption of amino acids, making it an appropriate strategy for increasing specific glucosinolates.