Volume 36, No. 2, 2014

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(pp. 103-113)
Chlorophyll Fluorescence in Developing ‘Top Mark’ Cantaloupe (Cucumis melo) Seeds as an Indicator of Quality
H.T. Wilson, Osamah Khan and G.E. Welbaum*
ABSTRACT:
Seed maturity at harvest is one important factor that determines quality. Separating low-vigor developing seed from bulk-harvested lots is difficult because they often have the same physical characteristics as fully mature high-vigor seed. Non-destructive sorting based on chlorophyll fluorescence (CF) has the potential to remove low-vigor immature seed. This study examined whether CF may be used to identify and separate low-vigor, immature from high-vigor mature cantaloupe (Cucumis melo cv. Top Mark) seeds in the same lot.

A SeedMaster Analyzer measured CF of seeds from nine stages of development, and values were compared to percentage germination and 4-day root lengths, which served as an indicator of seed vigor. Seeds harvested 25 days after anthesis (DAA) did not germinate but had the highest CF values of 815 pA on a relative scale of 1000. All 55 DAA seed germinated and had the longest 4-day root lengths but lowest CF with readings of only 207 pA. Seed vigor and germinability were negatively associated (r = −0.81) with CF across all stages of development. In mature seeds, the endosperm and embryo tissues produced the greatest CF. Using CF, low-vigor immature seeds can be differentiated and separated from high-vigor mature cantaloupe seeds of the same size and weight.
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(pp. 115-122)
Seed Production from Aeschynomene Genetic Resources Rescued and Regenerated Using Aeroponics
J.B. Morris
ABSTRACT:
Jointvetch (Aeschynomene americana) and A. villosa are cover and forage crops. They require a long growing season and do not produce mature seed before the first hard freezes in Griffin, GA. Use of an aeroponic system was evaluated for rescuing and regenerating photoperiod and freeze-sensitive Aeschynomene accessions.

One-month-old seedlings from 11 accessions were field-planted in Griffin in 2012 and 2013. Four mature vegetative stem cuttings per accession, with at least 3 true leaves, were removed from plants that produced flowers but did not have enough time or photoperiod exposure to produce mature seed. Each cutting was placed in a hydroponic cloning machine. After approximately 2 wk, 4 cuttings with healthy root systems were transferred to an aeroponic system. Productive plants yielding mature seed (22–584 seeds) were regenerated from 100% of the accessions. The success rate for cuttings was 71%. Seed weight and number were influenced by production year. Seed weights and numbers ranged from 0.630–2.317 g and 110–584, respectively, in 2012. In 2013, only the Mexican accession PI 544176 produced significantly higher seed weight (0.390 g) with the most seeds (203), compared to other accessions. However, PI 544176 production was lower compared to 2012 due to exposure to two hard freezes in the field that damaged plants enough to make them less vigorous in the aeroponic system. The aeroponic system’s ability to produce productive plants demonstrated its usefulness for rescuing and regenerating seed from photoperiod and freeze-sensitive Aeschynomene accessions.
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(pp. 123-138)
Response of 1-Aminocyclopropane-1-Carboxylate Oxidase Activity to Selenium in Dormant Stylosanthes humilis Seeds
Raimundo S. Barros, Frank James A. Pinheiro, Claudinéia R. Pelacani, Thamires F. Pereira and Dimas M. Ribeiro*
ABSTRACT:
The enhancement of 1-aminocyclopropane-1-carboxylate oxidase (ACO) activity caused by soluble selenium (Se) compounds was observed in dormant seeds of Townsville stylo (Stylosanthes humilis) under in vitro (desalted extract) and in vivo (whole seed) conditions. Enzymatic activity was very low in dormant seeds, but was stimulated following an increase in 1-aminocyclopropane-1-carboxylic acid (ACC) content of Se-treated seeds.

 Although Se pretreatment of dormant seeds promoted a substantial increase in ACO activity in vivo, enzymatic activity, as measured in seeds supplied with ACC, was much higher in non-pretreated seeds, indicating that Se compounds limited to a certain extent the expression of the full enzymatic potential of the seeds. Based on results of this study, it can be concluded that seed dormancy breakage by Se results from a balance between a large accumulation of ACC and a significant but partial increase in ACO activity, leading to ethylene production.{/expand] Download entire article

(pp. 139-149)
Pomegranate Seed Germination and Dormancy Breaking Techniques 
Mohammad Naser Taheri, Mahdiyeh Gholami*, Bahram Baninasab, Mostafa Mobli and Samad Moradi
ABSTRACT:
Pomegranate (Punica granatum) propagation and seedling availability are fraught with difficulties. Dormancy and effectiveness of different seed treatments on germination performance and emergence of pomegranate seeds was investigated. Treatments included soaking seeds for 24 and 48 h at 25 °C in the dark in distilled water (hydropriming), 1 and 3% KNO3, and −0.4 and −0.8 MPa PEG (osmopriming), stratification in moist sand at 4 °C for 30 and 45 d, or scarification in 70% sulphuric acid for 10 and 20 min. A group of seeds was exposed to aril extracts during the germination period, instead of distilled water. Based on measured indices of germination performance and seedling quality, hydropriming for 24 h and KNO3 1% priming stimulated metabolism in pomegranate seeds. Stratification for 30 d resulted in seeds with the highest germination ability and best seedling quality, compared to other treatments. Both hydro- and KNO3-treated seeds performed better than control (untreated) seeds under drought stress, with a clear effectiveness of hydropriming in improving percentage germination at low water
potentials. When applied, aril extracts significantly inhibited germination. Hydropriming can be an effective method for promoting the propagation of the P. granatum fruit trees through mass production of seedlings, and would contribute to speeding up pomegranate breeding programs.

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(pp. 151-160)
Adoption of Improved Local Wheat Seed Production Systems in Meskan and Sodo Districts of Ethiopia
Shimelis Araya* and Hussien Mohammed
ABSTRACT:
Farmer-based improved seed production to satisfy smallholders’ demand for improved seed is an alternative and emerging approach in Ethiopia.  This study determined decision variables that significantly constrained farmers’ adoption of improved local seed production systems in the Meskan and Sodo districts of the Gurage zone, Ethiopia.

 Multi-stage sampling was employed to select study sites and sample farmers. A total of 130 farmers were randomly selected from adopters and non-adopters for the survey. Primary data were collected through structured interviews, individual case interviews and focus group discussion. In order to identify significant factors explaining farmers’ adoption decisions and extent of adoption, descriptive and econometric (tobit model) analyses were employed, respectively. Tobit analysis revealed that intensity of adoption was influenced by age of the household head, distance from the local market, farm size, livestock ownership and experience in seed production. Age of the household head and distance from the market center negatively affected adoption intensity. On the other hand, farm size, livestock ownership and more years of experience enhanced adoption intensity. These results have two major implications.  The first is that farmers need to have the resources to apply the necessary inputs, and therefore there is a need for capacity building the second is availability of key information affecting adoption intensity decisions.
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