bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Freezing Tolerance in Relation to Winter Survival of Rapeseed Cultivars
Authors: Teutonico Rita A. , Palta Jiwan P. , Osborn Thomas C.
Published: July 2010

Winter survival is a complex trait dependent on a number of parameters, including the morphological and physiological characteristics of the plant, soil conditions, and weather fluctuations. Freezing tolerance of the plant is a major factor determining winter survival and can be assessed indirectly by measuring ion leakage from leaves exposed to freezing temperatures. This study was conducted to determine the relationship between in vitro freezing tolerance and winter survival in rapeseed. Ten rapeseed cultivars (Brassica napus and B. rapa) were subjected to an in vitro controlled freeze and assayed for ion leakage both before and after cold acclimation for three weeks. In addition, these same cultivars were fall‐seeded at two field locations and their winter survival evaluated. Freezing tolerances determined by the in vitro freezing assay increased after acclimation, and cultivars differed significantly for freezin tolerance before and after acclimation. The increase in in vitro freezing tolerance of the cultivars after acclimation was correlated significantly with winter survival (r = 0.82–0.85, P < 0.05), and, therefore, this in vitro assay could be a useful predictor of field results. One exception to this correlation was B. napus cultivar Santana, which had a large capacity for acclimation but did not survive in either field location. These results suggest that freezing tolerance is an important, but not the only, component of winter survival.
Carbon Isitope Discrimination, Water Relations, and Photosynthesis in Tall Fescue
Authors: Johnson Richard C.
Published: July 2010

Carbon isotope discrimination (Δ) shows promise for estimating water‐use efficiency (WUE) in crop species. Research was undertaken to examine Δ and water relations of tall rescue (Festuca arundinacea Schreb.) accessions and to determine if low Δ is associated with high gas exchange WUE as predicted by theory. The accession PI 438522 had lower Δ than the accession PI 231522 in both a dryland and an irrigated field environment and at two sampling dates. Correlations among Δ, water potential, solute potential, and turgor pressure were not significant under irrigation. Under dryland conditions, correla. tions among these factors were generally significant and positive for PI 438522, but not significant for PI 231561. In a greenhouse experiment, plants selected for low Δ from the irrigated field environment had lower A and internal leaf [COz] (Ci), and a higher ratio of CO2 assimilation rate (A) to transpiration than high‐A selections. This was true for both well‐watered plants and plants stressed with a ‐0.38 MPa polyethylene glycol solution. Stomatal conductance and A were positively correlated with Δ, suggesting that lower stomatal conductance was a factor leading to lower C1 and Δ. The results suggest that associations between water relations and Δ vary depending on accession and environment, but selecting tall rescue plants for low Δ does identify genotypes with low C1 and high WUE. Using Δ for germplasm enhancement of WUE in tall rescue appears promising.
Planting Date and Plant Density Effects on Condensed Tannin Concentration of Cotton
Authors: Lege Ken E. , Smith C. Wayne , Cothren J. Tom
Published: July 2010

Condensed tannins are feeding deterrents to cotton bollworm [Helicoverpa zea (Boddie); syn. Heliothis zea], tobacco budworm [Helicoverpa virescens (F.); syn. Heliothis virescens], and spider mite (Tetranychus urticae Koch) in cotton (Gossypium hirsutum L.). This study was conducted to determine the effects of planting date and plant density on the condensed tannin concentrations of six plant parts of cotton sampled at two growth stages at College Station, TX, in 1988 and 1989. Cotton was sown every 2 wk to provide three planting dates beginning on 25 April in both years. Genotypes evaluated were ‘Tamcot CD3H’, ‘Arkot 518’, and four high‐tannin lines (TAM 86III24, TAM 86E3, TAM 86E8, and 86CC2) selected for spider mite resistance. The topmost unfolded leaf, a fourth mainstem leaf from the terminal, a 6‐d‐old bract, a 10‐d‐old sepal, and a bract and a sepal from a white bloom were sampled at first bloom and at 2 wk post first bloom from plants spaced 8 and 30 cm within rows spaced 1.02 m apart. Younger tissue consistently had a higher condensed tannin concentration than mature tissue. Condensed tannin concentrations were highest in TAM 86III24 and lowest in the two commercial cultivars, Arkot 518 and Tamcot CD3H. TAM 86E8, TAM 86E3, and 86CC2 were intermediate in tannins. Breeding cotton for high tannin concentration would require consideration of the tissue sampled because of the interaction of genotype with this factor.
An Approach to Reduce the Time Required for Bean Yield Evaluation in Coffee Breeding
Authors: Moncada Pilar , Casler Michael D. , Clayton Murray K.
Published: July 2010

Efficiency of plant breeding programs, particularly in perennial crops, may be improved by reducing the time required for evaluation prior to selection. The objective of this work was to study expected selection responses of several variables based on partial bean yields compared to total accumulated bean yield of coffee (Coffea arabica L.) during the first 48 mo of production. One hundred thirty‐eight F5 families of a cross between C. arabica cv. Caturra and Timor hybrid were randomly distributed among four experiments transplanted in 6 × 6 simple lattice designs. Beans were harvested by hand monthly from each tree. Fresh bean yield was determined for each tree on 48 harvests over a 4‐yr period. Sixty‐eight variables were created from bean yield data collected from the 48 harvests; the variables were based on meaningful subsets of the 48 harvests. Heritability was estimated on a family mean basis from components of variance for each variable. Direct selection response for total yield (R) as well as correlated response for total yield (CR), due to selection for a correlated variable, were also computed. The CR/R ratios exceeded 100% for accumulated bean yield of all harvests after 32 mo of age in each experiment. Confidence interval estimates (95% level) of mean CR/R or mean age at which CR/R exceeded 100% suggested an optimum age of 36 mo. Selection for accumulated bean yield at 36 mo‐of‐age was estimated to be 37% more efficient, per year, as selection at 69 mo‐of‐age. The only other variable with potential as an efficient selection criterion was accumulated bean yield for the 5 mo of typically maximum bean production during the first 2 yr, which still requires trees to be 43 mo old before selections are made.
Inheritance of Carbon Isotope Discrimination and Water‐Use Efficiency in Cowpea
Authors: Ismail Abdelbagi M. , Hall Anthony E.
Published: July 2010

Theory has been developed predicting an association between water‐use efficiency (WUE = total biomass/transpiration) and leaf discrimination against 13C (Δ), which could be used to indirectly select for WUE in C3 plants. Previous studies indicated variation in WUE and Δ among genotypes of cowpea [Vigna unguiculata (L.) Walp.] and due to drought. Moreover, a highly significant negative correlation between WUE and Δ was observed for both genotypic and drought effects, as expected based on theory. Present studies were conducted to investigate whether the inheritance of WUE and Δ is nuclear or maternal, and whether any dominance is present. Contrasting cowpea accessions and hybrids were grown over 2 yr in two outdoor pot experiments, subjected to wet or dry treatments, and under full irrigation in natural soil conditions in 1 yr. Highly significant differences in WUE were observed among cowpea parents and hybrids, and due to drought, which were strongly and negatively correlated with Δ, as expected based on theory. Data from reciprocal crosses indicated that both WUE and Δ are controlled by nuclear genes. High WUE and low Δ exhibited partial dominance under pot conditions. In contrast, high Δ was partially dominant for plants grown under natural soil conditions but in a similar aerial environment as in the pot studies. We speculate that differences in rooting conditions were responsible for the differences in extent of dominance for Δ of plants growing under pot conditions compared with natural soil conditions in a similar field aerial environment.
Heat‐Unit‐Based Description of the Reproductive Development of Pea
Authors: Ney Bertrand , Turc Olivier
Published: July 2010

Yield of pea (Pisum sativum L.) is strongly dependent on two yield components, seed number and individual seed mass, that depend on the sequential processes of reproductive development. In order to describe the reproductive development of pea, the progressions along the main stem of three stages of development—flowering, initiation of seed filling, and physiological maturity—were studied with three cultivars grown in different conditions. It was shown that the progressive development can be described by linear functions based on cumulative degree days (CDD), using the average between daily minimum and maximum temperatures and a base temperature of 0 °C. The rates of progression of flowering (RF) did not vary significantly in the most favorable growth conditions for individual plants, i.e., at low plant density. The rate of progression of the initiation of seed filling (RS) was not significantly different from that of RF. The time interval between the initiation of flowering and seed filling was also stable, for a given cultivar, but the time of physiological maturity varied widely and progressed faster than the other stages along the stem. At high plant densities, when competition between plants increased, RF and RS decreased, but as at low plant densities, both values were not significantly different. The time interval between initiation of flowering and seed filling remained stable. In order to assess the influence of plant density on development, RF was related the growth rate of the shoot during flowering (GR). The relationship showed that increased with GR until a threshold of GR. Above this threshold, which was similar for cultivars Solara and Frisson, RF remained constant. This asymptotic value, RFmax, differed between genotypes. If RFmax is known, a simple method is proposed to precisely estimate the periods of formation of yield components, seed number and individual seed mass, on a plant or even a node basis. Only three simple measurements—the time of initiation of flowering, time to maturity, and number of highest fruiting node at harvest—are required for this calculation.
Caryopsis Weight Patterns within the Sorghum Panicle
Authors: Heiniger Ronnie W. , Vanderlip Richard L. , Kofoid Kenneth D.
Published: July 2010

Understanding the intrapanicle pattern of caryopsis weights commonly found in sorghum [Sorghum bicolor (L.) Moench] fields and the factors that result in changes in this pattern would help in determining limitations on caryopsis weight. Our objectives were to determine the pattern of caryopsis weights found in the sorghum panicle, the effect of assimilate supply on the weight pattern, and whether this pattern resulted from the rate of grain fill or length of the effective fill period (EPP). Two dryland field studies were conducted at Manhattan, KS, in 1989 and 1990 on a Reading silt loam (fine‐silty, mixed, mesic Typic Argiudoll; 0–1% slope). In 1989, panicles of DeKalb ‘DK 46’ and Pioneer ‘8500’ tagged at anthesis were harvested at regular intervals. In 1990, seven population‐light treatments were applied to Pioneer 8500 either at anthesis or 7 d after anthesis. Panicles from both experiments were separated into four sections. Caryopses from these sections were used to determine differences in caryopsis weights, rate of grain fill, and length of the EPP. In 1989, caryopsis weights within the sorghum panicle increased from 20.2 mg caryopsis−1 at the base to 22.8 mg caryopsis−1 at the apex. In 1990, this same intrapanicle pattern was observed in all treatments that had medium or high plant populations during the EPP. This pattern was caused by increases in the rate of grain fill from the base to apex of the panicle. In the low population treatments in 1990, caryopses in the middle of the panicle were as heavy or heavier than those in the apex. This was the result of intrapanicle grain‐fill rates that were more uniform and an increase in the length of the EPP from the apex to the base of the panicle.
Influence of Pollination Pattern on Intrapanicle Caryopsis Weight in Sorghum
Authors: Heiniger Ronnie W. , Vanderlip Richard L. , Kofoid Kenneth D.
Published: July 2010

Recent studies have shown that changes in grain‐fill rates within the sorghum [Sorghum bicolor (L.) Moench] panicle cause caryopsis weights to decrease from the apex to the base. Pollination pattern in the sorghum panicle is also basipetal. The objectives of this study were to determine if pollination pattern influences intrapanicle caryopsis weights and to determine which components of grain fill are affected by pollination pattern. Field studies were done in 1990 at Manhattan, KS, on a Reading silt loam [fine‐silty, mixed, mesic Typic Argiudoll (0–1% slope)] and Hays, KS, on a Barney silt loam [fine, montmorillonitic, mesic Typic Argiustoll (0–1% slope)]. At Manhattan, eight pollination‐pattern treatments were applied to DeKalb DK 46 and its male‐sterile parent, 97A. At Hays, a male‐sterile hybrid, KS56A × KS47B, received four of the eight treatments. Panicles were divided into four equal sections; apex, upper middle, lower middle, and base. Different pollination patterns were applied to the sterilized panicles by exposing the appropriate sections to pollen. Differences in caryopsis weights and weight components were determined using analysis of variance and linear regression analyses. In all cases, intrapanicle caryopsis weights followed the pollination pattern applied. The panicle sections pollinated first had caryopses that were from 1.0 to 2.5 mg heavier than those found in the sections pollinated later. Pollination pattern influenced caryopsis weight by influencing grain‐fill rates within the panicle; the length of the grain‐fill period did not change. Apparently, caryopses that were pollinated first were better competitors for assimilates than those pollinated later.
A Rapid Technique for Measuring Breakdown Rate of Hardseededness in Subterranean Clover
Authors: Fairbrother T. E. , Pederson G. A.
Published: July 2010

An impermeable seedcoat or hardseededness is the most important germination regulation mechanism in subterranean clover (Trifolium subterraneum L.). Hardseededness breakdown rate has been evaluated by exposing hard seed to fluctuating temperature (60/15 °C) for 6 mo. Our objective was to compare four methods for evaluating breakdown rates of hardseededness from four subterranean clover cultivars and to determine if the Weibull model accurately described the loss of hardseededness with time. The Weibull model accurately described the loss of hardseededness with time of 24 legume genotypes with diverse softening rates from data reported in the literature. Hard seed from greenhouse‐grown plants of ‘Nungarin’, ‘Meteora’, ‘Trikkala’, and ‘Mount Barker’ were tested for hardseededness breakdown rate in 1988 and 1989. Hardseededness breakdown rate was determined by using diurnal fluctuating temperature methods of 60/15 °C in Australia or 47/25 °C in the USA and constant temperature method of 50 or 60 °C followed by 7 d of 60/15 °C fluctuating temperature. The Weibull model accurately described the loss of hardseededness with time of all treatments (Sy.x = 4.35). Meteora was the slowest to soften followed by Nungarin, Mt. Barker, and Trikkala. The U.S. temperature treatment softened seed the slowest followed by Australia's, 50 and 60 °C. All temperature methods ranked cultivars in the same order for hardseededness breakdown rate. Variation among cultivar softening rate was measured in 112 fewer days by the constant temperature methods compared to the fluctuating temperature methods.
Gauging Turfgrass Salinity Responses in Whole‐Plant Microculture and Solution Culture
Authors: Smith Mary Ann L. , Meyer Jeffrey E. , Knight Sharon L. , Chen G. Stanley
Published: July 2010

New methods for assessing salinity responses of turfgrass lines are required to identify selections for use on marginal sites. This study was conducted to quantify whole turfgrass plant responses to salt in solution‐culture and microculture test environments, and to evaluate the latter as an alternative system for identifying salt‐resistance characteristics. Paired cultivars of bermudagrass (Cynodon spp.), creeping bentgrass [Agrostis stolonifera L. var. palustris (Huds.) Farw. syn.] and St. Augustinegrass [Stenotaphrum secundatum (Walt.) p. Kuntze] were tested in treatments ranging from control (no supplemental salt) to 32.4 dS m−1 conductivity (NaCl in the growth medium). Direct comparison between test environments of the regression slopes for osmotic adjustment revealed no significant differences for bermudagrass, and salt‐sensitive cultivars of St. Augustinegrass and creeping bentgrass. Linear or quadratic regressions characterized reductions in all shoot growth parameters with increasing salt levels in both solution and microculture environments. More severe regressions were frequently observed for relatively salt‐sensitive cultivars. Root length and area data did not exhibit consistent regressions on medium conductivity level in either test system. These results demonstrate that the small‐scale microculture environment can be used to nonintrusively monitor turfgrass plant responses to salinity.
Temperature and Photoperiod Effects on Multifoliolate Expression and Morphology of Alfalfa
Authors: Juan Nestor A. , Sheaffer Craig C. , Barnes Donald K.
Published: July 2010

Alfalfa (Medicago sativa L.) cultivars with multifoliolate (MF) leaves are being promoted as a source of high quality forage, but information is lacking about the effect of environment on MF expression. We studied the influence of air temperature and photoperiod on the MF trait and its association with leaf and stem morphology. We grouped plants from four cultivars into four MF expression classes (very low, <10%; low, 10–29%; medium, 30–60%; and high, >60% MF leaves). These plants were grown in four growth chamber environments combining cool (20/11 °C day/night) and warm (29/17 °C) air temperatures with short (13 h) and long (16 h) photoperiods. Photoperiod had greater influence than temperature on MF expression (MF%, number of MF leaves total leaf number−1). Under long‐days, MF expression of plants in very low, low, and medium MF expression classes declined linearly with increased maturity. Under short‐days, MF% of these classes declined until bud, but then increased until maturity. Multifoliolate expression of plants in the high expression class decreased in the cool‐long day environment, but maintained or increased MF% in other environments. At harvest, MF%, leafiness, and leaflet number per MF leaf were greater for short vs. long photoperiods, but were not affected by air temperature. Multifoliolate expression was positively correlated (r = 0.43) with leafiness and number of leaflets per MF leaf (r = 0.96), but was not correlated with stem characteristics. Individual MF leaves had larger leaf area but similar specific leaf weight as trifoliolate leaves in all environments. In evaluation of MF expression, stage of maturity, and environmental conditions should be standardized.
New Evidence Relating the Pilose Allele and Micronaire Reading in Cotton
Authors: Kloth R. H.
Published: July 2010

Experiments were undertaken to determine whether close linkage between the pilose allele and a locus influencing cotton (Gossypium hirsutum L.) fiber fineness had been misinterpreted as pleiotropy. Pilose (T1), the dominant allele to the t1 locus, is phenotypically described by a high density of trichomes on the leaf surface, the presence of trichomes on the carpel wall, and increased micronaire. Two lines, 239‐17/6 and 250‐14/2, were derived from single plant selections of pilose plants in an ‘Empire’ genetic background. 239‐17/6 has atypically low micronaire readings. The 239‐17/6 line was crossed to 250‐ 14/2, a pilose, high‐micronaire line, and to lines carrying t1 (normally pubescent) and Tsm1 (glabrous). The F1 plants were selfed for F2 and backcrossefl to t1 and Tsm1 parents. Similar hybrids and backcrosses were made between 250‐14/2 and t1 locus recessives. The agronomic performance and fiber traits of 239‐17/6, 250‐14/2, Empire, and FTA (low micronaire check) were measured for 2 yr in replicated experiments. Lint yield, lint percent, and the fiber traits of elongation, maturity, micronaire, perimeter, span length, strength, and wall thickness were measured. 239‐17/6 expressed a T1 pilose phenotype. All 465 F2 seedlings from 239‐17/6 × 250‐14/2 and reciprocal cross had tomentose leaves. The combined results from crosses of 239‐17/ 6 and 250‐14/2 with t1 and Tsm1, and backcrosses of F1 to t1 and Tsm1 demonstrated that 239‐17/6 and 250‐14/2 both carry T1. The fiber of 239‐17/6 was not distinguishable from the fiber of either Empire or FTA for the wall traits of maturity, micronaire, and wall thickness. 239‐17/6 was shown to have the T1 phenotype and behave genetically like T1. Since T1 was associated with both high and low micronaire readings, the pleiotropic effect of T1 on micronaire appears unlikely. A more likely explanation is the T1 is linked to a gene or block of genes that influence micronaire.
Assessment of Screening Techniques for Heat Tolerance in Wheat
Authors: Tahir M. , Singh M.
Published: July 2010

Heat causes considerable damage to the wheat (Triticum aestivum L. em Thell.) plant. The present method of assessing heat tolerance in wheat, which is based on cell membrane thermostability, is not efficient for screening large numbers of genotypes. This study compares the efficiencies of two modified methods with that of the original method for measuring heat damage in wheat genotypes. Percent heat damage was analyzed by an errors‐in‐variables approach. Measurements of the original method were regressed on measurements of the new methods. The first modified method, is 25% more efficient than the original method and possesses similar accuracy. In the second method, the slope differed from unity by 3% and the intercept was −3.21, but the ranks of the tested genotypes did not change. Therefore, for screening heat‐tolerant genotypes relative to a check, the second method, which is 50% more efficient than the original method, is recommended because the relative classification of genotypes into tolerant and susceptible groups does not change with a constant difference in the measurements.
Heat Injury during Early Floral Bud Development in Cowpea
Authors: Ahmed Faisal E. , Hall Anthony E.
Published: July 2010

Heat stress during the vegetative and early reproductive stages induces floral bud abortion in cowpea [Vigna unguiculata (L.) Walp.] and several other crop species growing under long days, and can substantially reduce productivity. The objective of this study was to determine whether there is a specific developmental stage when heat stress causes abortion of floral buds. Cowpea plants were grown in four reach‐in growth chambers under either metal halide‐based (MH) or fluorescent‐based (FL) lighting systems with 14‐h photoperiod and thermoperiod. Heat injury to floral bud development was quantified as floral bud suppression; the percentage of peduncles on the first five reproductive nodes that did not produce at least one flower. In all cases, floral buds were initiated on these nodes. Light quality influenced plant responses, but similar responses to temperature were obtained when red/far red ratios were 1.3 for the MH system and 1.6 for the FL system. High night temperature (30 °C) caused complete suppression of floral buds, whereas development was normal at a night temperature of 20 °C. Transfer and heat‐pulse experiments demonstrated that plants were not sensitive to high night temperature at a particular stage of development but that the duration of heat experience may be critical for the suppression of floral bud development. Two weeks or more of consecutive or interrupted hot nights during the first 4 wk after germination caused complete suppression of the development of the first five floral buds on the main stem. Mechanisms for the effects of heat stress on floral bud development are discussed.
Distribution of Nitrogen among Leaves in Soybean Canopies
Authors: Shiraiwa Tatsuhiko , Sinclair Thomas R.
Published: July 2010

The N distribution among leaves in a plant canopy can theoretically have an important influence on crop photosynthetic activity. However, little detailed information is available on the specific leaf nitrogen (SLN, g N m−2) distribution in soybean [Glycine max (L.) Merr.] canopies. Experiments were established at Gainesville, FL and in Japan to examine the effects of cultivar, canopy maturity, plant density, and N fertility on SLN distribution. The SLN distribution was measured by dividing canopies by height or node number into relatively thin layers and determining SLN for each layer. Canopies with expanding leaves were found to have a fairly uniform SLN in the top 1.5 to 2.0 LAI. Below this top zone there was a linear decline in SLN with increased cumulative LAI. In contrast, mature canopies with fully expanded leaves only were found to have a continuous linear decrease in SLN with cumulative LAI from the top of the canopy. The SLN of the leaves at the top of the mature canopies were substantially greater than those canopies with expanding leaves. Neither plant density nor N fertility substantially altered the linear decline in SLN with cumulative LAI.
Cultivar and Winter Cover Effects on Bermudagrass Cold Acclimation and Crown Moisture Content
Authors: Shashikumar K. , Nus J. L.
Published: July 2010

A prime concern for turfgrass managers using bermudagrass [Cynodon dactylon (L.) Pers.] in temperate regions is its winter survival. Because bermudagrasses do not reach maximum hardiness until midwinter, they are susceptible to cold temperatures that may occur during early winter. Management strategies to reduce winter injury and hasten post‐dormancy growth include the use of protective winter covers. A 3‐year field study was initiated to test the effect of spun‐bonded winter covers applied in early December and removed in late May on bermudagrass cold acclimation and crown moisture content, and to assess the variation in the cold acclimation of eight selected cultivars. Cold acclimation was measured by electrolyte leakage and 2,3,5‐triphenyl tetrazolium chloride (TTC) reduction. Significant variation existed among the cultivars in cold acclimation. ‘Midiron’ was the most cold hardy and ‘Arizona Common’ the least hardy. ‘A‐22’ and ‘Tifway‘ ranked intermediate in hardiness by both electrolyte leakage and TTC.reduction methods. The presence of spun‐bonded covers improved cold acclimation (lowered hardiness reference temperature (LT50) by ≈2 °C during mid‐winter sampling) and increased crown moisture content from 100 to 200 g kg−1 of all cultivars tested. Results suggest the use of covers may significantly enhance the winter survivability of bermudagrass grown in the transition zone.
Forage Quality Responses of C3 and C4 Perennial Grasses to Shade
Authors: Kephart Kevin D. , Buxton Dwayne R.
Published: July 2010

Both C3 and C4 grasses exhibit similar morphological responses to shade, but they differ in photosynthesis‐related responses to shade, such as forage yield and growth rate. Morphological adaptation and reduced photosynthesis under shade may affect forage quality. The objective of this research was to determine the effect of adaptation to shade on forage quality of C3 and C4 grasses. The C3 species were tall fescue (Festuca arundinacea Schreb.), reed canary grass (Phalaris arundinacea L.), and deertongue grass (Panicum clandestinum L.); the C4 species were switchgrass(Panicum virgatum Michx.) and big bluestem (Andropogon gerardii Vit.). Grasses were established near Ames, IA, and grown under shade cloths which allowed 37 and 70% of ambient sunlight (AS) to penetrate. In addition, the grasses were subjected to a nonshaded (100% AS) treatment. Leaf blades, nonlaminar herbage, and total herbage samples were obtained at approximately 21‐d increments from late spring to early summer for 2 yr. Neutral‐detergent fiber (NDF) concentration in leaf blades was 18% greater in C4 species than in C3 species. Otherwise, few clear differences were observed between C3 and C4 types. Compared with the 100% AS treatment, NDF concentration in the 37% AS treatment was reduced 2 to 3%, whereas N concentration was increased by about 31% in nonlaminar herbage. In vitro digestible dry matter was increased 3 to 5% by shade. Nitrogen content per unit leaf area was not affected by shade, suggesting that nitrogenous compounds were concentrated by thinning of leaves. Thus, stressful growth conditions that limit photosynthate, such as shade, may improve forage quality.
Free Fatty Acids in Shrunken‐2 Sweet Corn Seed
Authors: Ratcliff Sherry L. , Wilson Dale O. , Knott Elizabeth A. , Mohan S. Krishna
Published: July 2010

High free fatty acid (FFA) levels have been reported in commercial shrunken‐2 (sh2) sweet corn (Zea mays L.) seeds. Objectives of this study included comparison of FFA content of sh2 corn seed with other genotypes and preliminary study of the source of the FFA. Kernel infection by seed‐borne fungi was not consistently correlated with FFA. With toluene extraction, sh2 sweet corn seed averaged 83.2 mmol kg−1 FFA compared with 2.1 mmol kg−1 from dent and 4.8 mmol kg−1 from sugary corn. Hot, water‐saturated butanol for 5 h (HWSB) extracted 57% more FFA from sh2 seed than did toluene. However, HWSB extracted 781% more FFA from dent corn seed than did toluene. Considering the four‐fold greater lipid content of sh2 kernels on a weight basis, this suggests that slightly more than half of the high FFA content of sh2 corn seed observed with toluene extraction resulted from relative lack of starch‐bound lipid in the sh2 endosperm.
Molecular Cytogenetic Analysis in Wheat
Authors: Gill Bikram S.
Published: July 2010

Two technical innovations led to major advances in the molecular cytogenetic analyses of the wheat genome. The first innovation, the application of banding techniques, permitted distinction between heterochromatic and euchromatic regions and led to individual identification of metaphase chromosomes. The second innovation, the development of in situ hybridization protocols, permitted molecular analysis of chromosome structure, and physical localization of specific DNA sequences in individual chromosomes. The applications of banding and in situ hybridization techniques in cytogenetics, plant breeding, gene mapping, and in assaying alien chromatin introgression are briefly discussed. A connection is made to the pioneering contributions of E.R. Sears, without which, rapid progress in the molecular cytogenetic analysis of wheat would not have occurred.
Chromosome Engineering in Tetraploid Wheat
Authors: Joppa L. R.
Published: July 2010

The progress in genetic research of tetraploid wheats has been limited by a lack of suitable cytogenetic stocks similar to those available in hexaploid wheat. Also, the tetraploid wheats, as a group, have received less attention from scientists, because they are grown on a small part of the world's total wheat production area and have limited use in the production of bread products. However, one of the varieties Triticum turgidum L. var. durum, is widely used in the production of pasta products such as spaghetti and macaroni. Therefore, investigations have centered on the production of several sets of aneuploid genetic stocks in durum wheat and on the development of methods for their use. The aneuploid stocks of the durum cultivar Langdon include double‐ditelosomics, dimonotelosomics, D‐genome disomic substitutions, intercultivar chromosome substitution lines, and homozygous recombinant lines. The knowledge obtained during the development of these aneuploids has suggested methods for their use. Some examples of useful studies are described.
Relationships between Barley Yellow Dwarf Virus Titer and Symptom Expression in Barley
Authors: Ranieri R. , Lister R. M. , Burnett P. A.
Published: July 2010

To investigate relationships between barley yellow dwarf virus (BYDV) titer and symptom expression in barley, enzyme‐linked immunosorbent assay (ELISA) was used to compare the titers of specific virus isolates in artificially infected plants of cuitivars previously assessed for symptom expression in field tests. Four Mexican isolates of BYDV were used: Mex‐PAV, Mex‐MAV, Mex RPV, and Mex‐RMV. The near‐isogenic lines ‘CM67’ (Yd2+) and ‘California Mariout’ (Yd2‐) were compared in most detail. The titer of Mex‐PAV was significantly lower in shoots and roots of the relatively tolerant line CM67 3 to 29 d after inoculation than in the relatively sensitive California Mariout. Similar differences were observed, but in roots only, for Mex‐MAV infections. For the Mex.RPV and Mex‐RMV isolates, no significant differences in virus content occurred between these lines. With each isolate and cultivar, maximum virus content occurred 11 d after inoculation. Assessments at this time indicated relatively low levels of some of the virus isolates used in the relatively tolerant cultivars ‘Shyri’, ‘Laurel’, ‘Agave’, and ‘Zarza’. The results with other cultivars were less consistent, but in general their virus contents were relatively high whether they had shown tolerance or sensitivity in field tests. The trends noted remained the same when the data were compared using a “susceptibility index” designed to provide a convenient comparison of cultivars across serotypes by compensating for differences in the reactivities of different antisera used for ELISA. The need for identification of the specific strains of BYDV involved in tests for tolerance and resistance is emphasized.
Seed Coat Cracking in Soybean
Authors: Yaklich R. W. , Barla‐Szabo G.
Published: July 2010

Elliptical cracks in the soybean [Glycine max (L.) Merr.] seed coat have been termed seed coat cracking. This imperfection of the seed coat is an avenue for pathogenic and adverse environmental factors to affect seed quality. To better understand this phenomenon, the time of occurrence and morphological changes involved in seed coat cracking were examined by light and scanning electron microscopy. Physical parameters of normal and cracked seed and the amount of seed coat cracking that occurs in a pod were also determined. Seed coat cracking began in the late R6 growth stage just prior to R7 growth stage (physiological maturity). The initial cracking of the tissues occurred around the hilum; the most common separation was perpendicular to the raphe. Separation also occurred on either side of the embryonic axis. As the seed matured and began to desiccate, the cracks elongated and became perpendicular to the hilum exposing the parenchyma cells. This separation was accompanied by a slight upward rolling of the parenchyma and underlying tissue. The cotyledonary tissue, that was beneath the cracked area was raised above the surrounding tissues, indicating that this area of the cotyledon possibly matured at a different rate than adjacentissues. Seeds with cracked coats were generally larger than seeds with normal seed coats. There was a significant probability (P < .001) that if one seed coat was cracked in a pod then all seeds in the pod contained cracked seed coats. The results suggest that separation of the palisade and hourglass tissues is caused by parenchyma or underlying tissues that do not contract normally during seed desiccation.
Incorporation of [14C]Glucose into Crystalline Cellulose in Aberrant Fibers of a Cotton Mutant
Authors: Kohel R. J. , Benedict C. R. , Jividen G. M.
Published: July 2010

Ligon lintless‐1 is a dominant simply inherited mutant of cotton (Gossypium hirsutum L.) containing markedly short cotton fibers with extensively thickened secondary walls. The incorporation of [14C]glucose into crystalline cellulose in the primary and secondary walls was studied to determine the relation between the extent of crystalline cellulose microfibril formation and the pattern of microfibril deposition to the aberrant growth and developmental pattern in the mutant cotton. The results show that the rate of crystalline cellulose formation in the primary walls of the mutant fibers correlates with the reduced rate of fiber elongation and primary wall formation. There is a five‐fold increase in the rate of crystalline cellulose formed per millimeter of fiber length during secondary wall formation in the mutant fibers compared to the rate in the wild‐type fibers. The Ligon lintless−1 gene mutation affects the growth and development of the cotton fibers with accompanying changes in the rate of formation of crystalline cellulose microfibrils in the primary and secondary walls. This increase in crystalline cellulose microfibrils in secondary walls is most likely due either to an increase in synthetic activity of the individual cellulose synthase complexes or to an increase in number of synthetic complex sites per unit of fiber length in the mutant.
Gametic Selection at Fatty Acid and Allozyme Marker Loci and Meiosis within Cuphea viscosissima × Cuphea lanceolata Populations
Authors: Brandt T. , Knapp S. J.
Published: July 2010

The seed oils of many of the 260 species of Cuphea (Lythraceae) are rich natural sources of medium‐chain fatty acids. Among them are C. viscosissima Jacq. (2n = 2x = 12) and C. lanceolate Ait. (2n = 2x = 12). These species show promise as oilseed crops and, as a consequence, are being domesticated. Hybrids were made between C. viscosissima (VS) and C. lanceolata f. silenoides (LNS) and between C. viscosissima and C. lanceolata f. typica (LNT) to assess their usefulness for breeding Cuphea. Microsporocytes of VS, LNS, LNT, and their hybrids were observed at metaphase I and anaphase I. Allozyme and fatty acid synthesis (FAS) marker loci were assayed within VS × LNS F2 and backcross populations to test for gamete and heterozygote selection. The cross VS × LNS was female‐ and male‐fertile, whereas VS × LNT was female‐ and male‐sterile. Bivalent pairing and regular chromosome segregation was observed for 94.0 and 0.0% of the microsporocytes from VS × LNS and VS × LNT, respectively. Mean chiasma frequencies within VS × LNS and VS × LNT were 0.53 and 0.26, respectively. Genome and arm affinity index estimates for VS × LNS were 0.98 and 0.65, respectively. Genome and arm affinity index estimates for VS × LNT were 0.52 and 0.34, respectively. Wildtype caprylic and capric acid percentage differences of VS and LNS were explained by an incompletely dominant natural mutation at the cap‐1 locus—two and three nonoverlapping phenotypic distributions were observed for caprylic acid percentage within backcross or F2 populations, respectively. Thirteen of 20 marker segregation ratios and 12 of 18 allele frequency ratios were distorted—LNS alleles were overabundant more often than VS alleles. The was an overall excess of LNS alleles of 7.9%. The VS × LNS populations are useful for breeding—they undergo bivalent pairing and normal chromosome segregation—while meiosis is abnormal within VS × LNT populations.
Additional Genes for Resistance to Frogeye Leaf Spot Race 5 in Soybean
Authors: Pace P. F. , Weaver D. B. , Ploper L. D.
Published: July 2010

Frogeye leaf spot (caused by Cercospora sojina Hara) is a common foliar disease of soybean (Glycine max L. Merr.) in the southeastern USA. Three major dominant genes (Rcs1, Rcs2, and Rcs3) have been identified that confer resistance to frogeye leaf spot. Our objective was to determine the inheritance and possible allelism to Rcsa of genes for resistance in ‘Lee’, ‘Stonewall’, and ‘Ransom’. Lee, Stonewall, and Ransom were all intercrossed, crossed with ‘Davis’, which has Rcs3, and crossed with known susceptibles. F2 plants of crosses were inoculated with a spore suspension of race 5 of C. sojina, placed in a moist chamber for 2 to 3 d, and identified as susceptible or resistant based on leaf symptoms 14 d after inoculation. All F2 populations segregated 3 resistant : I susceptible or 15 resistant : 1 susceptible. This indicated different dominant genes for resistance to race 5 in Ransom, Stonewall, and Lee and that each was nonallelic to Rcs3 and to each other.
Variation in Seed Protein among Nodes of Determinate and Indeterminate Soybean Near‐Isolines
Authors: Escalante Eduardo E. , Wilcox James R.
Published: July 2010

Soybean, Glycinc max (L.) Merr., seed protein differs considerably among seeds from different nodes of indeterminate plants. Determinate soybean plants grown in the northern USA have fewer nodes, shorter flowering periods, but similar reproductive periods compared to indeterminate plants. The objective of this study was to determine nodal variability in seed protein of determinate vs. indeterminate soybean near‐isolines. Ten pairs of near‐isolines from four soybean crosses were included in a 2‐yr study at West Lafayette, IN. Protein content was evaluated for seeds from individual fruiting nodes on three plants from the ten determinate and indeterminate near‐isolines each year. Seed protein increased linearly from 397 at Node 5 to 442 g kg−1 seed weight at Node 11 on determinate plants. On indeterminate plants, seed protein increased from 398 at Node 6 to 441 g kg−1 at Node 14. Protein contents of seeds from Nodes 12 through 16 of indeterminate plants were all high but values did not differ significantly among these upper nodes. The greatest range in protein among all nodes from three plants of an individual line was from 349 to 510 g kg−1 for indeterminate and from 34 to 487 g kg−1 for determinate plants. The data demonstrate that accurate protein determinations for determinate, as well as indeterminate soybean plants, requires adequate sampling to represent the nodal variability occurring in both plant types.
Ease of Floret Tripping in Alfalfa: Quantitative Inheritance and Expected Genetic Gain
Authors: Knapp Eric E. , Teuber Larry R. , Henning John A.
Published: July 2010

Breeding alfalfa (Medicago saliva L.) with florets that are easier for honey bees (Apis mellifera L.) to trip has been proposed as a means of increasing the efficiency of pollination and improving seed yield. The objectives of this study were to determine the mode of inheritance and develop breeding recommendations for ease of tripping. Thirteen plants were chosen at random from ‘CUF101’ and emasculated crosses were made in a 6 × 7 factorial mating design. Ease of tripping was evaluated on florets of the resulting progeny in the field at Davis, CA, in 1990 and 1991. Variance components were estimated with autotetraploid genetic models and used to predict expected genetic gain for different breeding methods. Variances due to both males and males × females were significant, whereas the variance due to females was not significant. Additive genetic variance was 9.15 x 10~6 and digenic genetic variances was 4.45 × 10−6. Narrow‐sense heritability for ease of tripping on an individual plant basis was 34% (SE = 16%). Expected genetic gain per year was greater for phenotypic recurrent selection than for mass selection, half‐sib family selection, half‐sib progeny test selection, and among‐and‐within half‐sib family selection. Phenotypic recurrent selection, based on a single year of evaluation, is recommended as the most efficient breeding method for improving ease of tripping of CUF101 alfalfa.
Outcrossing Rates of Alfalfa Populations Differing in Ease of Floret Tripping
Authors: Knapp Eric E. , Teuber Larry R.
Published: July 2010

Breeding alfalfa (Medicago sativa L.) with florets that are easier for honey bees (Apis mellifera L.) to trip has been proposed as a means of increasing the efficiency of pollination and improving seed yield, but the impact of selection for ease of tripping on the mating system is not known. This study was conducted to evaluate ease of tripping, self‐fertility, and outcrossing rate of alfalfa populations selected for ease of tripping. Easy‐to‐trip, hard‐to‐trip, and ‘CUF101’ parent populations were planted in a randomized complete block design with three replicates at Davis, CA. Ease of tripping of the populations was measured, self‐fertility evaluated, and open‐pollinated seed harvested in each of two years. The mode of inheritance of the Peroxidase‐2 and Fluorescent Esterase‐1 allozyme loci was verified. Allozyme genotype at these two loci was determined for progeny arrays grown from the open‐pollinated seed, and the data used to calculate outcrossing rate of each population using multilocus maximum likelihood estimation procedures. The easy‐to‐trip population was easier to trip and the hard‐to‐trip population was harder to trip than the unselected parent population. Self‐fertility did not differ among populations. Both Peroxidase‐2 and Fluorescent Esterase‐I segregated as expected for monomeric enzymes at single tetrasomic loci. The outcrossing rate of the easy‐to‐trip population (0.76) did not differ from the outcrossing rate of the hard‐to‐trip population (0.75) or the CUF101 parent population (0.77). Selection for ease of tripping is an easily utilized indirect method which may improve alfalfa seed yield and does not alter the proportion of self‐pollinated seed produced.
Responses of Recombinant Inbred Lines of Wheat to Saline Irrigations: Milling and Baking Qualities
Authors: Kelman Walter M. , Qualset Calvin O.
Published: July 2010

Disposal of salinized drainage water is a problem in the irrigated San Joaquin Valley of California and it has been proposed that this water could be used judiciously in the culture of wheat Triticum aestivum L.). This may require breeding of cultivars specifically for this cropping system and the effects of saline irrigation on end‐use quality may be affected. These considerations were addressed in a field study where salinity concentration of irrigation water was controlled and water uniformly applied over test plots. Two agronomically desirable cultivars, Anza and Cajeme 71, and 43 random recombinant inbred lines derived from their hybrid were studied for two successive years with two N fertilization levels and three salinity levels. Nitrogen effects were minimal in this study because of a high level of basal N in the experimental site. Wheat flour quality and baking performance were improved by saline irrigation in the first year, but in the second year, when grain filling was poor, quality was adversely affected by salinity. High‐molecular‐weight glutenin alleles from Cajeme 71 at the Glu‐l locus were associated additively with improved flour protein content (Glu‐Al, Glu‐Dl), breadloaf volume (Glu‐Bl), and SDS sedimentation (Glu‐Dl). There was little or no interaction of the Glu‐l alleles with salinity for flour protein content and mixing time. Only one epistatic interaction effect out of 80 tested was significant (αABD for bake water absorption at high salinity in 1986). The additive effects were generally similar at the two salinity levels although interactions were detected which were less than 10% of the phcnorypic variance.