bluuebunny/crossref_metadata_2025 huggingface dataset:
Recurrent Selection for Resistance to Iron Deficiency Chlorosis in Soybeans1
Authors: Prohaska K. R. , Fehr W. R.
Published: July 2010

The objective of our study was to evaluate the use of recurrent selection by S1 testing for development of a soybean [Glycine max (L.) Merr.] population with improved resistance to iron‐deficiency chlorosis on calcareous soil. An intermated population was developed with the 10 most resistant cultivars or experimental lines and the 10 most resistant plant introductions available in 1975. Each cycle of selection required 1 year and included the growing of S0 plants in Puerto Rico during the winter to obtain 100 S1 lines, evaluation of the S1 lines for chlorosis score on calcareous soil in Iowa, selection of the 10 most resistant lines before flowering, and recombination of selected lines for the next cycle of selection. Progress from selection was evaluated by comparing the mean performance of the parents for the cycle 0, 1, and 2 populations on calcareous soil in four Iowa environments.

There was a significant linear improvement in mean chlorosis score from cycle 0 to 2. The average genetic gain per cycle and year of 0.2 units was 9% of the cycle 0 mean. The highest frequency of resistant lines was from the cycle 2 parents. Genetic improvement in the population indicated that resistance to iron‐deficiency chlorosis is influenced by genes with additive effects. The results also indicated that early‐generation testing of F2‐derived or S1 lines should be effective in development of cultivars with the desired level of resistance.
The Fate of Nitrogen Fertilizer Applied to Turfgrass1
Authors: Starr J. L. , DeRoo H. C.
Published: July 2010

Field plots, instrumented with suction lysimeter and neutron probe access pipes, were used to study the fate of nitrogenous fertilizer applied to turfgrass grown on a sandy loam soil. Fertilizer N was applied to each plot at a rate of 195 kg ha−1 in each of the first 2 years and 180 kg ha−1 in the 3rd year to each plot. The fertilizer N was in a 50:50 split application in May and September of each year. Grass clippings were returned, after subsampling, to two of the four plots. In the 3rd year, the use of 15N as a tracer in conjunction with grass clipping management provided the means to quantify the N in the grass derived from fertilizer, soil, the current year's grass clippings, and the previous 2 years of grass clippings. For example, where clippings were not returned, about equal quantities of N were derived from soil and fertilizer. Where clippings were returned, the yield of grass increased by about one‐third and nearly equal proportions of N in the plant tissue came from soil, fertilizer, and grass clippings.
Contribution of Husk Leaves to Maize Grain Yield1
Authors: Cantrell R. G. , Geadelmann J. L.
Published: July 2010

Mechanical detasseling is a common procedure in hybrid seed production of maize (Zea mays L.) and is often accompanied by loss of leaves. No one has examined the potential of husk leaves, i.e., laminae extending from the husk, to compensate partially for leaf area lost during detasseling. We investigated the contribution of husk leaves to grain yield in three environments under normal conditions and under stress induced by partial defoliation prior to anthesis. The study involved four inbreds and two hybrids of early Corn Belt dent maize with high husk leaf area. Treatments consisted of a check, removal of the tassel plus the top two leaves prior to anthesis, and removal of all tissue above the uppermost ear prior to anthesis. Also, the husk leaves were either left intact (check) or removed when they are fully extended.

Reduction in grain yield due to the removal of only the tassel and the top two leaves averaged 9.2% over all genotypes. Removal of all tissue above the uppermost ear caused an average yield loss of 50.2%. The decrease in yield due to complete husk leaf removal was significant for four of the six genotypes, and the average reduction was 2.6% (1.2 q/ha). The contribution of the husk leaves to grain yield was similar across the various detasseling treatments. Therefore, selection of seed parent inbreds for husk leaf areas similar to those we studied would not greatly offset yield reductions caused by mechanical detasseling.
Performance Tests of Cytoplasmic Male‐Sterile Barley at Two Different Latitudes1
Authors: Ahokas H. , Hockett E. A.
Published: July 2010

Unrestored and restored derivatives of msm1, a cytoplasmic male‐sterile barley (Hordeum vulgare L.), were investigated at 46 (Bozeman, Mont.) and 61° (Elimaki, Finland) N Lat. The isoline derivatives of ‘Adorra,’ HA 6‐33‐02, ‘Hankkija's Aapo,’ ‘Hankkija's Eero,’ Kindred’ (uc2), ‘Kuoreton,’ ‘Mari,’ ‘Olli,’ and ‘Tammi’ were maintainers of sterility in both the environments. The isoline derivative of ‘Pirkka’ permitted 0.3% selfing at Elimaki, but was a maintainer of sterility at Bozeman, where it had some anthers of normal appearance. The female fertility in msm1‐Addora was normal in both the environments. Adorra‐like derivatives, heterozygous for the restorer gene Rfmla, had normal seed set under bags (similar to those in normal Adorra) in both environments. Some of the restored derivatives with approximately 50% of their genotype wild barley (ssp. spontaneum) and heterozygous for either Rfm1a, Rfm1b, Rfm1c, or Rfm1d had a slightly lower fertility than the control at Elimaki. This decrease in fertility was attributed to the fast vegetative development of these plants at Elimaki, where they headed 27 to 33 days after emergence. The rapid development in these crosses with spontaneum barleys was probably caused by the long light periods of the season that are up to 24 hours at 61° N Lat. Our results indicated that the msm1‐Rfm1 system can be used in hybrid seed production under both environmental conditions.
Inheritance of Ineffective Nodulation and Non‐nodulation Traits in Alfalfa1
Authors: Peterson M. A. , Barnes D. K.
Published: July 2010

Although the roots of alfalfa (Medicago sativa L.) usually form pink nodules capable of fixing atmospheric N2 when inoculated with Rhizobium meliloti Dang., one clone incapable of forming nodules (non‐nod) and five clones which produced ineffective nodules were recently discovered. These unusual nodulation traits are useful for research on root infection, nodule formation, and N2 fixation. The objectives of this study were to determine the inheritance of the non‐nodulating trait and of the ineffective nodulation in each of the five clones, to compare the genetic controls for ineffective nodulation in the five clones, and to determine the genetic relationship between ineffective nodules and non‐nodulation.

The non‐nod clone and the five ineffective clones were self pollinated, crossed in a diallel mating design, and crossed to two normal effective nodulating clones. F2 and backcross seed was produced on non‐nod ✕ normal and ineffective ✕ normal crosses. F2 seed was also produced on non‐nod ✕ ineffective crosses and ineffective ✕ ineffective crosses. Progenies were evaluated under nil‐nitrate greenhouse sand culture. Six weeks after planting, non‐nod plants were small, chlorotic, and had no nodules. Plants with ineffective nodules were small, chlorotic, and had white nodules. Plants with effective nodules were vigorous, dark green, and had pink nodules. Four of the five clones had a different basis for inheritance of ineffectiveness. Three were conditioned by a single tetrasomically inherited recessive gene (in1, in2, or in3), the nulliplex genotype in each instance producing ineffective nodules. The fourth was conditioned by two recessive genes (in4 and in5), the nulliplex condition at both loci being required for production of ineffective nodules. The non‐nod trait was conditioned by two tetrasomically inherited recessive genes (nn1, and nn2). The nulliplex condition at both loci resulted in non‐nodulation. The non‐nod trait and the four different types of ineffective nodules appeared to segregate independently of one another.
A Collection Receptacle for Field Abscission Studies in Common Bean1
Authors: Izquierdo Juan A. , Hosfield G. L.
Published: July 2010

A non tagging, non destructive, continuous, and inexpensive method was developed to evaluate abscission of reproductive organs in dry beans (Phaseolus vulgaris L.) under field conditions. Abscission collection receptacles (ACR) were built, using saran screen (1.5 × 2.0 mm mesh) and 2.5 × 5.0 cm redwood stock. Receptacles were placed in the field over a 1.25 m segment of row, and the floor was carefully fitted around competitively growing plants at the 2 to 3 true leaf stage. The method was tested on dry bean cvs., ‘Tuscola,’ ‘NEP II,’ and ‘Black Turtle Soup,’ selected because of their contrasting growth and flowering habits. Reproductive organs were collected every 4 days and taken to the laboratory where the data were quantified. Samples required 3 min per ACR. Abscission could be broken down into flower and pod drop components. Pod abscission accounted for most of the shedding of reproductive organs. The abscission of pods under 10 mm accounted for 64 to 82% of all reproductive structures abscised. The ACR was useful to study the seasonal patterns of flowering, abscission, and pod retention of genotypes. Differences in these parameters were detected among the three cultivars studied in this experiment. Low coefficients of variation associated with data collection indicated a good degree of precision in the experiments. Compared to unenclosed plants, the ACR had no significant effect on growth, vigor, yield, and yield components of enclosed plants.
Early Vegetative Growth of Cotton as Influenced by Leaf Type1
Authors: Ibrahim M. E. , Buxton D. R.
Published: July 2010

Cotton (Gossypium hirsutum L.) plants with mutant Okra (L0) and Super Okra (L5) leaves have several desirable characteristics in production systems with narrow rows and with standard rows where humidity and boll rot are high. These leaf types cause a modified fruiting expression in cotton plants. This investigation was conducted to determine the effect of the mutant leaves on rate of dry matter production, rate of leaf area development, assimilation efficiency, and dry matter partitioning during early growth of cotton plants. Three near‐isogenic lines of ‘Stoneville 7A’ (normal, Okra, and Super Okra leaves) were grown spaced field plantings during 2 years. The two mutant leaf types had significantly lower dry matter accumulation than the normal‐leaf type during both years. Values for Okra leaf‐plants were intermediate to the normal and Super Okra‐leaf plants. Initial size of cotyledons, mean net assimilation rate, and C exchange rate were similar among the leaf types and were not major factors causing the differential growth rates. The mutant types, especially Super Okra‐leaf plants, had low dry matter partitioning into leaf area. Relative leaf area growth rate of the Super Okra‐leaf plants was 12 to 20% lower than that of the normal‐leaf plants. The leaf area partition coefficient of the Super Okra‐leaf plants was 11 to 17% less than that of the normal‐leaf plants. Values for the Okra‐leaf plants were generally intermediate and frequently not significantly different from normal‐leaf plants. These factors are primarily responsible for the low growth rate of Super Okra‐leaf plants and probably to a lesser extent affect the growth of Okra‐leaf plants in a similar manner.
Evaluation of Soybean Cultivars in Monoculture and Relay Intercropping Systems1
Authors: McBroom R. L. , Hadley H. H. , Brown C. M. , Johnson R. R.
Published: July 2010

Cultivars of soybean [Glycine max (L.) Merrill] were grown in monoculture and in relay intercropping systems at Urbana, Ill. in 1978 and 1979 and at DeKalb, Ill. in 1979 to determine if there is a genotype ✕ cropping system interaction that would require separate breeding programs for maximum progress in developing new cultivars for use in different systems.

Relay intercropped soybeans were shorter, lodged less, and produced lower yields than soybeans grown in monoculture. No significant genotype ✕ cropping system interaction for yield was detected when soybeans were interplanted in small grains [winter wheat (Triticum aestivum L.) or spring oats (Avena sativa L.)] and planted in monoculture on the same day. Early season competition in intercropping was not sufficient in these experiments to cause differential performance among genotypes. Our results suggest that separate breeding programs are not required to develop cultivars for monoculture or intercropping.
Screening Alfalfa Germplasm for Seedling Drought Resistance1
Authors: Rumbaugh M. D. , Johnson D. A.
Published: July 2010

Seeds from open pollination of 1,077 alfalfa (Medicago sativa L.) introductions were tested for the ability of their seedlings to emerge at −6.5 bars of soil water potential in a laboratory environment. Emergent seedlings were then subjected to severe drought stress in a growth chamber as the second part of a two‐stage screening procedure. Morphological data were available from a nursery in Ames, Iowa, where the seeds were produced. Field emergence and seedling survival were measured at Nephi, Utah, during a summer with marked moisture stress for young plants. Medicago sativa L. subsp. sativa seedlings were better able to emerge and survive in the field than were those of other subspecies. Morphological data from Ames were of greater value in predicting field stand and survival than were results on laboratory emergence and growth chamber survival.
Inheritance and Identification of a Carotenoid Pigment in Orange Alfalfa Roots1
Authors: Brick M. A. , Barnes D. K. , Vance C. P.
Published: July 2010

An alfalfa (Medicago sativa L.) plant with orange root tissue was observed while evaluating for root disease resistance. The mode of inheritance and chemical nature of the orange color was investigated. Crosses were made between the orange‐rooted plant and a normal white‐rooted plant to produce S1, F1, F2, and backcross generations. Chemical analysis of the orange root pigment was conducted to determine its character and concentration.

Genetic studies revealed that the orange root color was controlled by a single recessive gene (or) with tetrasomic inheritance. The orange root phenotype was expressed only in the nulliplex condition. Chemical analysis indicated that the pigment which conditioned the orange root color was poly‐cis‐lycopene. The orange‐rooted genotype contained 107 ÷Mg/g fresh weight of the pigment in the root while the white‐rooted genotype contained only a trace of total carotenoids In the root. The carotenoid types and concentrations in the foliage were similar for both white and orange‐rooted phenotypes.
Reproductive Response of Soybeans to Night Interruption1
Authors: Lawrence B. K. , Fehr W. R.
Published: July 2010

Artificial lights may be used to delay flowering of soybean [Glycine max (L.) Merr.] cultivars. Previous research has suggested that night interruption imposed every other night would delay flowering as much as every‐night interruption. Our objective was to evaluate the reproductive development of cultivars when exposed to night interruption every night compared with exposure every other night. One cultivar of each Maturity Group 00 through V was grown in the field at Ames, Iowa during 1978 and 1979. The four light treatments imposed every night or every other night included illumination with incandescent light from sunset to sunrise, 2300 to 0030 hours, 0030 to 0200 hours, or 0200 to 0330 hours. Control plots were not exposed to artificial light.

The average number of days that reproductive development was delayed beyond the control was twice as great for the every‐night treatments as for the every‐other‐night treatments. Illumination from sunset to sunrise delayed reproductive development significantly more than the treatments of night interruption for 1.5 hours. Night interruption near the end of the dark period (0200 to 0330 hours) delayed reproductive development more than the earlier interruptions.

The results did not support the hypothesis that light treatments every other night would delay reproductive development as much as every‐night interruptions. The lighting regime needed to delay reproductive development will depend on the photoperiod requirements of the cultivars and duration of the delay that is desired.
A Greenhouse Screening Procedure for Root‐Knot Nematode Resistance in Soybeans1
Authors: Hussey R. S. , Boerma H. R.
Published: July 2010

Resistance in soybean [Glycine max (L.) Merr.] root‐knot nematodes is a valuable control measure for reducing losses to this pathogen. Screening only in the field has the disadvantages of seasonal restrictions and lack of uniformly infested soil. The objective of this study was to develop a simple and reliable greenhouse screening procedure. Root‐knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] eggs were grown under supplemental light in the greenhouse. Experiments were conducted comparing different genotypes, inoculum densities, and nematode collections. The similarity between the responses of genotypes to M. incognita in the greenhouse and in field tests indicated that this procedure provides a reliable evaluation of the reaction of soybean to this nematode.
Karyotypic Analysis of Safflower1
Authors: Pillai R. S. N. , Kumar H. , Singh R. B.
Published: July 2010

An efficient squash technique for resolving the somatic chromosomes of safflower (Carthamus tinctorius L.) was developed. It permitted the detailed analysis of the karyotype. The 12 pairs of chromosomes were classified and numbered from 1 to 12 on the basis of their descending order of length, centromere position and presence of satellites. The absolute chromosome length varied from 3.52 to 2.05 μ, the average being 2.90 μ. The arm ratios ranged from 1.25 to 4.50. The centromere was mostly median to submedian, being subterminal in two pairs of chromosomes. There were three pairs of satellite‐chromosomes, the nucleolus being organized by the short arm. A karyotype formula has been suggested.
Translocation Homozygotes in Safflower Identification and Frequency of Chromosomes Involved in the Interchanges1
Authors: Pillai R. S. N. , Kumar H. , Singh R. B.
Published: July 2010

Ten translocation homozygotes in safflower (Carthamus tinctorius L.) were established. The chromosomes involved in each interchange homozygote were identified through karyotype analysis by comparing the relative chromosome length (L%) and arm ratio (Pa‐value) with that of the standard line ‘I.C. 11842’. The chromosomes interchanged were 6‐8 (line 58), 1‐3 (line 66), 3‐12 (line 123), 3‐10 (line 131), 3‐6 (line 153), 4‐6 (line 186), 4‐8 (line 197), 3‐8 (lines 208, 279) and 5‐9 (line 290). The segment interchanges were not random, chromosome 3‐ (satellite‐chromosome) was involved in 6 of the 10 translocations.
Stem and Root Density in Kenaf and Rosselle At Different Harvest Dates1
Authors: Adamson W. C. , Minton N. A.
Published: July 2010

Since low density is one of the problems facing the potential new pulp crops kenaf (Hibiscus cannabinus L.), and roselle (H. sabdariffa L.), field work was initiated to measure density of different parts of roselle and kenaf entries at different times in the harvest season. In a 2‐year test involving a fiber‐type roselle (A59‐56), a root‐knot (Meloidogyne spp.), resistant kenaf (j‐1‐113), and a root‐knot susceptible kenaf (‘Everglades 71’), the density of stems and roots was found to decline from stem and root tips to the base of the plant, with the exception of Everglades 71 which showed no difference in density among sections. Stems and roots of A59‐56 and j‐1‐113 were more dense than those of Everglades 71. Density of stems and roots generally declined with later harvest, but stem‐tip density in the resistant kenaf and roselle increased until the last harvest, an indication of the later maturity of these entries. Density is likely to be a factor if kenaf and roselle cultivars are developed for pulp uses.
Genetics of Resistance to Phytophthora Rot in Soybean Cultivar PI 1714421
Authors: Kilen T. C. , Keeling B. L.
Published: July 2010

The genetics of resistance to phytophthora rot (caused by Phytophthora megasperma Drechs. var. sojae Hildeb.) was studied in the soybean [Glycine max (L.) Merr.] cultivar PI 171442. PI 171442 is the donor of one of the genes for resistance in the cultivar ‘Tracy,’ and is part of a uniform set of soybean differentials used to identify races of the disease‐inducing organism. The results indicate that the dominant gene found in PI 171442 occupies a locus different from Rps1 and Rps2, and that both PI 171442 and PI 86972‐1 have the Rps3 gene for resistance.
Diallel Analysis of the Photoperiodic Response of Maize1
Authors: Rood S. B. , Major D. J.
Published: July 2010

A diallel cross from eight early maturing maize (Zea mays L.) inbreds was used to investigate the inheritance of photoperiodic response and the role of this response in adaptation to high latitudes. Days from emergence to flowering increased for six of the inbreds and all of the hybrids as the photoperiod was increased from 14 to 22 hours. The photoperiodic response was divided into a basic vegetative phase, which is the time to flowering under ideal photoperiod conditions, and a photoperiodinduced phase. The maximum optimal photoperiod was the longest photoperiod at which no photoperiodinduced delay of flowering‐time was observed; the slope of the photoperiod response was the photoperiod sensitivity.

Incomplete dominance for decreased basic vegetative phase (BVP) was observed and an inheritance analysis of BVP produced values for the diallel that were very similar to those obtained previously for flowering‐time in field trials. Heritabilities were high for the basic vegetative phase and low for other photoperiod characteristics. Specific combining ability effects were significant for photoperiod sensitivity and maximum optimal photoperiod; reciprocal effects were not significant. General combining ability (GCA) efffects for the basic vegetative phase were correlated with GCA effects for flowering time from field trials in Alberta. For a photoperiod similar to that of 50° N Lat, the average photoperiod‐induced delay in floweringtime of the diallel hybrids was 1.5 days. Thus, photoperiod is of only minor importance in the developmental adaptation of the early maturing maize genotypes examined as flowering‐time in field trials was closely related to BVP alone.
Yields and Yield Components of Flax, Soybean, Wheat, and Oats Treated with Morphactins and Other Growth Regulators for Senescence Delay1
Authors: Dybing C. Dean , Lay Charles
Published: July 2010

Objectives of this work were to determine (a) effects of regulator‐promoted delay of senescence on seed yield of flax (Linum usitatissimum L.), soybean (Glycine max (L.) Merrill), wheat (Triticum aestivum (L.) em Thell), and oats (Arena sativa L.), and (b) morphological ponents of any such yield response. For flax, delay of leaf yellowing 40 to 60 days after full bloom was negatively correlated with yield for regulator applications made at vegetative, bud, and bloom stages. Postbloom applications of TIBA (9,3,5‐triiodobenzoic acid) or SD‐8339 (N‐(phenylmethyl‐9‐(tetrahydro‐9/‐/‐ pyran‐9‐yl)‐9H‐purin‐6‐amine) delayed canopy yellowing under field conditions without affecting yield. The morphactins chlorflurenol (methyl 2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate) and dichlorflurenol (methyl 2,7‐dichloro‐9‐hydroxyfluorene‐9‐carboxylate) applied postbloom at rates of 95 and 100 g/ha, respectively, consistently delayed senescence of flax. Chlorflurenol significantly enhanced yield in two of six trials; dichlorflurenol increased yield in one of five trials. In spite of morphactin effects prolonging leaf and chlorophyll retention, enhancing shoot growth, and renewing flowering and fruiting, yield effectiveness was sometimes lowered by reduction in size of primary seeds, pre‐harvest loss of primary fruits, and low seed set for secondary fruits. Yield enhancement by chlorflurenol was increased by application of a fungicide.

Senescence delay in soybean caused by chlorflurenol, dichlorflurenol, or BA (6‐benzylamino)purine) did increase yield. Chlorflurenol treatment (500 or 1,000 g/ha) after anthesis increased seed yield of wheat, and dichlorflurenol applied in boot stage at 1,000 g/ha increased yield of oats; rate of senescence was unaltered in both crops.
Effects of Defoliating Pests on Soybean Canopy CO2 Exchange and Reproductive Growth1
Authors: Ingram K. T. , Herzog D. C. , Boote K. J. , Jones J. W. , Barfield C. S.
Published: July 2010

Defoliation during reproductive growth of soybean [Glycine max (L.) Merr.] may significantly reduce yields. The objective of this study was to elucidate the relationships among organism‐induced defoliation, CO2 exchange rates, and reproductive growth in fieldgrown soybean. Soybean (‘Bragg’) plots were sprayed a factorial design with diflubenzuron (0.035 kg a.i./ha) and a benomyl‐maneb mixture (1.12 a.i./ha) on two dates, first at early flowering (5 August) and again at early pod set (19 August). Diflubenzuron application prevented defoliation by velvetbean caterpillar (Anticarsia gemmatalis Hubner). By 12 September, LAI was reduced from 5.5 to 2.8, leaf dry weight from 185 to 110 g/m2, and midday light interception from 94 to 72% in defoliated as compared to non‐defoliated plots. While canopy specific leaf weight (SLW) increased in all treatments during the experimental period, SLW was 1.0 mg/cm2 higher in defoliated than non‐defoliated plots. On 4 September defoliated plots were sprayed with diflubenzuron (0.035 kg a.i./ha) and carbaryl (0.56 kg a.i./ha) prevent further leaf loss.

Canopy CO2 exchange was measured at various photosynthetic photon flux densities (PPFD) to develop photosynthesis light response curves. Net canopy photosynthesis at 1,500 μE·m−2·sec−1 PPFD (PN1500) declined steadily in all treatments during seed growth. PN1500 and plant dark respiration, respectively, were reduced by 6.8 and 3.3 mg CO2·dm−2·hour−1 in defoliated compared to non‐defoliated plots. Soil CO2 efflux rates did not differ significantly (P < 0.05) between treatments. Differences in pod growth rates (7.6 and 9.21 g·m−2·day−1 and yields (434 and 502 g·m−2) between defoliated and non‐defoliated plots, respectively, were attributed to differences in canopy photosynthetic capacity. There was no apparent effect of defoliation on seed growth duration or seed abortion. Rather, yield reduction in defoliated plots was related primarily to slowing of the individual seed growth rate. Balance of carbon flux to seeds showed relationships between instantaneous canopy CO2 exchange measurements and sequential harvest data.
Embryological Analysis of Facultative Apomixis in Panicum maximum Jacq.1
Authors: Savidan Yves H.
Published: July 2010

Eighty apomictic accessions of Guineagrass (Panicum maximum Jacq.) collected mainly in East Africa, and 80 apomictic hybrids from sexual ✕ apomictic crosses, were studied for their mode of reproduction. The objective was to determine to what extent percentage sexuality in facultative apomixis can be modified following hybridization. Apomictic accessions with a high percentage sexual reproduction were observed among biotypes from South Africa and the Antilles. Three of the hybrids also exhibited a high percentage of sexuality, while almost all the others appeared to be obligate or nearly obligate apomicts. The average percentage sexual reproduction observed in apomictic hybrids was 5.6 compared to 8.1 in apomictic accessions. Thus hybridization did not increase sexuality in apomicts of P.maximum.

Embryological analyses appeared to be especially efficient and a rapid means for determining the mode of reproduction in P. maximum. However, because apomixis is essentially obligate or nearly obligate in this species, progeny tests are no less reliable than embryological analyses.

Based on these and previous findings, there is no doubt that apomixis, although facultative, can be easily manipulated in P. maximum.
Classification of St. Augustinegrass1
Authors: Busey Philip , Broschat Timothy K. , Center Barbara J.
Published: July 2010

St. Augustinegrass [S. secundatum (Walt.) Kuntze] varies genetically in many morphological and agronomic traits. The objective of this study was to classify a sample of St. Augustinegrass genotypes. By distinguishing natural groups, a classification would be useful in summarizing the genetic variation. A collection of Stenotaphrum genotypes was classified on morphological and performance traits from field plots and pots. Clustering was based on a standardized data set of 26 characters measured on 94 genotypes. Five groups of St. Augustinegrass were recognized from the cluster diagram. In order of distinctiveness and internal similarity, the groups included: Gulf Coast, Bitterblue, Dwarf, Roselawn‐Floratam, and Miscellaneous. The mean coefficient of determination for 26 characters was 51%. Over 85 % of the classified genotypes could be identified to a specific group by using a key. The taxonomic groups appeared to be natural and corresponded to several distinctive patterns, including geography, chromosome number, and adaptation. Economic characters such as rate of coverage, gray leafspot resistance, blueness of leaves, and overall size differed for various groups, and the classification can serve as a framework of orientation for a breeding program.
Selection Indices for the Improvement of Opaque‐2 Maize1
Authors: St. Martin S. K. , Loesch P. J. , Demopulos‐Rodriguez J. T. , Wiser W. J.
Published: July 2010

The need to improve agronomic and protein and kernel quality characters in opaque‐2 maize (Zea mays L.) mandates consideration of multiple traits in selection. Data from genetic studies in an opaque‐2 maize synthetic were used to calculate selection indices for use in recurrent selection. Grain yield was considered the only trait having explicit economic value. Restricted indices were used to achieve satisfactory gains in kernel hardness, moisture content, and protein content and quality.

The most important traits with respect to achieving the specified selection goals were yield, moisture content, kernel hardness, lysine content, kernel weight, and the degree of light transmission by kernels. Indices incorporating five traits were more efficient in that the addition of a sixth trait contributed very little to expected gains. The most effective combinations of traits for a recurrent selection scheme involving S1 testing were also the most effective for S2 testing and full‐sib testing.

The degree to which gains predicted for an index were dependent on accurate estimates of the population parameters was considered. Indices having weights that implied reliance on indirect rather than direct selection response were not recommended.

Substitution of single‐plant data for data from replicated progeny tests was considered in connection with each breeding scheme. The possibility of increasing the effective selection intensity, given that resources for replicated testing were fixed, by culling individual plants was investigated, but the use of individual plant data did not increase expected gain.

A measure of subjective judgment on the part of the breeder is probably required for the successful application of selection indices to complex problems.
Inheritance of Male Sterility in Safflower1
Authors: Heaton T. C. , Knowles P. F.
Published: July 2010

Genetic male sterility was found in safltower (Carthamus tinctorius L.) plants from USDA Plant Introduction (PI) 253914 from Afghanistan. The male‐sterile character was first observed in progeny of normal plants of PI 253914 that had been treated with colchicine. Male sterility was controlled by a single recessive nuclear gene, ms. Plants that were homozygousf or ms were completely male sterile and were not influenced by cytoplasmic factors. The ms gene did not adversely affect female fertility. Whole plant seed yield of open‐pollinated male‐sterile plants of PI 253914 did not significantly differ from that of adjacent male fertile plants. The number of seeds in open‐pollinated male‐sterile plants was reduced, but individual seeds were larger. Germplasm carrying the ms has been released as UC‐148 and UC‐149.
Catechin and Condensed Tannin Contents of Leaves and Bolls of Cotton in Relation to Irrigation and Boll Load1
Authors: Guinn Gene , Eidenbock Marie P.
Published: July 2010

Water deficit has been shown to decrease insect numbers in cotton, especially Lygus hesperus Knight and Heliothis spp. Condensed tannins have antibiotic activity and have been shown to decrease the feeding, growth rate, and survival of Heliothis spp. Condensed tannins are produced from various catechins, and their concentration has been reported to increase in some plants with various stresses, including drought. Therefore, we measured the catechin and tannin contents of leaves and 4‐day‐old bolls in cotton during irrigation cycles and after the final irrigation. We obtained no evidence that water deficit increases the concentration of extractable catechin or tannin in leaves or bolls. Therefore, other factors must be responsible for the suppression of insect activity in dryland cotton or in irrigated cotton during the dry part of the irrigation cycle. Partial defruiting did increase the catechin and tannin contents of leaves and bolls, suggesting that loss of fruit may cause biochemical changes that contribute to insect resistance.
Heritabilities, Gains from Selection, and Genetic Correlations for Characteristics of Soybeans Grown in Two Row Spacings1
Authors: Weaver D. B. , Wilcox J. R.
Published: July 2010

Heritabilities, gains from selection, and genetic correlations among maturity, lodging, height, and seed yield were calculated and compared for soybeans [Glycine max (L.) Merr.] in 30‐ and 76‐ cm row spacings over 2 years at West Lafayette, Ind. The primary objective was to determine if estimates of genotypic and environmental components of these characteristics that have been obtained in wide‐row spacings are applicable for selection, evaluation, and production in narrow‐row spacings. Experimental genotypes in both Maturity Groups II and III consisted of three adapted cultivars and 37 randomly selected F5 and F6 lines representing typical early generation breeding material.

Heritability estimates and expected responses to selection were similar for both row spacings and all characteristics except seed yield. The absence of a year ✕ genotype interaction for seed yield in narrow rows for both maturity groups resulted in a higher hcritability estimate for yield in narrow than in wide rows. This suggests more efficient selection for seed yield in narrow‐row test plots when selection is based on only 1 year's evaluation. Genotype ✕ row spacing interactions for all characteristics were not significant, and genetic correlations between wide and narrow rows were approximately 1.0, suggesting that genotypes ranked similarly for all characteristics in both environments. It was concluded that there was no penalty for early generation selection and evaluation in wide‐row plots with later evaluation and production in narrow rows.
Association of Volatile Aldehyde Production During Germination with Poor Soybean and Pea Seed Quality1
Authors: Harman G.E. , Nedrow B. L. , Clark B.E. , Mattick L. R.
Published: July 2010

We compared production of volatile aldehyde compounds (VACs) with seed quality as measured by field performance and laboratory germination of groups of selected soybean and pea seed lots. In 1978, we tested a group of four soybean (Glycine max. L.) lots with high levels of seedborne pathogens, particularly Phomopsis sojae Leh.; in 1979 a group of eight soybean lots with low levels of pathogens and high laboratory germination, and also a group of five sublots of pea (Pisum sativum L.) seeds that had been artificially aged (30C and 92% relative humidity for up to 10 weeks) in the presence and absence of storage fungi; and in 1980 ten lots of soybean seed that differed in amounts of seedborne pathogens and in laboratory germination. We found that seedborne microorganisms decreased the amount of VAC production, necessitating a benomyl plus thiram seed treatment before testing VAC levels. VAC production was up to 30‐fold higher in aged than in unaged pea seed lots and 3 to 7‐fold greater in poor than in high‐quality soybean seed lots. In. all years, there was a significant correlation between field emergence of fungicide‐treated seeds and VAC production. Correlations between field emergence of nontreated seeds and VAC production were not always significant at the 5% level, but r values were either large or higher than r values of correlations between laboratory germination and field emergence. VAC production is abundant in seed lots of poor quality and may be a useful measure of seed vigor.
Agronomic and Bread‐Making Performance of Fertile Alloplasmic Wheats1
Authors: Kofoid K. D. , Maan S. S.
Published: July 2010

The wild and cultivated relatives of common wheat (Triticum aestivum L.) that produce fertile alloplasmic lines may provide a large reservoir of cytoplasmic variability for this crop. To determine the effects of alien cytoplasms on agronomic and bread‐making quality performance, 14 alloplasmic lines, each with the nuclear genome of the hard red spring wheat cultivar ‘Selkirk’ and cytoplasm from a species of Triticum L., Alegilops L., or Haynaldia Schur., and the euplasmic control were evaluated at three locations in 1979. In general, the performance of the alloplasmic lines corresponded to the genomic similarity between the cytoplasm and nuclear doner species. Accordingly, lines with cytoplasm from Triticum species were superior to lines with cytoplasm from Aegilops species for days to head, grain yield, and kernels per spike. However, lines with cytoplasm from Aegilops species had more protein and better loaf volume than the Triticum cytoplasm lines.

Among the alloplasmic lines, only days to head differed among the lines with cytoplasm from Triticum. The alloplasmic line with Ae. variabilis Eig cytoplasm was inferior to the average of all other lines with cytoplasm from Aegilops for most of the agronomic traits studied. Differences between lines with cytoplasm from D genome Aegilops species (Ae. squarrosa L., Ae. cylindrica Host and Ae. ventricosa Tausch), and those with cytoplasm from M genome Aegilops species (Ae. uniaristata Vis. and Ae. juvenalis (Thell.) Eig) were found only for days to head and loaf volume. These results indicate a closer relationship among the D and the M‐genome Aegilops species than between these species and Ae. variabilis.

Since agronomic performance was reduced only by the cytoplasms of Ae. variabilis and H. villosa, the other male‐fertile cytoplasms should serve as useful sources to increase the cytoplasmic variability of common wheat.
Evaluation of Vigor Tests in Soybean Seeds: Relationship of Accelerated Aging, Cold, Sand Bench, and Speed of Germination Test to Field Performance1
Authors: Kulik Martin M. , Yaklich Robert W.
Published: July 2010

Laboratory and greenhouse vigor tests and seed size determinations were performed on 144 and 81 seed lots of soybean [Glycinemax (L.) Merr.] in 1975 and 1976, respectively. These consisted each year of the accelerated aging, cold, and the sand bench test. In 1976, the speed of germination test was included.

Results from these tests and seed weight determinations were compared with field emergence data obtained from these same seed lots at two locations (sandy vs. heavy soil) over three dates of planting each year. The accelerated aging, cold, sand bench, and speed of germination tests were significantly correlated with field emergence in both years, with many of the r values greater than 0.7.

Data from vigor tests presented in this paper and in previous reports were used in computing coefficients of determination and linear regression coefficients for the estimation of final emergence. The coefficients of determination indicated that the estimation of final emergence for a group of seed lots within a particular year may be achieved by using the germination‐total live seedlings, from the standard towel, accelerated aging‐normal seedlings, accelerated aging‐total live seedlings, tetrazolium staining‐viable seeds, conductivity/g seed wt., sand bench emergence, cold test emergence and speed of germination‐4 day total tests. Linear regression coefficients were not consistent over years for some of the vigor tests. Those vigor tests with the most consistent linear regression coefficients are suggested for use when estimating potential field emergence over years. The vigor tests with the most consistent linear regression coefficients over years were the cold test emergence, tetrazolium staining‐viable seeds, accelerated aging‐normal seedlings and accelerated aging‐total live seedlings. None of the tests are recommended for predicting field emergence.
Tillering in Barley: Genotype, Row Spacing, and Seeding Rate Effects1
Authors: Simmons Steve R. , Rasmusson Donald C. , Wiersma John V.
Published: July 2010

Production of tillers and their subsequent survival are important events in growth and development of barley (Hordeum vulgare L.) that affect the number of spikes produced per unit land area. Studies were conducted at St. Paul and Crookston, MN to evaluate tiller production, tiller mortality, and yield of 10 barley genotypes with different tillering capacities. In addition, these studies evaluated the influence of row spacing and seeding rate on tillering.

The genotypes differed significantly in shoot and spike number. Shoot number for the highest tillering genotype was 42 to 71% greater than for the lowest, depending on the study, but the genotypes ranked consistently over years and locations. The high tillering genotypes tended to form tillers more frequently at the coleoptile node, in the axil of the third leaf, and from the primary tiller in the axil of the first leaf on the main shoot. In general, absolute shoot mortality (difference between maximum shoot number and spike number) was higher in the high tillering genotypes. Genotype M72‐269 was an exception to this generalization in having high shoot number and low shoot mortality.

Row spacings of 7.5 and 15 cm had more shoots per unit area than the 30 cm spacing. However, narrower rows also had higher shoot mortality which led to similar spike numbers for the three row spacings. Higher seeding rates of 101 and 134 kg ha‐1 increased shoot number and spike number compared to the 67 kg ha‐1 rate. Changes in row spacing and seeding rate did not differentially affect shoot production or absolute shoot mortality among the genotypes.

Grain yields of both low and high tillering genotypes were as high or higher than those of intermediate tillering cultivars. The extremely high and low tillering genotypes were not consistent in their yield performance at Crookston, suggesting a possible association between tillering capacity and yield stability. Small stem diameter and a tendency to lodge were characteristic of the high tillering genotypes. Identification of apparent genetic diversity for tiller mortality provides material for further study of the relationship between tiller mortality and yield.
Genetic Variability and Relationships of Physical Grain‐Quality Traits in the BSSS Population of Maize1
Authors: Johnson D. Q. , Russell W. A.
Published: July 2010

The objective of this research was to determine the potential for selection of maize (Zea mays L.) genotypes that are superior for resistance to kernel breakage and to evaluate the relationships among several kernel characteristics affecting grain quality. Eighty random inbreds and 40 of their single‐cross hybrids were grown at two locations in 1976 to 1979. Data taken included date of anthesis, endosperm type, harvest moisture, Stein breakage test, 300‐kernel weight, 300 kernel volume, specific gravity, and a Fast Green dye test. The combined analysis of variance for inbreds and hybrids indicated highly significant differences among genotypes for all traits. Heritability estimates (entry mean basis) were relatively high for all traits (77 to 87%), except for specific gravity (39%). The estimated variance component for genotype ✕ environment was significant for all traits, but the relative magnitude was 25% to 58% as large as the estimate for genotype. Breakage‐resistant genotypes tended to have smaller flinty‐type kernels. Inbred‐hybrid correlations were calculated for the midparent values with their hybrid progeny. Correlations for an inbred trait with the same trait of the hybrid were relatively large (r = 0.54 to 0.79). Endosperm type (r = 0.34) and 300‐kernel weight (r = 0.53) of parents may predict resistance to breakage in hybrids. Selection differentials showed a restricted selection index controlling seed size would most likely improve resistance to kernel breakage.
Variability for Quality and Agronomic Traits in Forage Sorghum Hybrids1
Authors: Pedersen J. F. , Gorz H. J. , Haskins F. A. , Ross W. M.
Published: July 2010

The variation among 49 F1 forage sorghum [Sorghum bicolor (L.) Moench] hybrids from a 7 ✕ 7 cross‐classified design was explored in 1979 and 1980 for the following traits: dry matter (DM), crude protein (CP), in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL). Differences were found among hybrids for all traits. Parental means for males generally had a wider range of variation than for females. The means of hybrids involving the male parent, ‘White Collier’, were highest in IVDMD, and lowest in NDF, ADF, and ADL.

IVDMD was the only trait that showed significant differences among hybrids averaged over both males and females. General combining ability (GCA) effects were more important than specific combining ability effects.

Our results suggest that the most rapid way to improve forage sorghum quality would be by improving IVDMD. Significant differences among hybrids averaged over both male and female parents were shown for this trait; it was affected relatively little by year effects and exhibited high GCA effects.
Amount of Outcrossing on Different Male Steriles of Rice1
Authors: Azzini L. E. , Rutger J. N.
Published: July 2010

The amount of outcrossing on three short stature male steriles of rice (Oryza sativa L.) was studied when planted in alternate rows with pollinators constituted of a mixture of tall cultivars. The seed set observed on the ‘Calady’ and ‘Earlirose’ genetic male steriles was very poor, indicating that neither can be considered useful in hybrid seed production or population improvement. The ‘Bit‐Co’ cytoplasmic male sterile source showed average seed set of 5.4% in 1978 and 32.5 % in 1979. The higher seed set in 1979 apparently was due to better synchronization of flowering of male and female plants. Some selfing occurs in this source, amounting to 3.5% in 1979.