bluuebunny/crossref_metadata_2025 huggingface dataset:
Soybean Growth and Light Interception: Response to Differing Leaf and Stem Morphology
Authors: Wells Randy , Burton Joseph W. , Kilen Thomas C.
Published: July 2010

Altered canopy light environments created by plant architectural changes may increase plant productivity. Two morphological traits in soybean [Glycine max (L.) Merr.], brachytic stems (shortened internodes) and lanceolate leaflets, could be used for genetic manipulation of canopy structure. These traits were examined in various combinations in ‘Tracy‐M’ (maturity group VI) and ‘Wright’ (maturity group VII) backgrounds in 1990 (two environments) and 1991 (one environment with two row width‐plant population combinations). Throughout the season, plant height and photosynthetically active radiation (PAR) interception were monitored. At maturity, stem dry weight, seed yield, and yield components were determined. Brachytic stem genotypes were ≈40% shorter at harvest than the normal genotypes. Plant height was significantly associated with PAR interception during vegetative grown in both years R2 ≥ 0.58), and during reproductive growth in wide rows at Clayton irrespective of year (R2 ≥ 0.66). In 1991, seed yield was positively related to PAR interception during reproductive growth in the wide row‐low population combination (r2 = 0.49), when all genotypes were included in the analysis. For the Tracy‐M background, the same relationship was significant in all widerow environments. The data indicate that brachytic genotypes do not fully intercept available PAR in wide rows and low populations, especially when combined with lanceolate leaflets. Significant seed yield differences, despite 95% PAR interception by all genotypes in some environments, indicate the presence of yield limiting factors other than PAR interception. The present data fail to indicate significant improvements in performance due to the brachytic stem or lanceolate leaflet.
Stem Carbohydrate and Lignin Concentrations in Sorghum Hybrids at Seven Growth Stages
Authors: McBee George G. , Miller Fred R.
Published: July 2010

Grain yield and quality of vegetative material from sorghum [Sorghum bicolor (L.) Moench] are affected by carbohydrate and lignin partitioning within the plant and translocation of nonstructural carbohydrates (NSC) to the kernels. This field study was conducted during two growing seasons to determine concentrations of NSC, hemicellulose (HC), cellulose~ and lignin in four sorghum hybrids at seven growth stages from panicle differentiation through 45 days post anthesis (DPA) of plants. Stem NSC increased to 148 g kg−1 in ATx378 × RTx7000, 208 in ATx378 × RTx430, and 268 in ATx623 × SC599‐ 11E from PD to ≈15 DPA, decreased to 47, 85, and 183 between 23 and 32 DPA (kernel blacklayer) and then increased to 280, 340, and 380 at 45 DPA. Stem NSC increased at most stages in ATx623 × Hegari from panicle differentiation to a maximum of 450 g kg−1 at 32 DPA. Hemicellulose decreased and cellulose increased from panicle differentiation to preboot, but concentrations remained relatively stable from anthesis to 45 DPA, with ranges of 425 to 475 g HC kg−1 neutral detergent fiber (NDF) and 440 to 490 g cellulose kg−1NDF. Lignin increased from panicle differentiation to 15 DPA and then stabilized, with concentrations ranging from 75 to 105 g kg−1 NDF. The concentration patterns indicate plant breeders can increase stem NSC in hybrids during kernel filling with careful selection of R.lines and that quality of vegetative material intended for forage or CH4 production can be influenced by harvest at selected growth stages.
Cultivated and Wild Rices Do Not Accumulate Glycinebetaine Due to Deficiencies in Two Biosynthetic Steps
Authors: Rathinasabapathi Bala , Gage Douglas A. , Mackill David J. , Hanson Andrew D.
Published: July 2010

Many cereals, grasses and other plants accumulate glycinebetaine in response to drought or salinity. Glycinebetaine can act as a nontoxic or protective cytoplasmic osmolyte, and is therefore a biochemical component of drought‐ and salt‐stress resistance. It is synthesized by a two‐step pathway: choline → betaine aldehyde → glycinebetaine. There are contradictory literature reports as to whether cultivars of rice (Oryza sativa L.) accumulate glycinebetaine. To resolve this conflict, we used sensitive and specific fast atom bombardment mass spectrometry methods to analyze 35 diverse rice cultivars, together with accessions of nine wild rices. No glycinebetaine accumulators were found; levels of glycinebetaine were in all cases < 1 μmol g−1 dry wt., and no other betaines were detected. We then applied fast atom bombardment mass spectrometry to determine why rice, unlike other cereals, does not accumulate glycinebetaine. Rice leaves supplied with deuterium‐labeled betaine aldehyde did not convert it to glycinebetaine, and they lacked an endogenous betaine aldehyde pool. Together, these results indicate that rice lacks both the steps in the glycinebetaine biosynthesis pathway. Levels of the precursor choline, however, were comparable to those found in betaine‐accumulating cereals. Rice cultivars are therefore rational candidates for the introduction of heterologous genes for glycinebetaine biosynthesis, with the aim of improving resistance to drought and salinity.
Soybean Genotype Effects on Bigeyed Bug Feeding on Corn Earworm in the Laboratory
Authors: Powell Janine E. , Lambert Lavone
Published: July 2010

Corn earworm, Helicoverpa zea (Boddie), is a serious pest of many crops, including soybean, Glycine max (L.) Merr. This study was conducted to determine whether or not plant pubescence could be used to enhance predator activity. The influence of plant pubescence or insect resistance of soybean on predation of corn earworm eggs by the bigeyed bug, Geocoris punctipes (Say), was investigated in the laboratory. Bigeyed bug adults were allowed to feed on corn earworm eggs that were placed on foliage of soybean genotypes isogenic for dense, normal, or no pubescence, and on genotypes susceptible or resistant to foliar feeding insects. Percent egg puncture by males was similar on all foliage types whether or not choices were offered. Females punctured significantly (P < 0.05) more eggs on normal leaflets in a no choice situation. Significant differences (P > 0.05) were not detected in percent egg puncture on soybean genotypes resistant to foliar feeding insects as compared with susceptible genotypes (‘Centennial’ and ‘Davis’). Development of soybean cultivars with reduced pubescence, which is less preferred by corn earworm for oviposition and/or foliar feeding, will probably not influence this beneficial predator, since egg predation was not adversely affected by plant pubescence or insect resistance under laboratory test conditions.
Genes Controlling Nodulation in Soybean: Rj5 and Rj6
Authors: Pracht J. E. , Nickell C. D. , Harper J. E.
Published: July 2010

A number of genes have been identified that affect root nodule formation in soybean [Glycine max (L.) Merr.] when inoculated with Bradyrhizobium japonicum (Kirchner) Buchanan. The non‐nodulating mutant, NN5, used in this study was isolated from N‐nitroso‐N‐methylurea mutagenized ‘Williams’ seed. The objectives of this study were to determine the number of genes responsible for non‐nodulation in NN5 and the relationship between the genes in NN5 and the other known non‐nodulation genes. From this study it was found that non‐nodulation genes in NN5 were not allelic to the rj1 gene. One of the genes responsible for non‐nodulation in NN5 was allelic to the previously identified, but unnamed single recessive gene found in nod139, a non‐nodulating mutant of ‘Bragg’. A second recessive gene controlling non‐nodulation was identified in NN5 when crosses were made with ‘Harosoy 63’. Harosoy 63 was shown to contain a non‐allelic dominant gene that conditions nodulation when in combination with the gene found in nod139 and NN5. The gene symbol Rj5 is given to this new nodulation gene found in Harosoy 63, and the symbol rj6 is given to the allelic gene conditioning non‐nodulation in nod139 and NN5. Several other cultivars, Williams, Williams 82, Chapman, Resnik, and Chamberlain, do not contain the dominant gene Rj5.
Role of Nitrogen in Resistance to Striga Parasitism of Maize
Authors: Mumera Louis M. , Below Fred E.
Published: July 2010

Striga [Striga hermonthica (Del.) Benth.] is a parasitic angiosperm that infects tropical cereals causing severe yield losses. This study was conducted to determine if Striga damage in maize (Zea mays L.) can be mediated by the amount, form, and timing of N availability; and if the efficacy of N is contingent upon its regulation of assimilate partitioning. Two experiments were conducted in Kibos, western Kenya, in 1989 and 1990 on fields that had uniform Striga infestation. One experiment evaluated N rates of 0, 30, 60, and 90 kg N ha−1 supplied as either urea, calcium ammonium nitrate, ammonium sulfate, or ammonium sulfate plus the nitrification inhibitor dicyandiamide, while a second experiment evaluated similar N rates applied at 14, 21, 28, and 35 d after planting. Although Striga infection generally declined with increasing N availability, the impact was partially dependent on the severity of infestation as all N rates decreased infection in 1990, while only 90 kg N ha−1 reduced infection in 1989. Under high parasite densities in 1989, only urea reduced Striga (26%), while in 1990, infection was significantly decreased (an average of 30%) by all sources of N. In both years, N application at 28 d after planting resulted in the least Striga infection. Although assimilate partitioning during vegetative growth was unresponsive to N treatments, N availability during reproductive growth altered dry matter partitioning in favor of the ear over the vegetation. Averaged across N rates, this alteration resulted in increases in grain yield (64%) and harvest index (27%), and a decrease in source‐sink partitioning (41%) and in the concentration of nonstructural carbohydrates in the stalk (16%). Based on these data, N fertility can mediate the impact of Striga infestation on maize by altering assimilate partitioning in favor of the ear.
Sequential Development of Flowers and Seeds on the Mainstem of an Indeterminate Soybean
Authors: Munier‐Jolain Nathalie G. , Ney Bertrand , Duthion Claude
Published: July 2010

In indeterminate soybean [Glycine max (L.) Merr.], yield is largely dependent on seed number, so understanding of the dynamic of seed setting is important. This study was conducted to describe the development of the plant, taking into account the progression of the reproductive stages of the seed along the stem. ‘Maple Arrow’ plants were grown under field conditions in Guadeloupe (French West Indies, tropical climate, ferralic Fluvisol) and at Dijon (France, temperature climate, clayey eutric Cambisol) for 2 yr in order to investigate the pattern of development under contrasting environments. The stages of the seed after flowering were determined by the seed water content (WC) relative to the fresh weight. During the early phase, WC remained constant at about 0.85 g g−1. Then, WC decreased until physiological maturity, when WC reached 0.60 g g−1. When WC began to decrease below 0.85 g g−1 at a node, the seed number at that node was fixed. This critical value corresponds to the beginning of seed filling. The three reproductive stages, namely flowering, beginning of seed filling, and physiological maturity, progressed linearly along the stem as a function of cumulative degree‐days (base temperature 6 °C). The rates of progression of these stages along the stem were constant under the two environments and between years. Conversely, durations of the lag‐phase and seed‐filling periods at the first node, calculated respectively between flowering and WC = 0.85 g g−1 and between WC = 0.85 and 0.60 g g−1, varied widely among experiments. Seed WC appears to be a convenient criterion to determine the different periods of soybean seed development and conforms to a general pattern of seed development in relation to their position on the stem.
Irradiance and Nitrogen to Potassium Ratio Influences Sweetpotato Yield in Nutrient Film Technique
Authors: Mortley Desmond G. , Bonsi C. K. , Hill Walter A. , Loretan P. A. , Morris C. E.
Published: July 2010

Sweet potato [Ipomoea batatas (L.) Lam] is being grown with the nutrient film technique as part of the National Aeronautics and Space Administration's Controlled Ecological Life Support System (CELSS) program for long‐termed manned space missions. Our objective was to evaluated the effects of two levels of photosynthetic photon flux (480 and 960 μmols m−2s−1 PPF) and three N/K ratios (1:1.1, 1:2.4, and 1:3.6) on yield of sweetpotato when grown using this technique. Vine cuttings (15‐cm length) of ‘Georgia Jet’ and T1‐155 were grown in each treatment for 90 or 120d, respectively, in controlled‐environment growth chambers. Storage root growth for Georgia Jet and T1‐155 increased with light intensity, while foliage growth decreased with high K levels. The number of storage roots produced by each plant increased with intensity only for Georgia Jet but was not significantly influenced by higher K levels for either cultivar. Light by N/K interactions were not significant. The level of PPF exerted a greater effect in enhancing sweetpotato storage root yield in nutrient film than did N/K ratio.
Carbon Isotope Discrimination and Gas Exchange of Cowpea Accessions and Hybrids
Authors: Ismail Abdelbagi M. , Hall Anthony E.
Published: July 2010

Carbon isotope composition may be useful for selection in plant breeding. Theory predicts a negative association between 13C discrimination (Δ) and the ratio of CO2 assimilation (A) to leaf diffusive conductance (g) in C3 plants. In cowpea [Vigna unguiculata (L.) Walp.] previous studies showed that the association between Δ and gas exchange efficiency (A/g) agreed with theory for drought‐induced effects, but not for genotypic effects when gas exchange was measured in the afternoon. Field studies were conducted for 2 yr to evaluate the association between Δ and A/g measured during different time periods within the day. Four cowpea genotypes were grown either on weekly irrigation or stored soil moisture in 1 yr, and under weekly irrigation, together with two hybrids between low and high Δ parents, in the second year. Cultivars CB46 and Prima had higher leaf Δ than genotypes UCR 237A and TVx 309‐1G with different irrigation treatments, sampling dates and years. The hybrids had values of Δ and gas exchange close to their midparent means. A negative correlation was observed between Δ and A/g for both drought‐induced and genotypic effects. Genotypic mean values of Δ were more strongly correlated with A/g when measured early in the morning than in the afternoon. Both A and leaf conductance to water vapor (gh) were significantly higher early in the morning and then decreased progressively towards the end of the day. Early morning measurements were most effective in detecting genotypic differences in A/g, and they were associated with genotypic differences in Δ, as expected, based on theory, but with some unexplained variation. Low Δ was associated with high photosynthetic rate for TVx 309‐1G, but low stomatal conductance for UCR 237A.
Yield and Grain Protein Response of Spring Barley to Ethephon and Triadimefon
Authors: Bulman Patrick , Smith Donald L.
Published: July 2010

Barley (Hordeum vulgare L.) is used principally as a feed crop in Québec. Consequently, a high protein concentration in the grain is desirable. A 2‐yr field study was conducted to study the effects of ethephon [(2‐chloroethyl)phosphonic acid] and a late application of triadimefon [l‐(4‐chlorophenoxy)‐3,3‐dimethyl‐1‐(1H‐l,2,4‐triazol‐1yl)‐2‐butanone] on yield and grain protein concentration (GPC) of three cultivars of spring barley. Recommended rates of ethephon were applied at booting, and of triadimefon at heading. Ethephon consistently reduced plant height, and reduced lodging when lodging occurred in control plots. Ethephon and triadimefon effects on yield and GPC were inconsistent. In 1987 triadimefon applied in the absence of ethephon increased the yield of Cadette 22%. Ethephon increased yield of Leger 24%, and decreased yield of Argyle 19%. Increased spikelet sterility at the distal end of main stem spikes was responsible for the yield reductions in Argyle. Ethephon and triadimefon had no significant effect on yield in 1988. Ethephon could alter GPC by reducing the nonprotein dry matter component of the grain, by increasing protein per grain, or by altering the distribution of grain sizes in harvested samples. In 1987 ethephon significantly decreased total and nonprotein dry matter per grain for Argyle, but increased protein per grain, and consequently, GPC. In 1988, ethephon reduced nonprotein dry matter per grain in Cadette and Argyle. With Argyle, both total dry matter per grain and protein per grain were reduced so that GPC was not significantly affected. The results show that ethephon can influence GPC by altering the protein and nonprotein components of the grain.
Dry Matter Accumulation of Elephantgrass, Energycane, and Elephantmillet in a Subtropical Climate
Authors: Woodard K. R. , Prine G. M.
Published: July 2010

Tall genotypes of elephantgrass (Pennisetum purpureum Schum.) and energycane (Saccharum spp.) are potential biomass energy plants in subtropical areas because annual dry matter (DM) yields often exceed 40 Mg ha−1. A field study was conducted to characterize crop performance of these C4 bunchgrasses during the 35‐ to 40‐wk warm season in north‐central Florida. Entries included two tall elephantgrasses (PI 300086 and N51), a tall energycane (L79‐1002), and intermediate pearlmillet [Pennisetum glaucum (L.) R. Br.] × elephantgrass hybrid (S41). In 1989 at Gainesville and in 1990 at another location 20 km away, the grasses were mowed on 28 March and fertilized 1 wk later with 200 kg N, 22 kg P, and 83 kg K ha−1. Onetime harvests of above‐ground biomass were made at 28‐d intervals from 16 May through 28 November. Final harvest DM yields (2‐yr means) were 46 Mg ha−1 yr−1 for PI 300086, 47 for N51, 49 for L79‐1002, and 37 for S41. Near‐linear DM accumulation continued for 140 to 196 d at mean crop growth rates ranging from 18 to 27 g m−2 d−1. For the tall bunchgrasses, DM production at any point during the season was accurately predicted from canopy height, since height was linearly related to the square root of DM yield (0.87 ≤ r2 ≤ 0.96). Gross energy yields (2‐yr means) in barrels of crude oil equivalent (158.8 L barrel −1) were 135 ha−1 yr−1 for PI 300086, 139 for N51, 141 for L79‐I002, and 106 for S41. The high‐yielding abilities of the grasses were related to the long linear DM accumulation period.
Isolation of Mature Cereal Embryos and Embryonic Axes
Authors: Morris Craig F.
Published: July 2010

Numerous areas of biological research (e.g., control of seed dormancy and protein synthesis, and development of cell‐free translation systems) are greatly aided by the use of large quantities of viable cereal embryos. The utility of a method that employs a commercial food blender for embryo isolation was assessed for mature caryopses of various grain lots of wheat (Triticum aestivum L. em Thell.), rye (Secale cereale L.), triticale (× Triticosecale Wittmack), barley (Hordeum vulgare L.), oat (Avena saliva L.), rice (Oryza saliva L.), pearl millet [Penniselum glaucum (L.) R. Br.], grain sorghum [Sorghum bicolor (L.) Moench.], and maize (Zea mays L.). The yield, physical condition, and morphology of embryos and embryonic axes were characterized using light and scanning electron microscopy. Viability of embryonic axes was assessed by germination assay. Intact embryonic axes free of damage and adhering tissues (i.e., scutellum and pericarp) were easily isolated from wheat, rye, triticale, and oat. The highest yield was obtained with wheat (≈10–15%). In hulless barley, pericarp always remained attached and covered the radicle portion of the embryonic axis. Embryonic axis isolation from hulled barley was poor. Rice embryos with adhering scutellum and pericarp were isolated as a unit with 2% yield, similar to rye, triticale, and oat. Intact axes of millet, sorghum, and maize were isolated infrequently and with difficulty. Viability of embryonic axes selected visually for intactness and lack of physical damage was similar to the viability of the parent grain lot.
Hard Seed and Field Establishment of Irrigated Alfalfa
Authors: Hall J. W. , Stout D. G. , Brooke B. M.
Published: July 2010

Alfalfa (Medicago saliva L.) seed lots contain a proportion of hard, water‐impermeable seed that does not germinate readily during a 7‐ d germination test. Opinions differ as to whether or not hard seeds make a delayed contribution to an alfalfa stand. Scarification by five freeze‐thaw cycles of 2 h at − 80 °C followed by at least 2 h at 20 °C can be used to make hard seeds permeable to water. A field experiment was carried out in 1990 and 1991 to determine the effects of hard‐seededness and freeze‐thaw scarification on the establishment and dry matter yield of irrigated alfalfa. Untreated (germination 50%) and scarified (germination 93%) seeds were sown at rates of 1, 5, and 10 kg ha−1 in two trials established 6 wk apart at different sites. Plant density increased 8‐fold with the 10‐fold increase in seeding rate but yield increased by only 42% in the first year and 13% in the second year. The results of the 7‐d germination test suggested that scarification should have increased the plant density by 86%, but the observed increase was only 40%. Thus, either a fraction of the seeds made permeable by scarification did not produce plants or scarification injured some of the seeds that were already permeable. Owing to compensatory growth, yield was unaffected by scarification.
Causes for Silk Delay in a Lowland Tropical Maize Population
Authors: Edmeades G. O. , Bolaños J. , Hernàndez M. , Bello S.
Published: July 2010

A shortened anthesis‐to‐silking interval (ASI) in maize (Zea mays L.) is associated with tolerance of stresses which occur around flowering. It is not known if this reflects differences in tassel and ear initiation dates, or in rates of development and growth. We examined these characteristics in selection cycles 0, 2, 4, 6, and 8 (designated Cx, where the subscript indicates the cycle number) of the lowland tropical maize population ‘Tuxpeño Sequía’, which was selected recurrently for drought tolerance and whose selection cycles differ for ASL Plants were grown at high plant density and under mild and severe drought stresses that occurred at flowering. Silking was delayed significantly, especially in C0 and C2 under severe drought. Stress treatments did not affect days to 50% tassel initiation, ear initiation, or anthesis. The interval between 50% tassel and ear initiation, the rate of spikelet initiation, and crop growth rate near flowering were unaffected by selection. Per cycle changes were −0.21 d in duration of ear spikelet initiation and −16.9 for spikelet number per ear at 50% anthesis. Selection changed relative growth rates at 50% anthesis by 0.005 d−1 cycle−1 for ears, 0.007 d−1 cycle−1 for spikelets and −0.009 d−1 cycle−1 for tassels. These changes were unaffected by stress level. Eight cycles of selection increased the mean ear and spikelet weights at 50% anthesis by 127 and 173%. The ASI increased rapidly when mean spikelet biomass at 50% anthesis was less than 0.8 rag. Results indicate that a decreased ASI arising from selection in this population is due largely to an increased rate of biomass accumulation per spikelet, and development of fewer spikelets per ear.
Vernalization and Seeding Date Effects on Yield and Yield Components of White Lupin
Authors: Putnam D. H. , Simmons S. R. , Hardman L. L.
Published: July 2010

Understanding the agronomic importance of planting date and cold temperatures during germination may lead to the development of better management strategies for spring‐sown white lupin (Lupinus albus L.). We conducted two experiments to determine optimum planting dates for spring‐sown white lupin and to determine the effect of vernalization on plant morphology, yield, and yield components. In Experiment I, field plots were planted in 15‐cm rows at five planting dates (14‐d intervals) at Staples, MN, from 1985 through 1989. In Experiment II, seeds were imbibed for 48 h and cold treated (vernalized at 1 °C) for 14 d, and hand planted in 76‐cm rows and compared with non‐vernalized controls at 4 planting dates (main plots) Staples and Becker, MN, in 1988 and 1989. Early to mid‐April plantings generally produced the highest yields. Delayed planting past this yield maximum resulted in a 53 kg ha−1 d−1 decrease in yield, averaged over 11 location‐years. Vernalization reduced node number 23 to 52% and plant height 8 to 53%. Height and node number were reduced by vernalization at every planting date, and varied widely across a range of temperatures to which the seedlings were exposed. This data provides evidence that vernalization is a continuous rather than discrete response. Yield was generally reduced by vernalization, except at later planting dates when 75% of the vernalized plot's yields were equal to or greater than controls (vernalization × planting date interactions were significant in all years). Yield differences were largely determined by the number of plants which produced fertile branch inflorescences. Pod number was increased at both the mainstem and the branch reproductive sites of these morphological types, compared with plants which set only mainstem pods. Seeds per pod and seed weight were also positively correlated with yield. Sowing white lupin within a relatively narrow window of seeding dates in mid.April is important to reduce the wide variation in performance often observed with this crop.
Early‐Generation Selection for Chemical Desiccation Tolerance in Winter Wheat
Authors: Haley Scott D. , Quick James S.
Published: July 2010

Post‐anthesis drought stress is a common problem in winter wheat (Triticum aestivum L.) production throughout the west‐central and southern Great Plains of the USA. Contact chemical desiccants have been proposed to simulate postanthesis drought stress in the field and to enable selection for postanthesis drought stress tolerance. This study was conducted to determine if early‐generation among‐cross selection for chemical desiccation tolerance is possible and if chemical desiccation tolerance of early‐generation bulks could be altered using mechanical mass selection for kernel weight. The chemical desiccation tolerance of four winter wheat single‐cross populations was evaluated in 1991 at two locations in Colorado, each location consisting of replicated F4‐bulk trials of populations that had been subjected to chemical desiccation [2% (w/v) NaCIO3 applied 10 d postanthesis] and divergent mechanical mass selection for kernel weight in the F2 and F3 generations. At both locations, a cross between tolerant parents showed lower (P ≤ 0.01) chemical desiccation injury (for grain yield, kernel weight, and test weight) than crosses between sensitive parents or between contrasting parents. Separation of F2 populations into selected‐bulks of differing height and maturity showed that selectedbulks from randomly‐selected and tall F2 plants suffered significantly (P ≤ 0.01) lower chemical desiccation injury (at one location only) than selected‐bulks from short plants or plants with similar anthesis dates. Mechanical mass selection within populations advanced with two cycles of chemical desiccation produced F4‐bulk populations with significantly (P ≤ 0.01) lower chemical desiccation injury. The potential for selective improvement of chemical desiccation tolerance of bulk populations was indicated by several instances of reduced chemical desiccation injury for populations advanced to the F4 with desiccant application and mechanical mass selection for high kernel weight. Our results provide evidence that crosses tolerant of chemical desiccation can be identified using early‐generation evaluation of bulk‐populations, prior to extensive line extraction and evaluation.
Growth and Architecture of Seedling Roots of Common Bean Genotypes
Authors: Lynch Jonathan , van Beem Johannes J.
Published: July 2010

Common bean (Phaseolus vulgaris L.) is an important food crop in the tropics, where its productivity is often limited by edaphic stress. Root growth and architecture may be associated with genetic adaptation to edaphic stresses. Our objective was to evaluate the effect of genotype, time, and root type on various root growth and architectural parameters in bean seedlings. Seeds of four bean genotypes representing distinct growth habits (erect determinate, erect indeterminate, prostrate indeterminate, and climbing) were grown in containers of Oxisol soil in Cali, Colombia. Plants were harvested at 3‐d intervals and roots divided into basal roots, taproot, and taproot laterals. Length, dry weight, and architecture (topological indices and fractal dimension) of each root class was determined until 14 d after planting. Significant genetic differences were observed in final root length, final root mass, number of basal roots, root growth rate, root elongation rate, number of root meristems, root topology, and root fractal dimension. Some association of shoot habit and root architecture was observed, with the climbing genotype HAB 229 having a more taproot dominated root system, and the prostrate genotype Carioca having a large number of root meristems. The nutrient‐efficient genotype Tostado had a vigorous, highly branched root system with numerous basal roots, while the nutrient‐inefficient genotype Porrillo Sintetico had a smaller, less branched root system. Root type (basal, tap, taproot lateral) and plant age had significant effects on architectural parameters, which may compromise the utility of these parameters as selection criteria.
Cool Temparature Effects on Cotton Fiber Initiation and Elongation Clarified Using In Vitro Cultures
Authors: Xie Wuzi , Trolinder Norma L. , Haigler Candace H.
Published: July 2010

An understanding of the mechanistic basis of adverse environmental effects on cotton fiber development is a prerequisite to future improvement through genetic engineering and aids in field management to minimize such adverse effects. In order to clarify previous results from field studies on the effects of cool temperatures on initiation, early elongation, and later elongation of cotton fibers, cotton ovules (Gossypium hirsutum L.) cultured in vitro were used as a manipulable and reproducible experimental system based on previous evidence that they provide a valid model. Culture temperature varied from a control of 34 °C constant to 34/15 °C cycling (12/12 h) to mimic a typical diurnal temperature cycle. Fiber initiation and early elongation were analyzed by scanning electron microscopy, and the progress of later elongation was determined by ruler measurements. The results demonstrated that fiber initiation and early elongation (up to about 0.5‐mm length) were independently delayed by cycling cool temperatures, but that later elongation preceded in a temperature‐independent manner. The early delay in fiber development caused by cycling cool temperatures was associated with a longer elongation period during which fibers could attain the control length. Therefore, the results suggest that there are three stages of fiber elongation as distinguished by different temperature responses: initiation, early elongation, and later elongation to attain the genetically determined potential. Consequently, the field temperature during fiber initiation and early elongation may have a profound effect on the final fiber length attained in a limited growing season.
Leaf Posture, Grain Yield, Growth, Leaf Structure, and Carbon Isotope Discrimination in Wheat
Authors: Araus José L. , Reynolds Mathew P. , Acevedo Edmundo
Published: July 2010

The purpose of this study was to examine how differences in leaf angle may affect grain yield of wheat by changes in the relative contribution of yield components or changes in the pattern of crop growth. Leaf structural changes and their influence on plant water status and carbon isotope discrimination were also studied. A collection of pairs of bread wheat (Triticum aestivum L.) lines (PL) differing in leaf angle were grown under irrigation during two consecutive years at Sonora, Mexico. Erect leaf lines did not have higher yields than droopy leaf lines, but erect lines did have 5 to 16% greater number of kernels per unit of ground area. Droopy lines had a lower number of spikes per unit ground area, a greater number of kernels per spike, and a greater weigh of mature kernels than droopy lines. Therefore, the lack of differences in yield apparently was associated with yield component compensation. Differences between PL in discrimination against 13C (∆) in mature kernels, relative water content of flag leaves, canopy temperature, leaf area, and degree of leaf tip burning suggested higher transpiration rates (and thus lower water use efficiency) in the erect lines. For example, ∆ in kernels was consistently higher in the erect lines than in the droopy lines. In addition there was a significant (r = −0.85, P < 0.05) negative correlation between canopy temperature during grain filling and ∆. Grain yield was positively correlated (r = 0.50, P < 0.05) with ∆ of kernels. Although wheat genotypes with erect leaves did not show conclusive superiority, nevertheless selection for a more erect growth habit may result in increased yield. However, the possible existence of allometric relationships among leaf erectness and smaller leaves, spikes, and stems make progress in increasing yield a complex task.
Tillage and Nitrogen Source Effects on Growth, Yield, and Quality of Forage Maize
Authors: Mataruka D. F. , Cox W. J. , Mt. Pleasant J. , van Es H. M. , Klausner S. D. , Zobel R. W.
Published: July 2010

Manure has not been evaluated as an N source for maize (Zea mays L.) production underidge tillage (RT). A 2‐yr field study was conducted on a Kendaia‐Lima silt loam (fine‐loamy, mixed, nonacid, mesic Aeric Haplaquept) to evaluate growth, yield, and quality of forage maize under moldboard plow (MP) and RT with fertilizer N (MPF and RTF) or with manure and supplemental fertilizer N (MPM and RTM, respectively). Soil water pressure and leaf carbon exchange rates (CER) were measured frequently; and plant N concentration, leaf area index (LAI), and dry matter (DM) accumulation were sured at the six‐leaf stage (V6), silking (R1), and harvest. The treatment generally had lower CER from V5 to V8, lower whole‐plant N concentrations at V6 in 1989 (24.7 g kg−1) and 1990 (28.2 g kg−1), and lower LAI and DM accumulation at V6 (0.39 and 37 gm−2) and R1 (3.27 and 844 gm−2, respectively) in 1989. In contrast, RTM compared to MPF and RTF had similar CER, whole‐plant N concentrations, LAI and DM accumulation on most measurement dates. The MPM treatment compared to MPF, RTF, and RTM had lower DM yields (13.6, 16.3, 15.7, and 14.9 Mg ha−1) and whole‐plant N concentrations (7.8, 8.5, 8.5, and 8.4 g kg−1) in 1989, and lower DM yields (13.7, 15.3, 15.0, and 15.9 Mg ha−1, respectively) in 1990. Surface application of manure before planting with supplemental fertilizer N at V5 was a viable N management system for forage maize under RT.
Planting Date and Seeding Rate Effects on Morphological Development and Yield of Turnip
Authors: Jung G. A. , Shaffer J. A.
Published: July 2010

Productivity of Kentucky bluegrass (Poa pratensis L.) pastures in midwestern and northeastern USA typically is low in late fall. A study was conducted to determine the influence of planting date and seeding rate on morphological development of turnip (Brassica rapa L.), and its potential to provide forage in late fall. Turnip was seeded in rows on Hagerstown silt loam (fine mixed, mesic Typic Hapludalt) soil, utilizing a split‐split block design with replicates nested within each whole block (planting date). Cultivar and seeding rate combinations were randomized within each replicate, and sampling date was the split‐split block. Total yield of turnip sometimes exceeded 10.0 t ha−1. With June or July plantings, turnip had 500 to 800 g kg−1 in its tops 60 d after planting, whereas with August plantings it had 700 to 900 g kg−1 in its tops. In December, the proportion in tops ranged from 250 g kg−1 for ‘Purple Top’ to 650 g kg−1 for ‘Tyfon’ planted in June or July; and from 500 g kg−1 for Purple Top to 850 g kg−1 for Tyfon planted in August. The proportion of total yield that remained until mid‐December varied with planting date, cultivar, and foliar disease severity. Yield of tops or roots of five turnip cultivars differed in 36 of 38 planting date/sampling date combinations. Seeding rates within the range 1.7 to 5.0 kg ha−1 generally did not affect root yields. Mean crude protein concentration ranged from 270 g kg−1 in ‘Forage Star’ to 250 g kg−1 in ‘Rondo’. Crude protein yield of Forage Star remained unchanged throughout the 120 d period whereas crude protein yields of ‘NZ Green Globe’, Rondo, and Purple Top decreased linearly and that of Tyfon showed a quadratic response (an initial gain followed by a sharp decline). Differences in turnip yields in late autumn were attributed to planting date, amount and time of summer precipitation, plant resistance to foliar diseases, cold tolerance, and leaf retention. Delaying summer planting date affected top/root proportions of Purple Top most, and those of Forage Star and Tyfon least.
Forage Quality of Maize Genotypes Selected for Extreme Fiber Concentrations
Authors: Wolf D. P. , Coors J. G. , Albrecht K. A. , Undersander D. J. , Carter P. R.
Published: July 2010

An understanding of the factors and relationships affecting wholeplant digestibility is needed to improve the nutritional quality of maize (Zea mays L.) forage. The objectives of this study were to: (i) determine the ranges among 24 maize genotypes for fiber composition and digestibility of stover and whole‐plant forage, and (ii) determine the relationships between fiber composition and digestibility. Twenty‐four S0.1 families (S0‐derived families in S1) exhibiting a range in neutral detergent fiber (NDF) and lignin at mid‐flower, were testcrossed to two commercial inbred lines (FR23 and LH74) to form two groups of F1 hybrids. A third experimental group was created by self‐pollinating the S0.1 families to form S0.2 families. These germplasms were evaluated in three Wisconsin environments. Ranges in S0.2 family means for fiber and digestibility were: NDF, 439 to 582 g kg−1 for the whole plant and 579 to 654 g kg−1 for the stover; and in vitro true digestibility (IVTD), 714 to 820 g kg‐1 for the whole plant and 689 to 757 g kg−1 for the stover. Narrower ranges were observed among LH74 and FR23 testcrosses. For S0.2 families, correlation coefficients for stover IVTD with stover NDF and lignin were −0.76 and −0.85, respectively. Correlation coefficients for whole‐plant IVTD with stover IVTD and lignin of S0.2 families were 0.44 and −0.49, respectively. The results of this study show that (i) significant variation exists for nutritional quality traits of the stover and whole‐plant forage and (ii) stover quality is an important factor influencing whole‐plant nutritional quality within the germplasm studied.
Water Stress and the Water Relations of Seed Development: A Critical Review
Authors: Bradford Kent J.
Published: July 2010

Water availability plays a major role in the regulation of seed development. Experimental evidence on the water relations of seed development is reviewed, with emphasis on the measured water potential values of well‐watered and water‐stressed seed, fruit, and leaf tissues. The hypothesis of hydraulic isolation of developing seeds from the water relations of the maternal plant, proposed on the basis of the maintenance of measured water potential (ψw) differences between these tissues, is examined and found to be problematic. Apparent ψw gradients have also been recorded for seeds developing within fleshy fruits or in vitro on defined medium, where hydraulic barriers would not be present. Current models of phloem transport to seeds are based on a turgor homeostatic mechanism in the unloading tissues that maintains high apoplastic solute concentrations to lower phloem turgor and promote import. The combination of turgor (or water potential) boo meostasis and active regulation of solute compartmentation in seed tissues may contribute to the apparent constancy of seed ψw when measured by thermocouple psychrometry, which requires long equilibration times after excision. The delivery of excess water to developing seeds via the phloem and its recirculation to the mother plant also present problems for the hydraulic resistance hypothesis and for the retention of apoplastic solutes in the unloading zone. It is hypothesized that modfied cell walls acting as semipermeable apoplastic membranes may retain solutes within the unloading tissues, while allowing the return flow of water to the parental xylem. The water relations of developing seeds are determined primarily by phloem transport, whether under well‐watered or water‐stressed conditions, so future studies should attempt to resolve the discrepancies between measured ψw and the requirements for maintenance of phloem import.
Flowering of Diverse Maize Cultivars in Relation to Temperature and Photoperiod in Multilocation Field Trials
Authors: Bonhomme R. , Derieux M. , Edmeades G. O.
Published: July 2010

The accurate prediction of time to flower is important for the efficient exchange of genetic material among environments. The objective of this research was to evaluate methods of calculating thermal time for the sowing‐silking interval (SSI) in a diverse group of 18 maize (Zea mays L.) cultivars, which were sown in a multilocation field trial at 53 planting date‐location combinations. These ranged in mean temperature from 13.2 to 29.4 °C during the SSI, and in photoperiod at tassel initiation from 11.7 to 19.5 h. Thermal time computed from daily maximum(T X) and minimum temperatures with a base of 6 °C, an optimum temperature (To) of 30 °C, and a linear adjustment for supra‐optimal values of TX such that TX = 30 − (TX − To), resulted in a lower coefficient of variation (CV) for thermal time across sites and cultivars (10.9%) than did other methods, though several of these methods gave similar results. The CVs for thermal duration of the SSI for cultivars adapted to temperate, lowland tropical and highland tropical environments averaged 7.8, 11.5, and 15.4% respectively. For tropically‐adapted cultivars, the increase in the sowing‐anthesis interval in day lengths >13 h averaged 47 °Cd h−1 (range 24–100 °Cd h−1), while temperate cultivars were virtually photoperiod insensitive. Photoperiod sensitivity was positively correlated with the anthesis‐silking interval [r = 0.62 (P = 0.01), 16 df]. This study confirms the need to determine photoperiod sensitivity and optimum temperatures for development of tropical cultivars if precise estimates of thermal time to flowering and maturity at sites with photoperiods >13 h are required.
RFLP Evaluation of Nine Medicago Accessions Representing the Original Germplasm Sources for North American Alfalfa Cultivars
Authors: Kidwell K. K. , Austin D. F. , Osborn T. C.
Published: July 2010

All alfalfa (Medicago sativa L.) cultivars grown in North America originate from nine germplasm sources introduced into the USA from different geographic regions. Nine accessions representing the original germplasm sources have been developed; however, the level of genetic diversity within and among these accessions is not known. Genetic diversity of these accessions was estimated by screening DNAs from 12 individuals of each accession, along with bulked samples containing equal amounts of DNA from 4, 6, or all 12 individuals, for nuclear RFLPs revealed by hybridization to 35 cloned alfalfa sequences. One hundred and eighty restriction fragments were scored as present or absent across all individuals from all accessions, and genetic similarity estimates (GSEs) of all pair‐wise comparisons were calculated from these data. The data were also examined by cluster analysis and principal Components analysis (PCA). Individuals within accessions were highly polymorphic, whereas very few accession‐specific polymorphisms were identified. Although individuals from two sources, M. falcata and Peruvian, formed distinct clusters, genotypes from the other seven accessions were not clearly discriminated by analyses of these data. The nondistinctiveness of most of these plant introductions (PIs) could be due to a similar genetic composition of the initial introductions, intercrossing of the different sources during maintenance, or genetic shift during maintenance. Based on PCA, bulked DNAs underestimated the level of genetic diversity both within and between accessions, as compared with estimates derived from analysis of individual genotypes from each source.
Lotus corniculatus Classification by Seed Globulin Polypeptides and Relationship to Accession Pedigrees and Geographic Origin
Authors: Steiner J. J. , Poklemba C. J.
Published: July 2010

The birdsfoot trefoil (Lotus corniculatus L.) accessions from the National Plant Germplasm System (NPGS) have not been systematically evaluated to determine the genetic relationships of individuals or groups of similar accessions. This study was done to classify and determine the diversity of a collection of birdsfoot trefoil accessions using high salt‐soluble globulin polypeptides (SGPP) and to compare their classification with geographic and ecological distribution, morphology, and known accession pedigrees.. Seeds of 128 plant introductions, germplasms, and cultivars that represented a wide‐range of geographic regions and collection site ecological habitats were analyzed for SGPPs. The accessions were grouped into five major classes based on 13 protein bands ranging in molecular weights from 23.1 to 65.3 kDa. Seventy‐nine percent of the accessions were placed into two major classes with subclass differences due to collection from either highland or lowland ecoregion sites. Sixteen percent of the accessions were placed in a third class and a limited number of accessions were placed into two distinct minor classes that exhibited atypical birdsfoot trefoil morphology. Approximately 79% of the cultivars and germplasms from North and South American and Europe have been selected from a limited base of genetic resources found in the two major classes. Few improved cultivars or germplasms have been developed from materials similar to accessions found in Class 3 (18%), Class (3%), and Class 5 (0%). Using established world ecoregion descriptions greatly assisted with the interpretation of the SGPP classification and provided a useful approach that should apply to other germplasm collections.
Leaf Rust‐Resistance Genes Lr41, Lr42, and Lr43 Transferred from Triticum tauschii to Common Wheat
Authors: Cox T. S. , Raupp W. J. , Gill B. S.
Published: July 2010

In order to diversify the genetic base of resistance in hard red winter wheat (Triticum aestivum L.) to leaf rust (caused by Puccinia recondita Rob. ex Desm.), five genes for resistance were transferred from the diploid goatgrass T. tauschii (Coss.) Schmal. to hexaploid wheat lines. One of the derived lines, KS90WGRC10, had a very low infection type when inoculated with 23 cultures of P. recondita. The others, KS91WGRC11, KS92WGRC16, U1865, and U1866, had low to intermediate infection types with three cultures. Their infection types varied similarly to those of lines carrying previously transferred alleles of Lr21. WGRC10 carries a completely dominant gene, Lr41, on chromosome 1D that segregates independently of any other T. tauschii‐derived leaf rust‐resistance genes. WGRC11 carries the partially dominant gene, Lr42, also on 1D, that is linked to Lr21 with a recombination value of 0.286 ± 0.023. WGRC16 carries a partially dominant gene, Lr43, that segregates independently of all known genes for seedling resistance from T. tauschii; its chromosome location is not known. The genes carried by U1865 and U1866 are allelic to Lr21. WGRC10, WGRC11, and WGRC16 have been released as germplasms by the Wheat Genetics Resource Center.