Explore the vast range of titles available.

The production of regenerable embryogenic callus is essential to sugarcane genetic improvement. However, some sugarcane cultivars display poor calli yields using established in vitro protocols. In this study, we tested the impact of methylglyoxal (MG) on embryogenic callus and plantlet development in cultivars NCo376 and N41. Calli were exposed to 0–10 mM MG at embryo maturation and germination stages. For both cultivars, the 2 and 4 mM MG treatments increased callus dry mass by up to 48%, but 70–80% decreases were observed when calli were exposed to 7 and 10 mM. The 2 and 4 mM MG treatments also produced more compact white embryogenic callus than the control. Incorporation of MG at the same levels during embryo germination promoted faster shoot morphogenesis in both cultivars and increase plantlet yield in NCo376 by 130% when treated with 4 mM MG. In both cultivars, MG levels higher than 7 mM had a negative or no effect plantlet production. Metabolic profiling revealed higher levels of sugars in MG-treated than in control calli, which may have contributed to development of more white compact calli. Separate clustering of NCo376 and N41 MG-treated calli in principal component and hierarchical clustering analyses of the metabolic profiles, suggested variations in MG metabolism among the genotypes that may account for variations in the MG-induced effect on somatic embryogenesis between the two cultivars. Although the effect may be genotype-dependant, low MG concentrations can induce improved embryogenic callus and plantlet development in sugarcane.

The nitrogen use efficiency (NUE) and parameters contributing to it, of four sugarcane varieties (NCo376, N36, N12 and N19) were determined in vitro at 4 and 20 mM nitrogen (N), supplied as NO3−-N or NH4+-N. Significant differences amongst varieties were apparent at the lower N supply (4 mM) in the sub-components of NUE (N uptake efficiency and N utilisation efficiency) and overall NUE. All tested varieties had a higher NUE on medium with NO3−-N than NH4+-N. A concentration of 20 mM N was deemed too high to resolve differences amongst genotypes. Evidence for different mechanisms of NUE amongst varieties was provided under 4 mM NO3−-N supply where NCo376 and N12 displayed the highest NUE but this was attributed to superior NUpE in the former and NUtE in the latter. The NUE response of NCo376, N12 and N19 were similar in vitro, while N36 behaved differently. To our knowledge, this is the first report on the contribution of NUpE and NUtE to NUE in sugarcane in vitro. In terms of biomass production, in all cases but one, in vitro plants accumulated more biomass on medium with NO3−-N than NH4+-N. Furthermore, there was an indication that the distribution of NO3−-N between shoots and roots might affect NUE since varieties with a high in vitro NUE stored less NO3−-N in roots (compared with shoots) or exhibited better translocation of NO3−-N from roots to shoots than those with low NUE. In addition, evidence of luxury N uptake even at 4 mM N was obtained.

Key message Mutagenesis had no effect on number of stalks/plot, stalk height, fibre and sucrose content of mutants. Imazapyr tolerance is likely due to a S622N mutation in the acetolactate synthase gene. The herbicidal compound imazapyr is effective against weeds such as Cynodon and Rottboellia species that constrain sugarcane production. This study aimed to compare agronomic characteristics of three imazapyr tolerant mutants (Mut 1, Mut 6 and Mut 7) with the non-mutated N12 control after 18 months of growth, and to sequence the acetolactate synthase ( ALS ) gene to identify any point mutations conferring imazapyr tolerance. There were no significant differences in the number of stalks/plot, stalk height, fibre and sucrose contents of the mutants compared with the N12 control. However, Mut 1 genotype was more susceptible to the Lepidopteran stalk borer, Eldana saccharina when compared with the non-mutated N12 (11.14 ± 1.37 and 3.89 ± 0.52% internodes bored, respectively), making Mut 1 less desirable for commercial cultivation. Molecular characterisation of the ALS gene revealed non-synonymous mutations in Mut 6. An A to G change at nucleotide position 1857 resulted in a N513D mutation, while a G to A change at nucleotide position 2184 imposed a S622N mutation. Molecular dynamics simulations revealed that the S622N mutation renders an asparagine side chain clash with imazapyr, hence this mutation is effective in conferring imazapyr tolerance.

An in vitro system was established for the characterisation of inorganic nitrogen uptake by sugarcane plantlets of variety NCo376. After multiplication and rooting, plantlets (0.27–0.3 g fresh mass) were placed on N-free medium for 4 days, and then supplied with 2–20 mM N as NO3−-N only, NH4+-N only or NO3−-N + NH4+-N (as 1:1). With few exceptions, on all the tested N media, the in vitro plants always had a higher Vmax for NH4+-N (28.69–66.51 μmol g−1 h−1) than for NO3−-N uptake (10.24–30.19 μmol g−1 h−1) and the Km indicated a higher affinity for NO3−-N (0.02–7.38 mM) than for NH4+-N (0.06–9.15 mM). When N was applied as 4 and 20 mM to varieties N12, N19 and N36, the interaction between variety, N form and concentration resulted in differences in the Vmax and Km. The high N-use efficient varieties (N12 and N19), as determined in previous pot and field trials, behaved similarly under all tested conditions and displayed a lower Vmax and Km than the low N-use efficient ones (NCo376 and N36). Based on this finding, it was suggested that the N-use efficient designation (from pot and field trials) may not be ascribed solely to N uptake. Assessment of the relative preference index (RPI) for NO3−-N and NH4+-N uptake revealed that, at present, the RPI has no application in sugarcane due to its preferential uptake of NH4+-N.

KEY MESSAGE : A combination of in vitro culture and mutagenesis using ethyl methanesulfonate (EMS) followed by culture filtrate-mediated selection produced variant sugarcane plants tolerant and resistant to Fusarium sacchari. Eldana saccharina is a destructive pest of the sugarcane crop in South Africa. Fusarium sacchari PNG40 (a fungal strain harmful to E. saccharina) has the potential to be an endophytic biological control agent of the stalk borer. However, the fungus causes Fusarium stalk rot in sugarcane. In the current study, sugarcane plants tolerant and resistant to F. sacchari PNG40 were produced by exposing embryogenic calli to the chemical mutagen ethyl methanesulfonate (EMS), followed by in vitro selection during somatic embryogenesis and plantlet regeneration on media containing F. sacchari culture filtrates (CF). The incorporation of 100 ppm CF in the culture media at the embryo maturation stage, at germination, or at both, resulted in callus necrosis and consequent reduced plantlet yield. Subsequent trimming of the roots of regenerated plants and their exposure to 1,500 ppm CF served as a further selection treatment. Plants produced from EMS-treated calli displayed improved root re-growth in the presence of CF pressure compared with those from non-treated calli. The tolerance of CF-selected plants was confirmed in greenhouse tests by inoculation with F. sacchari PNG40, re-isolation of Fusarium spp. from undamaged tissue of asymptomatic plants and establishment of the identity of fungal isolates as PNG40 using molecular analysis. The restriction of PNG40 presence to the inoculation lesion in some plants suggested their resistance to the fungus. Genotypes exhibiting symptomless endophytic colonization by PNG40 were identified and will be utilised for testing biological control strategies against E. saccharina.

The purpose of this article is to evaluate mHealth as a tool for research and development of nursing theories. Mobile health (mHealth) is one of the most promising new advances in health care technology. mHealth is defined as the use of mobile technology in the provision of health care delivery or health promotion (Qiang, Yamamichi, Hausman, & Altman, 2011). The need for innovative and effective interventions for the prevention and management of chronic illness is evident. The use of mHealth interventions in the treatment and monitoring of chronic illness is still young but shows great promise. Currently, the public health and psychological sciences are using their theories to guide interventional studies by operationalizing concepts through mHealth's multifaceted capabilities for patient interaction. Outcomes measures from chronic illness-mHealth studies are thematically evaluated by using theoretical nursing outcome-related concepts of Meleis's transitions theory and Mishel's uncertainty in illness theory. Despite a small sample of articles, there are strong themes of activation and engagement within this literature review. The application of nursing theory in mHealth offers a new method to operationalize theoretical concepts, test theory-based interventions, and gain new contextual insight into the health-illness patient experience.

A possible strategy to produce variant sugarcane plants with beneficial traits was tested by promoting somaclonal variation in vitro through the action of the hypomethylation and mutagenic agent 5-Azacytidine (Azac). Treatment of calli in liquid medium caused high levels of necrosis. Consequently, 6- to 8-week-old calli of cultivar NCo376 were exposed to 50 and 100 μM Azac in semi-solid callus induction medium (CIM) (MS salts and vitamins, sucrose, casein hydrolysate, agar, with or without 3 mg l⁻¹ 2,4-D) for 1 week. They were then transferred to fresh CIM with 2,4-D and to CIM without 2,4-D, for 2 and 8–10 weeks, respectively. The highest callus necrosis (>60 %) and reduced recovery (<40 %) were recorded for calli treated with 100 μM Azac without 2,4-D, which also resulted in lower plant yield (12 plantlets/0.2 g calli) than the control (18 plantlets/0.2 g calli). From methylation-sensitive amplified fragment length polymorphism analyses, the highest polymorphisms (4.2 %) were also obtained from plants derived from the 100 μM Azac treatment without 2,4-D. After 9 months of field growth, Azac-derived plants exhibited phenotypic differences compared with the controls. Ex vitro screening resulted in the identification of one plant from the 100 μM Azac with 2,4-D treatment putatively tolerant to smut, and three plants from the 100 μM Azac with 2,4-D and one from the 50 μM Azac with 2,4-D treatments, potentially tolerant to the herbicide imazapyr.

Recent results showed that after 16 months in the field, micropropagated eucalyptus plants have an inferior root system to cuttings. Such differences may be due to the plant growth regulators supplied during the culture stages of standard protocols, which are targeted at optimising plantlet yields and not root quality. This study investigated such a proposal, focusing on auxins in an easy-to-root clone. Initial results showed that the auxin provided in the standard protocol (NAA for multiplication and IBA for elongation) enabled 100% rooting in auxin-free medium, where rooting was faster than on IBA-rooting media. When auxin supply was omitted from multiplication and restricted to NAA or IAA during elongation, rooting in an auxin-free medium was reduced to 68 and 31%, respectively, reflecting the stabilities of these auxins in plant tissues. Additionally, 15% of shoots from the NAA-medium and 65% from the IAA-medium produced roots with altered graviperception. GC–MS analysis of these shoots revealed a relationship between free IAA-availability and altered graviperception. This was further tested by adding the IAA-specific transport inhibitor 2,3,5-triiodobenzoic acid to rooting media with IBA, IAA or NAA, which resulted in 100, 70.9 and 20.6% rooting, respectively. At least 40% of the sampled root tips had atypical starch grain deposition and abnormal graviperception. It is proposed that, at least in this clone, while IBA and NAA can be used for in vitro root induction, IAA is necessary for development of graviresponse.

Responses to Al 3+ of embryogenic callus cells of an Al-sensitive (Al-S) and Al-resistant (Al-R) Cynodon dactylon genotype were evaluated with regard to Al 3+ toxicity and resistance. A chemical equilibrium speciation model (MINTEQA2) was used to ensure the availability of the Al 3+ ion in culture media, which was supplied as 0.08–2.3 mM Al 3+ for 2–8 weeks. Increasing Al 3+ concentration and exposure time had a greater negative impact on the Al-S than on the Al-R genotype, in terms of callus growth rate and frequency of non-embryogenic cells. Exposure to 0.8 mM Al 3+ for 2 weeks resulted in an 88% reduction in the Al-S meristematic cell number, whereas that of the Al-R genotype remained unaffected. In addition, the Al-S cells accumulated three times more Al in the nucleus than did the Al-R cells, suggesting that Al interfered with mitosis. The Al-R cells appeared to exclude Al 3+ from its cells through an increase in extracellular pH (4.34 in Al-R and 4.08 in Al-S) and by the immobilisation of Al in the cell wall (33% more in Al-R). The results showed that by studying the cellular responses to Al 3+ it is possible to discriminate between the Al-S and Al-R C. dactylon genotypes.

Sugarcane breeding, while key to continued improvement of pest and disease resistance and to increasing sucrose and biomass yields, is constrained by the length of time taken to release a new cultivar (10— 14 yr). Forty years of international research into sugarcane in vitro culture has delivered many well-developed systems that are routinely applied to research and commercial activities, namely: (a) micropropagation of genotypes; (b) production of disease-free material from excised apical meristems; (c) international germplasm exchange; (d) generation of somaclones; (e) rapid disease and pest resistance screening; and (f) germplasm conservation. This review outlines several in vitro techniques, discussing how protocols have been tailored to address pertinent research issues and exploring possible commercial applications in the sugar industry to reduce the time frame to release a new cultivar and decrease demands on resources such as land and labour.