Evaluation of shade tolerance of one annual and five perennial Medicago species under different artificial shade levels

Abstract

ABSTRACT The objective of this study was to evaluate the shade tolerance of one annual and five perennial Medicago genotypes under different artificial shade levels and determine the shade tolerant candidates for an intercropping system. The results showed that shade significantly affected branch number and plant dry weight, but not plant height and leaf area. The mean branch number and dry weight plant−1 (g) across the tested genotypes were 42.5 and 2.2 under non-shade condition, decreased to 39.5 and 2.0 at 25% shade level, and were further reduced to 17.2 and 0.4 at 75% shade level, respectively. The mean chlorophyll content (mg g−1) and maximum quantum yield of Photosystem II (Fv/Fm) across the tested genotypes at 75% shade level (38.8; 0.6) were significantly lower than other shade levels (46.6–47.3; 0.69–0.70). Antioxidant enzyme activity and malondialdehyde production in Medicago leaves increased concomitantly with increased shade levels compared to non-shade control. The evaluation showed that annual M. polymorpha ‘Jinhuacai’ (range of mean: 0.97–5.97 g) significantly out-yielded those perennials (range of mean: 0.26–2.57 g) by a wide margin at all shade levels. This study would provide baseline information on shade tolerance of Medicago species for the selection of intercropped candidates in an intercropping system.