Changes in Secondary Metabolites and Free Amino Acid Content in Tomato with <i>Lamiaceae</i>Herbs Companion Planting

The present experiment was conducted to evaluate the influence of Lamiaceae herbs companion planting on growth and secondary metabolites changes in tomato plants. Furthermore, the free amino acid changes in tomato due to companion planting were also evaluated using tomato-basil companionship as a model. Four-week-old seedlings of tomato were grown in a pot containing autoclaved commercial soil with basil, peppermint and hyssop as a companion plant separately in different density. Four weeks after companion planting, tomato plants under 1:1 companionship with the herbs showed significant increase in dry weights of shoots compared to control. Higher density of the herbs on the other hand expressed a growth suppression on tomato possibly due to nutrient competition. By the LC-MS analysis, shikimic acid and apigenin were identified as the major secondary compounds found in tomato plants and 1:1 companionship with basil seemed to have a positive influence on their content in tomato shoots. On the other hand, in case of peppermint and hyssop, the increase was observed in all parts of tomato plants. In addition, promotion in several free amino acid contents was also observed in tomato plants with basil companion planting compared to control. Thus, tomato plants grown with herb companion planting in 1:1 ratio seems to have a positive impact on growth of tomato. This positive influence might be related to the increase in some secondary metabolites and changes in the free amino acids observed in this study.

Interaction between Allelochemicals and <i>Fusarium</i>Root Rot in Asparagus Seedlings Cultured <i>In Vitro</i>

The interaction between Fusarium root rot and 4 allelochemicals in asparagus seedlings was estimated in vitro to clarify the relationship between biotic and abiotic factors in asparagus decline. In in vitro culture of Fusarium oxysporum f. sp. asparagi (Foa) with or without addition of 4 allelochemicals (caffeic acid, ferulic acid, quercetin, malic acid;0.01%, 0.1%, w/v) using Czapec-Dox media, Foa propagation was suppressed in all the treatments. The degree of suppression became higher in 0.1% than 0.01% among all the allelochemicals. As for the axenic culture of asparagus (Asparagus officinalis L., “Welcome”) seedlings with the 4 allelochemicals, dry weight of both shoots and roots became lower compared to control in 0.1% and 0.01% of caffeic acid, 0.1% ferulic acid, 0.01% quercetin, only dry weight of shoots decreased in 0.1% malic acid. Two weeks after Foa inoculation with Foa-cultured PDA cubes in vitro, incidence of Fusarium root rot reached 100% in most of the plots. The severity of root rot increased in 0.01% and 0.1% caffeic acid, 0.1% ferulic acid, 0.1% malic acid compared to control. From these results, the 4 allelochemicals used in this study are supposed to suppress asparagus growth, and such growth reduction might enhance the disease severity of Fusarium root rot as an indirect effect. In addition, such effect might differ with the allelochemicals and concentrations in asparagus.

Suppression of Fusarium Crown Rot and Increase in Several Free Amino Acids in Mycorrhizal Asparagus

Disease suppression of Fusarium crown rot and the changes in free amino acid contents in mycorrhizal asparagus (Asparagus officinalis L., cv. “Welcome”) plants were investigated. Sixteen weeks after arbuscular mycorrhizal fungus (AMF;Glomus intraradices) inoculation, mycorrhizal plants showed higher dry weight of shoots than non-mycorrhizal plants, and AMF colonization level in a root system reached up to 73.3%. Ten weeks after Fusarium proliferatum (Fp;N1-31, SUF1207) inoculation, control plants showed 100% incidence and high severity in the 2 Fp isolates. However, AMF plants showed lower severity than non-AMF plants in the 2 Fp isolates. Ten weeks after Fp (N1-31) inoculation, the increase in 7 constituents of amino acids (glutamine, arginine, aspartic acid, alanine, citrulline, GABA, glycine) in shoots, and 9 in roots (asparagine, arginine, threonine, serine, glutamine, citrulline, valine, GABA, histidine) occurred in AMF plants. From these findings, plant growth promotion and suppression of Fusarium crown rot occurred in mycorrhizal asparagus plants, and the disease tolerance was supposed to be associated with the symbiosis-specific increase in free amino acids.