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This study was conducted to investigate the effects of mild mass selection for adaptation on the performance, genotypic variance, combining ability, S1 family-testcross correlation, and midparent heterosis of S1 families derived from a sweet corn (su) × tropical maize (Zea mays L.) composite (Composite 1R). Four cycles of random mating followed by 10 cycles of 10% stratified mass selection were conducted for earliness, plant and ear type, and freedom from pests. Selection significantly (P < 0.01) decreased plant height, ear height, percentage barrenness, and ear length, and significantly (P < 0.01) increased stalk breakage, earliness (Celsius heat units to 50% anthesis and silking), and kernel row number of both S1 families and their testcrosses. Juvenile plant height at 45 days after planting increased in testcrosses only. Percentage tip blanking and pericarp thickness did not change. For most traits, the greatest response occurred during the first five of 10 selection cycles. Cycle 10 testcrosses performed at least as well as elite check testcrosses for eight of 10 traits. The tropical parents improved combining ability for increased juvenile plant height and kernel row number, and decreased percentage of stalk breakage. As a result of selection, genotypic variance among S families decreased by >40% for heat units to 50% anthesis and silking, ear height, and percentage of barrenness, although for all traits measured, significant genotypic variation persisted following 10 cycles of mass selection for adaptation. S1-testcross correlations and percentage midparent heterosis tended to be consistent across selection cycles. Five cycles of mild stratified mass selection increased the adaptation of a temperate sweet corn × tropical maize composite to the temperate zone of the United States while maintaining significant genotypic variation.
Abstract
MN 13 and MN 150 are extra-early maturing cowpeas [Vigna unguiculata (L.) Walp.] adapted to northern regions possessing a continental climate. They reach the mature-green harvest stage at about 1000 heat units (10°C base, air temperature) under Minnesota conditions, and can be harvested in early August from a late-May sowing. Both lines appear to be tolerant to bacterial blight (Xanthomonas vignicola Burkh.), based on field observation.
Abstract
Nitrogen uptake by two N-deficient turfgrass species was characterized by measuring N depletion from a complete nutrient solution. The uptake rate of both
Abstract
Compared to no pruning, pruning of seedling roots of four tree species during transplantings from the seed flat to peat pots and of the peat-pot liners into gallon cans more than doubled the number of plants with acceptable root systems. Survival and growth were neither significantly nor adversely affected by root pruning done over a range of transplanting dates.
Abstract
Root pruning and care during the first two nursery transplantings of 4 tree species significantly increased the percentage of plants with good root systems. The 4 species were Eucalyptus sideroxylon A. Cunn., red iron bark; Pinus radiata D. Don., Monterey pine; Pistacia chinensis Bunge., Chinese pistache; and Quercus ilex L., holly oak. The percentage of trees with good root systems decreased the longer seedlings stayed in the seed flat and in peat pot liners, particularly those not root pruned. In all but one case, the earlier plants were moved from the seed flat into peat pots and on into into gallon cans, the more the plants grew in caliper and height.
Plants root pruned during the early moves were larger than those not root pruned. However, root pruning at the later moves resulted in smaller plants than those moved earlier or than those moved at the same time but not root pruned. The combination of lengths of time in the seed flat and in the peat pot (time in the greenhouse) which resulted in the best combination of quality root systems and large plants was only 1/2 to 2/3 the time now common nursery practice (90-120 days).
Abstract
Ammonia volatilization from urea-N applied to Kentucky bluegrass ( Poa pratensis L. ‘Bensun’) was investigated using a chamber trapping procedure. Urea was spray-applied in a 0.2 cm depth at N of 5 g·m−2 with and without additional irrigation of 0.5, 1, 2, or 4 cm. Losses up to 36% of the applied N occurred when urea was applied without irrigation. Supplemental irrigation of as little as 1.0 cm reduced the loss to 3-8%, while a 4.0-cm irrigation further reduced losses to about 1%. Of the ammonia volatilized, most was lost in the first 24 hr. Maximum N loss was associated with the thatch layer, a zone having high urease activity.
Abstract
The depletion of N applied to a moderately N-deficient Kentucky bluegrass (Poa pratensis L.) turf was measured using a soil sampling procedure. Nitrogen as either Ca(NO3)2 or (NH4)2SO4 was applied in solution at 5 g N/m2 and washed into the thatch and soil with an additional 0.3 cm of water. Both N forms were located primarily in the thatch and upper 1 cm of soil. The
Abstract
Artificial infestation with egg masses to simulate severe natural second brood European corn borer, Ostrinia nubilalis (Hubner), infestation caused less stalk and stalk-associated damage in the resistant field corn inbred ‘B52’ Zea mays L. than in susceptible sweet corn inbreds. Relatively severe damage, however, occurred on and around the region of the primary ear in both ‘B52’ and the sweet inbreds. Because direct kernel damage is of paramount economic importance in sweet corn as opposed to field corn, forms of second-brood resistance in addition to that found in ‘B52’ should be sought in sweet corn improvement. For stalk tunneling and number of sheath and collar lesions the resistance of F1 and F2 progenies was intermediate between the resistance of ‘B52’ and the sweet inbreds. Although there were no parental differences in damage to the ear, F1 and F2 means showed some indication of resistance.
Abstract
The response of rabbiteye blueberry plants (Vaccinium ashei Reade) to rates and modifications of deep well water (pH 8.7) containing 0.695 dS·m-1 electrical conductivity (EC), a sodium adsorption ratio (SAR) of 29.7, and a bicarbonate concentration of 7.89 meq·liter-1 was compared to plants irrigated with rain and surface waters applied to 3 soils in a glasshouse-container study. Fresh weight increase and root fresh and dry weight were greater on plants irrigated with rainwater or pond water compared to plants irrigated with different rates of deep well water, or deep well water modified by the addition of gypsum or acidified with H2S04. Fresh weight increase, root fresh and dry weight, leaf fresh weight, and top:root ratios were higher on a loamy sand soil than on sandy loam or clay loam soils. Plant weight gain was positively correated with the percentage of sand, and negatively correlated with the percentage of clay and saturation-extract SAR. An increase in soil pH resulted from irrigation with deep well water which, along with its modifications, resulted in increased leaf Na and decreased leaf Ca and Mn, compared to rain or surface-water irrigations, which slightly lowered soil pH.
Field experiments were conducted from 2008 through 2010 near Lyons, GA, to develop integrated weed management systems for organic Vidalia® sweet onion (Allium cepa) production. Treatments were a factorial arrangement of summer solarization, cultivation with a tine weeder, and a clove oil herbicide. Plots were solarized with clear plastic mulch during the summer fallow period before transplanting onion. Cultivation treatments were twice at 2-week intervals, four times at 2-week intervals, and a noncultivated control. Herbicide treatments were clove oil plus vinegar, clove oil plus an emulsified petroleum oil (EPO) insecticide used as an adjuvant, and a nontreated control. ‘Savannah Sweet’ onions were transplanted in early-December each year, with cultivation and herbicide applications events occurring the following January and February. Onions were harvested the following spring. In addition to yield measurement, a subsample of harvested onion was stored in a controlled atmospheric (CA) storage facility to evaluate treatment effects on diseases of stored onion. Summer fallow solarization did not control the cool-season weeds present in these trials. Cultivating transplanted onion with a tine weeder effectively managed cutleaf eveningprimrose (Oenothera laciniata) and swinecress (Coronopus didymus) and improved onion yields in 2 of 3 years. There was little difference in overall performance between two cultivations and four cultivations with the tine weeder. The 1 year of marginal weed control with the tine weeder was due to persistently wet soils during winter months that inhibited optimum performance of the implement. Clove oil, combined with vinegar or an EPO insecticide, provided marginal weed control and had no effect on onion yield. Diseases of stored onion were unaffected by any of the treatment combinations, although overall incidence of diseases of stored onion was higher in 2010 compared with other years. This corresponds with the 1 year of marginal weed control with the tine weeder, suggesting that the presence of weeds may be a factor related to disease incidence during storage.