bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Recurrent Restricted Phenotypic Selection Increases Bahiagrass Forage Yields1
Authors: Burton Glenn W.
Published: July 2010

This paper describes the restrictions that make improved recurrent restricted phenotypic selection (RRPS) more efficient than mass selection for increasing Pensacola bahiagrass forage yields. Eight cycles of RRPS have given a consistent first‐year space‐plant forage yield increase of 16.4% per cycle. Cycle 6, compared with commercial Pensacola bahiagrass as the control, yielded 91% more in the spaced‐plant‐progress test and 84% more in a seeded small‐plot test. Cycle 4 yielded 16% more liveweight gain than the control in a 3‐year replicated grazing trial which was expected based on forage yields from a small plot clipping test. In a seeded test, Cycle 6 yielded two‐thirds as much as F1 hybrid 2 × 3 in the first year and almost as much as the hybrid in the unusually dry second year. In vitro dry matter digestibility of the forage was not reduced by six cycles of RRPS. Improved RRPS allows one cycle per year and is four times more efficient than ordinary mass selection in increasing bahiagrass yields.
Nodulation of Soybean Cultivars with Rhizobium spp. and their Response to Inoculation with R. japonicum1
Authors: Pulver E. L. , Brockman F. , Wien H. C.
Published: July 2010

The effect of inoculation with R. japonicum on nodulation, plant growth, and yield of diverse soybean [Glycine max (L.) Merr.] cultivars was studied in Nigeria and Tanzania. Experiments were conducted on soils not previously cropped with soybean. Local cultivars from Nigeria and Indonesia nodulated with indigenous Rhizobium spp. at two sites in Nigeria. Inoculation with several strains of R. japonicum occasionally increased nodule mass of the local cultivars but seldom plant growth or yield. In contrast, U.S. bred cultivars nodulated poorly without inoculation. Large increases in growth and yield were obtained when the U.S. cultivars were inoculated. Similarly, cultivars bred and selected in Tanzania were compatible with native Rhizobium spp.; whereas Bossier (U.S. origin) did not nodulate unless inoculated. The local cultivars used in these experiments were promiscuous and recognized Rhizobium ssp. that were ineffective on U.S. bred material. However, the local cultivars have low yield potentials due to poor agronomic characters. In contrast, the cultivars of U.S. origin are agronomically superior but require inoculation with R. japonicum to realize their yield potential. A breeding program based upon transferring the promiscuous character of some local cultivars to improved U.S. material could produce varieties that do not require inoculation with R. japonicum and still produce high yield.
Hybrid Vigor and Combining Ability in a High‐Low Yielding, Eight‐Parent Diallel Cross of Soft Red Winter Wheat1
Authors: Bitzer M. J. , Patterson F. L. , Nyquist W. E.
Published: July 2010

A high‐low, eight‐parent diallel cross of soft red winter wheats (Triticum aestivum L. em. Thell.) was grown in hills to study hybrid vigor and combining ability for three components of grain yield and grain yield, using moderately diverse parents which varied in yielding ability. Diversity was based on plant type and parentages of the eight cultivars and lines. All were adapted for production in Indiana. Four parents were low in yield and four were high. This design provided 6 hybrids from low × low crosses, 16 from low × high, and 6 from high × high.

Hybrids with grain yields which were significantly above that of the higher parent occurred infrequently, but such hybrids did occur in each crossing group. Heterosis above the midparental value was about 30% for low × low crosses, 25% for low × high crosses, and 19% for high × high crosses. Hybrid vigor for yield in low × high crosses was not significantly different from that in like by like crossing groups.

The preponderance of the variability for yield components and grain yield was attributed to general combining ability. Successful hybrid wheats will most often come from high × high crosses because of the preponderance of general combining ability effects in wheat.
Evaluation of Resistance in Soybeans to Soybean Mosaic Virus Strains1
Authors: Cho Eui Kyoo , Goodman Robert M.
Published: July 2010

Virulent strains of soybean mosaic virus (SMV) cause a severe necrotic disease in soybeans [Glycine max (L.) Merr.] possessing resistance to less virulent SMV strains. Forty‐six soybean cultivars or lines thought to possesss resistance to at least one SMV isolate were tested for reactions to seven SMV strains. Five lines developed in Korea (Suweon 86, Suweon 94, Suweon 95, Suweon 97, and Suweon 106) were immune to all seven SMV strains. The other accessions tested produced either systemic necrosis or mosaic symptoms in response to infection with one or more of the virus strains; 28 of these possessed resistance to some but not all strains.
Water Deficits and Mineral Uptake in Rice1
Authors: O'Toole J. C. , Baldia E. P.
Published: July 2010

Water deficits result in decreased gas exchange between plant leaves and the atmosphere. Decrease in transpiration from water stressed plant leaves is well known; however, the relationship of transpiration to uptake of N, P, and K during water stress is less well documented. Rice plants (Oryza sativa L.) were grown in containers and subjected to water stress. Soil and plant water potential, transpiration rate, leaf area, dry wieght, uptake of N, P and K and atmospheric evaporative demand were monitored over an 18 day drying period. Decreased transpiration rate was the most sensitive variable to water stress. Transpiration of the stress treatment differed significantly from control plants when soil water potential was in the range −0.02 to −0.15 MPa. Dawn leaf water potential, alternately used to estimate soil water potential, was between −0.06 and −0.25 MPa when transpiration and N, P and K uptake of stressed plants deviated from control plants. Although extrapolation of container experiments must be done with care, our results show transpiration and nutrient uptake to be highly correlated during the development of even mild soil and plant water stress. However, interpretation of results, even in this simple system, is complex. The linear and curvilinear relationships among elements of the soil‐plant‐atmosphere continuum are discussed as aides in interpretation of results.
Reference Sets of Genotypes and Selection for Yield in Unpredictable Environments1
Authors: Fox P. N. , Rosielle A. A.
Published: July 2010

The concept of using a reference set of wheat (Triticum aestivum L.) cultivars to monitor genotype × environment interaction and to position each environment relative to a breeding target was introduced. Techniques were examined for weighting trial information based on the similarity of trials to the target. These techniques were compared with selection based on mean performance before and after discarding trials with high coefficients of variation. Two weighting procedures based on distance measures were studied, namely canonical correlation and pattern analysis. Pattern analysis seemed superior but improvement compared to selection based on unweighted mean performance was marginal. The techniques may warrant further investigation for larger data sets and with a more restricted range of genetic diversity than used in this study.
Grain Yield of Two Synthetics of Corn after Seven Cycles of Selection for Lodging Resistance1
Authors: Thompson D. L.
Published: July 2010

Two synthetics of corn (Zea mays L.), that had undergone seven cycles of recurrent selection for lodging resistance, were evaluated for grain yield in crosses with two relatively unrelated testers. The combined regression of grain yield on selection cycles indicated a yield reduction of 0.34 q/ha per cycle in tester crosses or a reduction of 4%. The individual regressions for each synthetic averaged over both testers indicated a reduction of 0.38 for Syn 8 and 0.31 q/ha per cycle for Syn 9. Although there were significant yield reductions resulting from selections for lodging resistance, the reductions did not appear unduly detrimental because the reductions were minimized in hybrid combination with unrelated testers. The improvement attained for lodging resistance in these synthetics should not seriously limit future progress in breeding for increased grain yield.
Influence of Seedling Age and Duration of Vernalization on Flowering of Cicer Milkvetch1
Authors: Townsend C. E.
Published: July 2010

Although most plants of cicer milkvetch (Astragalus cicer L.) require vernalization before flower induction, information is lacking on the influence that seedling age and duration of the chilling period have on receptivity to the vernalization stimulus. Therefore, treatments involving these two factors were evaluated to determine their effect on the flowering process. The influence of date of transplanting to the field in the spring on subsequent flowering also was investigated. In all studies the seedlings were from six polycross progenies that represented a wide range for date of flowering during the seedling year. Five to 6 weeks of exposure to 5 C night/20 C day temperatures in an environmental chamber provided excellent vernalization for seedlings in the 9th‐leaf stage of development. Six to 8 weeks of chilling provided good to excellent vernalization for seedlings in the 5th‐leaf stage of growth. However, flowering following 3 weeks of vernalization at the 5th‐leaf stage was poor. Flowering following 7 weeks of vernalization at the primary‐leaf stage and at the 3rd‐leaf stage was relatively poor, also. Flowering in the greenhouse without vernalization was exceptionally poor in the autumn, but was somewhat better in the spring. Flowering of seedlings in the 9th‐leaf stage was much better when the vernalization treatment included a dark period than when the vernalization treatment had continuous light. Progenies differed significantly in their response to the vernalization treatments. Their chilling requirements ranged from slight to considerable. Percentage of plants flowering and date of flowering in the seedling year were significantly correlated with date of transplanting to the field in the spring.
Breeding Low‐Tannin Sericea. I. Selecting for Resistance to Rhizoctonia Sp.1
Authors: Donnelly E. D.
Published: July 2010

A severe epiphytotic of a foliar disease caused by Rhizoctonia sp. occurred in nursery plants of sericea lespedeza [Lespedeza cuneata (Dumont) G. Don], in a breeding program to develop a low‐tannin cultivar. From approximately 6,000 low‐tannin nursery plants, 82 were selected that were free from disease symptoms. Most S1 progenies of these plants proved to be susceptible in a field test; however, some appeared highly resistant. There was a close association in reaction of low‐tannin lines to the fungus between 2 years. Tannin content of low‐tannin lines was correlated with disease severity: as tannin decreased, disease severity increased. However, results indicated that tannin in low‐tannin lines accounted for only 18% of the variation in disease severity. The remaining 82% apparently was caused by one or more genes for resistance other than the one major gene for tannin. No disease was observed on high‐tannin lines. The high‐tannin control cultivar had twice the tannin content as the mean of low‐tannin lines.
Inheritance of Resistance to Fusarium Wilt in Alfalfa1
Authors: Hijano E. H. , Barnes D. K. , Frosheiser F. I.
Published: July 2010

Fusarium wilt caused by Fusarium oxysporum f. sp. medicaginis is an important disease of alfalfa (Medicago sativa L.) which has not been studied genetically. In our study the inheritance of resistance was determined for two unrelated alfalfa germplasm sources. Alfalfa clones, ranging from resistant to very susceptible, were selected from both winterhardy and nonhardy germplasm sources. One set of six parents from each germplasm source was crossed in a complete diallel design with reciprocals. In addition, each parent was selfed and testcrossed onto a susceptible clone. Selected crosses also were made between parents from different germplasm sources. Progenies from all generations were grown simultaneously in the greenhouse for 10 weeks, then inoculated and transplanted into the field. Plants were rated for disease severity three months after transplanting. Qualitative genetic analyses indicated that resistance in both the winterhardy and the nonhardy germplasms was controlled by two genes, a dominant gene (FW1) and an incompletely dominant gene (FW2). Phenotypic recurrent selection should increase Fusarium wilt resistance in most alfalfa populations.
Compensation against Ineffective Nodulation in Soybean1
Authors: Singleton P. W. , Stockinger K. R.
Published: July 2010

Two cultivars of soybean [Glycine max (L.) Merr.] were inoculated with nine ratios of ineffective (SM‐5) and effective (CC709) strains Rhizobium japonicum. Plants were grown in the greenhouse and harvested after 33 days. Nitrogenase activity, total shoot N, nodule number, nodule mass, and the proportions of nodules formed by each strain were determined. Nodules were identified serologically by the fluorescent antibody technique. Significant increases in total N in the shoot occurred as both the proportion and number of nodules formed by effective strain CC709 increased. Shoot N was highly correlated with nitrogenase activity and nodule mass. The relationship between percent effective nodules and shoot N was nonlinear so that 95% of maximum N accumulation was obtained when only 75% of the nodules (on a nodule number basis) were effective. The average size an effective nodule was at least 2.5 times larger than an ineffective nodule and their average weight increased from 2.38 to 4.88 mg/ nodule as the proportion of effective nodules declined from 100 to 18.8%. The proportion of total nodule tissue that was effective was greater than the corresponding percent effective nodules. This compensatory mechanism tended to keep the amount of effective nodule tissue constant up to a point even though the proportion of effective nodules declined. There was a deleterious effect on N2 fixation only when infection by the ineffective strain was great enough to reduce total nodule mass.
The Effects of Genes Controlling Barley Leaf and Sheath Waxes on Agronomic Performance in Irrigated and Dryland Environments1
Authors: Baenziger P. S. , Wesenberg D. M. , Sicher R. C.
Published: July 2010

Epicuticular waxes have been associated with drought tolerance in numerous species. Several barley, Hordeum vulgare L., mutants have been identified that alter, generally lessen, epicuticular leaf and sheath waxes. These mutants have been used to study the biochemistry of leaf and sheath wax synthesis, however, they have not been examined for agronomic performance in droughty environments. Fourteen isolines and cultivars were grown in three irrigated and three dryland environments to determine the effect of barley leaf and sheath wax mutants on agronomic performance in irrigated and dryland environments. The irrigated environments had significantly greater yields and 1,000 kernel weights, but were not significantly different for test weight and kernel plumpness. A significant irrigated vs. dryland by cultivar interaction was found only for yield. No mutant isoline was significantly better than its normal counterpart for any of the agronomic traits measured in either the irrigated or dryland environments. Some of the mutant genes were deleterious as their isolines were significantly inferior to their normal counterpart in both the irrigated and dryland environments. Photosynthetic measurements made in a growth chamber were similar for the mutant isolines and their normal counterparts and were unable to explain the observed field inferiority of the mutant isolines.
Performance of Four Sources of Breeder Seed of ‘Vantage’ Reed Canarygrass1
Authors: Rincker C. M. , Carlson I. T.
Published: July 2010

Similarity in genetic composition of breeder seed lots produced in different years or locations is required for stability of forage crop synthetic cultivars during seed increase. The main objective of this study was to determine whether breeder seed of ‘Vantage’ reed canarygrass (Phalaris arundinacea L.), produced in two geographical locations in two different years, were similar in agronomic characteristics. Polycross progeny from each parent clone produced in isolated crossing blocks at Ames, Iowa and Prosser, Wash. in 1973 and 1974 were evaluated in space‐planted field experiments at both locations. Plants produced from the breeder seed from the four seed sources were similar in anthesis date, plant height and panicle production. Polycross progeny of the six parent clones differed significantly in performance for those traits. Performance was positively correlated with previously published parental clone performance for each trait. We concluded that Vantage breeder seed produced at either location could be used as reliable planting stock for the production of foundation seed.
Variability of Morphological and Agronomic Traits in Eastern Gamagrass Accessions1
Authors: Wright L. S. , Taliaferro C. M. , Horn F. P.
Published: July 2010

Eastern gamagrass, Tripsacum dactyloides (L.) L., may have potential for use as a grazed or stored forage if problems with establishment and stand persistence can be reduced and if its nutritive value is high enough to justify the relatively intense management that will likely be necessary for sustained production. In 1979 and 1981, 51 gamagrass accessions, primarily from Texas and Oklahoma were studied in detail near Perkins, Okla. in order to characterize the magnitude of phenotypic variability among them for several agronomic and morphological traits. Most of the accessions had been collected in Texas and Oklahoma. The traits studied were: spring vigor, anthesis date, leaf width, plant height, percent seed set, regrowth vigor, and percent in vitro dry matter digestibility (IVDMD). The IVDMD determinations were made for four sampling dates in 1979 and one sampling date in 1981. The first three 1979 samplings were at intervals of 4 weeks on progressively older plants. The fourth sampling in 1979 and the 1981 sampling were of 5‐week old regrowth following a uniform mowing of the nursery. There were highly significant differences (P < 0.01) among the accessions for all traits during each of the 2 years. Years constituted a significant source of variation (P < 0.01) for spring vigor, anthesis date, regrowth vigor, and IVDMD of regrowth forage. Accessions differed significantly (P< 0.01) in IVDMD at each of the four sampling dates in 1979 and the accession by sampling date interaction for IVDMD was also significant(P < 0.01). Accession by year interactions were significant (P < 0.01) for spring vigor, anthesis date, percent seed set, and regrowth vigor. The only partial correlation coefficients that were significantly different from zero were those for vigor of spring growth vs. vigor of regrowth (during both years and for the 2‐year mean), and vigor of spring growth vs. plant height (in 1979 and for the 2‐ year mean). The magnitudes of the ranges among accessions were relatively large for all the traits studied, indicating a wide array of variability that might be used in the genetic manipulation of the species.
Relationships Among Three Genes Conferring Specific Resistance to Rust in Soybeans1
Authors: Hartwig E. E. , Bromfield K. R.
Published: July 2010

This study was conducted in containment facilities to further elucidate the genetic basis of specific resistance to Phakopsora pachyrhizi Syd. (incitant of soybean rust) among three soybean [Glycine max (L.) Merr.] lines previously reported to each have a single dominant gene conferring resistance. F4 lines, D79‐9690 and D79‐9697, each having rust resistance derived from PI 230970, were crossed with PI 462312 (‘Ankur’) and PI 200492, respectively. The cross PI 462312 ✕ PI 200492 also was made. F2 populations and selected F3 lines were evaluated for their reactions to two soybean rust isolates, Taiwan‐72‐1 and India‐73‐1. For each plant tested, a leaflet of a single trifoliolate leaf was inoculated with the Taiwan rust isolate and another leaflet was inoculated with the India isolate. PI 230970 and the two breeding lines D79‐9690 and D79‐9697 gave a resistant reaction to both isolates. PI 462312 gave a resistant reaction to the India isolate and PI 200492 an immune reaction to that isolate, but both were susceptible to the isolate from Taiwan. Our results confirmed previously published reports that each soybean line carried a single dominant gene for resistance and demonstrated that each gene was at a different locus. The genotypes for rust reaction assigned to the three parental types were: PI 200492, Rpp1 Rpp1 rpp2 rpp2 rpp3 rpp3; PI 230970, rpp1 rpp1 Rpp2 Rpp2 rpp3 rpp3; and PI 462312, rpp1 rpp1 rpp2 rpp2 Rpp3 Rpp3
Performance of Near‐Isogenic Genotypes of Rice Differing in Growth Duration. I. Yields and Yield Components1
Authors: Van Dat Tran , Peterson M. L.
Published: July 2010

The yields of the full‐season (approx. 160 days) rice (Oryza sativa L.) cultivar Calrose 76 was compared with a spontaneous mutant from it identified as ED7 which has an 18‐day shorter vegetative growth period when both are sown in early May. The mutant ED7 is less sensitive to photoperiod than Calrose 76. The objective was to determine the effect of a shorter vegetative period on yield and yield components. Field trials were conducted in an environment having cool temperatures both early and late in the growing season. Cold nights about 2 weeks prior to heading can induce floret sterility. Under these conditions, ED7 yielded significantly more than Calrose 76 for both early (11 May) and later (21 May) sowings with the later sowing trial yielding significantly more than the earlier one. Calrose 76 yielded significantly more from the early than the late sowing thus resulting in a highly significant interaction between genotypes and sowing dates. Yield component analysis disclosed that ED7 had significantly higher 100‐grain weights, and fewer sterile florets than Calrose 76 for the later sowing. Cool night temperatures appeared to adversely affect Calrose 76 causing more sterility in the late‐sown trial and incomplete grain filling. Increased N fertilizer rates significantly increased grain yields, LAI, and panicles/m2, but decreased 100‐grain weights, and percent fertile florets. The genotype with shorter vegetative growth period (ED7) was more efficient in this cool environment.
Relationship Between Tillering and Forage Yield of Tall Fescue. II. Pattern of Tillering1
Authors: Zarrough Khames M. , Nelson C. J. , Coutts J. H.
Published: July 2010

Several reports suggest that cool‐season grasses produce few tillers in midsummer, but few studies have been conducted to simultaneously measure rates of tiller initiation and tiller death. To evaluate the role of tillering in yield differences among tall rescue (Festuca arundinacea Schreb.) genotypes, live and dead tillers were counted weekly during the growing season. Genotypes were selected for low (LYT), medium (MYT), and high yleld/tiller (HYT), and in plant studies they exhibited a high, medium, and low rate of tillerlng, respectively. A mathematical technique was developed to estimate equilibrium tiller density, i.e., the density where appearance of new tillers occurred at the same rate as other tillers died. Three separate field experiments were established by vegetatively propagating the genotypes and allowing them to develop into sward‐llke conditions. In two experiments cutting heights of 5 and 10 cm above‐ground level were compared, and in one experiment, plants of birdsfoot trefoil (Lotus corniculatus L.) were grown in mixture with the genotypes to evaluate genetic effects on competitive ability of the grass component. Plants were harvested four times and remained in a vegetative condition throughout the growing season. Live tiller density increased until early summer after which it decreased and then increased again in fall. Decline in summer was due to an increased death rate as well as a decreased initiation rate. The LYT genotype had the highest rate of tillering and developed the highest tiller density at equilibrium, about 31, 35 and 44 vegetative tillers/dm2 for Exp. I, II, and III, respectively, whereas the HYT genotype maintained the lowest density of about 16, 16, and 30 vegetative tillers/dm2, respectively. The MYT genotype was intermediate in all experiments. Death rate of tillers was also highest in the LYT genotype and lowest in the HYT genotype. Cutting height had little effect on tillering pattern or density. The reasons why the HYT and MYT genotypes did not reach the same tiller density as the LYT genotype are unclear.
Photosynthesis and Growth of Bermudagrass Swards. I. Carbon Dioxide Exchange Characteristics of Swards Mowed at Weekly and Monthly Intervals1
Authors: Morgan J. A. , Brown R. H.
Published: July 2010

Bermudagrass (Cynodon dactylon L. Pers.) is a highly productive subtropical species widely grown in the southern United States for pasture and hay. This work was undertaken to determine the response of CO2 exchange rate (CER) of the canopy to photosynthetic photon flux density (PPFD) and to leaf area index (LAI) as influenced clipping frequency. An experiment was conducted during the growing season on an established sward of ‘Coastal’ bermudagrass. One series of plots was mowed to a height of 6 cm every week and another series every month. Quadrats, 0.25 m2 in size, were hand harvested weekly to ground level to estimate phytomass yields and LAI. Carbon dioxide exchange rates were measured weekly over a wide range of PPFD with a chamber technique. The response of CER of bermudagrass canopies to PPFD followed a rectangular hyperbola with the curves becoming more linear and maximum CER increasing as LAI increased. Rates at near full sunlight (2,000/μmol‐2 sec‐1 PPFD) w ere about 9.5 g m−2 hour−1 for plots with the highest LAI. Dark respiration rates of the canopy plus soil ranged from 1.3 to 1.9 g m−2 hour−1 and were not influenced by LAI. Optimum LAI was 4.7 at 1,600‐2,000 μ m−2 sec−1 PPFD; the critical LAI (95% PPFD interception based on a canopy PPFD extinction coefficient of 0.62) was 4.8. Swards mowed weekly had much lower CER than plots mowed monthly, except just after the monthly mowing when LAI was low and the treatment effect was reversed. For weekly‐mowed plots LAI usually ranged from 1 to 3, whereas on monthly‐mowed plots LAI ranged from near zero to 6.5. Lower CER of swards mowed weekly was attributed mostly to the lower LAI, although at comparable LAI values CER was also lower in weekly mowed plots. Plants in weeklymowed plots had lower dark respiration rates and lower initial slopes of the light response curves than monthly‐mowed plants. These observations confirm the lower productivity often reported for frequently harvested grass swards and indicate the cause to be low LAI.
Photosynthesis and Growth of Bermudagrass Swards. II. Growth Patterns as Estimated by Harvest and Gas Exchange Techniques1
Authors: Morgan J. A. , Brown R. H.
Published: July 2010

Yield of ‘Coastal’ bermudagrass [(Cynodon dactylon (L) Pers.)] is reduced by frequent mowing. A field experiment was conducted to examine the influence of mowing frequency on dry matter yields and compare growth patterns estimated by harvest and CO2 exchange techniques. Plots were mowed either monthly (6 weeks in one cycle) or weekly from 20 June to 1 October. Dry matter yields, leaf area index, and CO2 exchange rates of the canopy (CER) were measured each week and dry matter accumulation was compared to estimates made from CER integrated over 24‐hour periods and summed over sampling intervals. Yields of total phytomass during the experimental period were 2,115 and 770 g m‐2 for plants cut monthly and weekly, respectively. Corresponding estimates from CER were 1,612 and 698 g m‐2. Lower leaf area indices and photosynthetic photon flux density (PPFD) interception in weekly‐ than in monthly‐cut plots largely accounted for the lower yields and CER. However, plants cut weekly also exhibited lower CER than plants cut monthly at equivalent PPFD interception values. The lower CER (per unit of intercepted PPFD) for plants cut weekly was attributed to accumulation of older leaves below the mowing height, whereas nearly all leaves were removed by monthly mowing. The methods used for measuring CER and predictions of growth from such measurements may be useful in studying carbon balance in grazed pastures.
Variability in Rooted Stem Production among Tall Fescue Genotypes1
Authors: D'Uva P. , Bouton J. H. , Brown R. H.
Published: July 2010

Rooted stems (both rhizomes and stolons) have been observed tall rescue, Festuca arundinacea Schreb., but variation in this characteristic has not been studied. Rooted stem number and length and plant area were determined for 24 genotypes at Athens, Ga., on a Cecil sandy clay loam soil (clayey kaolinitic, thermic Typic Haplu dult), and at Americus, Ga., on a Redbay sandy loam soil (fine loamy siliceous thermlc Rhodlc Paleudults). There was no genotype ✕ location interaction for rooted stem number or length. Significant differences were found among the tall fescue genotypes in number and length of rooted stems and plant area (measured at soil surface). Positive correlations were obtained between plant area and rooted stem number and length. The variability in rooted stem production and the high degree of development of this character in some genotypes indicates its potential use in breeding tall rescue for better adaptation in marginal areas or for turf usage.
Inheritance of the H1, H2, and Sm2 Genes in Cotton1
Authors: Endrizzi J. E. , Ramsay G.
Published: July 2010

Based on early genetic studies of inter‐ and intra‐specitlc crosses in cotton, the genes for increased plant pubescence, H1 and H2 are independently inherited. More recent studies with aneuploids of Gossypium hirsutum L. showed that the H1 and H2 genes and the Sm2 gene (that removes trichomes from the plant) all are located on chromosome 6, and that the H2 and Sm2 are located in the long arm of the chromosome. The H2 gene was mapped 4 units from the centromere. Based on the latter data, the three genes may either be closely linked or alleles. In this study, we used aneuplolds to show that the H1 and Sm2 genes also are located 4 map units from the centromere in the long arm of chromosome 6. In addition to the cytogenetic approach, we also studied the F2 populations of the three crosses of H1 ✕ H2, H1 ✕ Sm2, and Sm2 ✕ H2 and found that the three genes segregated as alleles. In view of these results, a revised nomenclature for the smooth‐halriness genetlcal system in cotton is needed.
Genotypic Variation for Glycinebetaine Accumulation by Cultivated and Wild Barley in Relation to Water Stress1
Authors: Ladyman J. A. R. , Ditz K. M. , Grumet R. , Hanson A. D.
Published: July 2010

The accumulation of betaine (glyclnebetalne, N,N,N‐trimethylglycine) in barley (Hordeum vulgate L.) during water stress may be of adaptive value. The objective of this research was to evaluate the variability for betalne level among genotypes of H. vulgare and H. spontaneum C. Koch in preparation for a physiological‐genetic assessment of the adaptive value of betaine accumulation. Betaine was determined using either a pyrolysis/gas chromatographic method or a periodide spectrophotometric assay, specially modified for screening. In controlled environment tests, 339 genotypes were grown to the four‐leaf stage under well‐watered conditions and analyzed for shoot betaine level; 145 of these were also tested under water‐stressed conditions. There were significant differences for betaine level among genotypes, both without and with water stress (approximate ranges of betaine levels: 10 to 40 μmol/g dry wt in well‐watered conditions; 35 to 90 μtmol/g dry wt under stress). The betaine levels of stressed plants were significantly correlated with those of unstressed plants of the same genotype. Thirteen H. vulgare cultivars which were high and low accumulators in controlled environments were grown in the field under simulated dryland conditions and betaine was analyzed in the upper leaves. At the ear emergence stage, significant variation for betaine level was observed among cultivars although there were no significant differences in their water status. Those cultivars that accumulated either high or low levels of betaine in controlled environments accumulated respectively high or low levels in the field, the correlation among cultivars in the two environments was highly significant (r = 0.71). These results indicate that genotypic variability for betaine level is expressed in both controlled environments and in the field, and that this variability is unlikely to be due solely to variability for water status. Physiological‐genetic studies of the adaptive role of betaine may thus be possible.
Cytological Examinations of Two Tall Fescue Genotypes and Their Sterile Hybrids1
Authors: Beuselinck P. R. , Vasquez R. M. , Frakes R. V. , Chilcote D. O.
Published: July 2010

Hybrids between two fertile accessions of tall fescue, Festuca arundinacea Schreb., (PI 234906, from Switzerland, and PI 174209, from Turkey) were highly sterile, with indehiscent anthers and negligible seed set (<0.01%). Both parents and the hybrids had 2n = 6x = 42 chromosomes, without gross karyotypic variation or appreciable meiotic irregularity. The parents differed in number of secondary constrictions (8 in PI 174209 and 10 in PI 234906), indicating potential for cryptic structural hybridity in the F1 hybrids. Although the frequency was low, the hybrids also had signficantly more univalents per cell than their parents (0.72 vs. 0.31 and 0.14). Since meiotic irregularities did not seem to account for the hybrid sterility, we believe it may be under genic, probably sporophytic, control.
Karyotypic Analysis of Lens ervoides Brign1
Authors: Sindhu J. S. , Slinkard A. E. , Scoles G. J.
Published: July 2010

A karyotype analysis of five accessions of Lens ervoides Brign. was done to assist in determining phylogenetic relationships within the genus Lens. There were no differences in gross chromosomal morphology of the different lines. The diploid chromosome number was 14 and the total chromosome length was 42.9 μ. The karyotype was characterized by four submetacentric and three acrocentrlc chromosome pairs. The fifth longest chromosome pair carried a conspicuous secondary constriction. The karyotype formula was: K(n = 7) = 3 Sm + 1 Sm Sc + 3 Acro. A karyogram and idiogram were prepared to assist in further phylogenetic studies. The karyotype of L. ervoides is similar to that of the cuhlgen L. culinaris Medik., suggesting that speciation involved chromosomal rearrangements that left minimal evidence in the karyotype.
Recurrent Selection for Grain Yield in a Maize Population1
Authors: Mulamba N. N. , Hallauer A. R. , Smith O. S.
Published: July 2010

Mass selection for improved grain yield was conducted in the ‘Krug’ (BSK) maize (Zea mays L.) population. Effectiveness of 14 cycles of mass selection for grain yield in BSK was measured in nine environments using the original (CO) and the even‐numbered cycles of selection (Cn) as populations per se and two sets of testcrosses (Cn ✕ CO and Cn ✕ B73). Unselected S1 lines derived from the original, the 14th cycle of mass selection, and the eighth cycles of half‐sib and S1 progeny selection were evaluated in four environments to estimate the effect of the three recurrent selection procedures on genetic variability and on grain yield improvement of S1 progenies per se. Linear response per cycle of mass selection for grain yield was obtained for the populations per se (0.024 ± 0.009 Mg ha−1) and testcrosses with the CO population (0.026 ± 0.010 Mg ha−1) and B73 (0.028 ± 0.010 Mg ha−1). Average yield response to mass selection in BSK per se was 0.49% per cycle or 6.9% after 14 cycles of mass selection. Increased yield was accompanied by later flowering, increased root and stalk lodging, increased grain moisture at harvest, and higher ear placement. The mass selection methods we used for improving grain yield in BSK apparently require modification to include selection for other agronomic traits, but such modifications would increase the complexity of mass selection and perhaps reduce gain for yield. Estimates of genetic variability among S1 progenies for grain yield showed a decrease in genetic variance for the S1 and half‐sib derived populations for most traits and no change for the mass‐selected population.
Effect of Half‐Sib and S1 Recurrent Selection for Increased Grain Yield on Allozyme Polymorphisms in Maize1
Authors: Kahler A. L.
Published: July 2010

Allozyme frequencies at nine enzyme loci were monitored over eight cycles of selection for grain yield with the half‐sib (HT) and S1 progeny methods in maize (Zea mays L.) population ‘Krug BSK.’ Allozyme frequencies generally weres table over cycles in the presence of repeated small population size and high ~10% selection intensity. The average amount of genetic polymorphism for the nine enzyme loci was not different from the original population after the eight cycles of HT and S1 recurrent selection. Simple linear regression suggested the possibility of directional selection for changing allozyme frequencies at locus Peroxidase 1 (Prx1) in HT selections and loci Alcohol dehydrogenase 1 (Adh1), Malate dehydrogenase 2 (Mdh2), Acid phosphatase 1 (Acp1), and Prxl in S1 selections. However, more precise chi‐square analyses indicated that directional selection alone could not account for the observed allozyme frequency changes for any of the enzyme loci studied. It is concluded that stabilizing selection or random genetic drift associated with restriction of population size when lines were chosen to advance to the next cycle, or perhaps these two factors combined with undetected (because of small populatlon size) super imposed directional selection, can account for the observed allozyme frequency changes in the BSK populations studied.
Kinetics of Tall Fescue Leaf Elongation: Responses to Changes in Illumination and Vapor Pressure1
Authors: Parrish David J. , Wolf D. D.
Published: July 2010

When measured at high resolution, elongation of tall fescue (Festuca arundinacea Schreb.) leaves is shown to be rapidly and highly responsive to step changes in illumination and atmospheric water potential. Furthermore, elongation rates are seen to be quite unstable under presumably constant conditions; sharp fluctuations and rhythmic oscillations are often observed when no external changes are imposed. The diurnal pattern of leaf elongation (15/9 hour day/night, 25 C) displayed higher nighttime rates, a sharp burst of growth at the beginning of the dark period, and a temporary depression of growth at the beginning of the light period. Lag times for responses to changes in illumination were 5 to 6 min. A decrease in vapor pressure deficit from 1.7 kPa to 0.3 kPa resulted in a nearly immediate (<1 min lag time) acceleration of leaf elongation rate. The response to increased vapor pressure was seen in the light and dark. Plants growing in the light and at vapor pressure deficits of around 1.7 kPa frequently exhibited growth oscillations. The frequency of the oscillations in elongation rates ranged from 2 to 3 cycles cycles hour−1, and the amplitudes ranged from 0.05 to >1 mm hour−1. Concurrent measurements of transpiration and carbon exchange revealed those two processes to be cycling at the same frequency; however, they were out of phase with elongation. Leaf elongation was at or near a cyclic maximum when transpiration and photosynthesis were at a cyclic minimum. It is argued that leaf elongation rate is, a priori an indicator of the flux of water into the cells that drive leaf expansion. Only changes in leaf water status, as modulated by stomata and vapor pressure deficits, could account for the observed rapid, reversible, and rhythmic changes in elongation/water flux. The results suggest that tall fescue leaf elongation is frequently limited by leaf water status, even in well‐watered plants and that stomatal movement and leaf extension are modulated within a common range of leaf water potentials.
Simultaneous Selection for Yield and Resistance to Brown Stem Rot of Soybean in Hill Plots1
Authors: Ertl D. S. , Fehr W. R.
Published: July 2010

The yield of soybean [Glycine max (L.) Merr.] grown in row plots can be reduced by brown stem rot [caused by Phialophora gregata (Allington and Chamberlain) W. Gams]. Our objective was to evaluate the effectiveness of simultaneous selection among soybean lines for yield and resistance to brown stem rot in hill plots planted on soil infested with the causal organism. Ninety‐six random F4‐derived lines from an intermated population were grown in three replications of single, unbordered hill plots on four fields infested with P. gregata and on four uninfested fields. Selection for yield alone was not effective in identifying lines with a low percentage of stem browning. The correlation between yield and percentage of stem browning (r = −0.19) was not significant. Twenty‐three of the 48 lines with the highest average yield had below‐average resistance to brown stem rot. There was a high correlation for yield of the 96 lines on infested and uninfested soil (r = 0.80, P <0.01). When hill plots are used to determine the yield potential of soybean lines, resistance to brown stem rot should be evaluated independently by growing the lines on infested soil and splitting stems to determine the extent of infection. Evaluation of yield potential in hill plots can be done equally well on infested and uninfested soil.
Comparisons among Pollen Viability Measurement Methods in Cotton1
Authors: Barrow Jerry R.
Published: July 2010

Methods for measuring pollen viability were compared to determine their relative value in evaluating cotton (Gossypium hirsutum L.) pollen. Pollen was treated at constant temperature of 30, 33, 35, 37, 40, and 43°C for 15 hours prior to anthesis. Treated and untreated pollen were evaluated using several common techniques. Pollen killed at the highest temperature (43°C) stained readily with a cytoplasmic stain indicating that stains of this type may determine pollen maturity, but not viability. Pollen treated at 33 to 40°C responded positively to vital staining and germinated both on artificial media and on the stigma while pollen treated at 43°C did not. However, pollen fertility (as measured by pollen tubes penetrating the lower style and ovules) was severely reduced at 33°C and absent at 35°C. The best available criterion for pollen fertility appears to be tube penetration into the lower style or ovules. Staining and pollen germination methods are not accurate indicators of pollen fertility in cotton.
Anatomical Basis for Seed Shattering in Kleingrass and Guineagrass1
Authors: Burson Byron L. , Correa Jairo , Potts Howard C.
Published: July 2010

Anatomical studies of abscission layer development in kleingrass (Panicum coloratum L.) and guineagrass (P. maximum Jacq.) were conducted to determine the sequential histogenesis of the abscission layers which lead to seed shattering and to relate layer development to identifiable morphological stages of developing inflorescences. Two different abscission layers were present in each species. A primary layer was located in the pedicel near the base of the glumes, and a secondary layer extended across the rachilla which supports the fertile floret. The primary layer became histologically identifiable at the early boot stage of floral development in both species but was initiated earlier in guineagrass. By anthesis, cells in this layer were fully developed. Primary layer cell disintegration started 8 to 9 days after anthesis in kleingrass and continued until the spikelet was eventually attached to the pedicel only by the epidermal and vascular cells. Spikelet disarticulation normally occurred by the 14th day after anthesis in kleingrass. In guineagrass, the same progression of events accounted for seed abscission but they occurred over a shorter time span with shattering occurring 10 days after anthesis. The secondary abscission layer was not identifiable until the inflorescences had emerged from the leaf sheaths in both species. The layer consisted of a thin layer of oblong parenchyma cells extending across the rachilla. By anthesis the cells near the outer edge of the layer became sclerified and the sclerification process continued inwardly until abscission occurred 12 to 15 days following anthesis. The abscission mechanism at this layer was assumed to be mechanical, because there was no evidence of cell disintegration. The major contributor to seed shattering in both species was the primary abscission layer. In kleingrass, 81% of the seed shattered at the primary layer and 19% at the secondary layer.
Measuring Racial Differentiation in Maize Using Multivariate Distance Measures Standardized by Variation in F2 Populations1
Authors: Martinez W. Orlando J. , Goodman Major M. , Timothy David H.
Published: July 2010

Thirty F2 maize (Zea mays L.) populations were studied to evaluate the use of various statistical distance measurement between parents, relative to their F2 populations, and to estimate racial differentiation between maize races. The parental and F2 populations, obtained from crossing 47 maize races, were grown at Raleigh, N.C., or Homestead, Fla., as appropriate to their adaptation. Five morphological characters of the ear were measured. Six statistical procedures were utilized to measure racial divergence: Euclidean distance, Mahalanobi's distance, generalized distance, modified generalized distance, approximate Dempster's distance, and Dempster's distance. The relationship among the measures, their advantages in geometrical representation, and their facility of computation were discussed. The degrees of relationship estimated were in general agreement with previous studies based on classical taxonomic methods and multivariate analyses. These results suggest that morphological studies of racial F2 populations can be useful in understanding the variability and relationship among maize races.
Root Effects on Cotton Growth and Yield1
Authors: Carmi Avner , Shalhevet Joseph
Published: July 2010

The growth of cotton (Gossypium hirsutum L.) plants and the distribution of assimilates between their vegetative and reproductive organs were strongly affected by their root zone volume. Reduction of root growth resulting from growing the plants in small pots was accompanied by a considerable decrease in vegetative growth and an increase in the proportional accumulation of dry weight in the reproductive organs. The rate of vegetative growth, characterized by shoot weight and stem length, was positively correlated to the root zone volume which was limited by using pots of 2, 5, 10, or 25 L capacity. The ratio in dry weight of seed cotton to vegetative organs increased as the shoot growth decreased. Restriction of the root growth led to the development of a compact plant, characterized by short internodes, fewer leaves, and high ratios in dry weight of bolls to vegetative organs. Such a plant may be useful in increasing yields in dense canopies. Analyses of N, P, and K in the shoot, as well as measurements of water potential and stomatal resistance in the leaves, showed no significant differences between plants grown in different root zone volumes. It was concluded that the differences in growth rate were not caused mainly by N, P, K deficiency or by water stress, but were due to the differences in development of the root system as affected by the pot capacity.