2020 Volume 19 Issue 3 Pages 293-298
It was previously reported that the content of β-cryptoxanthin in juice sacs of Satsuma Mandarin was increased by mulching cultivation. In this study, to further clarify the mechanisms of mulching regulating β-cryptoxanthin accumulation, the effects of mulching on the expression of carotenoid metabolic genes were investigated in the juice sacs of Satsuma Mandarin ‘Aoshima unshiu’, which were planted in two different fields (Fields A and B) of Shimizu-ku, Shizuoka. In the mulching treatment, the β-cryptoxanthin content in the juice sacs and flavedo was 30 and 50% higher than that of the control, respectively. The changes in expression of carotenoid biosynthetic genes by mulching were different between the two fields. In fieldA, the expression of CitZDS was up-regulated, while the expression of CitHYb and CitZEP was down-regulated by mulching treatment in juice sacs. In fieldB, the expression of CitPSY, CitZDS, CitLCYb1, CitLCYb2, CitHYb, CitZEP, CitNCED2, and CitNCED3 in juice sacs was significantly up-regulated by mulching treatment. In particular, the transcript levels of the upstream carotenogenic genes were much higher on mulching treatment in fieldB. These results suggest that the transcription of carotenoid biosynthetic genes in Satsuma Mandarin is induced by mulching treatment. In addition, the high expression of upstream carotenogenic genes (high-level supply of β-carotene) was considered to be a key mechanism leading to the marked accumulation of β-cryptoxanthin in juice sacs treated by mulching.
