A preliminary screening experiment was conducted to evaluate 47 cowpea [Vigna unguiculata, (L.) Walp.] genotypes for use as a weed-suppressing cover crop. Lines evaluated in this study included forage varieties, PI accessions, experimental breeding lines, and land races of unknown origin. Of these, 11 were selected for further testing on the basis of vigorous growth and weed-suppressing ability. In a field experiment repeated over 4 years, the selected genotypes were not different from the leading cover crop cultivar, `Iron Clay', in biomass production. Vigor ratings, vine growth ratings, and canopy widths of some genotypes exceeded those of `Iron Clay'. Vigor ratings and canopy measurements were efficient selection criteria that could be useful for breeding cover crop cowpea cultivars. All selections except an African cultivar, `Lalita', were highly resistant to southern root knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood], and the genotypes varied in seed size, photoperiod, and response to diseases.
`Lovell' peach seeds were stratified for 0 to 12 weeks at 4°C under moist conditions. Differential Scanning Calorimetry (DSC) was used to study the respiratory capacity for the cytochrome (CP) and alternative (AP) pathway of the embryos during this period. Azide and SHAM titration curves were obtained by measuring the heat of metabolism produced by the excised embryos after vacuum infiltration with appropriate combinations of the two inhibitors.
Uninhibited total respiratory activity increased steadily with the stratification treatment. AP capacity of the embryos was higher than CP capacity for the first 4 weeks of stratification. Between 4 and 6 weeks, CP capacity increased markedly and after 6 weeks was at least 40% higher than AP capacity. This rise on CP capacity coincided with the point at which an increase in seedling vigor and germinative capacity was observed and is in agreement with previous studies suggesting a change in respiratory efficiency as being responsible for the increase in seedling vigor.
Rhizoctonia solani infection of potato causes seed piece decay and stem and tuber lesions, resulting in delayed emergence and uneven stands, low-vigor plants and unmarketable tubers. Rhizoctonia prevention effectiveness of three fungicide/fir bark dusts and nontreated tubers were compared on three varieties. Seedpieces of Viking, Atlantic and Norkotah 278 were treated and planted in separate commercial fields. A randomized complete-block design with four replications with four 26-foot rows per treatment plot included four treatments: 0.5 lb Maxim, 1.0 lb Tops MZ, and 1.5 lb Nubark Captan dust/100 lb seed. Plant stems, stolons and tubers were examined for Rhizoctonia infection at the tuber initiation stage and tubers were examined again at mature stage. Maxim and Tops MZ reduced stolon infection in Atlantic and Norkotah 278 and reduced stem infection in Norkotah 278. Plants from Maxim treated tubers produced more stems/plant in Norkotah 278 and produced more weight of tubers weighing less than four oz in all three varieties. Differences in seed tuber conditioning and mechanical damage in seed handling increase variability of treatment effects. Repeated testing of potato seed piece treatments in Texas High Plains conditions is the best way to confirm potential of beneficial effects of seed treatment.
Long-term preservation of seed germplasm is a high agricultural priority. It assures that genetic diversity will be available for future generations for continued plant improvement. This experiment reports on the affect that storage temperature had on the viability of 65 selections of lettuce seed stored for 30 years. The average seed moisture content was 5.5% ± 0.5% (fresh weight basis). Fresh seed samples were placed at 5 °C storage in 1969. In 1975 they were then transferred to -18 °C storage. Viability remained at 98% ± 5% for the first 14 years of 5 /-18 °C storage, then viability declined. At 17 years storage, the average viability had dropped to 75% and continued to drop at about 4%/year. At the 17-year mark, individual samples were split, one-half remained at -18 °C the other half was placed under liquid nitrogen vapor (lnv) conditions (about -150 to -190 °C). The -18 °C stored samples continued to deteriorate to 14% viability at the 30 year test period (1999). The samples placed in lnv did not decrease further in viability and remained at 75% viability at the 30-year mark. Seed vigor was reduced in the -18 °C stored seeds that were still viable. The lnv-preserved samples were significantly more vigorous. It is clear from this experiment that lnv preservation was significantly superior to -18 °C storage and, in fact, stopped or significantly reduced the rate of viability loss in samples that are rapidly deteriorating.
Poster Session 17–Seed and Stand Establishment 19 July 2005, 12:00–12:45 p.m., Poster Hall–Ballroom E/F
The cessation of protoplasmic streaming is one of the first observable effects of chilling in sensitive plant tissue. If the lack of protoplasmic streaming contributes to the development of chilling injury, then impeding protoplasmic streaming at the chilling threshold temperature should induce chilling injury symptoms in tissue that would normally not exhibit symptoms at that temperature. A centrifuge was constructed to subject entire germinating cucumber (Cucumis sativus L., cv. Poinsett 76) seeds to centrifugal forces of up to 20 xg at 2.5, 10 and 12.5°C. Subjecting cucumber seeds with 5-mm-long radicles to high centrifugal forces (18 xg) at a marginal chilling temperature of 10°C for up to 3 days had no significant effect on subsequent radicle elongation of the entire population. In one experiment, spun seedlings were 7.4 ± 0.52 cm long, while the controls were 6.1 ± 4.3 cm long after 48 hr at 25°C. When analyzed by individual seed, the spinning treatments had no effect on high-vigor seedlings, while an 18 xg treatment significantly improved subsequent radicle elongation of low vigor seedlings. The effect of increased centrifugal forces on the respiration, metabolism and chilling sensitivity of cucumber seedlings will be discussed.
to instructions by Phytodetek ® ABA Test Kit (Agdia, Elkhart, IN). Vigor index and average radicle length measurements were determined on 80 seeds per replication (two groups of 40) using the Seedling Vigor Imaging System (SVIS, Ohio State
., 2017 ; Lordan et al., 2019 ; Reig et al., 2019 ). Over the past several decades orchards have been turned over and replanted with new, higher density planting systems. A persistent challenge in managing tree health and vigor at the onset of orchard
Differences in the field emergence of seed lots with high laboratory germination or in germination after storage are referred to as seed vigor ( Dornbos, 1995 ; TeKrony, 2003 ), a concept that comprises various aspects of quality and indicates
Polyculture mixtures of several species of cover crops may be the best way to optimize some of the benefits associated with cover crop use. In the first year of a three year study, 16 polyculture mixtures of cover crops (4 species/mixture) were screened at seven sites throughout the state. Five of the mixtures were seeded at two planting dates. Fall evaluation of the cover crop mixtures included ease of establishment, vigor, percent groundcover, plant height, and relative biomass. The two mixtures with the highest percent groundcover were (1): sudex, rye, mammoth red clover, and subterranean clover (62% and 80% groundcover, one and two months after planting respectively), and, (2), annual alfalfa, hairy vetch, ryegrass, and rye (56% and 84% groundcover one and two months after planting respectively). The six mixtures with the highest percent groundcover did consistently well, relative to other mixtures, at all locations. Mixture (1) above also had the highest relative biomass throughout the state. Yellow and white sweet clovers, hairy vetch, winter oats, subterranean clover, red clover, rye and barley established well and maintained high vigor ratings throughout the fall. Ladino clover, timothy, and big flower vetch consistently had poor vigor ratings.