bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon Balance of Water‐Deficient Grain Sorghum Plants1
Authors: Wilson D. R. , van Bavel C. H. M. , McCree K. J. 
Published: July 2010

Experiments were performed to determine how water deficits affect the rates of production and utilization of photosynthetic substrates in whole plants. Substrate utilization was characterized by two parameters which were estimated from an analysis of the C fluxes into and out of plants during a 24‐hour period. These were the efficiency of conversion of substrate used in growth processes to new plant dry‐matter (Yg, growth efficiency), and the daily substrate requirement per unit dry‐matter for maintenance of existing plant material (m, maintenance coefficient).Measurements were made on grain sorghum [Sorghum bicolor (L.) Moench cv. RS610] plants at the eight‐leaf growth stage, in which daytime leaf water potentials ranged from −1.4 to −24.6 bars, and nighttime potentials from −1.0 to −10.9 bars. Carbon dioxide exchange rate (CER) measurements were made in an assimilation chamber at air temperature 30 C, dewpoint 22 C, and photosynthetic photon flux density 1,800 µE.sec‐1.m ‐2. Leaf water potentials were measured regularly. Leaf areas and plant dry weights were measured at the end of each test.Water deficits did not affect Yg, its mean value being 0.71 ± 0.02, comparable to previously reported values for unstressed plants. As water deficits became more severe, m decreased from 60 to 30 mg.g‐1.24hours‐1. The cause of the decrease could not be determined from these experiments.The dry‐matter accumulation rate of the plants was greatly reduced by water deficit. This reduction occurred for two reasons: (i) the leaf area index was reduced, (ii) the substrate production rate per unit of leaf area by photosynthesis decreased.The total C efflux rate from the plants in the dark was decreased by water deficit. This decrease was mainly attributable to the reduced quantity of available substrate, as shown by separating the C efflux into growth and maintenance components. Of the 58% reduction of the C efflux rate, 22% was attributable to the reduction of the maintenance component and 36% was caused by the reduction of the growth component.
Comparative Performance of Semideterminate and Indeterminate Soybean Lines1
Authors: Wilcox J. R. 
Published: July 2010

Forty semideterminate and 40 indeterminate soybean [Glycine max (L.) Merr.] lines from each of three crosses were evaluated in 0.5‐ and 1.0‐m row spacings for 2 years at Lafayette, Ind. The objectives of the study were to compare the agronomic characteristics of the two plant types and to determine if the plant types responded differently to row spacings.Yields of the 0.5‐m rows averaged 13% higher than those of the 1.0‐m rows in the 2 years of the study. This response was due primarily to increased yields in the 2nd year of the test.The indeterminate progenies were an average 5% higher in seed yield, 1 day later in maturity, and 12 cm taller than the semideterminate progenies. Interactions of plant type ✕ row spacing were not significant for any characteristic evaluated except maturity in one cross. These data indicated that both the semideterminate and indeterminate lines responded similarly to the two row spacings used in this study.Regression of seed yield on plant height for the two plant types showed similar regression coefficients in most of the comparisons, indicating that the increases in seed yield associated with increased plant height were similar for the two plant types. Only half the regression coefficients were significant for lodging scores regressed on plant height for the two plant types. Significant coefficients were similar for the two plant types, indicating that neither plant type resulted in superior lodging resistance. The data indicated that among soybeans adapted to the Midwest, either plant type could be used successfully in a soybean improvement program.
Relationship of Component Frequency to Compensatory Response in Soybean Blends1
Authors: Fehr W. R. , de Cianzio S. Rodriguez 
Published: July 2010

We evaluated the effect of component frequency on the compensatory response of soybean (Glycine max L. Merrill) blends. The component frequency of a blend of ‘Corsoy’ and ‘Amsoy 71’ was varied by 2.5% increments from 100:0 to 0:100. The 41 entries were evaluated for yield at four environments in Iowa during 1973 to 1975.There were no significant differences among component frequencies for average yield across environments. All deviations of blend yields from the weighted mean of the two cultivars in pure stand were attributed to random error. The environment × component frequency interaction was significant due to changes in rank of entries across environments. The results demonstrate the difficulty of differentiating between random error and true overcompensation or undercompensation in soybean blends.
Water Relations and Carbon‐14 Assimilation of Cotton with Different Leaf Morphology1
Authors: Karami E. , Krieg D. R. , Quisenberry J. E. 
Published: July 2010

The purpose of this research was to determine the usefulness of simply inherited genetic differences in cotton (Gossypium hirsutum L.) leaf morphology (normal, laciniate, and superokra) as it relates to drought tolerance or water use efficiency. This initial report describes the leaf water potential components, C02 fixation rates, and the rate of loss of assimilated 14C from various source leaves on plants subjected to soil water stress at select growth stages under glasshouse conditions.No significant genotypic differences were observed in leaf water potential components or in CO2 fixation rates when the soil water content was near field capacity. Trends did exist for the superokra to be slightly superior to the normaleaf type. Significant differences were observed in both the rate and extent of 14C loss from different source leaves in the various genotypes. The superokra genotype had the highest activity, whereas the normal leaf genotype was the lowest in activity.As soil water availability began to affect leaf water status, significant genotypic differences existed in all measured physiological parameters. The superokra genotype was able to maintain a more favorable leaf water status through a combination of higher leaf water potential and lower osmotic potentlal than the normal leaf genotypes. Photosynthetic rates were reduced by water stress in all genotypes; however, the magnitude of the reduction varied significantly among the genotypes reflecting specific differences in turgor pressure. The removal of assimilated 14C from various source leaves subjected to water stress also exhibited significant genotypic differences both in the rate of removal and in the total amount of assimilate removed during a 24‐hour period. As water stress intensified the photosynthetic assimilation of 14CO2 was found to be more sensitive than the removal of assimilate from the source leaf.The results of these experiments indicate a possible advantage of altered leaf morphology when cotton leaves are subjected to soil water stress. The benefits of improved water relations and CO2 assimilatlon to yield in the altered leaf types of cotton remain to be evaluated.
Use of Pod Width for Indirect Selection of Seed Weight in Soybeans1
Authors: Bravo J. A. , Fehr W. R. , de Cianzio S. Rodriguez 
Published: July 2010

We evaluated the use of pod width for indirect selection of seed weight in soybeans [Glycine max (L.) Merrill], Each of three experimental lines with relatively small seed was crossed to one of two large‐seeded cultivars, and each F1 was crossed to a different parent with intermediate seed weight. Width of the terminal pod cavity (suture‐to‐suture) and seed weight (g/100 seeds) were measured on individual plants and their progeny for the F1 of the three‐way crosses, F2 and F3 of all crosses, the eight parents, and a control cultivar.Selection for seed weight was more effective using pod width than was direct selection for seed weight per se on an individual‐plant basis. The phenotypic correlations between the two characters were highly significant (P< 0.01) and ranged from 0.55 on an individual‐plant basis to 0.64 on an entry‐mean basis. The genotypic correlation on an entry‐mean basis was 0.72. Heritabilities based on variance component estimates for pod width were 54% on a plant, 75% on a plot, and 92% on an entry‐mean basis, and for seed weight were 27% on a plant, 41% on a plot, and 71% on an entry‐mean basis. Average genetic response in seed weight obtained from individual plant selection of the top 25% of F1 F2, and F3 plants on the basis of pod width was 50% greater than for seed weight per se.Use of pod width permits more efficient selection for seed weight in soybean cultivars development. Implications of the results in breeding for seed weight are discussed.
Influence of Chemical Seed Treatments on Germination of Dormant Wild Rice Seeds1
Authors: Oelke E. A. , Albrecht K. A. 
Published: July 2010

Wild rice (Zizania palustris L.) seeds have a dormancy period of 3 to 5 months. This dormancy period can be partially broken right after harvest by dehulling the seeds and scarifying them. However, this is time consuming and the resulting seedlings are weak. The purpose of this research was to search for chemical means to decrease the dormancy period and increase the seedling vigor of wild rice.Seeds which had been stored in water at 3 C for 120 days were soaked in 0, 28, 43, 57, 71, 86, and 95% ethanol for various lengths of time up to 24 hours. Germination was increased from 15% with no chemical treatment to 61% with a 7‐hour soaking in 43% ethanol.Seeds which had been harvested for 1 week were shaken in 95% ethanol for 15 sec, then in chloroform for 1 min and again for 15 sec in 95% ethanol. After treatment the seeds were stored in water at 3 C and germination samples taken over a period of 180 days. Germination at the end of 60 days was 42% for the treated seed compared to 16% for untreated seed.Freshly harvested seeds were scarified by tumbling with granite grit for 60 min and then placed for 24 hours in all combinations of 0, 0.005, 0.05, 0.5, and 5.0 mM gibberellic acid (GA3) and 0, 0.063, 0.125, 0.25, and 0.5 mM 6‐benzyl adenine (BA). A combination of the highest concentration of both resulted in the highest germination after 21 days in water; 64% compared to 7% with no chemical treatment. However, seedling survival in the greenhouse, 51 days after treatment, was the highest with the lowest concentration of GA3 and the highest concentration of BA. Treating freshly harvested dehulled and scarified seed with 2.63% sodium hypochlorite for 2 hours increased germination from 2 to 19% and seedling survival from 50 to 87%, compared to no chemical treatment.Pretreating wild rice seeds with ethanol in combination with chloroform can decrease the dormancy period without dehulling and scarifying seeds. Seedling vigor of scarified seeds can be increased by treating them with GA3 and BA.
Seven Cycles of Reciprocal Recurrent Selection in BSSS and BSCB1 Maize Populations1
Authors: Martin J. M. , Hallauer Arnel R. 
Published: July 2010

Reciprocal recurrent selection was proposed as an efficient method of improving the population cross of two broad‐genetic base populations. Seven cycles of reciprocal recurrent selection for grain yield have been completed in ‘Iowa Stiff Stalk Synthetic’ (BSSS) and ‘Iowa Corn Borer Synthetic no. 1’ (BSCB1) maize (Zea mays L.) populations. To determine the effectiveness of reciprocal recurrent selection for grain yield improvement, we evaluated the C0, C1, C3, C5, and C7 of BSSS(R) and BSCB1(R), and the C0 ✕ C0, C5 ✕ C5, and C7 ✕ C7 population crosses in six Iowa environments. Data were collected to determine the direct response to selection for grain yield and the correlated responses for eight other agronomic traits. Observed response for grain yield was compared with computer simulated reciprocal recurrent selection as it was conducted with BSSS and BSCB1. Ten cycles of reciprocal recurrent selection were simulated for starting conditions with three levels of dominance and two initial gene frequencies.Grain yield of the BSSS(R) ✕ BSCB1(R) crosses increased 1.75 ± 0.37 q/ha per cycle, but yield of the parental populations did not change significantly. Observed midparent heterosis increased from 14.9% for the C0 population cross to 41.7% for the C7 population cross. Mean yield of the population crosses increased from 58.5 q/ha for the C0 population cross to 70.7 q/ha for the C7 populations cross. Estimates of genetic components of variance determined from the yield selection trials for each cycle showed no evidence that genetic variability in BSSS(R) and BSCB1(R) was declining because of selection. The greatest correlation between observed and simulated responses was obtained for the starting condition of complete dominance and equal initial allele (p=q=0.5) frequencies in the simulated populations.
Ancestry of Improved Cultivars of Asian Rice1
Authors: Hargrove Thomas R. , Coffman W. R. , Cabanilla Victoria L. 
Published: July 2010

The 1970 attack of southern corn leaf blight (Helminthosporium maydis, Nisik and Miy.) was conditioned by cytoplasmic uniformity in the U.S. maize (Zea mays L.) crop. Researchers at the International Rice Research Institute (IRRI) studied the genetic diversity of improved Asian cultivars of rice (Oryza sativa L.), focusing on their maternal ancestry because cytoplasmically controlled traits are inherited through the female parents.All cultivars released by late 1979 under the IR designation trace to the same maternal parent ‘Cina,’ which indicates they might carry similar cytoplasm. Cina is the ultimate maternal parent of 62% of the post‐‘IR8’ cultivars in Bangladesh; 22% in India; 74% in Indonesia; 60% in Korea; 75% in Sri Lanka; and 25% in Thailand. More than half of the Philippines' riceland is planted to maternal derivatives of Cina. Among 79 entries from 10 nations and IRRI in the 1978 International Rice Yield Nursery, 59% trace their maternal ancestry to Cina. From 36 to 92% of the elite materials in other nurseries and IRRI screening trials derive from Cina. Of the 20,000 hybridizations made at IRRI by 1979, 44% of the female parents can be traced to Cina but the trend is declining.All named IR cultivars, except ‘IR5,’ and virtually all semidwarfs developed in national programs, carry the dwarfing gene from the Chinese dwarf cultivar ‘Dee‐geowoo‐gen.’The cytoplasmic similarity of modern cultivars, while posing no immediate practical problem, is of sufficient relevance to demand a prompt broadening of the maternal genetic base of improved rice cultivars. Recommendations are made for diversifying the maternal origin and the genetic base of subsequent semidwarfs.
Flexible Alfalfa Management: Early Spring Utilization1
Authors: Wolf D. D. , Blaser R. E. 
Published: July 2010

Providing low‐cost high quality grazing for livestock early in the spring when pasture and hay are limited may increase body weights at economical prices. Current alfalfa (Medicago sativa L.) varieties may be suitable for such grazing if either stands or yields are not greatly reduced by early spring harvests. To evaluate the possibilities of early spring alfalfa grazing, two severities of cutting to simulate grazing were imposed at several spring dates by removing one‐half the leaf area index (LAI) and all the LAI by cutting to a 5‐cm stubble height. Spring utilization dates, based on accumulating 1, 2, 3, and 4 LAI units, occurred on about 9 April, 27 April, 6 May, and 25 May, respectively. During the remainder of the season, harvesting hay at onetenth bloom was considered lenient management for recovery. The 9 April grazing cut, leaving about onehalf the LAI, enhanced the first hay yields as compared with removing nearly all the leaf area. However, at 6 May with an LAI of about 3, leaving one half the leaf area, resulted in lower yields and decreased quality of the following hay harvest as compared with a grazing cut at 5 cm which removed all leaf area. Regrowth from tall stubble remaining after the 6 May grazing cut generally orginated from branches at axillary buds which had smaller stems than those growing from crown buds. Early spring grazing cuts delayed the first hay harvest. This delay is desirable since favorable hay‐making weather is more likely later in the season. Number of regrowth days to one tenth bloom decreased between April and mid‐June and increased thereafter. Regrowth after early August cuts did not flower due to short days of late summer.Total season yields were similar for all treatments. Residual yields in subsequent years showed no detrimental effects due to date or severity of spring grazing cuts. Utilization of alfalfa in early srping by grazing and taking the first hay harvest about 3 weeks later than normal appears to be a feasible alternative system for flexible alfalfa management.
The Manifestation of Dehydration Avoidance in Wheat Breeding Germplasm1
Authors: Blum A. , Gozlan G. , Mayer J. 
Published: July 2010

The genetic improvement of wheat for conditions of drought stress requires an evaluation of specific physiological attributes related to drought resistance, as a basis for developing a working screening procedure. An important component of drought resistance is dehydration avoidance.Dehydration avoidance is defined as plant ability to maintain a relatively higher leaf water potential under conditions of soil moisture stress.The purpose of this investigation was to document the existance of and variability in dehydration avoidance within a random sample of advanced and well‐adapted wheat (Triticum sp.) genotypes.Midday leaf water potentials (Ψ1), as a measure of dehydration avoidance, were monitored with a pressure chamber in the various wheat genotypes, simultaneously subjected to soil moisture stress in three different field tests. Leaf diffusive resistance (R1) was monitored with a diffusion porometer in two of the tests.Genotypes varied significantly in their midday leaf water potentials. About 2 bars of Ψ1 were sufficient to differentiate significantly between genotypes. Variations in Ψ1 were greater than variations in R1 among genotypes. The largest difference in Ψ1 between extreme genotypes, as observed in these tests, reached 12.9 bars.In one test, where drought stress developed during the spike development stage, leaf water potential (but not leaf diffusive resistance) was correlated with the final number of grains per spike across genotypes of similar phenology.Linear regressions developed for each genotype between Ψ1 and R1 revealed large variations among genotypes in stomatal response to Ψ1. These relationships lead to the conclusion that dehydration avoidance in only a few of the genotypes may have resulted from stomatal sensitivity and closure at low stress levels. Most of the avoidant genotypes, however, maintained relatively open stomata.
Agronomic Evaluation of Soybean Genotypes Resistant to Iron Deficiency Chlorosis1
Authors: Niebur W. S. , Fehr W. R. 
Published: July 2010

Soybean [Glycine max (L.) Merr.] breeders are interested in the development of cultivars with high yield and resistance to iron deficiency chlorosis on calcareous soil. Our objective was to determine if there was a genotype × soil type interaction that would influence selection for yield on noncalcareous or calcareous soils among lines with a high level of resistance to iron chlorosis. Nineteen lines of Maturity Groups I and II with the best available level of resistance to iron chlorosis were evaluated on calcareous and noncalcareous soils at each of three locations in Iowa during 1979. Iron chelate applied to the plants permitted the evaluation of the genotype × soil type interaction in the absence of chlorosis symptoms.There was no genotype 4 soil type interaction for yield, maturity, height, lodging, seed weight, protein, or oil content. The rank correlation coefficient for mean yield of lines between calcareous and noncalcareous soils was 0.95. The top three lines for yield were the same on the two soil types. The results indicated that selection can be practiced for yield and other agronomic characters among lines resistant to iron chlorosis as effectively on noncalcareous as on calcareous soil.Significant yield reduction occurred on lines that showed slight yellowing in the absence of the iron treatment. This result indicated that complete elimination of yield loss due to iron chlorosis requires the use of cultivars or agronomic practices that prevent any chlorosis expression.
Simulated Comparisons of Single Seed Descent and Bulk Population Breeding Methods1
Authors: Muehlbauer F. J. , Burnell D. G. , Bogyo T. P. , Bogyo M. T. 
Published: July 2010

Two plant breeding methods generally used in breeding self‐pollinated crops, the bulk‐population (BP) and the single‐seed‐descent (SSD) methods, compared by computer simulation to determine which retained the most additive genetic variation after four generations of inbreeding. Various levels of fecundity were simulated in the BP method, and various probabilities of plant survival were used in the SSD method simulation. All simulations were done with a hypothetical crop having seven chromosomes with six loci on each and various degrees of linkage.In the F6, the additive genetic variance in the BP method was smaller than that in the SSD method; this difference was attributed to losses in genetic variability in BP during generation advance. Within BP a considerable proportion of the total additive variance originated from within‐line variance, as opposed to that which originated from between‐line variance. When the inbreeding coefficient was larger than 0.9, the difference between within‐line and between‐line variances was considerable. In the SSD method, all additive variance must originate from between‐line variance.Fecundity affected the genetic variability in BP, whereas the probability of individual plant survival was important in SSD. When the standard deviation of fecundity was greater than 25 seeds per plant, progeny from 75% of the original F2 plants were not represented in the population after four generations of advance by BP. About the same number of lines were lost after four generations when seedling survival dropped below 70% in each generation of advance by SSD. Linkage had little effect on additive genetic variance in either system, unless the two lines of the original cross had considerably different sets of alleles.