bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating Genetic Variance in Sugarcane Using a Factorial Cross Design1
Authors: Hogarth D. M. , Wu K. K. , Heinz D. J. 
Published: July 2010

Progeny from seven factorials of crosses were studied to examine the quantitative genetics of a breeding population of clones used in the Hawaiian sugarcane (Saccharum spp. L.) breeding program and the applicability of quantitative genetic theory to sugarcane. Nonadditive genetic effects were equally important to additive genetic effects, which suggests that increased yields could result from utilizing both polycrosses and crosses where both parents are known. There was relatively little genetic variability for sugar content as measured by refractometer solids compared to the genetic variability for yield of cane as measured by volume. Thus, the greatest progress in breeding and selection is more likely to come from increasing the yield of cane rather than from increasing sugar content.The estimates of additive genetic variance, σ2A1 and σ2A2, were obtained, respectively, from the regression of progeny means on mid‐parent means and the progeny analysis; the estimates of total genetic variance, σ2G! and σ2G2 were obtained, respectively, from the analysis of parental clones and the progenies. The ratios of σ2A1/σ2A2 and σ2G1/σ2G2, however, were generally less than one, which suggests that the assumptions underlying quantitative inheritance analysis were violated. This is probably because the clones in the breeding population were highly selected for yield potential.
Improved Lamb Performance Associated with Breeding for Alkaloid Reduction in Reed Canarygrass1
Authors: Marten G. C. , Jordan R. M. , Hovin A. W. 
Published: July 2010

We earlier documented that indole alkaloid concentration of vegetatively propagated reed canarygrass (Phalaris arundinacea L.) clones was inversely associated with average daily gains of lambs and steers. Our objectives were to determine whether alkaloid concentration and type in two commercially available cultivars (‘Rise’ and ‘Vantage’) and in a low‐alkaloid, tryptamine‐carboline‐free strain (MN‐76) were associated with performance and health of grazing lambs. These seed sources of reed canarygrass were each planted in three pastures (0.27‐ha/pasture) in a randomized complete block design.Lambs that grazed MN‐76 gained from 51 to 95% more per day than did those that grazed Rise and from 14 to 87% more than did those that grazed Vantage during a 2‐year period. Rise contained a mean of 0.28 to 0.32% dry wt of a mixture of gramine and tryptamines‐carbolines, Vantage contained 0.20 to 0.33% gramine, and MN‐76 contained 0.09 to 0.12% gramine. The three grasses did not differ in most other quality components, but MN‐76 had up to 8% less cell walls and up to 9% more crude protein during the 2 years, as well as up to 28% more Ca during Year 1. The correlation between total indole alkaloid concentration of the grasses and lamb average daily gain was −0.97 in Year 1 and −0.66 in Year 2. Incidence of diarrhea among lambs was 4 to 26 times greater when they grazed Rise compared to Vantage or MN‐76.We conclude that the indole alkaloid concentration threshold in reed canarygrass at or above which lambs will show reduced gain is about 0.20% dry wt, that diarrhea in grazing lambs specifically caused by consumption of reed canarygrass is very likely due to tryptamine‐carboline alkaloids, and that MN‐76 is a biologically significant grass breeding advance.
Genetic Variances and Selection Responses in an Advanced Generation of a Hybrid of Widely Divergent Populations of Maize1
Authors: Moll R. H. , Smith O. S. 
Published: July 2010

A resonable approach to the utilization of exotic germplasm of maize (Zea mays L.) is through the development and improvement of composites of exotic and locally adapted maize populations. The effectiveness of conventional recurrent selection procedures relative to the large genetic variances anticipated has not been adequately investigated. A series of experiments was undertaken in a composite of two widely divergent populations, one of which is locally adapted. Experiments were designed to (1) carry out five cycles of full‐sib family selection and S1 progeny selection for yield, (2) evaluate the responses to the two selection methods, (3) characterize genetic variances for yield the composite population before and after selection, and (4) compare expected responses based on variance estimates with responses observed.Full‐sib family selection was conducted in duplicate, and the selection responses obtained were in close agreement. The rate of response over five selection cycles was slightly greater than those reported for locally adapted populations. Response to S1 progeny selection was approximately 50% greater than responses to fullsib family selection.Predictions of selection responses computed from estimates of genetic variances were too high when compared with realized responses. Selection resulted in a reduction of genetic variance by about one‐third.In view of the mean yield of the original composite and the rates of gain with selection, the implications with regard to utilization of semi‐exotic composites in practical breeding programs are encouraging.
Inter‐population Improvement Procedures for Alfalfa1
Authors: Rowe D. E. , Hill R. R. 
Published: July 2010

We compared methods of improving a synthetic cultivar with parentage that traced to two different populations. Theoretical equations that expressed changes in the mean of a twd‐population synthetic were developed for three methods of selection: (1) selection within each population followed by combination of the selected individuals into a synthetic (CS); (2) selection based on top‐crossing each population to a common tester and combining the selected individuals (TX); and (3) reciprocal recurrent selection (RRS) in which each population served as the tester parent for the other. Theoretical responses were compared for additive, dominant, duplex dominant, and overdominant genetic models in a two‐allele, single locus autotetraploid population. Two pairs of alfalfa (Medicago sativa L.) populations were compared experimentally to test the effectiveness of polycross and topcross selection for resistance to Colletotrichum trifolii Bain, an index of resistance to C. trifolii and regrowth after cutting, and an index of these two traits plus resistance to Leptosphaerulina briosiana (Poll.) Graham and Luttrell.Each of the selection methods had the same theoretical response with the additive genetic model. The efficiency of TX relative to CS and RRS varied with gene frequency combinations for all nonadditive genetic models. With complete dominance a tester parent existed for which TX selection would be at least as effective as CS or RRS, although differences were small for some gene frequency combinations. Response with TX selection was greater with complete dominance when the tester parent was inferior to the base population. Generalizations could not be made about relative effectiveness of the methods for the duplex dominance model. Negative responses to selection for a trait with overdominance could occur at some gene frequency combinations with CS and TX selection, but response was never negative with RRS.Experimentally, topeross selection was more effective than polycross selection for resistance to C. trifolii when the tester parent had less resistance than the base population, and topeross selection was less effective when the tester parent was more resistant. Comparisons could not be made for the two‐character index selection, but good agreement with theoretical expectations was observed with the three‐character index.
Use of Small‐seeded Soybean Parents for the Improvement of Large‐seeded Cultivars1
Authors: Bravo J. A. , Fehr W. R. , Rodriguez de Cianzio S. 
Published: July 2010

We studied the segregation for seed size in two‐ and three‐way crosses of soybeans [Glycine max (L.) Merr.] involving adapted small‐ and large‐seeded parents. Three lines with small seeds (15.3 to 19.8 g/100 seeds) were crossed to one of two large‐seeded cultivars (25.6 to 28.2 g/100 seeds), and the F1, was crossed to a third parent with intermediate seed size (22.1 to 23.0 g/100 seeds). Seed size of 60 F2‐derived lines in F3 from three two‐way and three three‐way crosses were evaluated with the eight parents in two environments.The observed population mean was closely predicted by either the arithmetic or geometric mean of the parents. The mean seed size of a three‐way compared with its two‐way cross was directly related to seed size of the third parent. Only four of the 360 F2‐derived lines evaluated had a mean seed size within the confidence interval of the smallest or largest parent in the cross. Our results indicated that, utilization of small‐seeded cultivars for improvement of large‐seeded types will require special care in population development to obtain the desired frequency of large‐seeded segregates.
Epistasis in Related and Unrelated Maize Hybrids Determined by Three Methods
Authors: Moreno‐Gonzalez J. , Dudley J. W. 
Published: July 2010

The objectives of this study were (1) to estimate genetic parameters in maize (Zea mays L.), (2) develop and apply a genetic model capable of measuring variance associated with additive, dominance, and two factor epistatic effects in a diallel cross including segregating generations, (3) to measure epistasis as difference of three‐way crosses from the nonparental single crosses, and (4) to compare different methods measuring the importance of epistasis. Three inbreds derived from Stiff Stalk Synthetic and three inbreds related to the Lancaster variety were used to make all possible crosses, their segregating, selling and backcross generations.Heterosis for yield and other traits was larger in crosses involving unrelated lines than in crosses involving related ones. No apparent association of genetic effects estimated from the generation mean analysis with crosses involving related or unrelated lines was found. Dominance effects were the most important genetic effects controlling the performance of all traits. Generation mean analysis was a poor method for measuring additive effects. Significant epistatic effects were found in several crosses. Dominance × dominance effects were consistently negative for all traits except yield, suggesting that selection for yield prior to release of the inbreds might have reduced the diminishing effect of this type of epistasis in cross combinations. Dominance effects for yield were larger than the mean of the pooled additive effects of the lines, suggesting that homozygous beneficial genes (with + effects) and homozygous deleterious (with ‐ effects) were present in lines.In the diallel analysis, the mean squares for dominance effects were larger than for additive effects for yield and plant leaf area, but smaller for plant height, ear height, ear length, and ear diameter. Epistatic variation was significant but small compared to additive and dominance variation. Interactions of genetic effects with locations were significant. When tested against the appropriate interaction mean squares only the dominance mean squares were significant for grain yield. Epistasis was significant in 13 of 54 three‐way crosses. The sign of epistasis was predominately positive for yield, suggesting that lines selected for yield may have certain combinations of genes that are expressed favorably in hybrids. Mean epistatic effects over all crosses were significant for yield, ear height, ear length, and ear diameter.
Grain Yield and Protein Relationships in a Wheat Cross1
Authors: Halloran G. M. 
Published: July 2010

The relationships between grain yield and protein content were examined in segregating populations from a cross between a locally‐adapted high‐yielding, low protein wheat cv. ‘Olympic’ (Triticum aestivum L.) and a lower‐yielding high protein cv. ‘Kenya B.’Segregation for grain protein content in the F3 was continuous with no dominance. In the F4 and F5, it was again continuous but there was partial dominance for low grain protein. Yield segregation in the F4 and F5 was continuous with partial dominance for low yield.Grain yield and protein content in the F4 and F5 populations of the cross Olympic × Kenya B were found to be negatively correlated [r = ‐0.13 NS for the F4 and r = ‐ 0.58 (P < 0.01) for the F5]. While low protein and high yield were significantly associated in the F5 it would appear that there were no strong genetic limitations to improvement in protein percentage of the cv. Olympic at its present level of yield.
Recurrent Phenotypic Selection for High and Low Photosynthesis in Two Maize Populations1
Authors: Crosbie T. M. , Pearce R. B. , Mock J. J. 
Published: July 2010

Photosynthesis is a primary trait influencing yield potential of maize (Zea mays L.), but limited breeding work has been done to increase photosynthetic rate per unit leaf area. We conducted five cycles of recurrent phenotypic selection for high CO2‐exchange rate (CER) in two maize populations, BSUL1(RPH) and BSUL2(RPH), and three cycles of selection for low CER in BSUL2(RPL).Selection advance for high CER was significant in both populations. Actual genetic advances for high CER for BSUL1(RPH) were 1.6 and 1.3%/cycle at vegetative (CER 1) and grain filling (CER 2) growth stages, respectively. BSUL2(RPH) showed a per cycle increase of 1.7% at CER 1 and 1.3% at CER 2. Estimates of Δpα clearly showed that selection for high CER at CER 1 caused significant weighted‐average changes in allelic frequencies at CER 1 (0.28 ± 0.05) and CER 2 (0.25 ± 0.09) in BSUL1(RPH) and in BSUL2(RPH) at CER 1 (0.29 ± 0.05) and CER 2 (0.26 ± 0.09). Actual advance for low CER in BSUL2(RPL) was statistically significant at CER 1, but it was only 0.7%/cycle. Correlated responses in CER at CER 2 for BSULl(RPH) and BSUL2(RPH) provided additional evidence that similar genetic mechanisms control CER of maize at both developmental stages. Our data demonstrated that leaf photosynthesis of maize can be improved by recurrent selection.
Improved Flowering and Pollen Fertility in Sugarcane under Increased Night Temperatures1
Authors: Berding Nils 
Published: July 2010

A shortage of male fertile sugarcane clones often restricts cross‐pollination at the Meringa Sugar Exp. Stn. Extensive pollen testing revealed substantial variability on a micro‐environmental scale, indicating the environment may be sub‐optimal for pollen development.Four clones from each of three flowering groups (early, mid, and late season) were chosen on the basis consistent flowering but variable pollen stainability. Two adjacent replicated field trials were planted. One trial was enclosed at night with a mobile plasticsheathed shed and maintained at 22 to 23 C from 22 March, 2 weeks after photoinduction commenced, until 15 June 1979, 6 days before routine cross‐pollination finished. After 22 March, the average external minimum temperature was usually well below 21 C, regarded as critical for good pollen fertility development in sugarcane.The heated environment produced more profuse flowering (77 vs. 61%, for the whole season; 64 vs. 35%, during cross‐pollination), increased panicle availability for crossing (84 vs. 57%), and accelerated flowering by an average of 12 days. This latter effect provides an additional technique for making crosses among clones which do not normally flower at the same time.Pollen production in both environments was similar but stainability (starch‐iodine test) was significantly higher in the heated environment (19 vs. 9%, stained grains). The later the flowering group, the greater was the improvement obtained.Crosses using male flowers from the heated environment produced significantly more seedlings (614 vs. 325/5 g “seed”, in 16 paired crosses; 572 vs. 225, over 78 crosses).The heated environment significantly increased flowering, pollen stainability, and germination count and is expected to have an important practical application.
Pod Formation in Soybeans at Low Temperatures1
Authors: Hume D. J. , Jackson Ann K. H. 
Published: July 2010

Most soybean [Glycine max (L.) Merr.] cultivars cease forming pods at temperatures near 15 C. Our research was conducted to confirm a recent report that some genotypes are capable of forming pods at lower temperatures and to determine how much extra cold tolerance these genotypes possess. A total of 36 selected genotypes were grown indoors at day/night temperatures of 25/19 C until flowering and then subjected to 2‐week treatments at temperatures of 19/15, 17/15, 15/15, 15/14, 15/13,15/12, 15/11,15/9 and 15/7 C. Six genotypes formed no pods at temperatures below 15/15 C, 12 had no pods below 15/13 C, and 18 formed pods at lower temperatures down to 15/9 C. None of the U.S. cultivars tested formed any pods below 15/13 C, with the exception of 'McCall', which formed several pods at 15/11 C. The most cold‐tolerant cultivars formed pods at 15/9 C, with two plants forming pods at 15/7 C. In all cases where pedigrees could be determined, the most cold‐tolerant genotypes were related to the Swedish cultivar ‘Fiskeby V.’Outdoor trials were planted at monthly intervals to confirm indoor rankings. Most genotypes planted on 2 January at Palmerston North, New Zealand, exhibited cold damage after one or more cold nights in February. When cold tolerance of genotypes grown outdoors was calculated as the percentage of total nodes with normal pods, this parameter was closely related (r−0.93) to the minimum temperatures at which these genotypes could form pods indoors.
Selection for Apparent Photosynthesis and Related Leaf Traits in Early Generations of Soybeans1
Authors: Wiebold W. J. , Shibles Richard , Green D. E. 
Published: July 2010

Evidence suggests that photosynthate production may be yield‐limiting in soybeans [Glycine max (L.) Merr.]. This study was designed to estimate potential for selection of CO2‐exchange rate (CER), specific leaf weight (SLW), leaf thickness (LT), and leaf density (LD) in early generations of soybeans.Two crosses (‘Amsoy’ ✕ ‘Ford;’ ‘Corsoy’ ✕ ‘Hawkeye’) involving adapted cultivars high (Amsoy, Corsoy) and low in leaf CER were used. CER, SLW, LT, and LD were measured in parents, F1s and F2s. CER was measured in selected F3 and F4 lines of one cross, whereas the other variables were measured in all F3 and F4 lines.All traits showed quantitative inheritance without dominance effects. Broad‐sense heritability, based on parental, F1 and F2 variances, was low to moderate for CER (0.36, 0.56); it was low to very low for the other variables. Selection for either high or low CER in the F2 or F3 was ineffective. Gain from hypothetical selection for SLW was about 596 in the F2 and 5‐11% in the F2. Gain from hypothetical F3 selection in LT was about 5%. LD showed poor gain.Use of pure lines from advanced generations may give an entirely different picture of the potential for direct selection for increased photosynthesis than that shown by this study.
Evaluation of Techniques for Screening for Drought Resistance in Wheat1
Authors: Clarke John M. , McCaig Thomas N. 
Published: July 2010

Three techniques were evaluated for screening for drought resistance in rainfed and irrigated Triticum aestivum L. em Thell., and T. turgidum L. var. durum field plots, viz., leaf diffusive resistance as measured with an autoporometer, leaf temperature as measured with a hand‐held infrared thermometer, and drying rate of excised leaves. Eight durum and 10 hexaploid cultivars of diverse origin were grown in each of two years. Yields under rainfed relative to irrigated conditions were used to characterize the drought resistance of the cultivars.Neither diffusive resistance measurements nor leaf temperature were suitable screening techniques since differences between cutivars were not detected. There were marked differences in leaf temperatures between the rainfed and irrigated environments. Cultivar differences were detected in excised leaf water loss rate. Water retention capability was greatest early in the season, and dropped markedly after anthesis. The drought‐hardy durum cultivar Pelissier had the best water retention capability. Progeny of a Pelissier ✕ Hercules cross showed a range of retention capabilities between the parental values. Visual rating of excised leaves identified the genotypes with superior water retention capabilities. It was concluded that measurement of excised leaf water retention capability showed the most promise of the three techniques evaluated
Recurrent Selection for Kernel Weight in Spring Wheat1
Authors: Busch R. H. , Kofoid K. 
Published: July 2010

Successful recurrent selection in cross‐pollinated species is well documented, but few reports of its use in self‐pollinated species are available. Our objectives were to determine the gain from stuctured recurrent selection for kernel weight of wheat (Triticum aestivum L.) and to determine its indirect effects on other traits. Ten lines, selected for high kernel weight from 100 lines screened, were intercrossed to form the initial C0 population. Selection among S1 plants for high kernel weight was used with approximately 22 plants selected each cycle. The selection intensity varied from 1.5 to 2.9% per cycle and averaged 2.2%.Eighty random S3 and S4 lines each from C0 and C2, respectively, were used to compare variances and means. In addition, C1, C2, C3, and C4 were grown as populations for evaluation of gain.Kernel weight increased 3% per cycle from C0 through C2 as measured by the lines, and 7% per cycle from C1 through C4 as measured by the populations. Genetic variance for most measured traits remained as high in the C2 as the C0 population. Two cycles of selection resulted in lines with kernel weight higher than any lines in the C0 population. These results were further confirmed by the results of the population tests which indicated continued gain for kernel weight through Cycles 3 and 4.Negative indirect effects of selection for kernel weight were observed for days to head, spikelets per spike, kernels/cm of spike, and spikelets/ cm of spike. Grain protein increased slightly while plant height, grain yield, and test weight did not differ over cycles of selection.Structured recurrent selection produced a population with much higher kernel weight than did single crossing and selection among segregating progeny, even though the original population was selected for high kernel weight and a high selection intensity was used.
Factors Determining Flag Leaf Curvature in Wheat1
Authors: Ledent J.‐F. , Renard CH. 
Published: July 2010

Flag leaf curvature is a major aspect of canopy configuration. A knowledge of factors determining its occurrence might be important for understanding yield. Effects of genotypes and N application on the proportion of straight (S) and curved (C) flag leaves were, therefore, investigated. The two types of flag leaves were also compared for characters expected to affect curvature: leaf size, internal leaf structure (anatomy, chemical analysis of cell wall material), water status and N content.Most genotypes displayed both straight and curved flag leaves. The proportion varied greatly with N treatment and genotype. Curved leaves were longer and wider and were associated with higher tillering. There was no clear relation with cell wall material or sclerenchyma content. The midrib along was unable to maintain leaf rigidity. In detached leaves water status affected markedly leaf curvature, but in intact plants there was no significant difference in water status between C and S leaves. In the material tested, higher yielding varieties tended to display a greater number of straight flag leaves.