Effects of inoculated mycorrhizal fungi and non-mycorrhizal beneficial micro-organisms on plant traits, nutrient uptake and root-associated fungal community composition of the Cymbidium hybridum in greenhouse.

AIMS: The aim of this study was to assess the effects of beneficial micro-organisms on the growth, nutrient accumulation and root-associated fungal species composition of pot orchids grown in the greenhouse. METHODS AND RESULTS: A greenhouse pot experiment was conducted to investigate the beneficial effects of a mycorrhizal fungus, Epulorhiza repens isolate ML01, an endophytic fungus, Umbelopsis nana isolate ZH3A-3 and a mixed commercial inoculum Rem, alone or in combination. Nested PCR assays showed that both isolates ML01 and ZH3A-3 can successfully establish in inoculated soil. All the inoculants significantly increased the plant total dry weight of Cymbidium hybridum 'Golden Boy', whereas only co-inoculation with the endophytic fungus ZH3A-3 and the Rem enhanced the fresh weight and height of host plants. The mycorrhizal fungus positively affected P, K, Ca, Mg content in shoots and Zn content in roots, while the endophytic fungus improved N, P, Ca accumulation in shoots and roots. Co-inoculation with the Rem and ML01 improved root to shoot translocation of Fe and Zn. In addition, inoculation with ZH3A-3, ML01+Rem and ZH3A-3+Rem decreased the relative frequency of Fusarium sp. on orchid roots. Trichoderma sp. were isolated from the roots treated with ML01, ML01+Rem and ZH3A-3+Rem. CONCLUSIONS: Both mycorrhizal and endophytic fungi had the potential to create favourable microflora in the orchid roots and stimulate the growth of transplanted plantlets under greenhouse condition. SIGNIFICANCE AND IMPACT OF THE STUDY: The newly isolated endophytic strain ZH3A-3 showed significant application value in orchid production.

Identification of warm day and cool night conditions induced flowering-related genes in a Phalaenopsis orchid hybrid by suppression subtractive hybridization.

The influence of warm day and cool night conditions on induction of spikes in Phalaenopsis orchids has been studied with respect to photosynthetic efficiency, metabolic cycles and physiology. However, molecular events involved in spike emergence induced by warm day and cool night conditions are not clearly understood. We examined gene expression induced by warm day and cool night conditions in the Phalaenopsis hybrid Fortune Saltzman through suppression subtractive hybridization, which allowed identification of flowering-related genes in warm day and cool night conditions in spikes and leaves at vegetative phase grown under warm daily temperatures. In total, 450 presumably regulated expressed sequence tags (ESTs) were identified and classified into functional categories, including metabolism, development, transcription factor, signal transduction, transportation, cell defense, and stress. Furthermore, database comparisons revealed a notable number of Phalaenopsis hybrid Fortune Saltzman ESTs that matched genes with unknown function. The expression profiles of 24 genes (from different functional categories) have been confirmed by quantitative real-time PCR in induced spikes and juvenile apical leaves. The results of the real-time PCR showed that, compared to the vegetative apical leaves, the transcripts of genes encoding flowering locus T, AP1, AP2, KNOX1, knotted1-like homeobox protein, R2R3-like MYB, adenosine kinase 2, S-adenosylmethionine synthetase, dihydroflavonol 4-reductase, and naringenin 3-dioxygenase accumulated significantly higher levels, and genes encoding FCA, retrotransposon protein Ty3 and C3HC4-type RING finger protein accumulated remarkably lower levels in spikes of early developmental stages. These results suggested that the genes of two expression changing trends may play positive and negative roles in the early floral transition of Phalaenopsis orchids. In conclusion, spikes induced by warm day and cool night conditions were complex in Phalaenopsis orchids; nevertheless, several molecular flowering pathway-related genes were found. The acquired data form the basis for a molecular understanding of spike induction by warm day and cool night conditions in Phalaenopsis orchids.

Molecular cloning and characterization of two novel NAC genes from Mikania micrantha (Asteraceae).

NAC proteins, which are plant-specific transcription factors, have been identified to play important roles in plant response to stresses and in plant development. The full-length cDNAs that encode 2 putative NAC proteins, designated as MmATAF1 and MmNAP, respectively, were cloned from Mikania micrantha by rapid amplification of cDNA ends. The full-length cDNAs of MmATAF1 and MmNAP were 1329 and 1072 bp, respectively, and they encoded deduced proteins of 260- and 278-amino acid residues, respectively. The proteins MmATAF1 and MmNAP had a calculated molecular mass of 29.81 and 32.55 kDa and a theoretical isoelectric point of 7.08 and 9.00, respectively. Nucleotide sequence data indicated that both MmATAF1 and MmNAP contained 2 introns and 3 exons and that they shared a conserved genomic organization. Multiple sequence alignments showed that MmATAF1 showed high sequence identity with ATAF1 of Arabidopsis thaliana (61%) and that MmNAP showed high sequence identity with NAP of A. thaliana (67%) and CitNAC of Citrus sinensis Osbeck (62%). Phylogenetic analysis showed that the predicted MmATAF1 and MmNAP proteins were classified into the ATAF and NAP subgroups, respectively. Transient expression analysis of onion epidermal cells indicated nuclear localization of both MmATAF1-GFP and MmNAP-GFP fusion proteins. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis indicated that MmATAF1 was expressed in all the tissues tested, but in varying abundance, while MmNAP was specifically expressed in stems, petioles, shoots, and leaves, but not in roots. The transcript levels of MmATAF1 and MmNAP in shoots and in infected stems were induced and strengthened by wounding, exogenous ZnSO(4), abscisic acid, salicylic acid, and Cuscuta campestris infection on the basis of semi-quantitative RT-PCR and real-time PCR analyses, respectively. Collectively, these results indicated that MmATAF1 and MmNAP, besides having roles in M. micrantha adaptation to C. campestris infection and abiotic stresses, also integrated signals derived from both C. campestris infection and abiotic stresses.