bluuebunny/crossref_metadata_2025 huggingface dataset:
Epistasis in Related and Unrelated Maize Hybrids Determined by Three Methods
Authors: Moreno‐Gonzalez J. , Dudley J. W.
Published: July 2010

The objectives of this study were (1) to estimate genetic parameters in maize (Zea mays L.), (2) develop and apply a genetic model capable of measuring variance associated with additive, dominance, and two factor epistatic effects in a diallel cross including segregating generations, (3) to measure epistasis as difference of three‐way crosses from the nonparental single crosses, and (4) to compare different methods measuring the importance of epistasis. Three inbreds derived from Stiff Stalk Synthetic and three inbreds related to the Lancaster variety were used to make all possible crosses, their segregating, selling and backcross generations.

Heterosis for yield and other traits was larger in crosses involving unrelated lines than in crosses involving related ones. No apparent association of genetic effects estimated from the generation mean analysis with crosses involving related or unrelated lines was found. Dominance effects were the most important genetic effects controlling the performance of all traits. Generation mean analysis was a poor method for measuring additive effects. Significant epistatic effects were found in several crosses. Dominance × dominance effects were consistently negative for all traits except yield, suggesting that selection for yield prior to release of the inbreds might have reduced the diminishing effect of this type of epistasis in cross combinations. Dominance effects for yield were larger than the mean of the pooled additive effects of the lines, suggesting that homozygous beneficial genes (with + effects) and homozygous deleterious (with ‐ effects) were present in lines.

In the diallel analysis, the mean squares for dominance effects were larger than for additive effects for yield and plant leaf area, but smaller for plant height, ear height, ear length, and ear diameter. Epistatic variation was significant but small compared to additive and dominance variation. Interactions of genetic effects with locations were significant. When tested against the appropriate interaction mean squares only the dominance mean squares were significant for grain yield. Epistasis was significant in 13 of 54 three‐way crosses. The sign of epistasis was predominately positive for yield, suggesting that lines selected for yield may have certain combinations of genes that are expressed favorably in hybrids. Mean epistatic effects over all crosses were significant for yield, ear height, ear length, and ear diameter.
Grain Yield and Protein Relationships in a Wheat Cross1
Authors: Halloran G. M.
Published: July 2010

The relationships between grain yield and protein content were examined in segregating populations from a cross between a locally‐adapted high‐yielding, low protein wheat cv. ‘Olympic’ (Triticum aestivum L.) and a lower‐yielding high protein cv. ‘Kenya B.’

Segregation for grain protein content in the F3 was continuous with no dominance. In the F4 and F5, it was again continuous but there was partial dominance for low grain protein. Yield segregation in the F4 and F5 was continuous with partial dominance for low yield.

Grain yield and protein content in the F4 and F5 populations of the cross Olympic × Kenya B were found to be negatively correlated [r = ‐0.13 NS for the F4 and r = ‐ 0.58 (P < 0.01) for the F5]. While low protein and high yield were significantly associated in the F5 it would appear that there were no strong genetic limitations to improvement in protein percentage of the cv. Olympic at its present level of yield.
High Salt‐Tolerance Potential in Wheatgrasses1
Authors: McGuire P. E. , Dvôrák J.
Published: July 2010

To determine the potential of various species of wheatgrasses (Elytrigia Desv.) as gene sources for the improvement of salt tolerance in wheat (Triticum aestivum L. em. Thell.), six wheat accessions, previously identified as salt‐tolerant, and 36 wheatgrass accessions, representing 13 species, were grown from the seedling stage. Plants were grown in gradually increasing concentrations of NaCl in hydroculture with one‐half strength Hoagland's solution. Tolerance to the NaCl was determined for the wheat plants by scoring survival in 250 mM NaCl and for the wheatgrass plants by scoring survival in 500 mM NaCl and in 750 mM NaCl. while no wheat plants survived the stress with 250 nM NaCl, several wheatgrass accessions had large percentages of surviving individuals in 750 MM NaCl. The four most tolerant species were: Elytrigia scirpea (Presl) Holub, E. pontica (Podp.) Holub, E. junceiformis Love et Love, and E. diae (Runemark) nom. nud. Since these species are also among those most easily hybridizable with wheat, they are the best candidates for sources of salt tolerance.
Recurrent Phenotypic Selection for High and Low Photosynthesis in Two Maize Populations1
Authors: Crosbie T. M. , Pearce R. B. , Mock J. J.
Published: July 2010

Photosynthesis is a primary trait influencing yield potential of maize (Zea mays L.), but limited breeding work has been done to increase photosynthetic rate per unit leaf area. We conducted five cycles of recurrent phenotypic selection for high CO2‐exchange rate (CER) in two maize populations, BSUL1(RPH) and BSUL2(RPH), and three cycles of selection for low CER in BSUL2(RPL).

Selection advance for high CER was significant in both populations. Actual genetic advances for high CER for BSUL1(RPH) were 1.6 and 1.3%/cycle at vegetative (CER 1) and grain filling (CER 2) growth stages, respectively. BSUL2(RPH) showed a per cycle increase of 1.7% at CER 1 and 1.3% at CER 2. Estimates of Δpα clearly showed that selection for high CER at CER 1 caused significant weighted‐average changes in allelic frequencies at CER 1 (0.28 ± 0.05) and CER 2 (0.25 ± 0.09) in BSUL1(RPH) and in BSUL2(RPH) at CER 1 (0.29 ± 0.05) and CER 2 (0.26 ± 0.09). Actual advance for low CER in BSUL2(RPL) was statistically significant at CER 1, but it was only 0.7%/cycle. Correlated responses in CER at CER 2 for BSULl(RPH) and BSUL2(RPH) provided additional evidence that similar genetic mechanisms control CER of maize at both developmental stages. Our data demonstrated that leaf photosynthesis of maize can be improved by recurrent selection.
Variation in Photoperiod Sensitivity for Time of Flowering and Maturity Among Soybean Strains of Maturity Group III1
Authors: Nissly C. R. , Bernard R. L. , Hittle C. N.
Published: July 2010

In field screenings at Urbana, Illinois, in 1973 and in Puerto Rico in 1974‐75, soybean [Glycine max (L.) Merr.] strains of Maturity Group III exhibited a wide range in sensitivity to photoperiod. Several hundred strains were grown under natural day length, and the same strains were grown nearby under a photoperiod extended with incandescent light to either continuous light or with a 5‐hour interruption of the night. All strains grown under the extended photoperiod eventually flowered, but they showed a wide range in delay compared with those under natural day length. The frequency distribution of strains with respect to the length of delay approached a normal curve. At Urbana, extended photoperiod delayed flowering from ‐2 to 60 days. Of 515 strains, 25 were delayed less than 15 days and 5 were delayed more than 55 days. By first frost, 172 days after planting, 24 lines had matured under extended photoperiod. In Puerto Rico, flowering was delayed from 3 to 85 days by a continuous photoperiod. One strain was delayed less that 10 days and 3 were delayed more than 80 days. When the experiment was terminated at 235 days, 285 of the 439 strains were mature and 7 had matured within 170 days. Thirty‐two strains were identified as having low photoperiod sensitivity, and one of these, PI 317.334B (‘Kitami Shiro’), exhibited almost no photoperiod sensitivity at either location.
Improved Flowering and Pollen Fertility in Sugarcane under Increased Night Temperatures1
Authors: Berding Nils
Published: July 2010

A shortage of male fertile sugarcane clones often restricts cross‐pollination at the Meringa Sugar Exp. Stn. Extensive pollen testing revealed substantial variability on a micro‐environmental scale, indicating the environment may be sub‐optimal for pollen development.

Four clones from each of three flowering groups (early, mid, and late season) were chosen on the basis consistent flowering but variable pollen stainability. Two adjacent replicated field trials were planted. One trial was enclosed at night with a mobile plasticsheathed shed and maintained at 22 to 23 C from 22 March, 2 weeks after photoinduction commenced, until 15 June 1979, 6 days before routine cross‐pollination finished. After 22 March, the average external minimum temperature was usually well below 21 C, regarded as critical for good pollen fertility development in sugarcane.

The heated environment produced more profuse flowering (77 vs. 61%, for the whole season; 64 vs. 35%, during cross‐pollination), increased panicle availability for crossing (84 vs. 57%), and accelerated flowering by an average of 12 days. This latter effect provides an additional technique for making crosses among clones which do not normally flower at the same time.

Pollen production in both environments was similar but stainability (starch‐iodine test) was significantly higher in the heated environment (19 vs. 9%, stained grains). The later the flowering group, the greater was the improvement obtained.

Crosses using male flowers from the heated environment produced significantly more seedlings (614 vs. 325/5 g “seed”, in 16 paired crosses; 572 vs. 225, over 78 crosses).

The heated environment significantly increased flowering, pollen stainability, and germination count and is expected to have an important practical application.
Pod Formation in Soybeans at Low Temperatures1
Authors: Hume D. J. , Jackson Ann K. H.
Published: July 2010

Most soybean [Glycine max (L.) Merr.] cultivars cease forming pods at temperatures near 15 C. Our research was conducted to confirm a recent report that some genotypes are capable of forming pods at lower temperatures and to determine how much extra cold tolerance these genotypes possess. A total of 36 selected genotypes were grown indoors at day/night temperatures of 25/19 C until flowering and then subjected to 2‐week treatments at temperatures of 19/15, 17/15, 15/15, 15/14, 15/13,15/12, 15/11,15/9 and 15/7 C. Six genotypes formed no pods at temperatures below 15/15 C, 12 had no pods below 15/13 C, and 18 formed pods at lower temperatures down to 15/9 C. None of the U.S. cultivars tested formed any pods below 15/13 C, with the exception of 'McCall', which formed several pods at 15/11 C. The most cold‐tolerant cultivars formed pods at 15/9 C, with two plants forming pods at 15/7 C. In all cases where pedigrees could be determined, the most cold‐tolerant genotypes were related to the Swedish cultivar ‘Fiskeby V.’

Outdoor trials were planted at monthly intervals to confirm indoor rankings. Most genotypes planted on 2 January at Palmerston North, New Zealand, exhibited cold damage after one or more cold nights in February. When cold tolerance of genotypes grown outdoors was calculated as the percentage of total nodes with normal pods, this parameter was closely related (r−0.93) to the minimum temperatures at which these genotypes could form pods indoors.
Selection for Apparent Photosynthesis and Related Leaf Traits in Early Generations of Soybeans1
Authors: Wiebold W. J. , Shibles Richard , Green D. E.
Published: July 2010

Evidence suggests that photosynthate production may be yield‐limiting in soybeans [Glycine max (L.) Merr.]. This study was designed to estimate potential for selection of CO2‐exchange rate (CER), specific leaf weight (SLW), leaf thickness (LT), and leaf density (LD) in early generations of soybeans.

Two crosses (‘Amsoy’ ✕ ‘Ford;’ ‘Corsoy’ ✕ ‘Hawkeye’) involving adapted cultivars high (Amsoy, Corsoy) and low in leaf CER were used. CER, SLW, LT, and LD were measured in parents, F1s and F2s. CER was measured in selected F3 and F4 lines of one cross, whereas the other variables were measured in all F3 and F4 lines.

All traits showed quantitative inheritance without dominance effects. Broad‐sense heritability, based on parental, F1 and F2 variances, was low to moderate for CER (0.36, 0.56); it was low to very low for the other variables. Selection for either high or low CER in the F2 or F3 was ineffective. Gain from hypothetical selection for SLW was about 596 in the F2 and 5‐11% in the F2. Gain from hypothetical F3 selection in LT was about 5%. LD showed poor gain.

Use of pure lines from advanced generations may give an entirely different picture of the potential for direct selection for increased photosynthesis than that shown by this study.
A New Source of Cytoplasmic—Genic Male Sterility in Pearl Millet1
Authors: Aken'Ova M. E. , Chheda H. R.
Published: July 2010

A male‐sterile plant was discovered in a population of ‘ex‐Bornu’‘gero’ pearl millet [Pennisetum americanum (L.) Leeke] of northern Nigeria in which male sterility had not previously been found. To determine the relationship between the ex‐Bornu source of male sterility and the three known male‐sterility sources in pearl millet, ‘gero‐l’ and ‘gero‐2’, two plants that were good maintainers for male‐sterile ex‐Bornu, were each crossed with three pearl millet lines namely Tilt 23A1, 239A2, and 426A3, which represented the known malesterility sources in pearl millet. Gero‐1 and gero‐2 were good maintainers for 426A3 and 239A2, respectively, but neither was a good maintainer for all three sources. The results suggest a new pearl millet male‐sterility source operating in ex‐Bornu.
Evaluation of Techniques for Screening for Drought Resistance in Wheat1
Authors: Clarke John M. , McCaig Thomas N.
Published: July 2010

Three techniques were evaluated for screening for drought resistance in rainfed and irrigated Triticum aestivum L. em Thell., and T. turgidum L. var. durum field plots, viz., leaf diffusive resistance as measured with an autoporometer, leaf temperature as measured with a hand‐held infrared thermometer, and drying rate of excised leaves. Eight durum and 10 hexaploid cultivars of diverse origin were grown in each of two years. Yields under rainfed relative to irrigated conditions were used to characterize the drought resistance of the cultivars.

Neither diffusive resistance measurements nor leaf temperature were suitable screening techniques since differences between cutivars were not detected. There were marked differences in leaf temperatures between the rainfed and irrigated environments. Cultivar differences were detected in excised leaf water loss rate. Water retention capability was greatest early in the season, and dropped markedly after anthesis. The drought‐hardy durum cultivar Pelissier had the best water retention capability. Progeny of a Pelissier ✕ Hercules cross showed a range of retention capabilities between the parental values. Visual rating of excised leaves identified the genotypes with superior water retention capabilities. It was concluded that measurement of excised leaf water retention capability showed the most promise of the three techniques evaluated
Agronomic and Male‐Fertility Restoration Characteristics of Wheat Restorer Lines with Aegilops speltoides and Triticum timopheevi Cytoplasms1
Authors: Ghiasi H. , Lucken K. A.
Published: July 2010

The use of Aegilops speltoides Tausch cytoplasm in fertility restorer line breeding was evaluated by comparing the male fertility restoration and agronomic performance of segregating population pairs in Ae. speltoides and Triticum timopheevi Zhuk. cytoplasms. Each of 15 restorer/restorer (R/R), eight restorer/cultivar (R/B), and two male‐sterile/restorer (A/R) F1's was crossed onto ms(timopheevi)‘Butte’ and ms(speltoides)Butte or ms(timopheevi)ND537 sib and ms(speltoides)ND537 sib to obtain populations with comparable nuclear gene segregation in the two cytoplasms. There was no significant difference between F1 seed set of populations with T. timopheevi cytoplasm and those with Ae. speltoides cytoplasm (82% vs. 76%). F3 bulks from fertile plants in each population were evaluated in replicated yield trials. Populations in the two cytoplasms performed similarly for all agronomic and seed quality traits except anther extrusion. Populations with T. timopheevi cytoplasm had 10% higher mean anther extrusion than populations with Ae. speltoides cytoplasm. We believe Ae. speltoides cytoplasm can be used interchangeably with T. timopheevi cytoplasm in hybrid wheat breeding and provides an alternative which can effectively broaden cytoplasmic variability.
Effect of 43 Foreign and Domestic Cotton Cultivars and Strains on Growth of Tobacco Budworm Larvae1
Authors: Lambert Lavone , Jenkins Johnie N. , Parrott William L. , McCarty Jack C.
Published: July 2010

Weights were determined for tobacco budworm, Heliothis virescens F., larvae grown from hatching to 5 days of age on excised terminal leaves from a selected set of 35 foreign and eight 8 USA cotton, Gossypium hirsutum L., cultivars and strains. These data supplement previously published information from our laboratory for these cultivars and strains on resistance to three other insect pests and on agronomic, fiber property, morphological, and disease resistance measurements from Oklahoma. Larvae reared on ‘BJA 592’, ‘Laxmi’, ‘SATU 65’, MO‐HG, and HG‐BR‐8‐N were significantly (P = 0.5) smaller than those on ‘Deltapine 16’. Larvae reared on Laxmi were also significantly smaller than those on ‘Stoneville 213’.
Recurrent Selection for Kernel Weight in Spring Wheat1
Authors: Busch R. H. , Kofoid K.
Published: July 2010

Successful recurrent selection in cross‐pollinated species is well documented, but few reports of its use in self‐pollinated species are available. Our objectives were to determine the gain from stuctured recurrent selection for kernel weight of wheat (Triticum aestivum L.) and to determine its indirect effects on other traits. Ten lines, selected for high kernel weight from 100 lines screened, were intercrossed to form the initial C0 population. Selection among S1 plants for high kernel weight was used with approximately 22 plants selected each cycle. The selection intensity varied from 1.5 to 2.9% per cycle and averaged 2.2%.

Eighty random S3 and S4 lines each from C0 and C2, respectively, were used to compare variances and means. In addition, C1, C2, C3, and C4 were grown as populations for evaluation of gain.

Kernel weight increased 3% per cycle from C0 through C2 as measured by the lines, and 7% per cycle from C1 through C4 as measured by the populations. Genetic variance for most measured traits remained as high in the C2 as the C0 population. Two cycles of selection resulted in lines with kernel weight higher than any lines in the C0 population. These results were further confirmed by the results of the population tests which indicated continued gain for kernel weight through Cycles 3 and 4.

Negative indirect effects of selection for kernel weight were observed for days to head, spikelets per spike, kernels/cm of spike, and spikelets/ cm of spike. Grain protein increased slightly while plant height, grain yield, and test weight did not differ over cycles of selection.

Structured recurrent selection produced a population with much higher kernel weight than did single crossing and selection among segregating progeny, even though the original population was selected for high kernel weight and a high selection intensity was used.
Variation Among Alfalfa Genotypes for Reduced Nitrogen Concentration1
Authors: Phillips Donald A , Teuber Larry R. , Jue Sally S.
Published: July 2010

Kjeldahl N concentration was measured in ‘African’ and ‘Hairy Peruvian’ germplasm sources of alfalfa (Medicago sativa L.) grown first with N2 and then with 8 mM NH4NO3 to assess variation in shoot protein content for possible improvement of alfalfa quality. Shoot N concentration was determined on 120 seedlings from each germplasm source grown without combined N and inoculated with Rhizobium meliloti Dang. strain 102F28. Each plant shoot was harvested when the first flower opened during three successive growth cycles. After the second harvest following growth on N2, plants again were grown to flowering with 8 mM NH4NO3, and no significant contribution to N content was detected by the C2H2‐reduction assay. Although herbage dry weight and percent N generally were correlated negatively, it was possible to select two groups of plants from each germplasm source: I) high percent N in shoots on both sources with dry matter production near the average of the unselected population, and II) low percent N in shoots on both N sources with dry matter production near the average of the unselected population. Herbage of plants selected for high percent N averaged 13 to 16 % greater crude protein concentration on the two N sources than the original population and 30 to 35 % greater crude protein concentration than seedlings selected for low percent N. Ramets established from three seedlings within each selected population were tested separately for percent N content on each N source in two trials. All ramets within a N treatment produced similar herbage yield, and genotypes selected for high percent N had significantly higher shoot N concentration on both N sources than genotypes selected for low percent N. The results show that when N nutrition is controlled carefully by separating combined N and Rhizobium effects, a small percentage of alfalfa genotypes with superior crude protein content and normal dry matter production can be identified.
Factors Determining Flag Leaf Curvature in Wheat1
Authors: Ledent J.‐F. , Renard CH.
Published: July 2010

Flag leaf curvature is a major aspect of canopy configuration. A knowledge of factors determining its occurrence might be important for understanding yield. Effects of genotypes and N application on the proportion of straight (S) and curved (C) flag leaves were, therefore, investigated. The two types of flag leaves were also compared for characters expected to affect curvature: leaf size, internal leaf structure (anatomy, chemical analysis of cell wall material), water status and N content.

Most genotypes displayed both straight and curved flag leaves. The proportion varied greatly with N treatment and genotype. Curved leaves were longer and wider and were associated with higher tillering. There was no clear relation with cell wall material or sclerenchyma content. The midrib along was unable to maintain leaf rigidity. In detached leaves water status affected markedly leaf curvature, but in intact plants there was no significant difference in water status between C and S leaves. In the material tested, higher yielding varieties tended to display a greater number of straight flag leaves.
A Hybrid Between Agropyron trachycaulum and A. desertorum1
Authors: Napier K. V. , Walton P. D.
Published: July 2010

An interspecific hybrid between Agropyron trachycaulum (2n = 28) as female and A. desertorum (2n = 28) was obtained by controlled crossing in a greenhouse, followed by embryo culture. The purposes of this study were to describe the morphology and cytology of this new hybrid. Most vegetative and spike characteristics of the hybrid were intermediate between those of the parent species. The allopolyploid A. trachycaulum, designated SSHH, regularly formed 14 bivalents at meiotic Metaphase I, and A. desertorum, designated CCCC, behaved as an autotetraploid, with an average configuration of 8.4II and 2.8IV. The hybrid, 2n = 28, represented by the formula SHCC provided a new genome combination and genetic background in which to study pairing of the three genomes. An average of 9.24I, 8.62II, 0.47III and 0.031V per cell was observed with a range of 6 to 12 bivalents (47% closed). Seven bivalents were attributed to autosyndetic pairing of A. desertorum genomes. Trivalents may have been formed from S chromosomes associated with a CC bivalent. Additional bivalents must have been formed by associations between the S and H genomes of A. trachycaulum. This indicates that these chromosomes may be sufficiently homologous (homoeologous) to enable pairing to occur in certain genetic backgrounds.
Variation, Heritability, and Relationship to Yield of Physiological Characters in Peas1
Authors: Hobbs S.L.A. , Mahon J.D.
Published: July 2010

Seven quantitative physiological characters [photosynthetic CO2 exchange rate (CER), specific leaf weight, N2(C2H2) fixation, root respiration, respiratory cost of N2(C2H2,) fixation, growth duration, and relative growth rate] were examined in 25 pea( Pisum sativum L.) genotypes. To assess the possible use of these traits as criteria for selection in plant breeding, studies were carried out in three field environments, and four yield characters (total plant dry weight, seed dry weight, harvest index, and seed N) were determined.

Despite the significant environmental effects on all characters except seed N, overall genotype means differed significantly for all but the cost of N2 fixation and relative growth rate. These last two characters were affected by large genotype ✕ environment interactions which may have obscured the significant within‐environment genotypic differences. Genetic coefficients of variation for the physiological characters varied from 2 to 13% and estimates of broad sense heritability were high except for cost of N2(C2H2) fixation and relative growth rate. Significant correlations were found between yield characters and physiological characters [total weight and growth duration; total weight and cost of N2(C2H2) fixation (negative); seed N and N2 fixation (negative); harvest index and specific leaf weight; harvest index and CER]; and among physiological characters (N2 fixation and root respiration; CER and relative growth rate).

For areas with short growing seasons, rapid growth for a limited period with more assimilate being placed into seeds (high harvest index) may be desirable. The combination of such characters might produce maximum potential yield in the short time available. Because CER appears to be correlated with these traits and is highly heritable, selection on the basis of this non‐destructive character might be profitable in breeding such conditions.
Measurement of and Correlations among Selected Seed Quality Factors for 36 Texas Race Stocks of Cotton1
Authors: Shaver Ted N. , Dilday Robert H.
Published: July 2010

Five seed quality factors (gossypol, oil, protein, and kernel percentages, and seed index) were measured for 36 Texas race stocks of cotton (Gossypium hirsutum L.) and three controls. Linear correlation coefficients were then calculated for all possible combinations of the five traits taken two at a time to determine whether those traits were related in this material.

Texas race stocks were detected with significantly higher gossypol, oil, or protein percentages than the controls, but not with higher kernel percentages or seed indexes. Positive relationships were demonstrated between kernel and oil percentage (r = 0.71), kernel and protein percentage (r = 0.62), kernel percentage and seed index (r = 0.62), and protein percentage and seed index (r = 0.48). A negative relationship existed between seed index and gossypol percentage (r = −0.47). Gossypol level among the stocks was not related to the percentages of oil, protein, or kernel in the seed. In these stocks, increasing gossypol percentage for host plant resistance should not cause a reduction in quantity of oil or protein in the seed.
Effects of Okra‐Leaf, Frego‐Bract, and Smooth‐Leaf Mutants on Pink Bollworm Damage and Agronomic Properties of Cotton1
Authors: Wilson F. D. , George B. W.
Published: July 2010

Eight isolines of cotton, Gossypium hirsutum L., which carried all possible combinations of Okra leaf (L°2), frego bract (fg), and Smooth leaf (Sm2) vs. their normal‐leaf and normal‐bract equivalents in the La 71‐7 (a Stoneville) background, were grown in replicated experiments for 3 years in Arizona in insecticide‐free environments. Percentage of seed damage caused by pink bollworm (PBW), Pectinophora gossypiella (Saunders), and 11 agronomic properties were studied.

Mean seed damage in the Okra‐leaf isolines was 82% of that in the corresponding normal‐leaf lines, a significant reduction. The Okra‐leaf isolines were comparable to the normal‐leaf types in agronomic properties. Their only negative effect was an 8% lower lint yield (which was significant). Okra leaf interacted with frego bract only for boll size and with Smooth leaf only for seed index. Okra leaf interacted with years for seed damage because the Okra‐leaf isolines had 76% as much damage as the normal‐leaf stocks in 1979, but 85% as much in 1978 and 88% as much in 1980. Seed damage in the frego‐bract isolines was not significantly different from that in its normal‐bract counterparts. Frego bract interacted significantly with Smooth leaf for lint percent and with years for seed damage, total lint yield, bolls/plant, boll size, lint percent, and plant height. When closely examined, the interaction for seed damage suggested that frego bract afforded a slight advantage during the years when seed damage was relatively high. However, deficiencies in numerous agronomic properties (including a 24% lint yield reduction) and the five year ✕ agronomic property interactions offset any advantages in reduced seed damage afforded by frego bracts. Smooth‐leaf isolines unexpectedly displayed more seed damage than the hirsute‐leaf lines. Smooth‐leaf isollnes were also inferior to the hirsute‐leaf types in all agronomic properties except seed index and displayed significant interactions between years and percent lint yield at second and third harvest, total lint yield, bolls/plant, and date of first flower. For PBW resistance and agronomic performance, Okra leaf appears to have value, frego bract does not, and Smooth leaf must be reevaluated.
Plant Density Effects on Combining Abilities of Early Maize Synthetics1
Authors: Cross H.Z. , Hammond J.J.
Published: July 2010

Five early maize (Zea mays L.) synthetics were evaluated for general combining ability (GCA), specific combining ability (SCA), average heterosis, and reciprocal effects to estimate the optimum plant density for combining ability analysis in early improved synthetics, and the importance of reciprocal differences in early maize synthetics. Yield and agronomic data were obtained for the five parental synthetics and 20 synthetic crosses grown at 45,500, and 57,000, and 67,500 plants/ha in each of four environments.

The absence of GCA interactions with plant densities indicated that a single density within the range of those tested should adequately evaluate these synthetics. Significant reciprocal effects for ear moisture at harvest, kernel depth, and kernel rows/ear indicated that cytoplasmic effects were important in these synthetics. Reciprocal differences of more than 3% for ear moisture at harvest between synthetic crosses indicated careful choice of the female parent could be a means of reducing crop drying costs and facilitating earlier harvest.

The absence of detectable SCA effects for these synthetics indicated inter‐population improvement methods would not be advantageous within this group of synthetics.

Average heterosis for grain yield in this study was 10.7%. This heterosis can be attributed to increased kernel size and kernel number which is consistent with the idea that heterosis may be produced by an increased effective filling period duration (EFPD).
Interrelationships of Morphological and Economic Characters of Sunflower1
Authors: Beard Benjamin H. , Geng Shu
Published: July 2010

Two phenotypically dissimilar open pollinated sunflower (Helianthus annuus L.) cultivars, ‘Peredovik’ and ‘Tchernianka’, and two hybrids, ‘Romsun 52’ and ‘Seedtec 304’ (produced by genetic and cytoplasmic male sterile systems, respectively), were sown at different dates and seeding rates for two years. The four cultivars were planted as a 4 × 4 latin square. Within each of the four replications, dates of sowing were randomly assigned to strips across the four cultivars. Within each cultivar‐sowing date combination, plant spacings were randomly assigned as 6‐row subplots. Data were collected from ten plants per plot for a number of morphological characters and from the plants in the two center rows for yield and oil characters.

Principal component and path coefficient analyses indicate that even though these cultivars are phenotypically and genetically different, the response to date of planting, and the biological systems controlling the interrelationships between morphological, yield, and oil characters are similar. This may explain why some sunflower cultivars are superior at a wide range of locations, and at the same time are sensitive to environmental changes such as planting dates. The results also suggest that yield improvement through better management should apply to many types of cultivars in a wide range of environments.
Effects of Diurnal Variation in Temperature on the Carbon Balances of White Clover Plants1
Authors: McCree K. J. , Amthor M. E.
Published: July 2010

In principle, the respiratory loss associated with the synthesis of plant biomass from a given amount of available photosynthate should be independent of temperature, while the maintenance loss rate should increase geometrically with increasing temperature. When the whole plant carbon balance is considered, the daily carbon gain with a diurnal cycle of temperature should therefore be smaller than with a constant temperature of the same mean, which is the opposite of that commonly assumed.

The carbon balances of dense stands of white clover (Trifolium repens L. ‘Regal’) were determined from integrated CO2 exchange rates (CER). The carbon balances with a diurnal cycle of temperature (30 C day/20 C night, 30 C day/10 C night) were shown to be predictable from the balances at constant temperatures of 30 C, 20 C, and 10 C. With a 30 C day, the daily carbon gain (growth rate)increased as night temperature decreased. The gain with a 30/10 C diurnal cycle was less than that with a constant 20 C. These results agree with the above principles.

The daily substrate input of carbon from photosynthesis, calculated as the integral of the CER in the light minus the CER in the dark during the daytime, was the same with the 30/10 C diurnal cycle as with a constant 20 C. The CER in the light (the so‐called “net photosynthetic rate”) was much smaller with the diurnal cycle, while the daytime CER in the dark was much more negative. This was attributed to accelerated use of substrate that could not be used during the cool night.

Hourly changes in the CER and in the levels of the various pools of substrate were simulated using a dynamic carbon balance model after Thornley. Parameters of the model were varied until the simulated pattern of the CER matched the observed pattern at a constant 30 C, then the rate of use of substrate and the rate of degradation of biomass were reduced by a factor of 2 for each 10 C drop in temperature, day or night.

There was good agreement between simulated and observed CER for all combinations of temperature tested. Minor differences were attributed to deviations from the assumed steady state of substrate production and use, and to accelerated senescence of leaves at 30 C. An additional limitation is that developmental effects were excluded. Nevertheless, it is clear that the daily carbon balance with a diurnal cycle can be expected to differ only slightly from the balance with a constant temperature having the same mean value.
Variability for Morphological and Physiological Traits Associated with Barrenness and Grain Yield in the Maize Population, Iowa Upright Leaf Synthetic #11
Authors: Smith C. S. , Mock J. J. , Crosbie T. M.
Published: July 2010

Barrenness, the failure of a plant to produce a normal ear, is a major limitation to efficient conversion of light energy into grain in maize (Zea mays L.) grown at high plant densities. Our research was conducted to determine magnitudes of genetic variability and heritabilities for various traits of the maize population Iowa Upright Leaf Synthetic #1 (BSUL1) and to determine which traits were associated with barrenness and grain yield at high plant densities.

We grew 144 S1 lines from BSUL1 for 2 years at one location and at two plant densities. Results indicated that BSUL1 contained large amounts of genetic variability for the 14 traits studied at 42,300 and 96,800 plants/ha. Significant heritabilities ranged from 0.31 for grain/leaf area at the high density to 0.91 for tassel branch number (low density). Phenotypic and genotypic correlations indicated that silking traits, pullen‐shed‐to‐silking interval, and grain/plant were highly correlated with grain yield and barrenness at both densities. Canopy orientation traits generally showed weak associations with grain yield and barrenness. Correlations and genotype × year interactions suggested that selection at a low density (42,300 plants/ha) in one location for traits correlated with barrenness should improve BSUL1 for tolerance to high plant densities.
Evaluation of Alfalfa Synthetic Varieties: Prediction of Yield in Advanced Generations and Average Clone Effects1
Authors: Rowe D.E. , Gurgis R.Y.
Published: July 2010

First, second, and third generations of nine synthetic varieties derived from combinations of two to nine clones selected from the alfalfa (Medicago sativa L.) variety ‘Cherokee’ were harvested in field plots for three seasons to evaluate the effectiveness of a prediction formula for yields and to estimate genetic factors affecting yield. The Syn 1 yields were predicted as the average of all possible Fls. Yields of F1s were previously determined in a nine clone diallel. The Syn 2 yields were predicted as a function of the Syn 1 predictions adjusted by subtracting the average S1 yields of the clones in the synthetic variety.

Observed yields were compared to predicted yields using product moment correlation analyses. The predictions of Syn 1 yields were inaccurate while those of Syn 2 were very good. For Syn 2 the overall means of the predicted and observed yields were the same with a highly significant correlation (r = 0.86).

A genetic model was developed to determine average effects of the individual clones in synthetic varieties, the linear generation effect, the quadratic generation effect, and the interaction of the linear generation effect and the clone effects on the yields of the synthetics. All effects except the quadratic generation effect and the interaction term were statistically significant. The average effects of the individual clones suggested that two of the nine clones were much inferior to the others and may have been misclassified in the initial selection of clones. The advantages of this modeling approach are outlined.
Effect of Preripe Harvest and Artificial Drying on the Milling and Baking Quality of Soft Red Winter Wheat1
Authors: Kirlies Allen W. , Housley Thomas L. , Emam Abdallah M. , Patterson Fred L. , Okos Martin R.
Published: July 2010

Soft red winter wheat (Tritricum aestivum L. em Thell.), grown in 1979 and 1980 crop years, was combine harvested at various preripe stages, artificially dried at 38, 66, and 93 C to 13 to 15% moisture and subjected to analytical, milling, and baking tests in order to determine the effect of preripe harvesting and artificial drying on end use quality. Moisture content in the preripe wheat fell steadily, from 41.8 to 17.1% moisture and from 35.7 to 16.2% moisture over 14 and 7 day periods in crop year 1979 and 1980, respectively. Patterns of change in quality data were more closely related to moisture content at harvest than to number of days preripe. Maximum test weight and grade were obtained for wheat harvested at a moisture content of 30 % or lower and were usually unaffected by drying temperature, whereas thousand kernel weight was not affected by wheat moisture content or drying temperature. Wheat protein and ash content showed very little change throughout the period studied. Acceptable milling quality was achieved only when wheat was allowed to ripen to about 30 to 35 % moisture before cutting. Drying temperatures of 66 or 93 C lowered the milling quality of wheat harvested above 38% moisture. Cookie baking quality was normal for all preripe wheat samples except for those dried at 93 C.
Use of Transpiration Decline Curves to Identify Drought‐Tolerant Cotton Germplasm1
Authors: Quisenberry J. E. , Roark Bruce , McMichael B. L.
Published: July 2010

Traditional plant breeding approaches have not been very effective in the development of higher yielding cotton (Gossypium hirsutum L.) cultivars for growth under water‐deficient field conditions. The purpose of this research was to evaluate the ability of a laboratory technique to identify cotton genotypes with higher growth rates under water stress conditions in the field. The technique consisted of detaching cotton leaves from the plant at sunset and hydrating those leaves overnight. The following day, the leaves were placed under a light‐bank in the laboratory and weighed every 2 min as they dried. From that data, transpiration decline curves were plotted. The curves exhibited stomatal and cuticular transpiration phases. The point where those two linear phases intersected was termed “mean stomatal closure” (MSC), and both time and relative water content (RWC) at that point were estimated. Sixteen entries were evaluated for transpiration decline curve components and growth rates in irrigated and dryland field plots in 1978 at Big Spring, Tex. In 1980, 12 different entries were evaluated for the same traits under dryland conditions at the same location.

In 1978, entry differences occurred for all transpiration decline curve components in the irrigated test and for all components, except stomatal transpiration rates, in the dryland test. The interaction between entries and water levels was significant for all components. In 1980, only RWC at MSC and cuticular transpiration rates were different among entries. Growth rates among entries could not be separated statistically within any experiment. However, large negative correlation coefficients were measured between mean RWC at MSC and mean growth rates in the dryland tests in both 1978 and 1980. This relationship indicated that growth rates tended to be higher when the stomates remained open to a lower RWC before closure. The relationship was not significant in the 1978 irrigated test. Transpiration decline curves appear to be useful in screening cotton genotypes for differences in growth rates under conditions of water stress.
Cultivar ✕ Environment Interactions in Sugarbeet Yield Trials1
Authors: Campbell L. G. , Kern J. J.
Published: July 2010

Sugarbeet (Beta vulgaris L.) yield and quality data from 5 locations and 4 years were used to determine the presence and magnitude of cultivar ✕ environment interactions in a major sugarbeet producing area, the Red River Valley of North Dakota and Minnesota. The cultivar ✕ location interaction for root yield indicated that cultivars tended to rank consistently different in the 4 years of testing at individual locations. Cultivar ✕ location, cultivar ✕ year, and cultivar ✕ location ✕ year variance components for sucrose, sodium, and potassium concentration were relatively small, compared to the cultivar variance component, indicating consistency in the relative expression of these characters. Years had a greater effect than locations on relative concentration of sucrose, sodium, potassium, and amino‐nitrogen, whereas cultivar ✕ year and cultivar ✕ location interactions were more nearly equal for yield. Second order interactions were significant for all traits except potassium concentration.

Regression of cultivar mean yield on environmental mean yield and the contribution of individual cultivars to the cultivar ✕ environment variance component indicated that cultivars differed in their genetic potential to respond to a favorable environment. Regression coefficients for individual cultivars ranged from 0.85 for ‘ACH‐14 ’ to 1.11 for ‘Beta 1443 ’, with cultivar yields being 45.3 and 53.5 metric tons/ha, respectively. Three years of testing at five locations appeared to be adequate for characterizing cultivars for yield, sucrose concentration, and recoverable sucrose/ha.
Short‐Term Growth Responses of Tall Fescue to Changes in Soil Water Potential and to Defoliation1
Authors: Wolf D. D. , Parrish David J.
Published: July 2010

Plant elongation growth is modulated by soil water availability and other environmental factors. With limited soil water, plant water potential will be low and cellular elongation will be inhibited. In this study, we measured leaf elongation of tall fescue (Festuca arundinacea Schreb.) during and after periods of limited water availability to roots. Elongation, as measured with angular displacement transducers, was more rapid in plants exposed to a −0.1 bar than a −8 bar water potential rooting medium. Growth in the −0.1 bar rooting medium was less susceptible to inhibition by low relative humidity (RH) or illumination. Flushing the rooting medium of the −8 bar treatment with a −0.1 bar solution gave evidence of rapid recovery. Tillers with short‐term, severe drought stress (wilted) displayed rapid elongation immediately after watering. With long‐term severe drought stress (wilted for 26 to 28 hours), no elongation occurred for almost 2 hours after rewatering. We propose that chronic drought stress causes disruptions in the continuity of water columns between roots and leaves that are repaired by positive root pressures. Low soil water availability and low RH limited elongation in darkness, but the effects were much more dramatic in the light when open stomata accelerated water loss. Partial defoliation immediately increased elongation rates of remaining leaves. This response may partially explain the very rapid elongation frequently observed in recently cut grasses.
Environmental Relationships with Forage Quality of Warm‐Season Perennial Grasses1
Authors: Pitman W. D. , Holt E. C.
Published: July 2010

Seasonal patterns of digestibility of warm‐season perennial grasses in the southwestern U. S. A. generally show peaks in early spring and low values in mid‐summer. This research was conducted to determine if the patterns of digestibility of kleingrass (Panicum coloratum L.), green sprangletop [Leptochloa dubia (H.B.K.) Nees], and plains bristlegrass (Setaria macrostachya H.B.K.) were related to temperature, rainfall, relative humidity, and daylength under field conditions. Two selections of kleingrass (‘Kleingrass 75’ and Kleingrass 75‐25), and one each of green sprangletop and plains bristlegrass were harvested at 2, 4, and 8‐week frequencies during 1978 and 1979. Samples were separated into leaf and stem fractions with in vitro digestible organic matter (IVDOM) determined each fraction. From analyses with all four grasses combined, leaf and stem IVDOM was negatively correlated with temperature (r‐values from −0.353 to −0.419, all significant at 0.001 level) and daylength (r‐values as great as −0.378 with all significant at least at the 0.01 level). In general, leaf and stem IVDOM was positively correlated with measures of moisture conditions (r‐values up to 0.523 and 0.445 for rainfall and relative humidity, respectively).

The environmental factors monitored were used in multiple regression models of leaf IVDOM, stem IVDOM, and percent leaf. Statistically significant models were obtained in most cases with R2 values up to 0.96. However, in a few cases less than 20% of the variation in IVDOM was accounted for by models maximizing R2 (with R2 values as low as 0.12). Distinct r elationships are apparent from these analyses; although, R2 values, partial regression coefficients, and individual environmental factors contributing significantly to the models were too variable for these models of leaf and stem IVDOM and percent leaf to be of general use. Overall trends in digestibility can be anticipated from knowledge of environmental factors, but forage digestibility cannot be accurately predicted from macroenvironmental factors.