Co-entrapment of Trichoderma harzianum and Glomus sp. within alginate beads: impact on the arbuscular mycorrhizal fungi life cycle.

AIMS: This study was performed to explore the compatibility and applicability of plant beneficial micro-organisms (i.e. Trichoderma harzianum MUCL 29707 and Glomus sp. MUCL 41833) co-entrapped in alginate beads. METHODS AND RESULTS: Spores of Glomus sp. and conidia of T. harzianum were immobilized in alginate beads and the impacts of the saprotrophic fungi on the presymbiotic and symbiotic phase of the arbuscular mycorrhizal (AM) fungi evaluated under strict in vitro culture conditions. Our results demonstrated the capacity of both micro-organisms in combination to regrowth outside the calcium alginate coating. The presence of T. harzianum did not hinder the AM fungal development but rather stimulated its spore production and fitness. CONCLUSIONS: The combination of T. harzianum MUCL 29707 with Glomus sp. MUCL 41833 in alginate beads may represent a reliable alternative inoculum formulation for application in sustainable agriculture. SIGNIFICANCE AND IMPACT OF THE STUDY: The entrapment in the alginate beads of two fungi (i.e. a saprotroph and a symbiont) having beneficial effects on plants represents a promising formulation for the development of inoculants adapted to field application.

Spatial and temporal distribution of sucrose synthase in the radish hypocotyl in relation to thickening growth.

Sucrose synthase (SuSy) is a key enzyme in the development of storage root of radish. Clarification of its spatial and temporal expression during the thickening growth of radish hypocotyl, which later develops into storage root, was carried out immunologically using light microscopy. Sequential harvests at 3, 7, 11 and 13 d after sowing (DAS) were performed on two radish cultivars having different sink capacity. A very low level of SuSy was observed 3 DAS for both cultivars. White Cherrish (WC; strong storage root) showed the maximum level of SuSy between 7 and 11 DAS with increased cell development (thickening), while in Kosena (K; low storage root) the level remained high after 13 d of growth. A high level of SuSy was found in companion cells, which was consistent with previous observations, but SuSy was also found in the xylem parenchyma and in some cortical cells. The level of SuSy differed according to the localization and depended highly on cell development. Both cell division and cell enlargement were stimulated in WC compared with K. The role of SuSy during thickening growth of radish hypocotyl is discussed in terms of utilizing photosynthates.