The commercial pecan [Carya illinoinensis (Wangenh.) K. Koch] nursery industry relies on open-pollinated seed for rootstock production. Current choice of seedstocks by commercial pecan nurserymen was surveyed by telephone. Nurseries were called if they appeared in the directory used for the 1994 release of `Navaho'. Factors influencing the choice of seedstock include seed availability, nut fill, nut size, nut shape, seedling vigor, stand uniformity, and root characteristics. Local availability is important in the choice of seedstock. Those who harvest from their own trees usually credit the seedstock with other valuable characteristics, such as improved germination or vigor. Those who purchase seed usually target a preferred seedstocks for particular reasons but plant available seed in its absence. Well-filled nuts are recognized as being important for good germination. Small nuts are often preferred, especially when seed is purchased because more nuts per pound increases potential production. Round nuts are generally preferred over long nuts due to improved performance in some mechanical planters. Distinct regional preferences are apparent in the choice of seedstocks. Regionally preferred seedstock selections are generally validated by a survey of the research literature. Patterns of selection are consistent with climatic and geographic constraints. Tree procurement patterns have changed: many small nurseries have gone out of business, many large nurseries transport trees far from the nursery for sales, and quarantine restrictions have altered procurement patterns in Arizona. Recommendations are made to nurserymen, pecan growers, and researchers concerning continued progress toward improving regionally adapted pecan rootstocks through seedstock selection.
Soil particle size was found to affect expansion and contraction of soil mass as moisture changed; thus all other seedling emergence stresses changed. Cohesion between soil particles is changed by soil type, content, and particle size, which in turn changes seed energy requirements for survival and emergence. The rates of germinating/emerging; seed/seedlings accelerated or stopped depending on moisture fluctuations and water degradation of aggregates. The same moisture content may be damaging in one soil and not in another. Many seedlings with developed radicals and hypocotyls did not emerge and were found in pockets of fine soil below 0.5mm; or as if their energy had been used up. Stands after emergence frequently varied greatly in vigor and survival by many units. Vigorized seed produced variable results depending on soil stress limitations during emergence. That is, laboratory differences did not always reflect in the field. The least critical stress period was between planting and the emergence of the radical--about 1/3 of the emergence time. Ideal seed beds often produced poor stands when water management and temperature were stressful. Packing density was found a good measure of seed-bed soil quality.
Science and Technology is one that gives a good overview of the whole area of seed development, dormancy and germination, including hormonal regulation of seed germination as well as seed quality aspects such as testing, seed vigor, seed-borne pathogens
Muscadine grape industry in the southeastern United Sates is expanding in recent years. To provide necessary information for the growing industry, 50 muscadine grape cultivars were evaluated for vigor and fruit characteristics at Florida A&M Univ., Tallahassee, Fla. Vine vigor was measured by winter pruning weight and varied from 5.4 lb/vine to 35.7 lb/vine. Among these cultivars, Triumph, Summit, and Tara were the least vigorous, while `Carlos', `Fry Seedless', and `Gold Isle' produced the most pruning weight. Dry scar ranged from 60.6% (Darlene) to 97.7% (Dixie Red). Among the most important table grapes, `Nesbitt', `Alachua', `Jumbo', `Fry', `Triumph', and `Scarlete' showed more than 70% of dry scars. Fruit rot ranged from 0.3% (Gold Isle) to 31.8% (Dixie Land). `Noble', `Scarlet', `Nesbitt', and `Carlos' were the important cultivars with less than 5% rotted fruits. Commercial fruit index were different significantly among the cultivars, ranged from 45.5% to 96.4%. Higher commercial fruit index of table grapes were found with `Magnolia', `Rosa', `Scarlet', and `Tara', while `Dixie Land' (45.5%) was the least. Seeds per fruit varied among the cultivars, ranging from 2.4 to 4.9. Fewer fruit seeds were found in `Fry' and `Nesbitt', while `Granny Val', `Senoria', `Darlene' and `Triumph' had more seeds per fruit than the others. Seed size also differed among the cultivars. `Sugar Pop' had the largest seeds (0.144 g/seed), which was twice as the size of the smallest seeds of `Welder' (0.056 g/seed). Fruit soluble solids content (SSC) ranged from 11.7% to 16.9% among the cvs. evaluated. Higher SSCs were found in `Welder', `Fry Seedless', `Scarlet', and `Cowart', while `Senoria' and `Jumbo' had relatively low SSC.
Multiple electroconductivity readings (μAmps) of leachates from individual seeds during the first 6 hr of imbibition was examined as a possible predictor of seed quality. Readings from each sample of 100 seeds were formed into frequency distributions and the mean, median. and internal slope were calculated using an automated computer retrieval system. Internal slope is a non-central tendency measure based on the slope of a line tangent to the inflection point of the S-shaped cumulative frequency distribution (CFD) of μAmps. Radicle lengths (3 days) and germination (7 days) percentages were regressed on each of the two measures of central tendency and also the CFD shape indicator, internal slope. None of the three predictors were satisfactory for estimating seed vigor (root lengths) of maize (Zea mays L.) or wheat (Triticum aestivum L.) or germination of wheat seed lots. Internal slope was useful in estimating viability of artificially aged maize seeds (r2= 0.91), which compared favorably with our previous results using naturally aged red clover (Trifolium pratense L.) seed lots. Overall the seed quality of the unaged wheat lots was fairly high and the electrolyte leakage test was not sensitive enough to detect differences within these lots.
that could facilitate hybridization between them, and record fruit yield and estimate seed production per plant among native and nonnative blue honeysuckles and invasive red-fruited honeysuckles. The results provide information regarding the competitive
All of the major California almond varieties are self-incompatible necessitating the interplanting of pollinizer varieties. The incorporation of self-compatibility into the dominant variety Nonpareil through mutation or genetic engineering would greatly improve cropping efficiency. Negative effects of inbreeding on resultant seed and seedling quality could negate production advantages. Inbred seed of Nonpareil were obtained by: a) enclosing mature trees in pollination cages containing bees at flowering, and, b) controlled crosses to a Nonpareil mutation (Jeffries) which is unilaterally compatible when used as the seed parent. Selfed seed set from caged trees was less than 0.001% of available flowers. Seed set from crosses to the Jeffries mutation averaged 34.4% which was not significantly different than outcrossed controls. No significant loss in kernel weight and dimensions were observed in any of the inbred material when compared with outcrossed controls though a higher proportion of the inbred seed and seedlings failed to develop fully. Both average tree height and trunk diameter after 1 year of growth was significantly lower in inbred vs. outcrossed material. Results suggest no major penalty to kernel quality following self-pollination, though losses in progeny vigor should be a concern when utilizing selfed seed in variety development programs.
141 POSTER SESSION 21 (Abstr. 833-841) Seeds and Seedlings
A seedling disorder of broccoli (Brassica oleraceae L. var. italica) characterized by chlorotic cotyledons and delayed seedling growth is described. This disorder, termed “yellow cotyledon”, has been observed in field plantings under high temperatures with some broccoli seed lots. Yellow-cotyledon disorder can be observed in laboratory germination tests if they are conducted under illumination, where unaffected seedlings will develop green cotyledons. Little relationship was found between overall seed vigor and the expression of yellow cotyledon by use of early germination counts and accelerated aging tests, although the most severely affected seed lots had been stored for several years. Field trials in 2 years showed that although seedlings with yellow-cotyledon disorder developed into normal plants, maturity was delayed and total yields were reduced.
A preliminary screening experiment was conducted to evaluate 47 cowpea [Vigna unguiculata (L.) Walp.] genotypes for use as a weed-suppressing cover crop. 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 except one selection were highly resistant to southern root knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood], and the selections varied in seed size, photoperiod, and response to foliar diseases.