bluuebunny/crossref_metadata_2025 huggingface dataset:
Regeneration in Cereal Tissue Culture: a Review
Authors: Bhaskaran Shyamala , Smith Roberta H.
Published: July 2010

This review examines the literature on successful establishment of regenerable cell cultures in the economically important cereal crops. Some of the major trends and strategies for the establishment of in vitro cultures that express totipotency are discussed as well as current approaches. It is apparent that in cereal tissue culture, not all cells express totipotency. Generally the auxin 2,4‐dichlorophenoxyacetic acid (2,4‐D) is critical for the production of regenerable callus; however, the addition of cytokinin can be significant. Meristematic cells from immature tissues are the targets for plant growth regulator action. Some genotypes produce embryogenic cultures, while others are recalcitrant to in vitro manipulation. Regeneration occurs either by somatic embryogenesis or adventitious bud and shoot development with subsequent rooting. In these meristematic tissues, plastids are at the undifferentiated proplastid stage of development. The development of a white, nodulated embryogenic callus in somatic embryogenesis and the formation of green buds during organogenesis suggest divergent modes of plastid differentiation during morphogenesis. Plant growth regulators may be involved with inducing or directing different pathways of plastid differentiation. Genotypic differences in morphogenesis may be due to differences in endogenous hormone levels.
Recurrent Selection for Protein Yield of Oat
Authors: McFerso J. K. , Frey K. J.
Published: July 2010

Grain yield and protein concentration may be inherited independently in oat, suggesting that both of these traits can be utilized to enhance protein yield. Techniques and procedures have been developed that allow the testing of S1 lines of oat (Arena sateva L.) for protein yield. Each cycle of selection takes I yr. This study was conducted to evaluate three cycles of recurrent selection for increasing groat‐protein yield in three oat populations.Four oat lines selected for high grain yield were cross to 10 high‐protein lines to form the initial CO population. Selection applied to SO2(S02 equals S0‐derivered S2 lines;S0 = F2)lines from CO for protein yield provided parents to form three populations (i.e., lines of descent). The lines of descent with high grain yield(HG)and high protein content (HP) were initiated with five parents each, and the one with high protein yield per se (HGP)was intiated with the 10 lines used for HG and HP.U poinn termatin3g0, 0S Oali nes weree valuatepde r line of descent, and 20 lines were selected for high protein yield. The C1 through C3 methodology consisted of intermating 20 selectionis in a partial diallet, growing the resulting So plants in the greenhouse, and evaluating 300 So‐a1 lines in the field. for each line of descent, random samples of lines from the CO, CI, and C2; the parents from all cycles;a set of checks; and 300 lines from C3 were evaluated to estimate gain from selection. There was a significant linear increase in great‐protein yield of 27±3 kg ha‐1 in HP and 21 ± 2 kg ha‐1 in HG and HGP. Heritabilities ranged from 0.41 to 0.59 in CO to C3,and genetic variances remained high and significant. Groat‐protein yields of the best lines in C3 were higher than those of the best CO lines. Several lines had both high groat‐protein yield and acceptable agronomic performance. The results indicate that S01 line recurrent selection can be effective for rapidly improving an oat population for the trait under election without losses in performance for other traits.
Variation among Full‐sib Families of Corn for Different Generations of Inbreeding
Authors: Rodriguez O. A. , Hallauer A. R.
Published: July 2010

Recurrent selection for improvement of yield of corn (Zea mays L.) germplasm emphasizes early testing of either S0 or S1 progeny testcrosses. On the basis of early testing information, progenies are selected and intermated to form populations for continued selection. This study was conducted to determine if early testing was effective in identifying superior full‐sib families of S0 plants in reciprocal fullsib selection. The effectiveness of early testing was investigated by comparing the relative genetic variability and genetic correlations of 136 full‐sib families for the S0 S1, S2, S3, and S4 generations of in breeding. Full‐sib families and six hybrid checks were evaluated in three environments for each generation for grain yield and five other agronomic traits. The among full‐sib component of variance for grain yield tended to increase with inbreeding of the parents, and there was evidence that variability among full‐sib families was reduced in stress environments. Genetic correlations for yield between generations of inbreeding ranged from 0.87 for S0‐S1 generations to 0.31 for S0‐S4 generations. Genetic correlations decreased as the number of intervening generations increased. Selection of the 20 highest and lowest‐yielding S4 full‐sib families included only three and four, respectively, of the 20 highest‐ and lowest‐yielding S0 full‐sib families. None of the 20 lowest‐yielding S1 full‐sib families, however, was included in the 20 highest‐yield S4 full‐sib progenies. The objective of early testing in reciprocal full‐sib selection was achieved because none of the poorer performing families was included for intermating.
Recurrent Restricted Phenotypic Selection for Yield Alters Morphology and Yield of Pensacola Bahiagrass
Authors: Werner B. K. , Burton G. W.
Published: July 2010

Sixteen cycles of recurrent restricted phenotypic selection (RRPS) have resulted in consistent forage yield increases of space‐planted Pensacola bahiagrass (Paspalum notatum Függe var. saurae Pexodi) plants. The purpose of this study was to assess morphological changes occurring as a result of RRPS for yield. Tests were established in the field in 1988 and 1989. Approximately 100 spaced 1st‐yr plants of each of commercial Pensacola and Cycles 9 and 16 were compared for culm number per plant, racemes per culm, height, leaf length and width, raceme length, plant diameter, plant weight, culm weight, and leaf weight. Differences existed among cycles for all traits. Cycle 16 plants had the highest values and Pensacola plants had the lowest values, except for plant diameter, which decreased as cycles increased. Increases in culm number per plant, plant height, and leaf length increased from Pensacola bahia to Cycle 16 by 32, 44, and 79%, respectively. Mean leaf, culm, and whole plant weights increased by 423, 308, and 382%, respectively. Plant diameter decreased by 15%. Multiple linear regression analysis showed that, in general, plant weight could be closely predicted with two variables, leaf length and number of culms per plant. It was concluded that RRPS for yield has resulted in an increase in size or number of all measured morphological traits while reducing plant diameter. Cycle 16 contained enough variability that progress is expected to continue in future cycles.
Genotype‐Environment Interactions in Two Wheat Crosses
Authors: Yang R.‐C. , Baker R. J.
Published: July 2010

Genotype‐environment interactions can arise from heterogeneity of variances or change in genotype ranks (or both) from one environment to another (genetic correlation < 1). The purpose of this study was to characterize the interactions for five quantitative traits in two spring wheat (Triticum aestivum L.) crosses, ‘Potam’ ✕ ‘Ingal’ (P ✕ I) and RL3147 ✕ Ingal (R ✕ I). Three F3‐derived lines in each of 48 F2 families were evaluated in the F5 (1986) and F6 (1987) generations at the University of Saskatchewan. A nested split‐plot design was used with four groups of 12 families as whole plots and 36 F3‐derived F5 or F6 lines in each group as subplots. Days to heading, plant height, kernels per spike, kernel weight, and kernel hardness were examined. Variation and covariation among‐ and within‐F2 families were significant for all traits in both crosses. Significant family ✕ year interactions were detected for all traits except kernel hardness in P ✕ I and for days to heading, kernels per spike, and kernel hardness in R ✕ I. Significant line ✕ year interactions were detected for kernel weight in hardness in R ✕ I. These interactions were primarily due to heterogeneity of variances, but not to change in genotype ranks, for all traits. In contrast to crossover interactions, these noncrossover interactions should have little impact on selection; however, the noncrossover interactions may seriously limit the estimation of linkage and epistasis from variances and covariances between relatives.
Inheritance of Reduced Palmitic Acid Content in Seed Oil of Soybean
Authors: Fehr W. R. , Welke G. A. , Hammond E. G. , Duvick D. N. , Cianzio S. R.
Published: July 2010

Reduction of the palmitic acid content of soybean [Glycine max (L.) Merr.] would lower the total saturated fatty acid content of the seed oil. A mutant line, A1937NMU‐173, with ≈30 g kg‐1 less palmitic acid than commercial soybean cultivars was obtained by the treatment of seeds of the cultivar A1937 with N‐nitroso‐N‐methyl‐urea (NMU). To determine the genetic control of the reduced palmitic acid, A1937NMU‐173 was crossed reciprocally to C1726, a line with the fap1 allele that lowers the palmitic acid content. No maternal effect for palmitic acid was observed from the analysis of F1 seeds from reciprocal crosses. The segregation observed from the analysis of individual F2 seeds for palmitic acid content satisfactorily fit a ratio of 9 greater than either parent: 2 within the range of the parents: 5 less tahn either parent. The F2 segregation ratio and the segregation of F3 seeds from F2 plants indicated that A1937NMU‐173 and C1726 have different alleles at two independent loci. The allele in A1937NMU‐137 has temporarily been designed fapx. the genotype fap1 fap1 fapx fapx has ≈ g kg‐1 of palmitic acid, which is the lowest content known in soybean.
Resistance to Russian Wheat Aphid in Wild Hordeum Species
Authors: Kindler S. D. , Springer T. L.
Published: July 2010

The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious pest of cultivated barley, Hordeum vulgare L., grown where the aphid is endemic. Russian wheat aphid resistance identified in several wild Hordeum spp. may provide genetic variation necessary to breed Russian wheat aphid‐resistant cultivated barleys. Eighty‐four accessions representing seven species and four subspecies of wild Hordeum were screened to identify resistance to the Russian wheat aphid. Resistance was measured by plant damage, aphid reproduction, and aphid survival when confined to the plant for 14 d. Thirty‐six of the 84 accessions were killed in the initial screening. Of the remaining 48 accessions, the damage rating scores (1 = no injury, 9 = dead plants) ranged from 1.33 to 7.67. There were intra‐ and interspecific differences among accessions, with the highest levels of resistance in H. bulbosum L. and H. brevisubulatum (Trin.) Link subsp. violaceum Boiss. & Hohen. One accession of H. bogdani Wil. had an intermediate level of resistance. Several accessions of H. bulbosum and one accession of H. brevisubulatum subsp. violaceum had low damage ratings, low aphid reproduction, and low leaf‐curling ratings compared with other wild Hordeum accessions and the cereal checks. Broadening the genetic base of cultivated barley by the introduction of resistant alien genes may provide additional protection from new virulent strains or biotypes of the Russian wheat aphid.
Aberrant Cytological Behavoir in Tobacco Androgenic Doubled Haploid ✕ Parental Cultivar Hybrids
Authors: Reed Sandra M. , Wernsman E. A. , Burns Joyce A.
Published: July 2010

Amplication of DNA has been reported for another culture‐derived doubled haploid (DH) lines of tobacco (Nicotiana tabacum L.). The purpose of this study was to evaluate the cytological changes associated with this DNA amplification. Crosses were made between three second‐cycle DHs and their source cultivars, NC95 and C139. Examination of chromosome pairing in pollen mother cells (PMCs) revealed that two of the hybrids produced a single quadrivalent at metaphase I, whereas the other hybrid formed two quadrivalents. In all of the hybrids, quadrivalents either were in a ring, or consisted of two ring bivalents connected by a single strand of chromatin. This latter form, which was termed a side‐arm quadrivalent, appears to represent pairing between amplified homologous chromosome regions in nonhomologous chromosomes. These findings suggest that at least some of the DNA that is amplified in tobacco DHs is present in large blocks, and occurs in identical or similar sequences located on different chromosome pairs. Observations of chromosome and spindle behavior in somatic anaphases and meiotic anaphase I and tetrad cells revealed the presence of a low frequency of spindle errors in the hybrids. while the genotypic effectofr the frequency of abnormal mitotic anaphases was not significant, a highly significant genotypic effect was found fot the frequency of abnormal anaphase I cells. All hybrids had significantly more anaphase I errors than did their parental lines. These spindle errors may be caused by the amplification of specific sequences within the DH lines or by the differences between the parental lines in amount of DNA.
Tillering and Yield Responses to Ethephon in Three Barley Cultivars
Authors: Foster Kenneth R. , Reid David M. , Taylor John S.
Published: July 2010

Ethephon (2‐chloroethyl phosphonic acid) is applied to cereal crops to control lodging. Tillering and yield may also be affected, although the response depends on the species, cultivar, and rate and time of application. A field study was conducted during 1988 and 1989 at Lacombe, AB, to assess ethephon effects on tillering and yield in irrigated spring barley (Hordeuvmul gate L.). Ethephon was applied at 0.3 and 0.6 kg ha−1 at Zadokgsr owtsht age4 3 to ‘Klages,’ ‘Leduc,’ and ‘Bonanza’ barley. There was no lodging in either year. Ethephon reduced plant height in both years. Tillers were separated into three groups at harvest:(i) early fertile, if they had been formed early in the season and produced mature grain,( ii) early sterile, if formed early and produced no grain, or (iii) late, if produced post treatment. In 1988, all cultivars produced significant late tiller number and biomass m‐2 increases (6‐ to 8‐fold and 9‐ to 16‐fold, respectively, at 0.6 kg ha−1) in response to ethephon (K lages > Leduc > Bonanza). In Klages, early fertile tiller number m−2 was reduced at 0.3 kg ha−1 ethephon, while the number early sterile tillers m−2 increased by a factor of 2.5 with each increase in ethephon rate. Yield and harvest index were reduced by ethephon treatment in all the cultivars. Grain mass was unaffected by treatment; however, grains spike−1)decreased significantly (by 26–36%at 0.6 kg ha−1) with increasing rate. In 1989, a significant increase in number and biomass of late tillers m−2 was observed in two cultivars(Klages > Bonanza) response to ethephon. Averaged across cultivars, the number of early sterile tillers m‐2 increased twofold with each increase in ethephon rate. There was no effect of ethephon on yield in 1989, although the harvest index of Klages was reduced due to the increased late tiller biomass. Ethephon induces tillering in barley when applied at Zadoks 43, although the degree of tillering is dependent upon cultivar and environmental conditions.
Starch Gel Electrophoresis Used for Identification of Turf‐type Cynodon Genotypes
Authors: Vermeulen P. H. , Beard J. B. , Hussey M. A. , Green R. L.
Published: July 2010

A reliable technique is needed to facilitate the identification of cultivars of turf‐type Cynodon species because of difficulties encountered using morphological traits alone. This study was conducted to determine the potential for using starch gel electrophoresis to identify 21 Cynodon genotypes. Six enzyme systems (aconitase, alcohol dehydrogenase, phosphoglucomutase, phosphoglucoisomerase, shikimic acid dehydrogenase, and triosephosphate isomerase) were used because of ease of resolution. Plant material was grown in a greenhouse or growth chamber and crude protein extracts were made from recently emerged leaf blades. Examination of banding patterns allowed identification of 16 unique genotypes (‘A‐22’, ‘A‐29’, ‘Bayshore’, ‘Everglades’, ‘FB‐119’, ‘Midiron’, ‘Midway’, ‘Ormond’, ‘Santa Ana’, ‘Sunturf’, ‘Tiffine’, ‘Tifgreen II’, ‘Tiflawn’, ‘Tifway’, ‘Tifway II’, and ‘Vamont’) using three of the enzyme systems (aconitase, phosphoglucomutase, and phosphoglucoisomerase). The five remaining genotypes were separated into two distinct groups: (i) ‘Pee Dee’, ‘Tifgreen’, and ‘Tifdwarf’ and (ii) ‘Texturf 10’ and ‘Texturf if’. It was concluded from this study that starch gel electrophoresis is useful in genotypic identification with Cynodon species. Additional isoenzyme characterizations are required to achieve individual identification of all genotypes in the collection.
Sequential vs. Pedigree Selection Method for Yield and Leafspot Resistance in Peanut
Authors: Branch W. D. , Kirby J. S. , Wynne J. C. , Holbrook C. C. , Anderson W. F.
Published: July 2010

A sequential selection method is proposed to minimize genotype ✕ environment interactions. The sequential method involves cycling early‐generation selections through different environments, as opposed to practicing selection at the same location each year. To evaluate this method, a cooperative peanut (Arachis hypogaea L.) selection study was conducted in Georgia, North Carolina, and Oklahoma. Pedigree and sequential selections and single seed descent were compared each of 3 yr for yield and leafspot [Mycosphaerella arachidis Deighton (anamorph: Cercospora arachidicola S. Hori) and Mycosphaerella berkeleyi Jenk. (anamorph: Phaeoisariopsis personata Berk. & M.A. Curtis/Arx)] resistance. Sequential selections were comparable to or significantly better than the pedigree selections in leafspot rating and yield performance. Individual sequential selections were also found with combined leafspot resistance and high yield. In general, the sequential selection method proved to be an alternative approach for peanut breeding.
Performance of Open‐Pollinated Maize Cultivars selected from 10 Tropical Maize Populations
Authors: Pandey Shivaji , Vasal S. K. , Deutsch J. A.
Published: July 2010

Open‐pollinated cultivars (OPCs) continue to occupy a larger portion of maize (Zea mays L.) production area than hybrids in the developing countries. We studied the possibility of extracting superior OPCs during an ongoing recurrent selection program for use in the developing countries. Forty experimental cultivars (ECs) were developed from 10 maize populations adapted to lowland tropics, using 7 to 14 full‐sib families. Families were selected for performance at one site (Poza Rica, Mexico) or across five to six sites, (Across) around the world, from CO (ECs‐C0) or from C3 or (ECs‐last cycle). The effects of selection were evaluated in four environments to measure performance and stability. Percent superiority of ECs‐last cycle over ECs‐C0 was 9.5 (P < 0.01) for yield, −2.6 for days to 50% silking, −5.1 for plant height, −9.6 for ear height, 5.6 for ears per plant, 1.9 for 1000‐seed weight, and −11.7 for ear rating. Poza Rica‐ECs were lower (P < 0.01 ) in plant and ear height (−6.1 and −10.3%, respectively) than Across‐ECs daring summer at Poza Rica and Across‐ECs had fewer (−1.19%) days to 50% silking than Poza Rica‐ECs at the other three sites. for yield, the b1 (regression of entry means to environmental index) values for Across ECs‐last cycle were lower than those for Poza Rica ECs‐C0, Across ECs‐C0, and Poza Rica ECs‐last cycle (P < 0.01 and P < 0.25 with environments considered fixed and random, respectively). The results indicate that ECs developed from advanced cycles of selection of populations undergoing recurrent selection yield higher (P < 0.01) and are more stable (P < 0.01 and P < 0.12 with environments considered fixed and random, respectively) than those developed from the original cycle.
Allelism among Genes for Resistance to Soybean Mosaic Virus in Strain‐Differential Soybean Cultivars
Authors: Chen P. , Buss G. R. , Roane C. W. , Tolin S. A.
Published: July 2010

Five soybean [Glycine max (L.) Merr.] cultivars that have been used to differentiate strain groups of soybean mosaic virus (SMV) were studied to determine the allelic relationships among genes conditioning reaction to SMV. The cultivars PI 96983, ‘Ogden’, ‘York’, ‘Marshall’, and ‘Kwanggyo’ (PI 406710) are each known to have single dominant gene conditioning resistance to SMV. These parents were crossed in all possible combinations with each other and with a susceptible cultivar. The crosses were evaluated in the F2 and with F2‐derived F3 lines in the field and in the greenhouse for reaction to inoculation with the G1 strain of SMV (SMV‐G1). Results confirm that each of the resistant cultivars has a single dominant gene for resistance to SMV‐G1, but that dominance is sometimes incomplete. The lack of segregation for susceptibility in F2 and F3 progenies from the resistant ✕ resistant crosses indicates a high probability that the resistance genes in these cultivars are alleles at a common locus. Gene symbols Rsvy1, Rsvm1 and Rsvk1 are proposed for the resistance alleles in York, Marshall, and Kwanggyo, respectively. The systemic necrosis reaction that sometimes occurs following SMV‐G1 inoculation of segregating populations is highly associated with plants heterozygous for the resistance gene, but may be influenced by environment and genetic background.
Differential Reactions of Russian Wheat Aphid to Various Small‐Grain Host Plants
Authors: Worrall W. D. , Scott R. A.
Published: July 2010

There are no standardized procedures for evaluation of host‐plant resistance of small grains to Russian wheat aphid (RWA), (Mordvilko), Diuraphis noxia. Research results, therefore, often are ambiguous. One possible source of ambiguity is the host genotype on which aphids are reared prior to being used on test plants. In this study, two collections of RWA were cultured separately on TX78V2290‐36‐1 wheat (Triticum aestivum L. em Thell), TXGHI0989 wheat, ‘Nora’ oat (Avena sativa L.) and ‘Eronga’ triticale (✕ Triticosecale Wittmack). After a 30‐d period on the culture plants, the aphids were removed and placed on tester plants to determine whether the host‐plant genotype used for colony maintenance affected aphid performance on testers. The tester plants were the same as those used for colony maintenance. Aphids were placed on testers from source plants in all possible combinations and aphid response to tester genotypes was determined by counting the number of embryos produced per aphid. Results showed that the source genotype had a significant effect on subsequent performance of aphids. The TX78V2290‐36‐1 wheat provided the best overall rearing environment of the genotypes tested. Aphids originally maintained on TX78V2290‐36‐1 successfully discriminated wheat from oat and oat from triticale, as well as distinguishing the different levels of resistance of the two wheat genotypes.
Genotype ✕ Sucrose Interactions for Somatic Embryogenesis in Soybean
Authors: Komatsuda Takao , Kaneko Kazuhiko , Oka Seibi
Published: July 2010

Somatic embryogenesis is a route of plant regeneration in soybean [Glycine max (L.) Merr.]. This study was undertaken to test the ability of immature soybean embryos to produce somatic embryos across several sucrose concentrations. Cotyledons isolated from immature embryos of 16 soybean (G. max and G. gracilis Skvortz.) cultivars were cultured on embryogenesis media containing sucrose at concentrations of 5, 10, 20, and 30 g L−1. After 28 d in culture, the number of somatic embryos per pair of cotyledons was counted. The analysis of variance showed that the effects of genotype, sucrose concentration, and genotype ✕ sucrose interaction were all highly significant. The genotype ✕ sucrose interaction was analyzed further by regression of each cultivar on the mean of all varieties for each sucrose concentration. Highly significant heterogeneity of regression among the cultivars was recognized. Stability, as expressed by regression, and average response of cultivars to the various sucrose concentrations appeared to be under separate genetic control.
Potential of Creeping Bluestem for Improvement of Grazing on Florida Range
Authors: Kalmbacher R. S. , Brown W. F. , Martin F. G. , West S. W.
Published: July 2010

Improvement in forage quality through management of Florida range is limited, but could come from seeding better quality forages. To this end, the potential of creeping bluestem [Schizachyrium scoparium (Michx.) Nash var. polycladus (Scribner & Ball) Braner (Syn. S. stoloniferum Nash)] to improve Florida range was evaluated. Two hundred plants were collected from Florida in 1982 and established in an unfertilized, replicated nursery at Ona. Soil samples taken at each collection site were analyzed for P, K, Ca, Mg, pH, and organic matter (OM) content. Entries were evaluated for in vitro organic matter digestion (IVOMD) in 1984 and 1985 and caryopsis production, germination, and dry matter (DM) yield 1984 to 1986. Creeping binestem grew on a wide range of soil P (x̄ = 12 mg kg−l), K (x̄ = 13 mg kg−1), Ca (x̄ = 450 mg kg−l), Mg (x̄ = 30 mg kg−1), pH (x̄ = 5.5), and OM contents (x̄ = 25 g kg−1). Differences (P < 0.001) existed in caryopsis production, with 153 and 145 entries out of 200 producing caryopses in 1984 and 1985, respectively. Spikelets with caryopses averaged 28 and 26% in 1984 and 1985, respectively, with highest values of 90 and 70%, respectively. Caryopsis yield in 37 entries that demonstrated consistently high potential from 1984 to 1986 ranged from 0.34 to 6.80 g m−2 and averaged 1.06 g m−2. Germination varied with year, and differences were found in 2 of 3 yr (x̄ = 46%, 30%, and 76% in 1984 to 1986, respectively). Differences (P > 0.001) in vegetative plant IVOMD (x̄ = 530 g kg−1, range = 380 to 640 g kg−1) and DM yield (P > 0.01) were found (x̄ = 120, 647, and 2360 kg−1 in 1984, 1985, and 1986, respectively). There is potential for breeders to develop a creeping binestem cultivar for seeding Florida and perhaps Southeastern range for improved cattle production.
Hypocotyl Elongation and Swelling of Cotton as Affected by Soil Temperature, Moisture, and Physical Impedance
Authors: Chu Y. N. , Coble C. G. , Jordan W. R.
Published: July 2010

Hypocotyl elongation and swelling affect the time required for a seedling to emerge and the potential emergence force of the seedling against soil impedance. This study was conducted to evaluate effects of soil physical conditions on hypocotyl elongation and swelling of cotton [Gossypium hirsutum L.] seedlings. Effects of soil temperature, moisture, and physical impedance on hypocotyl growth were investigated by applying a constant downward force on the hypocotyls at different temperature and moisture conditions under controlled environments. Average hypocotyl elongation, in a 3‐d period decreased with increasing downward force from 9.7 cm under no load to 1.8 cm under a 180‐g load. Hypocotyl elongation increased with increasing soil temperature from 22 to 32 °C and soil water potential from −300 to −10 J kg−1. The swelling index, calculated by dividing the fresh weight of the hypocotyl by its length, increased quadratically with increasing downward load. Total fresh weight decreased with increasing downward load and decreasing soil moisture. Hypocotyl swelling generated potential emergence forces exceeding downward loads in the tested range, 0 to 1.8 N. The potential emergence force was lower and the response to greater downward load was reduced at a soil water potential of −300 J kg−1
Combining Abilities of Creeping Foxtail Parents Selected for Seed Retention
Authors: Boe A. , Ross J. G.
Published: July 2010

Creeping foxtail (Alopecurus arundinaceus Poir.), a strongly rhizomatous, cool‐season perennial grass native to Eurasia, has great forage and conservation potential in wetlands and mountain meadows throughout the northern USA and adjacent Canadian provinces. The objective of this study was to determine general (GCA) and specific (SCA) combining ability for vegetative and reproductive traits of six parents previously selected for seed retention. Fifteen diallel progenies were evaluated in a spaced‐plant nursery at Brookings, SD, in 1972 and 1973. Significant differences were found among parents for GCA effects for leafiness, plant height, seed yield of five panicles, and seed set. Specific combining ability effects were consistently much lower than GCA effects, even though parents varied significantly in SCA for all variables except plant height in 1973. Parents capable of transmitting either desirable height or seed set characteristics to their progeny were identified, but parents with high GCA for all the vegetative and reproductive traits measured were not obtained from this selected group. Based on the magnitude of GCA relative to SCA effects, recurrent selection should result in a gain for forage and seed production in this species.
Cytology, Reproductive Behavior, and Forage Potential of Hexaploid Dallisgrass Biotypes
Authors: Burson B. L. , Voigt P. W. , Evers G. W.
Published: July 2010

During the past 25 yr, several different dallisgrass (Paspalum dilatatum Poir.) biotypes have been discovered, but little is known regarding their cytology and reproductive behavior. This study was undertaken to determine the cytology, method of reproduction, and fertility of three biotypes and the forage yield and quality of two of them. Two biotypes, Torres and Uruguaiana, were introduced from southern Brazil and the third, Uruguayan, was collected in Uruguay. All three are hexaploids with 2n = 6x = 60. The Torres biotype was meiotically irregular, with a mean chromosome association of 58.74 univalents and 0.63 bivalents per cell. Two accessions of the Uruguaiana biotype were studied; they had a mean meiotic chromosome association of 9.62 univalents, 25.17 bivalents, and 0.01 quadrivalents. Eleven accessions of the Uruguayan biotype were studied; their mean chromosome associations were 1.26 univalents, 29.28 bivalents, and 0.04 quadrivalents. It was proposed that the lack of chromosome pairing in the Torres biotype is genetically controlled. The genomic formulas of the Uruguaiana and Uruguayan biotypes are proposed to be AABBC1C2 and AABBCC, respectively. An examination of megasporogenesis and embryo sac development revealed that all three biotypes reproduce by apomixis, with apospory followed by pseudogamy. One Uruguayan accession was a facultative apomict with a small degree of sexuality. The forage yield potential and forage quality were determined for the Torres and Uruguayan biotypes, as well as for common dallisgrass. Torres produced less forage than the other two. Common dallisgrass produced less forage than the mean of the Uruguayan accessions in most environments. In vitro dry matter disappearance (IVDMD) differences among accessions were relatively small. Common dallisgrass did not differ in IVDMD from any of the Uruguayan accessions.
Evaluation of a Method for Identifying Sources of Favorable Alleles to Improve an Elite Single Cross
Authors: Hogan R. M. , Dudley J. W.
Published: July 2010

A method has been developed for estimating the value of donor lines or populations for improving an elite single cross. The method provides estimation of : the relative number of dominant alleles in a potential donor line or population at loci for which an elite single cross to be improved is homozygous recessive. The method also allows estimation of , and: the relative numbers of alleles in a potential donor at loci for which the elite single cross is heterozygous. This experiment was conducted to determine whether these estimators correctly rank populations with known relative values of. and. Maize (Zea mays L.) hybrid FRB73 ✕ FRMol7 was the elite single cross to be improved; 15 potential donors were selected. Populations containing 75, 50, and 25% germplasm from individual donors were produced by crossing each donor to FRB73 ✕ FRMoI7 and backcrossing to each parent. Estimates of, and were obtained for grain yield, earliness of flowering, plant height, and ear height. For each donor, estimates were calculated for populations with 100, 75, 50, 25, and 0% donor germplasm (the 100% population was the donor and the 0% population was the elite single cross itself). These five populations correspond to proportions of 1.0, 0.75, 0.50, 0.25, and 0.0 times, respectively. For and and are 0.5 in FRB73 FRMo17 and may be larger or smaller in the donor. Linear regression of estimates on proportion of donor germplasm was performed using the array of populations from each donor. In general, when estimates of, or for the donors (100% populations) were significantly different from those of the F1, the proportion of variation explained by linear regression was highly significant. In addition, when estimates of were averaged across populations of each proportion, linear regression on proportion of donor germplasm accounted for 87 to 99% of the variation among mean estimates for all traits. Becausestimators precisely rank lines or populations relative to frequencies of useful new alleles to improve an elite single cross, they should be useful in selecting parents to improve single crosses.
Early‐Maturing, Short‐Statured American Pima Cotton Parents Improve Agronomic Traits of Interspecific Hybrids
Authors: Percy Richard G. , Turcotte E. L.
Published: July 2010

The commercial potential of interspecific cotton hybrids (Gossypium hirsutum L. ✕ G. barbadense L.) remains unrealized due to several fiber‐quality deficiencies and the agronomic traits excessive vegetative vigor and generally slow maturation rates. This study examined whether four G. barbadense strains, bred for short stature and early maturity, favorably affect hybrid plant height, earliness, and lint yield. The four strains and the G. barbadense commercial cultivar Pima S‐6 (PS‐6) were crossed to short‐staple G. hirsutum cultivars McNair 235, Stoneville 506, TAMCOT SP21‐S, and AZ107 to produce F1 hybrids. Hybrids and their parents were evaluated in replicated tests at Maricopa, AZ (1988), Safford, AZ (1988 and 1989), and Las Cruces, NM (1989). Maricopa is a low‐elevation desert site (358 m); Safford and Las Cruces are at 884 and 1180 respectively. The G. barbadense parents influenced hybrid plant height at Maricopa and Las Cruces, with PS‐6 producing the tallest hybrids. At Maricopa and Safford (1989), the later‐maturing PS‐6 parent produced later‐maturing hybrids and the early‐maturing strains 84514 and 8327 produced earlier‐maturing hybrids. Hybrid yields exceeded parent yields in the three higher‐elevation tests. The best hybrid yield exceeded the best parent yield (of either species) by 29.1% at Safford (1989), 49.1% at Safford (1988), and 87.5% Las Cruces. Significant G. barbadense contributions to hybrid yield performance were observed in all tests. At the three higher‐elevation locations, the best hybrid yields were obtained from crosses involving the early‐maturing, short‐statured strains 84514 and 8327. Under the higher‐elevation environments, which maximized hybrid yield heterosis, parent earliness was a better predictor of hybrid yield than was parent yield.
Inheritance of Expansion Volume and Yield in Two Popcorn ✕ Dent Corn Crosses
Authors: Dofing S. M. , D'Croz‐Mason Nora , Thomas‐Compton M. A.
Published: July 2010

Improvement of expansion volume, defined as the volume of popped corn per gram of unpopped corn, generally is considered the most important objective of popcorn (Zea mays L.) breeding programs. Popcorn, however, generally is inferior to dent corn with respect to yield and other agronomic characteristics. Detailed information on the inheritance of expansion volume and grain yield in popcorn ✕ dent corn crosses was not available in the literature. The objective of this study was to determine the inheritance of expansion volume and grain yield, including yield components, in two popcorn ✕ dent corn crosses. Generation means analysis was used to quantify genetic effects in the popcorn ✕ dent crosses Ia53 ✕ B73 and Ia28 ✕ Mo17. Significant additive genetic effects were detected for ail traits in both crosses. Significant dominance genetic effects were detected for expansion volume in the cross Ia28 ✕ Mo17, and for grain yield, ear length, ear diameter, and 5O‐kernel weight in both crosses. Dominance effects resulted in reduced expansion volume, and increased grain yield, ear length, ear diameter, and 5O‐kernel weight. Significant epistatic effects for grain yield were detected in the crosses Ia53 ✕ B73. Expansion volume was negatively correlated with all yield components except for number of kernel rows. Thus, relative to other yield components studied, selection for high kernel row number would appear to result in the least reduction of expansion volume. Results from this study indicate that breeding methodologies which exploit additive genetic variation assoicated with expansion volume and dominance variation associated with grain yield are most likely to result in concurrent improvement of these two traits.
Molecular Markers and Grouping of Parents in Maize Breeding Programs
Authors: Dudley J. W. , Maroof M. A. Saghai , Rufener G. K.
Published: July 2010

In maize (Zea mays L.) breeding programs identifying potentially high yielding hybrids, assigning new inbreds to heterotic groups, and determining the parental line in a hybrid to which a potential donor line is most closely related, are significant problems. Data from a diallel cross among 14 maize inbreds were analyzed to evaluate use of molecular marker date to (i) predict yield potential of hybrids, (ii) assign inbreds to heterotic groups, and (iii) determine to which of the two inbred parents of a single cross a donor line is most closely related. Four of the inbreds were from Iowa Stiff Stalk Synthetic background, five were from a Lancaster Sure Crop background and five were unrelated to either Stiff Stalk Synthetic or Lancaster Sure Crop. Allozyme genotypes at 14 loci and restriction fragment length polymorphism (RFLP) variant types for 52 cDNA clones were obtained for the 14 inbreds. Modified Roger's distance (MRD) values (a measure of genetic distance between inbreds based on marker data) were not significantly correlated with hybrid yields; however, a hybrid value based on the number of marker loci having the highest yielding genotype was significantly correlated with hybrid yield. Cluster analysis based on MRD values agreed well with pedigree information, but did not always agree with groupings based on yield. Where parents of hybrids were distantly related, a measure of relative relationship based on proportion of homomorphic marker loci was significantly correlated with a measure of relationship based on yield. Where parents of a hybrid were more closely related, however, such correlations were low.
Antimitotic Agents: Effects on Double Haploid Production in Wheat
Authors: Hassawi Dhia S. , Liang George H.
Published: July 2010

Chromosome doubling of microspore‐derived plantlets and calli is a critical step in haploid breeding programs. For anther culture experiments, colchicine, (S)‐N‐(5,6,7,9‐tetrahydro‐l,2,3,10‐tetramethoxy‐9‐oxobenzo[a]heptalen‐7‐yl)acetamide, is the most commonly used compound in doubling the chromosomes of seedlings derived from such experiments. Colchicine, however, is carcinogenic and expensive. We evaluated three antimitotic agents (colchicine; trifluralin, 2,6‐dinitro‐N,N‐dipropyl‐4‐(trifluoromethyl)benzenamine; and oryzalin, 4‐(dipropylamino)‐3,5‐dinitrobenzenesulfonamide) at two treatment durations (48 and 72 h) and two concentrations [colchicine at 0.0125% (313 μM) and 0.025% (626 μM), and both trifluralin and oryzalin at 5 and 10 μM each for their effects on the production of double haploids from anther‐derived calli of two wheat [Triticum aestivum (L.) em. Thell.] cultivars, Pavon and Kitt. Calli from Pavon were more responsive to the three agents than those from Kitt. Colchicine was the most effective in double the chromosome number. for Pavon, 89% of the plantlets from calli treated with colchicine were double haploids (2n = 6x = 42). However, treating calli for 72 h with colchicine at either concentration had a deleterious effect. No significant differences were observed between concentrations of any of the antimitotic agents. All the plantlets produced from the control treatment (without antimitotic agents) were polyhaploids (2n = 3x = 21). These results indicated that colchicine is still the most ffective compound for chromosome doubling, and colchicine treatment of anther‐derived calli is an effective method of obtaining a high frequency of double haploid plantlets through anther culture systems.
Chromosomal Interchanges in Six Hexaploid Oat Genotypes
Authors: Singh R. J. , Kolb F. L.
Published: July 2010

Intercultivar chromosomal interchanges in oat, 2n = 6x = 42, Avena sativa L., have not been extensively investigated. The objective of this research was to determine the occurrence of chromosomal interchanges among several cultivars of spring oat. Five oat cultivars (Andrew, Gopher, Hazel, Ogle, Otee) and one experimental breeding line (PA12422) included in this study carried expected 2n = 6x = 42 chromosomes, showed diploidlike meiosis with 2111 and set normal seeds. All the intercultivar F1 hybrids were vigorous and completely pollen‐ and seed‐fertile. Meiotic chromosome pairing at diakinesis of F1 hybrids revealed the following information: (i) Gopher and Otee contain similar chromosome structures and are differentiated from Andrew by a single chromosomal interchange; (ii) Hazel and Ogle possess identical chromosome structure and differ from Gopher and Otee by a single chromosomal interchange and by double interchanges from Andrew; and (iii) breeding line PA 12422 differs from Hazel and Ogle by two different interchanges, but the two interchanges involve the same chromosome giving a 1VI + 18II chromosome configuration. Thus, multivalents occurred frequently in the hexaploid spring oat F2 hybrids studied.
Nonstructural Carbohydrate Accumulation in Winter Oat Crowns Before and During Cold Hardening
Authors: Livingston D. P.
Published: July 2010

Most cool‐season grasses store large amounts of fructan during fall hardening. Fructan storage has been extensively investigated in most winter cereals, but very little research has been reported in oat (Arena sativa L). To compare fructan accumulation in crowns of representative winter cereals, two oat, two barley (Hordeum vulgare L.), one wheat (Triticum aestivum L.), and one rye (Secale cereale L.) cultivar were raised under controlled conditions for 5 wk at 15 °C and 3 wk at 2 °C. Starting at the end of Week 4, and at weekly intervals, carbohydrates were extracted from fresh crown tissue and separated by high performance liquid chromatography (HPLC). a dry‐weight concentration basis, oat crowns accumulated significantly less fructan of degree of polymerization greater than 9 (DP > 9) than all other cultivars and significantly more DP3 to DP7 fructan. The presence of large amounts of sucrose and DP3 to DP7 fructan suggested that substrate level was not limiting synthesis of DP > 9 fructan in oat.
Growth Habit, Planting Date, and Row‐Spacing Effects on Late‐Planted Soybean
Authors: Weaver D. B. , Akridge R. L. , Thomas C. A.
Published: July 2010

When soybean [Glycine max (L.) Merr.) is double‐cropped with small grains, as is often done in the southeastern USA, it yields less than full‐season soybean. Incorporation of indeterminate growth habit into adapted germplasm has been suggested as a means of reducing the yield loss associated with delayed planting of determinate soybean (the predominant plant type grown in the Southeast). Little is known about management of indeterminate soybean in late‐planted systems. Our objective was to compare response of determinate and indeterminate growth habit to row spacings and planting dates within a late‐planted, narrow‐row cropping system. Determinate ‘Braxton’ [maturity group (MG) VII] and ‘Kirby’ and indeterminate experimental genotypes G82‐8468 and G84‐9006 (MG VIII) were compared in 0.60‐ and 0.30‐m row spacings, and in June and July plantings for 4 yr in Alabama (32°30' N lat). Determinates yielded more than indeterminates, but indeterminates had less yield loss caused by delayed planting. Indeterminate plant height was reduced more by later planting, but was greater than determinates in both plantings. Seed‐filling period was reduced in the later planting in both determinate and indeterminate genotypes. Indeterminates had more mainstem pods and nodes per plant than determinates. Plants in 0.30‐m rows had fewer days to canopy closure, mainstem nodes, number of branches, pods per branch, and pods per plant than plants in 0.60‐m rows, but yields were not different. We concluded that row spacings <0.60 m between rows provide no advantage for late‐planted soybean, and neither growth habit has any advantage for yield in late‐planted, narrow‐row cropping systems.
Evaluation of Sweet Potato Genotypes for Adaptability to Hydroponic Systems
Authors: Mortley D. G. , Bonsi C. K. , Loretan P. A. , Morris C. E. , Hill W. A. , Ogbuehi C. R.
Published: July 2010

Sweet potato [Ipomoea batatas (L.) Lam.] is among eight crops selected by NASA for its Controlled Ecological Life Support Systems (CELSS) program. This research evaluated sweet potato genotypes for adaptability to hydroponic systems. Fourteen sweet potato genotypes were grown hydroponically using nutrient film technique (NFT) systems. Four vine cuttings from each genotype were spaced at 25 cm and grown for 120 d using 14 NFT channels (0.15 by 0.15 by 1.2 m) supplied with a modified half‐Hoagland nutrient solution. Genotypes responded differently to growth in NFT. ‘Jewel’ produced the highest mean total storage‐root yield of 470 g per plant. Individual plant yields ranged from 767 g for ‘Centennial’ to 36 g for ‘Bunch’. Inverse relationships between foliage weight and storage‐root yield were obtained with 11 genotypes. Edible biomass indices were comparable to those of potato (Solanum tuberosum L.) and lettuce (Lactuca sativa L.), and higher than those of wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.]. Based on their performance, Jewel, ‘Carver’, TU‐52, and Centennial sweet potato appear well adapted to growing in NFT.
Genetic Nomenclature in Clovers and Special‐Purpose Legumes: I. Red and White Clover
Authors: Quesenberry K. H. , Smith R. R. , Taylor N. L. , Baltensperger D. D. , Parrott W. A.
Published: July 2010

Clover and special‐purpose legumes (not including alfalfa, Medicago sativa L.) constitute the primary genetic resource of legumes for grass‐legume based pasture and hay systems. The group is diverse and contains species from the genera Trifolium, Lotus, Lespedeza, Vicia, and others. Although species in these genera have been the subject of research for at least six decades no systematic scheme for genetic nomenclature has been adopted and a variety of conventions and gene symbols have been used. Absense of a centralized repository for genetic marker stocks has contributed to the loss of seed stocks of named genes. This paper (i) outlines a set of rules for uniform nomenclature and symbolization for the clovers and special purpose legumes, (ii) defines the membership of a permanent committee on gene symbolism and designates a central repository for named genes, and (iii) tabulates gene symbols published to date for red clover (Trifolium pratense L.) and white clover (T. repens L.) and attempts to clarify cases of duplicate nomenclature with establishment of a list of recommended gene symbols. The inheritance and gene symbols are tabulated for 61 previously published red clover genes and 28 previously published white clover genes. The genetic behavior of 27 other traits in red clover for which gene symbols were not published is summarized. Gene nomenclature and symbols according to the rules outlined are proposed for 27 genes in red clover and 28 genes in white clover. Two linkage groups are described for white clover.