Morphological,SSR and ploidy analysis of water yam (<Emphasis Type="Italic">Dioscorea alata</Emphasis> L.) accessions for utilization of aerial tubers as planting materials

The high cost and supply shortage of seed yam propagules for planting are major constraints in yam production. In the water yam (Dioscorea alata L.), aerial tubers have potential as alternative sources of planting material. In this study, we investigated morphological, molecular and ploidy variation across multiple aerial tuber producing accessions of Dioscorea alata. Initial screening of over 800 accessions from the International Institute of Tropical Agriculture germplasm collection for aerial tuber production identified a subset (15 %) of accessions, which produced aerial tubers. The aerial tuber producing accessions (along with 18 non-aerial tuber accessions) were further characterized for phenotypic and ploidy variation. In addition, using SSR markers we characterized the genetic diversity amongst all of the aerial tuber producing accessions, along with six non-aerial tuber producing accessions. Multiple Correspondence Analysis (MCA) using morphological data grouped the accessions according to their aerial tuber production. The aerial tuber production characteristics of accessions were associated with phenotypic variables and ploidy levels. The MCA analysis revealed three main groups consisting of; Group 1) all non aerial tuber producing accessions (n = 15), hastate leaf shape, less or no anthocyanin pigmentation and diploid (2n = 2x = 40), Group 2) group with some aerial tuber producing accessions, different extent of anthocyanin pigmentation, sagittate leaf shape, mainly diploid (n = 44) and three triploid (2n = 3x = 60) and 3) a group where all individuals bear aerial tuber, cordate leaf shape, intermediate anthocyanin pigmentation and majority (n = 74) tetraploid (2n = 4x = 80) and three triploid individuals. Aerial tuber production may be subject to a genome dosage effect as an increase in aerial tuber production was associated with increased ploidy level. For instance, tetraploid plants produce more aerial tubers per sprout than either triploids or diploids. Principal coordinate analysis based on SSR markers using Jaccard’s coefficient also revealed distinct groups associated with the pattern of aerial tuber formation, leaf shape and anthocyanin pigmentation. Overall our study indicates the usefulness of combining SSR markers, ploidy level and phenotypic data for identification and classification of Dioscorea alata accessions according to their extent of aerial tuber production.     

Investigation of some characteristics of polyhydroxy milkweed triglycerides and their acylated derivatives in relation to lubricity

Most industrial lubricants are derived from nonrenewable petroleum-based sources. As useful as these lubricants are, their unintended consequences are the pollution of the Earth's environment as a result of the slow degradation of the spent materials. Native seed oils, on the other hand, are renewable and are also biodegradable in the environment, but these oils often suffer a drawback in having lower thermal stability and a shorter shelf life because of the intrinsic -C═C- unsaturation in their structures. This drawback can be overcome, yet the inherent biodegradative property retained, by appropriate derivatization of the oil. Pursuant to this, this study investigated derivatized polyhydroxy milkweed oil to assess its suitability as lubricant. The milkweed plant is a member of the Asclepiadaceae, a family with many genera including the common milkweeds, Asclepias syriaca L., Asclepias speciosa L., Asclepias tuberosa L., etc. The seeds of these species contain mainly C-18 triglycerides that are highly unsaturated, 92%. The olefinic character of this oil has been chemically modified by generating polyhydroxy triglycerides (HMWO) that show high viscosity and excellent moisturizing characteristics. In this work, HMWO have been chemically modified by esterifying their hydroxyl groups with acyl groups of various chain lengths (C2-C5). The results of investigation into the effect of the acyl derivatives' chemical structure on kinematic and dynamic viscosity, oxidation stability, cold-flow (pour point, cloud point) properties, coefficient of friction, wear, and elastohydrodynamic film thickness are discussed.     

CHANGES IN RESPONSE INDICES AS A FUNCTION OF TIME IN WINTER WHEAT

Nitrogen (N) responsiveness of crops can change with time as it is strongly influenced by in-season environmental conditions. This study was conducted to determine the relationship of N responsiveness using a response index (RI) as a function of time at five locations (Efaw, Stillwater, Lake Carl Blackwell, Perkins and Lahoma, Oklahoma) over a three-year period. Subplots of 4 m² were established at each experimental site that employed a randomized complete block design. Normalized Difference Vegetation Index (NDVI) readings were taken using a Greenseeker (NTech Industries, Inc., Ukiah, CA, USA) handheld sensor at various growth stages. The N responsiveness (RI_NDVI) was determined as the ratio of NDVI readings from a non-N limiting strip and the farmer practice. Then, RI was plotted against days where growing degree days (GDD = (T_min + T_max)/2—4.4°C) were > zero (DGDD > 0). At all sites, RI_NDVI increased with advancing stage of growth. Excluding Perkins 2005 and Stillwater 2006, the relationship between RI_NDVI and DGDD > 0 was positive and highly correlated. When the number of days from planting to sensing where DGDD > 0 was less than 60, it is unlikely that a reliable estimate of RI_NDVI could be obtained since values were all small (close to 1.0), consistent with limited growth at the early stages of growth. Averaged over years and sites for all growth stages, the correlation of RI_NDVI and RI_Harvest was positive and increased up to the Feekes 9 growth stage. Our results further suggested that once RI_NDVI is collected, it should be adjusted using the Equation RI_NDVIadj = RI_NDVI × [1.87/(DGDD > 0 ? 0.00997) + 0.5876].     

Fermentation of seeds of Teff (Eragrostis teff), grass-pea (Lathyrus sativus), and their mixtures: aspects of nutrition and food safety

Fermentation of pure teff (Eragrostis teff), pure grass-pea (Lathyrus sativus), and their mixtures, 9:1 and 8:2 (teff/grass-pea) has been done at two temperatures (room temperature and 35 degrees C) in duplicate using the strains of Lactobacillus plantarum, for bacterial fermentation, and Aspergillus oryzae and Rhizopus oligosporus in succession for solid-state fungal fermentation as inocula. In addition, the natural or spontaneous and back-slopping methods of bacterial fermentation have been done on the above four substrate groups. The pH and essential amino acid profiles of the different fermentation processes were compared. The back-slopping in teff at a temperature of 35 degrees C gave the sharpest pH drop. All fermentations done at 35 degrees C showed a steeper slope in their pH versus time plot compared to their room temperature counterpart. Fungal fermentation gave an improved amino acid profile for the essential ones in all of the substrate groups, except in pure grass-pea. Fermented teff/grass-pea (8:2) in this fungal fermentation has been found to be quite comparable in essential amino acid profile to an ideal reference protein recommended for children of 2-5 years of age. None of the bacterial fermentations produced a net change in their essential amino acid profile in any of the substrate groups investigated. Solid state fungal fermentation on pure grass-pea using the fungal strains R. oligosporous and A. oryzae in succession has shown that the neurotoxin beta-N-oxalyl-alpha,beta-diaminopropionic acid (beta-ODAP) in grass-pea has been removed by 80% on average for the high-toxin variety and by up to 97% for the low-toxin variety as determined by an improved chromatographic method with bioelectrochemical detection coupled on-line with refractive index detection.     

Comparative analysis of the field performances of a reversible animal-drawn prototype and conventional mouldboard ploughs pulled by a single donkey

The performance of two conventional animal-drawn mouldboard ploughs and a reversible prototype mouldboard plough were studied under field conditions in Kenya on previously ploughed and harrowed clay nitisol. The two mouldboard ploughs were a Victory plough, manufactured in the United Kingdom, and a cylindrical mouldboard plough manufactured by the Rumptstad factory of The Netherlands. The reversible prototype wooden mouldboard plough was developed at the Department of Agricultural Engineering of the Swedish University of Agricultural Sciences as a mouldboard type, modernized version of the ard type plough.

Simultaneous and dynamic measurement of forces, moments, ground speed and tillage depth were made. The results of the comparison between the three ploughs showed that both the horizontal and vertical components of forces resulting from the reversible plough were about 50 and 65% of the forces resulting from the Rumptstad and the Victory ploughs, respectively.

In the case of the reversible plough, the effect of a tail angle on horizontal and vertical forces was investigated. The results of field tests confirmed the laboratory results in that the form of graphs and equations describing the relationship between the forces and tail angle were similar to those obtained during the laboratory tests.

A single donkey was used to draw the implements throughout the experiment. It pulled about 25% of its body weight at an average speed of 0.8 m s⁻¹ and worked for 9 h per day.     

Determination of organic materials quality based on nutrient recovery,mineral fertilizer equivalency and maize (Zea mays L.) allometry

Crop production in Sub-Saharan Africa is primarily limited by soil fertility decline. In view of this, the fertilizer value of locally available organic materials (OMs) was assessed for their nutrient release to crop growth. Crop residues and farmyard manure (FYM) were evaluated along with mineral fertilizers to grow a test crop maize variety – Gibe 2. The maize allometric parameters, nutrient ratios (NRs), nutrient recovery (NRy) and mineral fertilizer equivalency (MFE) were used to assess the mineral fertilizer value (MFV) of OMs. MFE of OMs was estimated as the available mineral N and P out of the fraction of total nitrogen and phosphorus applied relative to mineral fertilizers supply. The results revealed that maize allometry, NRy and MFE were significantly influenced by fertilizer sources. OM amendment resulted in poor maize allometry and low NRy. Interestingly, MFE of OM amended ranged from ?201% with chickpea (CHP) residue to 63% with FYM. The results demonstrate that CHP has the poorest quality, while FYM is a good-quality OM as a fertilizer source.     

Relationship Between Coefficient of Variation Measured by Spectral Reflectance and Plant Density at Early Growth Stages in Winter Wheat

ABSTRACT

The use of by-plot coefficient of variation (CV) has not been evaluated in precision agricultural work. This study evaluated the relationship between CVs determined from normalized-difference vegetative index (NDVI) sensor readings, plant population, and sensing direction on NDVI values. Randomly selected plots, measuring 1 m² (2003) and 3 m² (2004), were established for this study. Plots in 2004 were divided into three 1 m² subplots with, 0 and 120 kg ha^?1 fall-applied N, and 80 kg ha^?1 topdress nitrogen (N). Sensor reading of subplots were taken at Feekes 5 and 7 using the Green Seeker hand-held sensor. Results showed that the relationship between vegetative RI (RI_NDVI) and harvest RI (RI_Harvest) improved with increasing CV values. The prediction of RI_Harvest was improved when CV was integrated into the RI_NDVI calculation. RI_Harvest can be better predicted with RI_NDVI when the CV of spectral radiance measurements is used in the RI_NDVI equation.     

Constraints and challenges of meeting the water requirements of livestock in Ethiopia: cases of Lume and Siraro districts

Compared to the total water use in livestock production systems, water for livestock drinking is small in amount but is an important requirement for health and productivity of animals. This study was carried out to assess constraints and challenges of meeting drinking water requirements of livestock in rural mixed smallholder crop–livestock farming districts in the Ethiopian Rift Valley area. Data was collected by individual interviews with randomly selected respondents and farmer group discussions. Farmers ranked feed and water scarcity as the two most important constraints for livestock husbandry, although the ranking order differed between districts and villages. Poor quality water was a concern for the communities in proximity to urban settlements or industrial establishments. Water provision for livestock was challenging during the dry season, since alternative water sources dried up or were polluted. Though rainwater harvesting by dugout constructions was practiced to cope with water scarcity, farmers indicated that mismanagement of the harvested water was posing health risks on both livestock and people. A sustainable water provision for livestock in the area, thus, depends on use of different water sources (intermittent or perennial) that should be properly managed. Industrial establishments should adopt an environment-friendly production to minimize pollution of water resources used for livestock consumption. Technical support to farmers is required in proper design and use of existing rainwater harvesting systems. Further investigations are recommended on effect of poor quality water (perceived by farmers) on performance of livestock.