bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of Heat Tolerance during Pod Set in Cowpea
Authors: Marfo K. O. , Hall A. E.
Published: July 2010

The productivity of cowpea (Vigna unguiculata (L.) Walp.] can be reduced substantially by hot weather during flowering. Inheritance and heritability of tolerance to heat during reproductive development were studied to develop efficient methods for breeding improved cultivars. Heat tolerant (‘Prima’ and TVu 4552) and heat sensitive (Barnbey 23, ‘Magnolia’ and 7964) cowpea genotypes were chosen for studies of heat tolerance during pod set under hot long days. Parental genotypes, F1, F2 and backcross progenies were evaluated under field conditions in the Imperial Valley of California during the summers of 1987 and 1988, and heat‐tolerant and heat‐sensitive F2's were selected in 1987 and evaluated as F3 families in 1988. Average daily minimum and maximum air temperatures were 24 and 43 °C, respectively, and the photoperiod decreased from 14 h 31 min to 13 h 20 min during flowering. Individual plants were scored for average number of pods per peduncle and plants with ≥ 1.5 (the mean of the value for the most tolerant parent and the average value for the sensitive parents) were classified as heat tolerant. Analyses of pods per peduncle and proportions of tolerant plants for F1, F2, and backcross populations indicated that heat tolerance is conferred by a single dominant gene in both Prima and TVu 4552. Narrow‐sense heritability obtained from variance components was 0.26. Comparison of pods per peduncle of F2 plants with their F3 families from crosses between heat‐tolerant and heat‐sensitive parents gave a realized heritability of 0.27. The low values for heritability were due to large environmental effects on pods per peduncle. Incorporating heat tolerance during pod set into other genetic backgrounds will require family selection in advanced generations to ensure that the trait is fixed, and, to partially overcome selection difficulties caused by environmentally induced variation.
Inheritance of Resistance to Stagonospora Leaf Spot in a Dillel Cross of Orchardgrass
Authors: Berg Clyde C. , Sherwood Robert T. , Hill Richard R.
Published: July 2010

Purple leaf spot of orchardgrass (Dactylis glomerata L.) caused by Stagonospora arenaria (Sacc.) Sacc. is prevalent and damaging in the northeastern USA. Most plants in existing cultivars are moderately to highly susceptible, but an occasional plant is resistant. This study was undertaken to examine the inheritance of resistance in a 10‐parent diallel cross involving five susceptible and five resistant parent plants selected from cycles 0 to 3 of a program on phenotypic recurrent selection for resistance. Parents, F1 single‐cross progeny, and their reciprocals were rated for lesion size and leaf coverage in two greenhouse inoculation experiments and during two natural epidemics in a field planting. A least squares analysis for a general diallel showed significant effects for general combining ability (GCA) and specific combining ability (SCA) for lesion size and leaf coverage. Sums squares for GCA were > 10 times larger than those for SCA indicating that additive genes were the major genetic component of resistance, but that nonadditive effects were also involved. Disease scores (high scores indicated susceptibility) of progeny from crosses of susceptible × susceptible, resistant × susceptible, or resistant × resistant parents were often greater than the midparent mean scores suggesting that there was some nonadditive dominance for susceptibility. Small, but significant, maternal effects were detected in the greenhouse experiments, and small reciprocal effects other than maternal effects were detected in the field. Two parents showed high susceptibility in the greenhouse, but intermediate susceptibility in the field. The GCA effects of these two parents were strong in the greenhouse, but weak or nonsignificant in the field indicating that these two parents and their progeny were environmentally unstable for resistance. Recurrent selection procedures that utilize additive effects would be the logical approach to developing resistant lines.
Genetic Variance Component Estimation in a Nested Mating Design with Positive Assortative Mating, and Application to Maize
Authors: Gouesnard Brigitte , Gallais André
Published: July 2010

Negative estimation of genetic variance components can arise in a nested mating design. This may be due to inaccurate estimates, experimental problems, sampling error, or failure of the assumptions of the genetic or statistical models. We examined the effect of assortative mating on male and female variance components (σ2M and σ2F, respectively) in a nested mating design. Two correlation coefficients were introduced to quantify the effect of assortative mating: the correlation coefficient between females mated to the same male (r) and the correlation coefficient between male and female (r′). Under positive assortative mating, additive variance is systematically overestimated and dominance variance is underestimated. If there is a correlation among females mated to a male but no correlation between male and female (r′ = 0, r ≠ 0), the additive variance is overestimated by 4 r σ2F and nonadditive variance is underestimated by 8 r σ2F. To investigate the presence of assortative mating in a nested design, expressions of correlations among parents were given as a function of the estimated components of variance and of the type of gene action. Correlations among parents were estimated utilizing experimental data for various traits in maize (Zea mays L.) from which negative estimates of dominance had been obtained. Estimates of r were positive and high for earliness traits indicating assortative mating relative to earliness, which may in part explain negative dominance variance estimates. However, correcting variance components estimates is difficult when genetic variation of the trait is not strictly additive.
Resistance to Iron‐Deficiency Chlorosis in PI 437654 Soybean
Authors: Mansur Levi
Published: July 2010

Breeding soybean [Glycine max (L.) Merr.] cultivars for resistance to both the soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) and Fe‐deficiency chlorosis (IDC) is an important objective for growing soybean on some calcareous soils. PI 437654 has the highest level of SCN resistance known in soybean; our objective was to investigate its level of IDC resistance. For this purpose, PI 437654 was evaluated along with eight soybean genotypes, including the highly resistant A13 and the highly susceptible T203. The test was conducted on calcareous Harps soils (fine‐loamy, mesic Typic Calciaquolls) at Ames, IA, in 1989, and at Ames and Humboldt, IA, during 1990. The IDC symptoms were visually rated on the scale 1 = no yellowing to 5 = severe yellowing and some necrosis. T203 had an average score of 4.9 and A13 had an average score of 1.4. PI 437654 had an average score of 1.7. Thus, PI 437654 is a good source for resistance to Fe‐deficiency chlorosis as well as soybean cyst nematode.
Inheritance of a Diterpene Constituent in Tobacco Trichome Exudate
Authors: Nielsen Mark T. , Severson Ray F.
Published: July 2010

Altering the levels of α‐ and β‐duvatrienediols (DVTs), diterpene constituents of trichome exudate, could enhance pest resistance and organoleptic properties of tobacco (Nicotiana tabacum L.). A field study was conducted in 1990 and 1991 to determine the inheritance of DVTs in three tobacco genotypes varying in DVT concentration. KDH 959, which has very low levels of DVTs, was used as a parent in crosses to ‘KY 14’, TI 1068, and KDH 960. The parents, Fl's, and segregating generations from these three crosses were grown in the field. Either DVT concentration or presence of DVTs on the leaf surface was determined using gas chromatography or thin layer chromatography. Results indicated qualitative and quantitative components of DVT inheritance. Segregation ratios suggested that KY 14 and KDH 960 each have a single gene controlling DVT production, but the available F2 data from the cross involving TI 1068 did not fit the expected ratio for a single gene. Broad‐sense heritability estimates for the concentration of DVTs were 0.69 for the two crosses involving KY 14 and KDH 960 and 0.38 for the T.I 1068 cross. These results suggest that selection for DVT concentration would be effective and may be an indirect means to alter pest resistance, flavor, and aroma of tobacco.
High Molecular Weight Glutenin Subunit Composition of Cultivars, Germplasm, and Parents of U.S. Red Winter Wheat
Authors: Graybosch Robert A.
Published: July 2010

Variation in high molecular weight (HMW) glutenin subunit composition is related to genotypic variation in wheat (Triticum aestivum L.) end‐use quality. No systematic survey of the HMW glutenin subunit composition of U.S. winter wheat has been conducted. The HMW glutenin subunit composition of 291 U.S. winter wheat cultivars, parental lines, and advanced experimental lines was determined by sodium dodecylsulfate‐polyacrylamide gel electrophoresis (SDS–PAGE). The most frequently observed subunits differed between soft red winter wheat (SRWW) and hard red winter wheat (HRWW). Most common subunits among SRWW were 1 (Glu‐A1), 7 + 8 (Glu‐B1), and 2 + 12 (Glu‐D1) and, among HRWW, 2* (Glu‐A1), 7 + 9 (Glu‐B1) and 5 + 10 (Glu‐D1). Examination of frequencies of subunits as a function of year‐of‐release (or introduction) revealed increases in the frequencies of subunits 7 + 9 and 5 + 10 in SRWW, and increases in the freqnencies of subunits 2*, 7 + 9 and 5 + 10 in HRWW. Decreasing frequencies of subunits 2 + 12, in SRWW, and subunits 1 and 2 + 12, in HRWW, were observed over time. The observed frequencies of deleterious (in terms of end‐use quality) and neutral alleles suggest the present HMW glutenin subunit frequencies are more dependent on random factors than on selection for enhanced quality characteristics.
Pollination Bags Affect Wheat Spike Temperature
Authors: Ball Shane T. , Campbell Gaylon S. , Konzak Calvin F.
Published: July 2010

Although breeders use pollination bags routinely in their crossing programs, the effect of pollination bag materials and sizes on wheat (Triticum aestivum L.) spike temperature has not been determined. Some bag materials may trap heat, like a miniature greenhouse, allowing spikes to reach lethal temperatures on hot days. The objectives of this study were to evaluate the effects of pollination bag types on wheat spike temperature, and to compare temperature estimates from an energy budget with measured values. In one field experiment, notable differences were detected in spike temperatures when dialysis tubing or white onion skin typing paper covered the emasculated (simulated) wheat spikes. The measured temperature differences between these pollination bag types were 2 to 3.5 °C at noon on clear days. The dialysis bag consistently produced the highest spike temperatures. Maximum spike temperatures were 6 °C above air temperature for bagged spikes. A second field experiment measured larger differences in spike temperature among five types of pollination bags. Measured spike temperature was highest with a glassine bag and lowest with a bag of white onion skin typing paper wrapped around the spike. Maximum differences at noon on clear days between these pollination bags were 4 to 6 °C, and maximum spike temperatures inside bags were 8 °C above air temperature. Such high temperatures could by physiologically damaging when air temperatures are high. Estimates of spike temperature using an energy budget model were similar to measured values. Both measured and modeled results show that the lowest spike temperatures will occur when a white, small‐diameter pollination bag covers the wheat spike.
Five Years of HOPE: The Hierarchical Open‐Ended Corn Breeding System
Authors: Cramer Michael M. , Kannenberg Lyndon W.
Published: July 2010

The hierarchical, open‐ended corn (Zea mays L.) breeding system (HOPE) is designed to enhance genetic diversity and breeding potential by continually introgressing a wide range of germplasm into breeding populations concurrently subjected to increasingly stringent recurrent selection procedures. This research evaluated the response to selection after 5 yr. The HOPE breeding system involves two heterotic (A and B) sets of four open‐ended populations based on a hierarchy of performance: elite (E), high (H), intermediate (I), and low (L). The 5 yr of selection included two cycles of reciprocal recurrent selection (RRS) at the E level, five cycles of modified ear‐to‐row (ME) selection at the H and I levels, and five cycles of stratified mass selection at the L level. Selection was for performance index (PI) = grain yield ÷ grain moisture. About 90% of the 408 introductions added to HOPE during this period were to the L level. In EA, RRS reduced grain moisture 2.7% per year relative to CO; this was offset by a decrease in grain yield of 3.2% per year. In EB, PI and grain yield increased by 2.0 and 2.7% per year, respectively. In the cross EA × EB, only grain moisture was improved. At the H level of performance, ME selection produced increases of 2.8 and 4.6% per year for PI, 1.4 and 6.9% per year for grain yield, and −0.9 and 1.8% per year for grain moisture, relative to C0, in HA and HB, respectively. At the I level, ME selection improved PI by 3.2% per year and reduced grain moisture by 2.2% per year in IA relative to C0. In IB, only grain moisture was improved. At the L level, mass selection increased PI by 4.0 and 2.1% per year and reduced grain moisture by 2.2 and 1.0% per year relative to C0 in LA and LB, respectively. Five years of HOPE resulted in genetic gains, suggesting that selection in open‐ended populations, arranged in a hierarchical structure, is a viable breeding strategy.
Milling and Baking Quality Attributes of Soft Red Winter Wheat Bulk Populations and Derived Lines
Authors: Bruckner Philip L. , Finney Patrick L.
Published: July 2010

Little information is available concerning relationships between milling and baking quality of soft red winter (SRW) wheat (Triticum aestivum L.) bulk populations and quality of lines derived in subsequent generations. Experiments were conducted to determine if quality evaluation of F4 bulk populations could provide useful information on quality potential of F5 lines. This would allow SRW wheat breeders using bulk systems of generation advance to develop appropriate selection strategies. Fifty‐eight F4 SRW wheat bulk populations were grown at Plains, GA, in 1988–1989. Milling and baking quality of each population was evaluated at the USDA‐ARS Soft Wheat Quality Laboratory. Random F4:5 headrows from eight populations with diverse F4 bulk quality characteristics were grown in 1989–1990 at Tifton, GA, and similarly evaluated for milling and baking quality. Except for flour protein concentration, quality attributes of F4 bulk populations were signficantly correlated with means of F5 lines derived from each population. Bulk populations with quality deficiencies produced higher proportions of lines with similar quality deficiencies. Higher proportions of lines with adequate and superior quality were identified in progenies of bulk populations having good quality. Milling and baking qualities of F5 lines derived from populations with only 50% SRW wheat parentage were more variable and less predictable based on F4 bulk evaluation than quality of F5 lines derived from populations of 100% SRW wheat parentage. Milling and baking quality of F4 bulk populations was indicative of the quality and potential of F5 lines derived from each bulk. Bulk evaluation could be used to cull lowquality‐potential populations before line derivation.
Recurrent Selection for Increased Grain Yield in Oat
Authors: Pomeranke Gary J. , Stuthman Deon D.
Published: July 2010

Grain yield is a primary consideration in choosing oat (Avena sativa L.) cultivars. This research examines gain from five cycles of recurrent selection for grain yield in oat, and compares the yield responses when evaluated in hill and row plots. A secondary goal was to examine the yield components that contributed to the yield gains in the two plot types. Parents of all five cycles of recurrent selection and the checks ‘Don’, ‘Hazel’, ‘Moore’, ‘Noble’, ‘Ogle’, ‘Starter’, and ‘Steele’ were grown in hill and row plots in 1988 and 1989 at St. Paul and Rosemount, MN. Experimental design for both experiments was a randomized complete block and data were recorded on grain yield (g m−2), seed weight (g 100 seed−1) and seed number (seed m−2). Grain yield gain per cycle, as measured by weighted linear regression, was 15.1 g m−2 in hill plots and 12.8 g m−2 in row plots. Examination of the yield components seed weight and seed number indicated that the grain yield gain resulted from an increase in both traits. The relationship between seed weight and seed number was numerically different in the two plot types, with seed weight showing a larger increase per cycle in row plots and seed number a larger increase per cycle in hill plots. Phenotypic correlations of parent performance in the two plot types were 0.85 for grain yield, 0.81 for seed weight and 0.69 for seed number (P < 0.01). The large gain in grain yield per cycle and the excellent agreement in performance of the parents of all five cycles in hill and row plots indicate the effectiveness of recurrent selection in oat.
Silicon, Disease Resistance, and Yield of Rice Genotypes under Upland Cultural Conditions
Authors: Winslow Mark D.
Published: July 2010

Silicon deficiency limits rice (Oryza sativa L.) yield on highly weathered upland soils in West Africa and can increase susceptibility to some diseases. A study at Onne, Nigeria, examined responses of different genotypes to increasing Si supply under upland cultural conditions. Without applied Si, average shoot Si concentration was one‐fifth of the minimum recommended value for rice, confirming deficiency. Application of 18.7 g Si m−2 as sodium metasilicate doubled plant Si concentration and increased grain yield by 48%, and significantly reduced the severity of husk discoloration, neck blast, sheath blight, and leaf scald diseases. When grown in flooded paddies on the same soil at Onne, and on a more fertile Alfisol at Ibadan, mean leaf Si concentrations were two to three times greater than in Si‐treated upland plots, and diseases were negligible. Under upland cultivation, African japonica upland rice genotypes had 50 to 100% higher Si concentration in mature flag leaves, and were more resistant to husk discoloration and neck blast, than Asian indica upland genotypes. The japonicas were equally susceptible to leaf scald, however, and more susceptible to sheath blight than the indicas. It is concluded that increasing the supply of Si to the crop through flooding is the most effective method of ameliorating Si deficiency. Where this is not practical, genes for higher Si content can probably reduce losses to some diseases, but other genetic factors seem also to have major effects.
Interactions between Carbon Dioxide and Water Deficits Affecting Leaf Photosynthesis: Simulation and Testing
Authors: Grant Robert F.
Published: July 2010

Atmospheric CO2 concentration is known to have contrasting effects on photosynthesis, particularly in C3 plant species. These effects may be produced mathematically through the combination of a biochemically based submodel of CO2 fixation in leaf chloroplasts with a physically based submodel of CO2 and H2O diffusion through leaf surfaces and atmospheric boundary layers. Water‐deficit effects may be represented in both submodels. The behavior of a combined model was tested against data recorded under atmospheric CO2 concentrations of 330 and 660 μmol mol−1 in the Soil—Plant—Atmosphere Research Units at the University of Florida. The model reproduced changes in the quantum requirements of CO2 fixation and in diurnal CO2 fluxes of soybean [Glycine max. (L.) Merr.] leaves at these different concentrations. Simulated CO2 fixation at midday responded more to increased CO2 concentration at high irradiance (22.9 vs. 42.0 μmol m−2 s−1 at 1050 μmol m−2 s−1) than at low (17.1 vs. 19.7 μmol m−2 s−1 at 330 μmol m−2 s−1), as found experimentally. Under water deficits (leaf water potential ψl = −1.55 MPa), light saturation of CO2 fixation occurred at lower irradiance, again consistent with experimental findings. Interaction between the water deficit effects in each submodel allowed the combined model to simulate a higher sensitivity of CO2 fixation at 660 μmol mol−1 (41.1 vs. 19.3 μmol m−2 s−1) than at 330 (22.9 vs. 14.2 μmol m−2 s−1) when ψl was reduced to −1.55n from −0.60 MPa, as observed experimentally. The theoretical basis for CO2 effects on photosynthesis is well established, allowing them to be reproduced with confidence in the absence of water deficits. However, the theoretical basis for water deficit effects on photosynthesis is incomplete, such that the reproduction of CO2 effects on photosynthesis in the presence of water deficits must still be regarded as speculative.
No Evidence of Cytoplasmic Male‐Sterility Systems Influencing Gas Exchange Rate of Sorghum Leaves
Authors: Krieg Daniel R. , Girma Fekade S. , Peng Shaobing
Published: July 2010

The presence of an extranuclear genome in the chloroplast (ctDNA) suggests possible cytoplasmic inheritance of photosynthetic characteristics of leaves. Recent evidence indicated a strong maternal influence on photosynthetic rates (A) of grain sorghum [Sorghum bicolor (L.) Moench] hybrids. Since essentially all commercial grain sorghum hybrid seed production is accomplished using cytoplasmic male‐sterility (CMS), we were concerned about the possible effects of CMS on photosynthetic rates of sorghum hybrids and about potential nuclear—cytoplasmic interactions. The purpose of this experiment was to evaluate the effect of different sources of CMS and potential nuclear—cytoplasmic interactions on photosynthetic rate (A) and stomatal conductance (g) of H2O for sorghum leaves under field and greenhouse conditions. Five sources of male‐sterility‐inducing cytoplasm (A1, A2, A3, A4, and 9E) and a male‐fertile line (B) were compared in a common nuclear background (TX398) to test the effect of source of cytoplasmic genotype on leaf gas exchange parameters. Additionally, eight commonly used sorghum lines with different nuclear backgrounds were used to determine nuclear—cytoplasmic interaction effects by comparing fertile with male‐sterile counterparts. No significant differences were observed among lines with different sources of CMS in a common nuclear background (TX398) for A or g. Significant genetic variation in A and g was observed within the eight lines having different nuclear backgrounds. However, no significant differences were observed in any of the gas exchange parameters between fertile and sterile lines within each nuclear genome. The interaction of cytoplasm with genotype or environment was not significant. Results from this study suggest that the genetic expression of leaf gas exchange rates was not influenced by CMS, nor were there any differences among the sources of CMS.
Cytology of 2n Pollen Formation in Diploid Crested Wheatgrass, Agropyron cristatum
Authors: Ray Ian M. , Tokach Mary K.
Published: July 2010

Hybrids between induced tetraploids of diploid crested wheatgrass, Agropyron cristatum (L.) Gaertn. (2n = 2x = 14), and tetraploid crested wheatgrass, A. desertorum (Fisch. ex Link) Schult. (2n = 4x = 28), have provided improved germplasm with unique agronomic traits. Introgression from diploids to tetraploids would be simplified if diploids that produce 2n gametes (gametes with the sporophytic chromosome number) could be identified. This study was initiated to determine if 2n pollen is produced in diploid crested wheatgrass and to determine the cytological mechanisms of 2n pollen formation. Pollen diameters were investigated by measuring 60 pollen grains from each of 600 diploid and 100 tetraploid genotypes. Pollen diameters averaged 37.9 μm (SE = 0.17) and 41.1 μm (SE = 0.33) for diploid and tetraploid genotypes, respectively, with a range of 35.3 to 41.3 μm among the diploids, and 39.7 to 46.8 μm among the tetraploids. Approximately 16% of the diploid genotypes produced some pollen grains with twice the mean volume of n pollen. Cytological analyses of 17 individuals that produced variable‐sized pollen indicated that 2n pollen was produced via restitution at the second meiotic division. Meiotic abnormalities that could give rise to 2n microspores include i) arrest at metaphase II, ii) lack of sister chromatid movement in anaphase II, iii) movement of all or most sister chromatids to a single pole in anaphase II, and iv) abnormal cytokinesis after telophase II. The formation of 2n pollen in diploid crested wheatgrass should facilitate efficient transfer of germplasm from diploids to tetraploids within the genus Agropyon.
Heading Synchrony and Yield Components of Barley Grown in Subarctic Environments
Authors: Dofing Stephen M. , Knight Charles W.
Published: July 2010

Synchronous heading is an important characteristic of barley (Hordeum vulgare L.) grown in subarctic conditions, in which short growing seasons, cool temperatures, and the potential of early snowfall necessitate timely harvest. Kernels on late‐developing spikes often fail to mature under these conditions, resulting in harvest delay and reduced grain quality. This study was conducted to determine the influence of seeding rate on heading synchrony and yield components of barley grown in subarctic environments. Three spring barley cultivars were evaluated at seeding rates of 22, 65, 108 kg ha−1 at Palmer and Fairbanks, AK, in 1990 and 1991. Heading synchrony was assessed by determining the range and standard deviation for the interval from sowing to spike appearance. for all cultivars at both locations, growing degree days (GDD) to spike appearance had a narrower range and a reduced standard deviation with higher seeding rates. Averaged across cultivars and environments, seeding rates of 22, 65, and 108 kg ha−1 resulted in standard deviations of GDD to spike appearance of 80, 68, and 64, respectively. Earliest maturity was obtained with the 108 kg ha−1 seeding rate, and grain yield was nearly identical to the 65 kg ha−1 rate. Increasing seeding rate from 65 to 108 kg ha−1 caused a greater compensatory decrease in kernels per spike than kernel weight. In similar environments, use of relatively high rates of seeding is recommended to reduce time to maturity, minimize number of late developing tillers, and optimize grain yield.
Alfalfa Yield and Plant Water Relations with Variable Irrigation
Authors: Grimes Donald W. , Wiley Paul L. , Sheesley W. Robert
Published: July 2010

In the arid and semiarid western USA, alfalfa (Medicago sativa L.) grown for forage requires large amounts of water for high productivity. Managing alfalfa to achieve the best possible water‐use efficiency (WUE) is essential for the crop to remain competitive for water supplies both within and outside agriculture. This study was conducted in the San Joaquin Valley of California, to define alfalfa forage yield and plant water relation responses of three alfalfa cultivars (CUF 101, Moapa 69, and WL 318) to contrasting irrigation intensities and establish critical plant water‐status values for irrigation scheduling. A single line‐source sprinkler system provided a variable water supply. The soil was a Hanford sandy loam, silty substratum (coarse‐loamy, mixed, nonacid, thermic typic xerorthent). Maximum total season crop evapotranspiration (ETc) of 1000 mm gave 26.3 Mg ha−1 of hay yield that was similar for the three cultivars. A linear hay yield (Yh)−ETc relationship was defined as Yh = −0.212 + 0.0265ETc (r2 = 0.82). Water‐use efficiency, 23.1 Mg ha−1 dry matter per meter of water used as ETc, was comparable with other C3 species. As midday plant water potential (ψw) declined below −1 MPa, yield reductions were observed for all cultivars. Increased crop water stress index (CWSI) was correlated (r = 0.84) with declining ψw below the −1 MPa yield‐limiting ψw threshold. Absolute values of ψw or CWSI associated with a given yield reduction were cultivar‐dependent; Moapa 69 and WL 318 responded alike, but each differed from CUF 101. Plant‐based water‐status measurements provided a practical and reliable index for assessing the adequacy of supplied irrigation water.
Genetic Analyses of Male Fertility Restoration in Wheat: VI. A Defective‐Seed Gene
Authors: Maan Shivcharan S.
Published: July 2010

Cytoplasmic male sterility (CMS) results from interactions between Triticum timopheevii Zhuk. cytoplasm and genes in the T. aestivum L. nucleus. Euploid plants with CMS genes are believed to exhibit no detrimental characteristics other than male sterility. However, seed viability and plant vigor are reduced in ‘Chris’ monosomics of Group 3. Similarly, a monosomic analysis of L222, an R‐line, showed that it has a defective seed gene (dfs), but dfs could not be linked to a chromosome with the materials and methods used previously. Our objective was to determine the linkage of dfs to a chromosome. Therefore, we compared the number of disomics, monosomics, seed viability, and fertility in F1, F2, and F3 from crosses of L222 with euplasmic and MS Chris monosomics of Group 3. In general, monosomics with reduced seed set produced fewer disomics and more monosomics than the expected 25 and 75%, respectively. Other results indicated that (i) dfs is located on chromosome 3B of L222; (ii) dfs reversed meiotic drive against 21‐chromosome heterosexual gametes or euploid zygotes in euplasmic monosomic 3B and all three CMS monosomics of Group 3; (iii) Rf was epistatic to dfs in L222 and fertile monosomics; (iv) compatibility between 21‐chromosome heterosexual gametes or viability of selfed seed with euploid and nullisomic embryos was reduced; and (v) aneuploid gametes and/or zygotes with misdivision products functioned more often than euploid heterosexual gametes or euploid zygotes.
Heterosis and Combining Ability of CIMMYT's Tropical × Subtropical Maize Germplasm
Authors: Vasal Surinder K. , Srinivasan Ganesan , González F. C. , Han G. C. , Pandey Shivaji , Beck David L. , Crossa José
Published: July 2010

Crossing maize (Zea mays L.) germplasm from different adaptation groups could result in better utilization of hybrid vigor. Such heterotic response is rarely exploited, due to problems in adaptation of some of these exotic materials. This study was conducted to determine the heterosis and combining ability between tropical and subtropical maize germplasm developed at CIMMYT. Six tropical and five subtropical populations were crossed in a Design‐2 mating scheme; the 30 crosses and 11 parents were evaluated in six environments. Data were recorded on days to silk, plant height, and grain yield. Midparent heterosis was calculated for the crosses and general combining ability effects (GCA) estimated for grain yield. The six environments were classified into three mega‐environments: tropical (TR), subtropical (ST), and transition and midaltitude (TM). Days to silk was lowest in TR environments (55.4 d), followed by ST (64.6 d) and TM (71.7 d) environments. Significant differences in grain yield were observed for entries, parents, crosses, and GCA effects under TR and ST environments. The three top‐yielding crosses that also showed high heterosis were Population 43 × Population 42 (7.43 Mg ha−1), Population 32 × Population 44 (8.31 Mg ha−1), and Population 22 × Population 47 (7.97 Mg ha−1) under TR, ST, and TM environments, respectively. Population 43 among tropical germplasm and Populations 42 and 44 among subtropical germplasm showed positive GCA for yield; both are ideal for hybrid development work. Population 47, which involves temperate germplasm, was a good combiner in TM environments. The results demonstrate the considerable potential that exists for improving the yield performance of subtropical germplasm by crossing to tropical materials; for the tropics, introgressing tropical with subtropical germplasm could be used to improve plant type and maturity. The well‐known Tuxpeño × ETO heterotic pattern, observed in many crosses, could be successfully exploited in many of these materials for hybrid development.
Genetics of Qualitative Traits in Pearl Millet: A Review
Authors: Kumar K. Anand , Adrews David J.
Published: July 2010

Pearl millet, Pennisetum glaucum (L.) R. Br., is the principal food cereal on 25 million ha of the drought‐prone semiarid regions of Africa and the Indian subcontinent. It is also used as a forage in Australia, southern Africa, South America, and the USA, and has shown regions. Recent increased levels of breeding and genetic research, now including gene mapping, have indicated a need for a current comprehensive review of accumulated genetic information on qualitative traits in this species. The present decriptive review attempts to meet this need and reports 167 studies. since 1934, on 145 characters in 12 categories: chlorophyll deficiencies, foliage striping, leaf characters, pubescence, plant form, pigmentation, earhead characters, reproductive structures and gamete formation, sterility, seed characters, earliness and maturity, and disease resistance. Gene symbols, where assigned by authors, are listed, and the nature of genetic effects are given. Known linkages and biochemical genetic markers are also reviewed. A comsistent nomenclature system should be developed and followed in the future, and a locaton designated for the deposition of genetic stocks.
Genotype and Genotype × Environment Interaction Effects on Forage Yield and Quality of intermediate Wheatgrass in Swards
Authors: Vogel Kenneth P. , Reece Patrick E. , Nichols James T.
Published: July 2010

Genetic differences among cultivars or strains for specific traits can be significantly reduced or increased by differential genotypic responses to environments. The objective of this study was to determine the relative magnitude of genotype and genotype × environment interaction effects, which are due to differential responses, on forage yield and quality of intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] when grown in seeded swards in the central Great Plains. Thirty‐four strains (genotypes), which included cultivars, experimental strains, and PI lines, were grown in replicated trials at Mead, North Platte, and Alliance, NE. The three sites differed markedly in precipitation and length of growing season. There were significant differences among strains for all evaluated traits. Genotype & location and genotype & year interaction effects were not significant for in vitro dry matter digestibility (IVDMD), indicating that this trait is quite stable across environments. Genotype & location interaction effects were significant for forage yield and protein concentration; genotype & year effects were significant for forage yield. Spearman rank correlations, used to test for consistency of ranking of the strains across environments, were high and significant for IVDMD, but were low and usually not significant for forage yield. Improving IVDMD should be emphasized in intermediate wheatgrass breeding programs, since there is substantial genetic variation for IVDMD, it is stable across environments, and it can improve livestock production per hectare.
Morphological Characteristics Associated with Lodging of Tobacco
Authors: Menchey E. Keith , Aycock Marvin K. , McIntosh Marla S.
Published: July 2010

Production of crops worldwide may encounter varying amounts of damage due to lodging each year. A 2‐yr study was conducted to determine if variability of morphological traits is related to various components of lodging resistance among tobacco (Nicotiana tabacum L) cultivars, and to determine if an efficient method could be developed to screen for lodging resistance. Eleven cultivars, representing four types of tobacco, were evaluated. Top and root fresh weights, top/root ratios (TRR), and root densities were obtained from greenhouse studies. Stalk and flower head traits and three lodging traits were measured in field studies. Artificial wind was generated to induce lodging. Significant variation was observed among cultivars for all traits examined. Phenotypic correlations among the various root, stalk, and flower head traits were not significnt (P ≤ 0.05), except for two flower traits: basal internode length and plant height/basal stalk diameter. No significant correlations between lodging and single morphological traits were found; however, correlations were highly significant among lodging traits. Multiple regression equations predicting severity rating indicated that TRR and basal stalk specific gravity (BSSG) explained 44% of the variation (severity rating = ‐2.36 + 0.66 TRR + 0.12 BSSG). Thus, lodging resistance could be increased by selection for larger root systems and lower BSSG. The amount of genetic variability present in the population and the relationship of TRR and BSSG to severity rating suggest that progress in developing loding resistant material is feasible using artificial wind for screening.
Simultaneous Improvement of Downy Mildew Resistance and Agronomic Traits in Tropical Maize
Authors: De leó C. , Granados G. , Wedderburn R. N. , Pandey S.
Published: July 2010

Downy mildew (DM) of maize (Zea mays L.), caused by Peronosclerospora spp., is a problem in lowland tropics, particularly in South‐east Asia. This study was conducted to measure progress from selection in DM resistance (DMR) and other agronomic traits in four broad‐based tropical maize populations. Selection among and withjin S1 and S2 families was basd on responses in DM nurseries at Suwan, Thailand, and at the University of Southern Philippines Agricultural Research Center (USMARC), Philippines. Bulks of C0, C1, C2, and C3 of the four populations were evaluated for reaction of DM in disease nurseries and for agronomic traits under disease‐free conditions at Suwan and USMARC. Correlations for DMR between Suwan and USMARC, based on C1‐S1 and C3‐S1 progenies of each population, were highly significant, positive in simultaneous and highly significant improvement of levels of DMR (‐11.0% cycle‐1) and grain yield (507 kg cycle‐1) over the four populations.
Flower Production and Honey Bee Density Effects on Meadowfoam See Yield
Authors: Norberg O. Steven , Seddigh Majid , Jolliff Gary D. , Fiez Timothy E.
Published: July 2010

Meadowfoam (Limnanthes alba Hartw. ex Benth. subsp, alba cv. Mermaid) is protandrous and entomophilous. Flower number and phenology, stigma receptivity, and timely honey bee pollination are highly weather dependent and were hypothesized to cause seed yield variation. The objective of this field experiment was to use a synchrony index, which is an estimate of flower receptivity and pollination timing synchrony, to relate variation in seed yield to number of open flowers and foraging honey bee (Apis mellifera L.) density. Transparent floating crop‐cover and shade cloth were used to alter flower number and flower phenology. The soil type was Amity silt loam (fine‐silty, mixed, mesic Argiaquic Xeric Argialboll). Cumulated open flowers and cumulated foraging bee density were derived from daily counts of flowers and foraging honey bees, respectively. Flower receptivity for each day was estimated using maximum air temperature for that day. Number of receptive flowers for each day was multiplied by the number of foraging bees for that day and summed for the bloom period to form cumulated synchrony index. A multiple regression model (R2 = 0.47, P < 0.001) indicated a linear positive association of seeds per flower with cumulated foraging bee density, and a quadratic negative (within the experiment range) association with cumulated open flowers. A simple linear regression explained 87% (P < 0.001) of the variation in seed number per area by difference in cumulated synchrony index. This confirms the importance of pollination timing, foraging honey bee activity, and total number of flowers for achieving high seed and oil yields and emphasizes the need for careful managemenat nd monitoring of these variables.
Growth Analysis of Corn Grown With or Without Starter Fertilizer
Authors: Bullock Donald G. , Simmons F. William , Chung I. M. , Johnson Gary I.
Published: July 2010

On soils with high residual P, N + P starter fertilizer commonly increases early‐season corn (Zea mays L.) growth without increasing final plant dry weight or grain yield. This study was conducted to quantify corn growth and ontogeny as affected by starter fertilizer. In 1990 and 1991 on a Drummer silty clay loam (fine silty, mixed, mesic Typic Haplaquoll), we compared the effect of starter (liquid ammonium polyphosphate [10‐15‐0]) applied in a band 5 cm below and 5 cm to the side of the seed at 108 L ha‐1 (15 kg N ha‐1 and 23 kg P ha‐1) and no starter on corn ontogeny and yield. Each year, the previous crop was soybean [Glycine max (L.) Merr.]. Early‐season plant dry weight was increased 15 to 20% by starter without affecting final plant dry weight. Early‐season leaf dry weight and leaf area index were increased by starter, but the midseason maximum was not affected and the late‐season decline of both leaf dry weigh and leaf area index was hastened by starter. Leaf area duration was not affected by starter. Net assimilation rate was increased during the early season by starter, but was not affected during grain fill. The normal ontological changes in crop growth rate were also hastened by starter. In both years, tassel and black‐layer appearance occurred 2 d (≈50 growing degree days) earlier for treated than for control plants. Treated plants also had less grain moisture at harvest. Grain yield was not affected. We propose that, for this hybrid and location, the lack of an increase in final plant size and grain yield is due to the hastening of maturation, which limits the benefit from increased early‐season leaf area index.
Reproductive Development of Eight Wheat Cultivars and a Triticale as Influenced by Sowing Date
Authors: Gardner Franklin P. , Barnett Ronald D. , Soffes Ann R. , Johnson Jerry W.
Published: July 2010

Vernalization generally is required for adaptation of winter cereals to temperate climates and is basic to breeding and selection of new cultivars. The objective of this study was to assess the reproductive development of eight winter‐sown wheat (Triticum aestivum L.) cultivars and a triticale (× Triticosecale Wittmack) as related to vernalization and heat accumulation using sequential sowing dates at four environments. The study was conducted at Gainesville, FL (29° 38′ N fat); Quincy, FL (30° 36′ N lat); and Griffin, GA (33° 15′ N fat), in 1987–1988 and was repeated at Gainesville in 1988–1989. Seed of cultivars were sown in field plots, beginning about 15 December and Continued biweekly through 1 March. Cold and heat units were computed from Class AB weather‐station air temperatures logged daily. Spring‐type wheat cultivars Florida 301, Florida 303, and Owens and Beagle 82 triticale developed spike primordia after ≈2 mo and headed in 100 to 120 d, irrespective of vernalization. Intermediate winter cultivars Florida 302, Hunter, and Phoenix had not initiated spikes by ≤3 mo, and headed only if sown on or before 15 February. In contrast to this response in 1987–1988, Hunter headed irrespective Of sowing dates at Gainesville in 1988–1989. Cultivars Coker 983 and Caldwell required vernalization, and headed only if sown by December in the warmer year (1988–1989) or if sown in December or January in the colder year (1987–1988). We conclude that spring‐type wheat cultivars and triticale reproduce normally without vernalization, and are adapted to a broad range of latitudes and sowing dates in southern USA. Winter‐type cultivars require vernalization and should be seeded in early winter at lower latitudes.
Carbohydrate Metabolism Enzymes in Developing Grains of Rice Cultured in Solution with Calcium Supplement
Authors: Wei Meng‐Lei , Sung Jih‐Min
Published: July 2010

Calcium is known to promote NH4 uptake and straw growth in rice (Oryza sative L). Calcium enhancement of grain development has received little attention, however. This study evaluated the efffect of 300 mg Ca L‐1 on grain growth in solution‐cultured rice plants. It was found that both short‐term and long‐term supplemental Ca stimulated carbohydrate accumulation, and subsequently resulted in greater rain growth. Stimulated carbohydrate accumulation was linked to Ca‐enhanced activity of enzymes, including sucrose synthase, invertase, PPi‐phosphofructokinase, uridine diphosphate‐glucose pyrophosphorylase, and adenosine pyrophosphorylase, which are involved in sucrose to starch conversion.
Genetic Linkage between the Trigenic Male‐Female Sterility and Oil Quality Alleles in Safflower
Authors: Carapetian Jirair , Knowles Paul F.
Published: July 2010

Several studies have shown that the proportions of oleic and linoleic acid in the seed oil of safflower (Carthamus tinctorius L.) are governed by two alleles at the ol locus. In some studies, however, fewer plants than expected had the olol genotype. The deviation from the expected ratio could have been caused by a genetic linkage between sterility and oleic or linoleic acid content. Although male‐female sterile plants appeared in the F2 of such studies, sterile plants were not used in measurements of fatty acid composition. The objective of this investigation was to detect possible genetic association between sterility and oil quality genes. We examine data from a cross of US‐10 with genotype OlOl (high linoleic acid) to 57–147, an introduction from India with genotype olol (high oleic acid). This cross gave sterile plants the F2. We measured the iodine value (IV) in bulk seeds from 217 selfed, fertile F2 plants and found a distorted ratio due to fewer than expected plants with low IV (genotype olol). Using the half‐seed technique to determine the fatty acid composition of 342 (fertile and sterile) F2 seeds from selfed F1 plants, there was no deficiency in the expected number of olol genotypes. The difference in the ratios of the F2 plants grown from half‐seeds and those used in fatty acid measurements indicate linkage between sterility and the ol locus. Of the genes involved in sterility, where sterile genotypes are s1s1s2s2S3—, s1s1S2—s3s3, and s1s1s2s2s3s3, a statistically significant deviation was detected due to linkage between the s1 and ol loci. This information should be considered by breeders of safflower who systematically use introductions from a multitude of gene centers in their breeding programs.
Predicted and Realized Gains from Selection for In Vitro Dry Matter Digestibility and Forage Yield in Switchgrass
Authors: Hopkins Andrew A. , Vogel Kenneth P. , Moore Kenneth J.
Published: July 2010

Improved forage yield and quality, which can lead to more efficient livestock production, are important goals in switchgrass (Panicum virgatum L.) breeding. Objectives of this study were to determine the effectiveness of multiple cycles of recurrent restricted phenotypic selection (RRPS) in improving forage yield in switchgrass and in improving in vitro dry matter digestibility (IVDMD), and to compare predicted and realized gains from selection. Six switchgrass populations were developed by selecting a base population for one cycle of low and three cycles of high IVDMD and two cycles for high yield. Half‐sib progenies of parents selected from the base population for high and low IVDMD were used to estimate heritability for IVDMD by parent‐progeny regression. Realized gains from selection were determined in a seeded sward trial that included the base and six selected populations. Estimated and realized heritabilities for IVDMD were 0.40 and 0.31, respectively. Predicted gains and (in parenthesis) realized gains from selection for IVDMD in grams per kilogram per cycle were −21 (−15) for the Low IVDMD Cycle 1, 16 (15) for High IVDMD Cycle 1 (‘Trailblazer’), 14 (4) for the High IVDMDCycle 2, and 19 (18) for the High IVDMD Cycle 3 populations. There was a low but positive genetic correlation between forage yield and IVDMD of 0.10. Forage yield was not improved by RRPS, probably because of lack of genetic variability for forage yield in the base population. It is concluded that RRPS is effective for improving IVDMD in switchgrass, but was not effective in improving forage yield in the populations evaluated, and that predicted gains exceeded realized gains from selection for IVDMD due to limited selection for traits other than IVDMD.