Semi-hard seed (SHS) in beans is defined as dry seed which does not imbibe water during a 24 hour soak, but which will gain moisture rapidly at high relative humidity within 14 days and then germinate normally. The inheritance of SHS was found to involve several genes. Soft seed was incompletely dominant to SHS. Narrow sense heritability ranged from 20 to 50% in populations studied. SHS was associated with excellent seed quality resulting in unusually vigorous seedlings.
Common bacterial blight (CBB), rust (RU), and white mold (WM) are serious diseases of great northern (GN) and pinto (P) beans in Nebraska and Colorado. The bacterial diseases halo blight (HB) and brown spot (BS) are sporadic. Severe Fe-induced leaf chlorosis (Fe ILC) occurs on calcareous sites. Separate inoculated disease nurseries are used to screen for resistance to the pathogens causing the above diseases. Yields and seed quality of lines are also determined in non-disease trials. Sources of exotic resistance to the above pathogens and to Fe ILD have been identified and their inheritance determined. A non-structured recurrent selection scheme has mainly been used, occasionally with a backcross program, to combine high levels of the desired traits. Selection for highly heritable traits such as seed size, shape and color, maturity, plant architecture, and RU resistance occurs in early generations while traits of low heritability, such as CBB resistance, WM avoidance, yield, seed coat cracking resistance, and canning quality, are evaluated in separate replicated tests over several years and finally for yield in on-farm-trials. A number of multiple disease resistant, high-yielding, well-adapted GN and P lines are or will be released; P `Chase' (on about 30,000 acres in 1996) and GN WM 3-94-9 (for possible release).
Sexual potato (Solanum tuberosum L.) seeds require many months of afterripening in dry storage to completely lose dormancy and germinate readily at >25C. We examined the relationship between storage temperature and seed dormancy, as assessed by the percentage of germination after 4 days. Two F1 hybrid lots of `Desiree' × 7XY.1 were used; one seed lot was produced by carefully removing half of the developing tubers from the mother plant during seed development, and the control remained undisturbed. Seeds were stored with 3.4% moisture (dry-weight basis) at 10, 20, 30, 40, and 50C and were tested eight times during 29 months for daily germination at 27/40C (21/3 h) for the first 8 days, followed by 6 days at 17C. After 29 months of storage, final germination was <97% only when control seeds were stored at 50C, in which germination was 72%. Germination after 4 days increased curvilinearly with increasing storage temperature, and both seed lots similarly lost dormancy (germination >90%) after 10 months at 40C. Optimum germination levels were maintained after 29 months at 40C. Seeds stored at 50C never completely lost dormancy, and after 7 months of storage, germination at 4 days gradually decreased to zero. Dormancy was eventually lost after 29 months in most seeds stored at <40C, and differences between seed lots suggest that removing tubers from the mother plant increased dormancy. We conclude that dry potato seeds can be safely afterripened at temperatures up to 40C; lower temperatures slow the rate of dormancy loss, and higher ones are detrimental to seed quality.
Brassica crops have indeterminate growth and flower over an extended period of time. Harvested seed is therefore comprised of seed of varying degrees of physiological maturity and quality. Using population-based threshold models, broccoli (Brassica oleracea L. Group Italica), brussels sprouts (B. oleracea L. Group Gemmifera), red cabbage (B. oleracea L. Group Capitata), and rapeseed (B. napus L.) were characterized during seed development with respect to sensitivity to abiotic stress (reduced water potential) and shelf life. Using these models our data suggests that the physiological patterns of seed development are the same in all brassica crops we have tested to date. These population-based models can be used to provide a biological basis in which to evaluate cultural, postharvest and storage practices to ensure the production and maintenance of seed vigor.
Achievement of head size uniformity at final harvest reduces loss and increases profitability for the hydroponic lettuce grower. Shoot fresh weight of `Cortina' lettuce (Lactuca sativa L.) at 7 or 21 days after planting (DAP) was inversely proportional to the number of days required for seedling emergence, and was greater for raw than for pelleted seeds. Head fresh weight at final harvest (61 DAP) was directly proportional to seedling length at 21 DAP, but raw and pelleted seeds produced equal head weights. Thus, initial seed (seedling) vigor differences were maintained to final harvest. Osmotic seed priming (–1.5 MPa KH2PO4, 20 h, dark) led to increased germination rate at 15, 25, and 35C; had no effect on germination synchrony; and increased germination percentage only at 35C. Covering raw or pelleted seeds sown in depressions of the phenolic foam trays with fine (No. 5) vermiculite compared to leaving the seeds uncovered, and soaking the trays in hydroponic solution rather than water, increased seedling shoot fresh weights. Seeds sown on their first day of germination or primed seeds gave greater seedling shoot fresh weights than pelleted seeds. However, the more uniform seedling shoot fresh weights from germinated seeds than from primed seeds was associated with more rapid and synchronous seedling emergence.
In a broad sense, the term “handling seed”can refer to everything that happens between planting stock seed for a seed crop and planting of commercial seed by a grower. In a narrower sense, the term can refer to events between harvest of a commercial seed crop and planting by a grower. These events usually include seed harvest, processing, drying, storage, and transportation. They may also include fermentation, chemical treatment, sizing, blending, encapsulation, coating, and taping. Modern methods of handling seed through these events require machinery.
The past quarter century has been a “Golden Era” for the development of a multitude of vegetable cultivars. We have seen the development of tomatoes that can be mechanically harvested with only slight injury to the fruit; sweet corn that is “super-sweet” with an extremely tender pericarp; green beans that are stringless and peas tha-t are very determinate and adaptable to mechanical harvesting. Countless other breeding achievements have been made in vegetable quality and adaptability, not to mention the broad spectrum of disease and insect resistance that has been bred into nearly every vegetable species. We can be thankful for our highly competitive system for bringing about so many of these advances in such a short time.
Quality seed is undamaged, has a high level of germination, and will produce uniform, vigorous seedlings without defects under various environmental conditions.
The effects of various drying conditions on seed quality and performance of matriconditioned `Bush Blue Lake 47' snap bean (Phaseolus vulgaris L.) seeds were studied. An exponential model based on the Page equation provided a good fit (R2 = 0.9) to changes in moisture content during drying. Drying matriconditioned seeds with high initial moisture content (47.2%) for 5 to 6 hours at 35C, 30% to 35% relative humidity, and 0.7 to 1.4 m·s-1 air velocity (v) retained, and in some cases augmented, the benefits derived from conditioning. Matriconditioning greatly reduced electrolyte leakage (34.3 vs. 94.7 μS·cm-1·g-1 for nontreated seeds); drying to 15% moisture content at 0.7 or 1.4 m·s-1 v moderately increased the leakage rate (59.1 to 60.9 vs. 34.3 μS·cm-1·g-1), while drying at 0.02 m·s-1 v (ambient) increased the rate to that of nontreated seeds. The leakage rate remained low (43.6 to 50.8 μS·cm-1·g-1) in matriconditioned seeds dried to 22% moisture content at all air velocities. In growth-chamber studies, rapidly drying matriconditioned seeds to 15% moisture content at 1.4 m·s-1 v improved the emergence percentage over that of nontreated seeds, increased the shoot fresh and dry weight over that of nontreated and nondried matriconditioned seeds, and increased the shoot fresh weight over that of seeds dried at 0.02 or 0.7 m·s-1 v. Drying matriconditioned seeds to 15% moisture content at 0.7 m·s-1 v improved plant fresh weight over that produced by nontreated seeds. Rapid drying to 22% moisture content at 1.4 or 0.7 m·s-1 v improved only shoot fresh weight over that of nontreated seeds. In a 1992 field planting, percent emergence of matriconditioned seeds dried at 0.7 or 1.4 m·s-1 v was similar to that of nondried matriconditioned seeds and higher than that of nontreated seeds. No significant differences were noted in plant yield among the treatments.
Endosperm mutants of maize often exhibit poor seed quality, as indicated by poor germination and seedling vigor. The measurement of seed leachate electrolyte conductivity (SLEC) is a rapid method of evaluating seed quality. Generally, high SLEC indicates poor seed quality. Other endosperm types in addition to sugary (su) are becoming important in the sweet corn industry. To facilitate the conversion of inbreds to new endosperm types and maintain acceptable levels of seed quality, it would be useful to determine the relationship between endosperm type and SLEC. The objective of this study was to determine the effects of inbred background, endosperm type, and inbred × endosperm interactions on SLEC and to determine the relationship between seed weight and SLEC. Ten seed weight and SLEC of six near-isogenic lines differing for 10 endosperm types were measured. Ten combinations of the following endosperms were used; sugary (su), waxy (wx), sugary-2 (su2), dull (du), and shrunken-2 (sh2). Significant differences in SLEC were found among endosperm types: sh2 had the highest SLEC (186.1 dS·m−1) and Su su2 the lowest (62.9 dS·m−1). Over endosperm types, 10-seed weight and SLEC were negatively correlated (r = 0.84**). This negative relationship may be due to damage suffered by the pericarp during the collapse of the endosperm of the lighter endosperm types. Significant differences in SLEC also were found among inbreds. Values ranged from 162.3 dS·m−1 to 55.7 dS·m−1. Among inbreds, SLEC and 10-seed weight was positively correlated (r = 0.82*). Endosperm by inbred interactions had significant effects on SLEC. This interaction is of importance to those converting inbreds to different endosperm types and should be considered when choosing seed parents for hybrid production.