Novel potato plants with enhanced cadmium resistance and antioxidative defence generated after in vitro cell line selection

It is of interest to apply plant tissue culture to generate plants resistant to toxic effects of cadmium (Cd) on plant growth. Callus cultures were initiated from leaf explants of micropropagated potato plantlets (Solanum tuberosum L., cv. Iwa) for in vitro selection comprising 18 different Cd treatments varying in Cd exposure timing and duration. Plantlets regenerated from two different lines of Cd-selected calli, L9 and L11, were found to exhibit enhanced resistance to 218 μM Cd compared to control (source plantlets for leaf explants used to initiate callus cultures for Cd resistance). In response to 218 μM Cd, L11 plantlets had lower levels of lipid peroxidation and hydrogen peroxide than control and L9 plantlets. In addition, antioxidative enzyme activities in L11 were generally higher than control. L11 also had a higher level of proline than control

Diverse forms of xylem-like cells and strand formation in Xylogenic Eucalyptus bosistoana callus culture

In vitro xylem induction system is a basic tool in physiological, biochemical, and molecular studies of secondary cell wall formation, lignin biosynthesis and deposition associated with tracheary element formation. Eucalyptus bosistoana is a Class 1 durable hardwood tree species, selected by the New Zealand Dryland Forest Initiative for good quality wood and high adaptability to the NZ growing conditions. Xylogenic E. bosistoana callus culture was established and up to 40% of the callus cells were xylem-like cells (XLCs) which may have differentiated from small, cytoplasmically dense or compact dividing, and exhibited increased lignin contents during culture. The eucalyptus XLCs showed diverse sizes, patterns of secondary cell wall thickenings similar to the xylem cells in the young shoots and organized development including cell–cell connections of the XLCs to form xylem strands. This is the first report of the organized development of XLCs in E. bosistoana callus culture

Characterization of inflorescence-predominant chitinase gene in Metroxylon sagu via differential display

Chitinase is an enzyme that catalyzes the degradation of chitin, commonly induced upon the attack of pathogens and other stresses. A cDNA (MsChi1) was isolated from Metroxylon sagu and expressed predominantly in the inflorescence tissue of M. sagu, suggesting its role in developmental processes. The chitinase cDNA was detected and isolated via differential display and rapid amplification of cDNA ends (RACE). Primers specific to M. saguchitinase were used as probes to amplify the 3′-end and 5′-end regions of chitinase cDNA. Transcript analysis showed that chitinase is expressed in inflorescence and meristem tissues but was not detected in the leaf tissue. Sequence analysis of amplified cDNA fragments of 3′-end and 5′-end regions indicated that the chitinase cDNA was successfully amplified. The M. saguchitinase cDNA isolated was approximately 1,143 bp long and corresponds to 312 predicted amino acids. Alignments of nucleotide and amino acid have grouped this chitinase to family 19 class I chitinase

Response of Potato (Solanum tuberosum L., cv. Iwa) nodal explants to low inorganic nitrogen supply in vitro

The effect of low inorganic nitrogen (N) supply on potato plantlets developed from nodal explants cultured in vitro on modified Murashige and Skoog media supplemented with 3% sucrose was investigated. Lowering the inorganic nitrogen supply from 60 mM to 1.88 mM, while keeping the ratio of ammonium and nitrate at 0.52, did not result in a significant decrease in the fresh and dry weights of the plantlets, the number of new leaves formed and shoot length. Moreover, the plantlets cultured on the medium supplemented with 3.75 and 7.5 mM inorganic N exhibited greater biomass and shoot lengths than those on the medium with 60 mM inorganic N. Lowering the inorganic N supply in the media resulted in increased chlorosis with accompanying decreases in the chlorophyll and carotenoid contents of the leaves, but faster development of lateral roots and increased phenolic content in the roots

Protection of Italian ryegrass (Lolium multiforum L.) seedlings to salinity stress following seed priming with L-methionine and casein hydrolysate

Seed priming with water (hydropriming or HP) has been shown to be beneficial for seed germination and plant growth. However, there is little information on the effects of seed priming with amino acids and casein hydrolysate (CH) compared with HP, particularly in relation to early post-germinative seedling growth under salinity stress. In this study, Italian ryegrass seeds (Lolium multiflorum L.) were primed with 1 mM of each of the 20 protein amino acids and CH (200 mg l–¹) before they were germinated in 0, 60 and 90 mM NaCl in Petri dishes for 4 d in darkness. Germination percentage (GP), radicle length (RL) and peroxidase (POD) activity in the root of 4-d-old Italian ryegrass seedlings were investigated. Generally, when the seeds were germinated in 0, 60 and 90 mM NaCl, there was no significant difference in GP of seeds among various priming treatments, except that a higher GP was observed in seeds of HP treatment compared with the non-primed seeds when incubated in 60 mM NaCl. When incubated in 60 and 90 mM NaCl, seedlings from seeds primed with L-methionine or CH exhibited greater RL (greater protection against salinity stress) and higher root POD activity than those from non-primed and hydro-primed seeds. Under salinity stress, there were higher levels of malondialdehyde (MDA) in the root of 4-d-old Italian ryegrass seedlings, a marker of oxidative stress, but seed priming with CH was effective in reducing the salinity-triggered increase in MDA content. These results suggest that priming with L-methionine or CH would be better than HP for the protection of seedling root growth under salinity stress and might be associated with enhanced antioxidative defence against salinity-induced oxidative stress

Urease producing microorganisms under dairy pasture management in soils across New Zealand

Urea, the most commonly used nitrogen fertiliser in New Zealand, can be quickly lost from the system via ammonia volatilisation or nitrate leaching following hydrolysis of urea by urease producing soil microorganisms (UPSMs). This study investigated UPSMs involved in urea degradation for upcoming research to reduce soil urease activity. Soils from under dairy pasture management across New Zealand, with a pasture species component of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) and aged between 9 months to 60 years old, were collected, and UPSMs were isolated and identified using both polymerase chain reaction (PCR)-based molecular and conventional methods. The fungal genera belonged to diverse taxonomical groups including the phylum Ascomycota: class: Dothideomycetes, Eurotiomycetes, Leotiomycetes and Sordariomycetes, the phylum Basidiomycota: class: Tremellomycetes and the phylum Zygomycota: order: Mucorales, all of which have a role in urea degradation in soil. Pasture soil-resident urease producing bacteria belonged to the Gammaproteobacteria and Betaproteobacteria. Cupriavidus sp. and Mucor hiemalis showed strong urease activity when cultured on urease medium. This is the first report on the urease activity of the pasture soil inhabitants Pochonia bulbillosa, Mariannaea elegans and Gliomastix sp. This study was part of a larger study underway to investigate control of UPSMs in soil to improve the efficiency of urea utilisation