Field conservation of vegetative propagated crops poses a major problem to curators of germplasm, especially in developing countries. An alternative method to ensure security of germplasm is the use of tissue culture techniques in media formulated for slow growth. However, tissues of plant species may require different nutrients for optimum growth. The objectives of this study were to a) assess the effects of sucrose on the performance of different cassava genotypes and b) recommend sucrose levels for in-vitro conservation of the genotypes. Four sucrose levels (0, 10, 20, and 30 g l -1 ) and apical meristems of five cassava genotypes (Bankye Hemaah, Bankye Botan, Tek Bankye, Doku Duade, and Essam Bankye) cultured in-vitro was studied at the Kwame Nkrumah University of Science and Technology’s plant biotechnology laboratory. Growth media were prepared using hormone-free Murashige and Skoog (MS) basal media formulation. Inoculated cultures were exposed to 16 hours of light and 8 hours of darkness with light illuminance of 3500 lux and also maintained at 24±2°C temperature and relative humidity of 70%. All genotypes Original Research Article Sintim and Akromah; IJPSS, 7(1): 45-54, 2015; Article no.IJPSS.2015.130 46 showed a direct regeneration without callus formation. Generally, sucrose enhanced the growth performance of plantlets; however, the genotypes responded differently to sucrose in leaf formation, plant height, and rooting ability with time. For long term conservation, growth medium must sustain the health of plantlets with infrequent need for sub-culturing. As such, sucrose levels of 10 g l for Essam Bankye, 20 g l for Doku Duade and Tek Bankye, and 30 g l for Bankye Hemaa and Bankye Botan were the recommended rates for in-vitro conservation.
Plastic mulch films are used globally in crop production but incur considerable disposal and environmental pollution issues. Biodegradable plastic mulch films (BDMs), an alternative to polyethylene (PE)-based films, are designed to be tilled into the soil where they are expected to be mineralized to carbon dioxide, water and microbial biomass. However, insufficient research regarding the impacts of repeated soil incorporation of BDMs on soil microbial communities has partly contributed to limited adoption of BDMs. In this study, we evaluated the effects of BDM incorporation on soil microbial community structure and function over two years in two geographical locations: Knoxville, TN, and in Mount Vernon, WA, USA. Treatments included four plastic BDMs (three commercially available and one experimental film), a biodegradable cellulose paper mulch, a non-biodegradable PE mulch and a no mulch plot. Bacterial community structure determined using 16S rRNA gene amplicon sequencing revealed significant differences by location and season. Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA where differences were observed between BDMs and no-mulch plots. Extracellular enzyme assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDMs and PE treatments. Overall, BDMs had comparable influences on soil microbial communities to PE mulch films.
Kinetin is an important growth hormone used for in vitro propagation, but its dynamic and temporal effects on Dioscorea alata have not been thoroughly evaluated.In this study, surface response models were developed to better elucidate the effects of kinetin on D. alata propagated in vitro.Nodal segments were obtained from Akaaba, an important D. alata cultivar in Ghana, and propagated in vitro under five kinetin rates (0, 2.5, 5, 7.5 and 10 µM).The models were developed using segmented multiple regression with time and kinetin as the predictors.The effects on plant height, the number of leaves, shoots and roots were assessed with three-dimensional figures for better observation of temporal trends.The model fit was very good with normalized root mean squared error (NRMSE) = 0.1, R-squared = 0.83 and adjusted R-squared = 0.82, averaged across the different growth parameters.Different kinetin levels elicited the maximum shoot, leaf and root formation, as well as the growth rates over time.Moderate kinetin levels (2-4 µM) provided better growth at early culturing period.Higher kinetin levels (5-10 µM) suppressed the growth of the plantlets at early stages, but the plantlets recovered from the stress and resumed normal growth thereafter.After 4-5 weeks, the growth rates of the moderate kinetin levels (2-4 µM) declined much faster and were lower compared to the higher kinetin levels, except plant height and the number of roots which were still higher at the moderate kinetin level even after eight weeks of culturing.Thus, kinetin requirements vary depending on the growth parameters of interest.
Leguminous crops such as sainfoin ( Onobrychis viciifolia Scop.) have low N 2 fixation; hence, supplementary N is usually provided to realize maximum yield. Nonetheless, N application should be justified by economic benefit to the cropping system. This study evaluated the productivity, nutritive value, and cost implications of N application in sainfoin under rainfed conditions at high elevations in Wyoming. The study was a 2‐factorial experiment set in a randomized complete block design with four replications, where four cultivars (Delaney, Remont, Rocky Mountain, and Shoshone) and four N rates (0, 40, 80, and 120 kg ha −1 ) were the treatments. Sainfoin was established in 2012, and N was broadcast‐applied in May 2013 and 2014 using urea as the N source. The profitability of the N application was assessed using a benefit–cost ratio analysis. Sainfoin yield and nutritive value was affected by cultivar and N application. Remont (1.08 Mg ha −1 ), Rocky Mountain (1.17 Mg ha −1 ), and Shoshone (1.16 Mg ha −1 ) produced higher forage dry matter (DM) than Delaney (0.84 Mg ha −1 ). The effect of N application on the forage DM was linear, but applying >80 kg N ha −1 did not result in significant increase in the forage DM. The benefit–cost ratios for the three N rates were less than one in both years, which indicated a net loss in revenue. In general, sainfoin DM and crude protein (CP) increased with N; however, the increase in forage DM with N application was not economical due to higher production costs.
Abstract Polyethylene (PE) plastic mulch films are used globally in crop production but incur considerable disposal and environmental pollution issues. Biodegradable plastic mulch films (BDMs), an alternative to PE-based films, are designed to be tilled into the soil where they are expected to be mineralized to carbon dioxide, water and microbial biomass. However inadequate research regarding the impacts of repeated incorporation of BDMs on soil microbial communities has partly contributed to limited adoption of BDMs. In this study, we evaluated the effects of BDM incorporation on soil microbial community structure and function over two years in two geographical locations: Knoxville, TN, and in Mount Vernon, WA. Treatments included four plastic BDMs, a completely biodegradable cellulose mulch, a non-biodegradable PE mulch and a no mulch plot. Bacterial community structure determined using 16S rRNA amplicon sequencing revealed significant differences by location and season. Differences in bacterial communities by mulch treatment were not significant for any season in either location, except for Fall 2015 in WA where differences were observed between BDMs and no-mulch plots. Extracellular enzyme rate assays were used to characterize communities functionally, revealing significant differences by location and sampling season in both TN and WA but minimal differences between BDMs and PE treatments. Limited effects of BDM incorporation on soil bacterial community structure and soil enzyme activities when compared to PE suggest that BDMs have comparable influences on soil microbial communities, and therefore could be considered an alternative to PE. Importance Plastic film mulches increase crop yields and improve fruit quality. Most plastic mulches are made of polyethylene (PE), which is poorly degradable, resulting in undesirable end-of-life outcomes. Biodegradable mulches (BDMs) may be a sustainable alternative to PE. BDMs are made of polymers which can be degraded by soil microbial enzymes, and are meant to be tilled into soil after use. However, uncertainty about impacts of tilled-in BDMs on soil health has restricted adoption of BDMs. Our previous research showed BDMs did not have a major effect on a wide range of soil quality indicators (Sintim et al. 2019); here we focus on soil microbial communities, showing that BDMs do not have detectable effects on soil microbial communities and their functions, at least over the short term. This informs growers and regulators about use of BDMs in crop production, paving a way for an agricultural practice that reduces environmental plastic pollution.
