Volume 38, No. 1, 2017

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(pp. 7-18)
Quality of On-Farm Sorghum Seeds in Lower Eastern Kenya
Catherine W. Muui*, Reuben M. Muasya, Duncan T. Kirubi and Andrew O. Egesa
Crop low yields in lower eastern Kenya have been associated with inaccessibility to good  quality seeds. Use of low quality seed is one of the factors that could be significantly  affecting the low production of sorghum in this region. The aim of this study was to  evaluate the quality of sorghum seed used by farmers in lower eastern Kenya.

A total of 44 sorghum landraces collected from farmers were subjected to purity analysis, viability, vigor and seed borne pathogenicity tests. Only 4% of the samples collected had low seed purity of 72%, while the rest were of high purity. Around 57% of the seed samples had high germination of above 90%, while 37% had relatively high mean germination time. Pathogen identification tests indicated that 85% of seed samples were contaminated with either Fusarium spp., Penicillium spp., Rhizopus spp., Aspergillus niger or Aspergillus  flavus. More than one quarter of on-farm saved sorghum seeds used by farmers for planting were of low quality. This proportion of seed could result in poor yields and hence cause food shortages. Understanding the quality of on-farm saved seed based on pre- and post-harvest handling practices is important for improving the techniques farmers use to enhance seed quality, crop performance and realize better yields.
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(pp. 19-31)
Germination and Seedling Growth of Silybum marianum Under Salinity Stress
M.A. Dorri, B. Kamkar*, M. Aghdasi and A. Safahani
Seed germination is a major factor limiting the establishment of plants under saline conditions.  This study investigated germination and seedling growth of milk thistle (Silybum marianum) subjected to salt stress imposed under seven NaCl salt concentrations, 50, 75, 100, 125, 150, 175 and 200 mM, plus a control (distilled water). Percentage germination (PG), mean germination time (MGT), seedling vigor index (SVI), shoot, root and seedling weight and length were measured.

Salinity had a significant effect on PG, MGT and SVI, as well as seedling weight and length (p ≤ 0.01), but did not significantly affect shoot:root length or shoot:root weight ratios.  As expected, germination decreased when salinity increased, while MGT increased.  MGT was 1.75 times higher than in the control at the highest salt concentration.  Differences in MGT were not significant between the 75 mM salt and control treatments, but MGT greatly increased by increasing the salt concentration from 150 to 200 mM.  Slope and salt tolerance index (STI) were estimated for germination (0.54 and 231.9) and seedling stage (0.24 and 237.4), respectively.  According to results from this study, milk thistle, a valuable medicinal plant, could be fit for successful production in fairly salinized areas.
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Heterosis Effects on Seed Vigor of White Kernel Maize (Zea mays)
D.J. Ogunniyan*, J.O. Olasoji and J.A. Adetumbi
Seed vigor determines potential crop establishment and agronomic performance,  but, unlike other traits, has not been properly improved through heterosis. This study examined  the effects of heterosis on seed vigor traits of hybrid maize. Seventy-five hybrid maize genotypes were evaluated along with their parents for seed germinability, vigor parameters, and grain yield (GY).

Percentage germination, speed of germination index and seedling vigor indices were estimated from data collected on germination and electrical conductivity. Vigor data were subjected to analysis of variance and correlated with GY. Heterosis was estimated for seed vigor traits and the hybrids were ranked based on effects of hybrid vigor. High genetic variability existed in heterosis expression for seed vigor among the hybrids. Several hybrids were identified as vigorous based on high percentage germination (PG), seedling length (SDL), seedling height (SDH), seedling vigor index-I (SV-I) and seedling vigor index-II (SV-II) and low leachate electrical conductivity (EC). Correlations between pairs of most of the seed vigor traits were highly significant. GY was only correlated with SDL and SDH. Negative correlations were obtained between EC and PG, SDL, SV-I or SV-II. Heterosis is recommended for improvement of seed vigor traits, especially the PG and EC of maize. Hybrids involving inbred lines BD74-399, TZEI 3, BD74-170, TZEI 188, BD74-31 and BD74-152 represent good candidates for seed vigor heterosis and could be recommended for farmers’ use and seed producers.
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(pp. 49-55)
Increasing Germination Speed of Common Bean (Phaseolus vulgaris) Seeds by Ultrasound Treatments
Soheila Lahijanian and Meisam Nazari*
Common bean (Phaseolus vulgaris) is one of the most important legumes worldwide for human consumption. However, seeds often have poor germination and the crop is unevenly established when cultivated in cool soils.  We studied the effect of several ultrasonic wave treatments on common bean seed germination and speed, as well as on cotyledon cell area, in a laboratory experiment.

Results indicated that the ultrasonic wave treatments significantly affected germination speed and the area of cotyledon cells. The highest cell area (1467.21 μ2) was achieved following 20 min of exposure to ultrasonic waves. Ultrasonic waves could enhance the germination speed of common bean seeds through creating micro-pores on the seed coat and weakening cell-wall rigidity of the cotyledon cells, resulting in higher and faster water imbibition by the seeds. The resulting enlargement of the cells followed by the faster release of α-amylase accelerated starch hydrolysis and increased germination speed.
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(pp. 57-67)
Appropriate Vigor Tests for Evaluating Maize Seed for Subtropical and Tropical Areas
Enayat Rezvani*, Farshid Ghaderi-Far, Aidin Hamidi and Elias Soltani
The cold and radical emergence tests have been proposed by AOSA and ISTA, respectively, as standard vigor tests for maize. However, several studies indicated that these methods were not suitable for assessing vigor of summer planted maize in subtropical and tropical areas. Twenty one samples from lots produced in two years and four regions of Iran were tested. Standard germination, radicle emergence and mean germination time (MGT), under standard, cold, and aging conditions were evaluated in the laboratory.

Field emergence percentage (FE), mean emergence time (MET) and dry weight of emerged seedlings was used for field performance evaluation. MGT after saturated salt accelerated aging (SSAA) had the highest significant simple correlation with individual field indicators, and had the highest standardized coefficient and correlation with the field indicators group in canonical correlation analysis. On the basis of predicting field performance of seed lots, MGT following SSAA was the most appropriate vigor test and classifying method for seed lots produced and planted in warm areas. Based on this test, seed lots with less than 56 h of MGT and FE above 87% were classified as vigorous, those with MGT and FE ranging between 57–68 h and 78–87%, respectively, were classified as risky, and those with MGT higher than 68 h and FE below 78% were classified as weak lots for warm areas.
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(pp. 71-79)
Antioxidant Properties, Fatty Acids, Mineral Content and FTIR Characterization of Blighia sapida Arilli and Seeds
Andrea Goldson Barnaby* and Ruth Williams
Ackee arilli and seeds were evaluated for their antioxidant activity, free radical scavenging properties and total phenolic content, utilizing the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the Folin-Ciocalteau spectroscopy assays. FTIR analysis was used to identify chemical functionalities.  The fatty acid profile was determined by gas chromatography-mass spectrometry, and mineral content by ashing.

  There was no significant difference in the antioxidant activity of the arilli and the seeds of the fruit. Infrared spectroscopy showed peaks characteristic of the presence of lipids, carbohydrates,  proteins and phenolics.  The arilli had higher lipid levels (50%) compared to the seeds (6%).  The major identified unsaturated fatty acids were gondoic acid (seed) and oleic acid (arilli). Arachidic acid (seed) and palmitic acid (arilli) were the major saturated fatty acids.  The mineral content was higher in the arilli compared to the seeds.  The seeds of the ackee fruit are currently underutilized, but can potentially serve as a source of starch, lipids, antioxidants and minerals.
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(pp. 81-86)
Protocol to Optimize the Tetrazolium Viability Test for Apera spica-venti
Marielle Babineau, Andrea Ferreira Hoffmann, Solvejg K. Mathiassen*, Michael Kristensen and Per Kudsk
The tetrazolium (TZ) test is an efficient way to evaluate seed viability.  However, TZ protocols vary greatly among species and need to be adjusted for each.  Loose silky bentgrass (Apera spica-venti) is an important grass weed in Central and Eastern Europe with very small seeds (3.0 × 0.5 mm).  Due to the small size of A. spica-venti seeds, it is very difficult to distinguish the different seed tissues.

  In this study, we optimized the TZ test protocol for small seeds by evaluating TZ staining times (2, 6 and 16 h), seed preparation (dry or 4 h and 22 h moistening), and scarification methods (perforation, sand paper scarification, latitudinal and longitudinal cuts) using a 1% TZ solution at 30 °C. Optimal TZ test results on A. spica-venti were obtained by perforation above the embryo followed by staining for 16 h, regardless of whether seeds were dry or imbibed.  This new protocol should be helpful in grass weed studies and biological investigations of small seeds.
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