bluuebunny/crossref_metadata_2025_split huggingface dataset:
Yield Potential Trends of Tropical Rice since the Release of IR8 and the Challenge of Increasing Rice Yield Potential
Authors: Peng S. , Cassman K. G. , Virmani S. S. , Sheehy J. , Khush G. S. 
Published: July 2010

ABSTRACTSince the release of IR8 in 1966, 42 additional indica rice (Oryza sativa L.) cultivars developed by the International Rice Research Institute (IRRI) for the irrigated and favorable rainfed lowlands have been released in the Philippines. The maximum yield of IR8 has been reduced by about 2 Mg ha−1 during the past 30 yr. Empirical breeding for population improvement within the indica germplasm has resulted in the maintenance of rice yield potential in the tropics of about 10 Mg ha−1. To break the yield barrier, several approaches are being explored. These include development of a new plant type (NPT) with low tillering capacity and large panicles from tropical japonica germplasm and exploitation of heterosis through intervarietal and intersubspecific hybrids. Hybrid rice between indicas increased yield potential by about 9% under the tropical conditions. The higher yield potential of indica/indica hybrids compared with indica inbred cultivars was attributed to the greater biomass production rather than harvest index. New plant type breeding has not yet improved yield potential due to poor grain filling and low biomass production. Factors that cause poor grain filling and low biomass production of the NPT lines have been identified. Selecting parents with good grain filling traits, introduction of indica genes into NPT's tropical japonica background, and a refinement of the original NPT design are expected to improve the performance of the NPT lines. Further enhancement in yield potential may be possible from use of intersubspecific heterosis between indica and NPT lines.
Synergy of Empirical Breeding, Marker‐Assisted Selection, and Genomics to Increase Crop Yield Potential
Authors: Stuber Charles W. , Polacco Mary , Lynn M. 
Published: July 2010

ABSTRACTThis paper was presented as part of the symposium entitled “Post‐Green Revolution Trends in Crop Yield Potential: Increasing, Stagnant or Greater Resistance to Stress.” In this presentation, we have focused on (i) uses of marker technology in determining the genetic basis of phenotypic expression and the manipulation of phenotypic variation in plants. This included the use of markers in understanding heterosis, in attempts to improve hybrid predictions, in quantitative trait locus (QTL) identification and mapping, in marker‐assisted selection (MAS), and in enhancing breeding success in the development of improved lines and hybrids; (ii) the role of genomics in developing a precise understanding of the genetic basis of phenotypic expression which will then provide more precision in the manipulation of phenotypic variation; and (iii) some attempts to integrate marker technology and genomics into empirical breeding strategies. In addition, we have focused on what has been successful as well as what has fallen short of expectations, and have suggested some of the possible reasons for the lack of success. Because of page limitations, we could not include an exhaustive review of the plant literature and have limited many of our examples to investigations in maize (Zea mays L).
Yield of Wheat in the United Kingdom: Recent Advances and Prospects
Authors: Austin R. B. 
Published: July 2010

ABSTRACTFrom 1948 to the present, wheat (Triticum aestivum L.) yields in the UK have increased by an average of 110 kg ha−1 each year. This rate of increase has been at least maintained in recent years. The greater yields have been associated with the adoption of cultivars of shorter stature, which are resistant to lodging and reach anthesis ≈1 wk earlier than old cultivars. In the last two decades, most of these cultivars have carried the rht D1b dwarfing gene. The full yield benefits from modern cultivars have depended on high rates of N fertilization and the use of herbicides and effective fungicides. Data from recent trials with candidate cultivars and F1 hybrids suggest that further genetic gain in yield will be achieved during the next decade. Improved crop protection through chemicals may also enable farmers to obtain greater yields. In the longer term, substantial genetic gain in yield may be achieved if breeders are able to produce cultivars with faster growth rates and greater biomass at maturity. One way to achieve this would be to modify the photosynthetic enzyme rubisco so that its oxygenase activity is reduced. However, cultivars with potentially faster growth rates would require even more N fertilizer if their greater yield potential is to be realized.
Genetics of Soybean Agronomic Traits: II. Interactions between Yield Quantitative Trait Loci in Soybean
Authors: Orf J. H. , Chase K. , Adler F. R. , Mansur L. M. , Lark K. G. 
Published: July 2010

ABSTRACTIn order to breed efficiently, it is necessary to identify individual quantitative trait loci (QTLs) as well as interactions between these loci and to determine which QTLs produce phenotypes that are environment specific. This can be done by linking QTLs to molecular markers. The objective of this research was to carry out such an analysis for yield, one of the most complex agronomic traits. To do this, recombinant inbred lines of soybean [Glycine max (L.) Merrill] were characterized for molecular genetic markers and analyzed for yield in different environments. Interactions between QTLs were identified by subdividing the segregants into four sub‐populations defined by molecular alleles at pairs of unlinked loci. Differences in the mean yields of these sub‐populations defined interactions between QTLs. Measurements of yield in genotyped, recombinant inbred populations derived from crosses of ‘Minsoy’ with ‘Archer’ (MA population) and ‘Noir 1’ with Archer (NA population) have identified a pair of interacting yield QTLs whose effect was independent of environment as well as a pair of loci whose interaction was environment specific. Each example of epistasis, involved an allele specific interaction between the two QTLs. In the NA population, a pair of QTLs was identified in which Noir 1 alleles interact to specify a significant increase in yield that is not environment specific. These loci, located on linkage groups (LG) U3 and U9, do not affect either height or maturity. In all environments, the interaction between the QTLs was significant. In the MA population, a pair of QTLs was identified in which the Minsoy alleles interact to specify a significant increase in yield. However, this significant interaction is environment specific. One of the loci (on LG U14) is also associated with effects on height, seed weight, and maturity that are found in other environments, but these latter effects do not appear to involve any interactions with other loci. The data from the MA population support the concept that interactions between QTLs also can result in location‐specific effects on quantitative traits.
Transfer of Wheat‐Rye Translocation Chromosomes Conferring Resistance to Hessian Fly from Bread Wheat into Durum Wheat
Authors: Friebe B. , Kynast R. G. , Hatchett J. H. , Sears R. G. , Wilson D. L. , Gill B. S. 
Published: July 2010

ABSTRACTThe Hessian fly, Mayetiola destructor (Say), is a damaging pest of bread wheat, Triticum aestivum L., and durum wheat, T. turgidum L. ssp. durum Desf. Husn., in many wheat production areas of the world. Breeding for host plant resistance is the most agronomically desirable way to control this pest. Twenty‐seven major genes conferring resistance to Hessian fly have been identified and used in wheat improvement. These genes confer resistance to specific biotypes of the Hessian fly. Recently, new sources of Hessian fly resistance derived from cultivated rye, Secale cereale L., have been reported that confer resistance to all known biotypes of the Hessian fly. The resistance gene H21 is present on the wheat‐rye whole arm translocation T2BS·2R#2L. H25 is present on an interstitial rye segment in the 4AL arm of the wheat‐rye translocation chromosome Ti4AS·4AL‐6R#1L‐4AL. The objective of the present study was to transfer H21 and H25 to tetraploid durum wheat, thereby making these genes available for the improvement of durum wheat. Homozygous T2BS·2R#2L and Ti4AS·4AL‐6R#1L‐4AL translocation durum lines were recovered that expressed the H21 and H25 resistance. The H25 durum translocation line was vigorous and set seeds similar to the durum wheat parental cultivar. Thus, the H25 transfer can be used directly in durum wheat improvement. Plant vigor and seed set of the H21 durum translocation line was drastically reduced, indicating that the missing 2BL arm in this translocation has genes that are essential for normal plant vigor and fertility. Further chromosome engineering is required to shorten the rye segment in this translocation before H21 can be used in durum breeding.
Molecular Mapping of Russian Wheat Aphid Resistance from Triticale Accession PI 386156
Authors: Fritz A. K. , Caldwell S. , Worrall W. D. 
Published: July 2010

ABSTRACTThe Russian wheat aphid (RWA), Diuraphis noxia Mordvilko, is an economic pest of wheat (Triticum aestivum L.) in some western growing regions. Sources of resistance occur within the wheat gene pool, but there are also high levels of resistance in wheat relatives, including rye (Secale cereale L.). An F2 population between PI 386156, a Russian wheat aphid‐resistant triticale (×Triticosecale Wittmack) from Russia and NE88T222, a susceptible triticale, was used to examine the inheritance of resistance. Five distinct classes of reaction to the RWA were observed, suggesting this trait is not controlled by a single dominant gene in this population. Bulked segregant analysis was performed with DNA from plants representing the most resistant (‘R’) and most susceptible (‘S’) classes. A co‐dominant marker amplified by primer OP‐M09 explained more than 55% of the variation observed for resistance. Sequencing results revealed a deletion in the ‘S’ parent relative to the ‘R’ parent. Using a set of wheat‐rye addition lines, we mapped the target fragment to chromosome 4R, which has previously been identified as the critical chromosome for RWA resistance from PI 386156 and other Russian triticales.
Mapping and Genetic Analysis of the Genes for Photoperiod‐Sensitive Genic Male Sterility in Rice Using the Original Mutant Nongken 58S
Authors: Mei M. H. , Dai X. K. , Xu C. G. , Zhang Qifa 
Published: July 2010

ABSTRACTPhotoperiod‐sensitive genic male sterility (PSGMS) rice has a number of desirable characteristics for hybrid rice production. In this study, we conducted a molecular marker‐based mapping and genetic analysis of PSGMS genes using two crosses involving the original mutant Nongken 58S as the PSGMS parent. The genomic locations of the PSGMS loci were determined following the “bulked extreme and recessive class” approach, in which the regions containing the PSGMS loci were identified by assaying the bulks of extreme phenotypes and the distances between the PSGMS loci and molecular markers were calculated from the highly sterile plants of the F2 populations. Two PSGMS loci, located on chromosomes 7 and 12, respectively, were identified in both crosses. The locus on chromosome 7 was the same as pms1, identified previously in a cross between an indica PSGMS line and an indica cultivar. The one on chromosome 12 was a new locus that we designated as pms3 Both loci had major effects on fertility and acted like a pair of classical duplicated genes in controlling male sterility. Comparison of the present finding with previous results indicated a complex genetic basis of PSGMS. The implications of such genetic complexity in breeding for PSGMS lines are also discussed.
Molecular Mapping of Loci for Agronomic Traits on Chromosome 3A of Bread Wheat
Authors: Shah M. M. , Gill K. S. , Baenziger P. S. , Yen Y. , Kaeppler S. M. , Ariyarathne H. M. 
Published: July 2010

ABSTRACTChromosome 3A of bread wheat (Triticum aestivum L.) cultivar ‘Wichita’ (WI) was previously found to differ from that of ‘Cheyenne’ (CNN) for genes affecting a number of agronomically important traits such as grain yield (GYLD), kernel number spike−1 (KPS), 1000‐kernel weight (TKWT), spike number m−2 (SPSM), grain volume weight (GVWT), plant height (PHT), and anthesis date (influenced by Eps locus). This study was designed to map the Eps locus and to identify regions of chromosome 3A of wheat associated with agronomic traits. A population of 3A recombinant inbred chromosome lines (RICLs‐3A) was previously evaluated in replicated field trials. Thirteen RFLPs and one morphological marker locus, Eps, were used to develop a genetic linkage map and to identify QTLs associated with agronomic traits. Individual loci explained from 8.9 to 38.2% of the total phenotypic variation for the measured traits. The major locus Eps was mapped distal to an RFLP marker locus Xcdo549 on the short arm of chromosome 3A and explained 38.2% of the total phenotypic variation for PHT, and 17.4% for both KPS and TKWT. Additional QTLs for PHT, TKWT, and KPS were identified on the chromosome. A QTL for SPSM on the long arm of chromosome 3A was tightly linked to QTL for PHT and KPS. QTLs for GYLD were identified only in a few individual environments whereas no QTL was detected for GVWT. No epistasis was detected between markers associated with QTLs. The QTLs identified across environments were consistent in all or most environments, hence should be useful in future marker assisted selection programs for breeding wheat cultivars.
Relationship between Photosynthesis and Seed Number at Phloem Isolated Nodes in Soybean
Authors: Bruening W. P. , Egli D. B. 
Published: July 2010

ABSTRACTSeed number is the primary yield component in soybean [Glycine max (L.) Merrill], but the mechanisms responsible for the regulation of this component are not fully understood. Three soybean cultivars (Elgin 87, Emerald, and Essex) with genetic differences in seed growth rate and seed size were grown in the field in 1995 and 1996 to determine the relationship between photosynthesis, sink characteristics, and seed number at individual nodes. The sixth node from the bottom of the main stem was isolated by heat girdling the stem below the node to disrupt phloem continuity and by removing the part of the plant above the girdled node when flowers first opened at this node. Photosynthesis was varied by defoliating (removing approximately 0, 33, 66, 83, or 100% of the leaf area) the leaf at the girdled node. Carbon dioxide exchange rate (CER) was measured at approximately weekly intervals for up to 40 d after girdling. Girdling temporarily reduced CER in four of six comparisons and defoliation tended to increase CER. Defoliation produced large differences in nodal carbon input (NCI) per node and seed number increased rapidly as average NCI per node increased from 0 to approximately 0.10 μmol CO2 node−1 s−2 However, there was no further increase in seed number as average NCI continued to increase to 0.5 μmol CO2 node−1 s−2, suggesting that isolated nodes respond differently than soybean communities. Maximum seed number per node was inversely related to cultivar differences in individual seed growth rate and seed size. The girdled node technique should prove useful to investigate seed number‐photosynthesis relationships in soybean.
Carbon Isotope Discrimination as a Tool to Improve Water‐Use Efficiency in Tomato
Authors: Martin Bjorn , Tauer Charles G. , Lin Robert K. 
Published: July 2010

ABSTRACTCarbon isotope discrimination (Δ) is a property that may be used to improve water‐use efficiency (WUE). This study tested the association between Δ and WUE with plant materials and growth conditions likely to disrupt the link between Δ and WUE. The cultivated tomato, Lycopersicon esculentum Mill. cv. UC82B, a drought‐resistant related species, L. pennellii (Cor.) D'Arcy accession LA716, and the F1 and F2 generations of the L. esculentum × L. pennellii cross were grown in containers in wet and dry field environments. The wet environment was repeated in a second year and plants were split into groups terminated early and late in the season. The F1 generation had greater mean WUE and dry weight (DW) than L. esculentum, but the DW advantage was not maintained in the F2 generation. Low Δ of L. pennellii suggested that leaf WUE was high, but its whole plant WUE varied relative to the other plant materials in the different environments. There was a negative correlation between Δ and WUE in the F2 generation, and WUE was generally positively correlated with DW. However, low Δ was associated with large DW in only one environment and with small DW in three environments. Averaged across environments, the top 10% of the plants ranked by WUE had 47% greater WUE than the bottom 10%. In comparison, the bottom 10% ranked by Δ had an average of 16% greater WUE than the top Δ group, but in three of the four environments the bottom group accumulated 33 to 47% less DW than the top Δ group. This study on tomato suggests that WUE can be increased by selecting low Δ, but selecting low Δ alone may identify a subpopulation of small plants. Dry weight could probably be increased by traditional breeding techniques.
Incompatibility Systems in Switchgrass
Authors: Martínez‐Reyna J. M. , Vogel K. P. 
Published: July 2010

ABSTRACTSwitchgrass (Panicum virgatum L.), a cross‐pollinated perennial, produces very little or no seed when self‐pollinated, indicating the presence of self‐incompatibility mechanisms. Knowledge of self‐incompatibility mechanisms is required to use germplasm effectively in a breeding program. The objective of this study was to characterize features of the incompatibility systems in switchgrass. Seed set and seed characteristics of reciprocal matings of tetraploid, octaploid, and tetraploid × octaploid plants were used as measures of incompatibility. Both bagged mutual pollination and manual emasculation and pollination methods were used to make crosses. The percentages of self‐compatibility in the tetraploid and octaploid parent plants were 0.35 and 1.39%, respectively. Prefertilization incompatibility in switchgrass is apparently under gametophytic control, since there were significant differences in percentage of compatible pollen as measured by percentage of total seed set between reciprocal matings within ploidy levels. Results indicated that the prefertilization incompatibility system in switchgrass is similar to the S‐Z incompatibility system found in other members of the Poaceae. A postfertilization incompatibility system also exists that inhibits intermatings among octaploid and tetraploid plants. In these interploidy crosses, two very distinctive types of abnormal seed were found. When the female parent was the tetraploid plant, the resulting seed was small and shriveled, while when the female parent was the octaploid, small seed with floury endosperm was obtained. These results are similar to those obtained for endosperm incompatibility due to the endosperm balance number system found in other species.
Analysis of Combining Ability for Ergot Resistance in Grain Sorghum
Authors: Reed J. D. , Tuinstra M. R. , McLaren N. W. , Kofoid K. D. , Ochanda N. W. , Claflin L. E. 
Published: July 2010

ABSTRACTErgot caused by Claviceps africana Frederickson, Mantle & de Milliano has become an important constraint to F1 hybrid seed production in North and South America. Identification and utilization of sources of host‐plant resistance would contribute to the effective control of this disease. A Design II mating scheme was used to test the combining ability of four reported sources of ergot resistance in sorghum [Sorghum bicolor (L) Moench]—IS8525, IS14131, IS14257, and IS14357. Male‐sterile hybrids of these accessions and a susceptible check, TxARG1, were produced using five cytoplasmic‐genetic male‐sterile seed parents—A3Tx430, A3Tx436, A3Tx7000, A3KS70, and A3Tx2737. Parent lines and hybrids were planted in three replications at three locations and were evaluated for ergot resistance following artificial inoculation at flowering. Differences in ergot severity and ergot breakdown point (EBP) were used to quantify differences in resistance. The combined analysis of variance showed that the expression of ergot resistance was not stable with significant entry × location interaction. The analyses from two locations showed significant differences among hybrids, while the third location showed no differences. Regression analyses were performed to determine the relationship between weather variables at flowering and observed ergot severity. These analyses indicated a strong relationship between maximum daily temperature and ergot severity. Ergot infection was higher in cooler environments regardless of genetic background. IS8525 appeared to have the highest expression of ergot resistance in male‐sterile genetic backgrounds on the basis of EBP and ergot severity ratings; however, the expression of resistance was only effective within a limited temperature range.
Stability of Grain Yield, Endosperm Modification, and Protein Quality of Hybrid and Open‐Pollinated Quality Protein Maize (QPM) Cultivars
Authors: Pixley Kevin V. , Bjarnason Magni S. 
Published: July 2010

ABSTRACTQuality protein maize (Zea mays L.) (QPM) can help alleviate human malnutrition and reduce costs of animal feed because it contains the opaque‐2 mutation, which results in increased lysine and tryptophan concentrations and a higher biological value as a food than normal maize. To be commercially successful, however, QPM cultivars must be agronomically competitive with normal‐endosperm alternatives while consistently achieving expected protein quality and endosperm modification (i.e., translucent or near‐normal phenotype) standards. To assess stability of grain yield, protein content and quality, and endosperm modification of QPM cultivars, we evaluated 18 single‐cross, 18 three‐way, and 18 double‐cross hybrids, and eight open‐pollinated cultivars (OPCs) grown at 13 tropical locations on four continents. Hybrids averaged 13% higher grain yield than OPCs (5.97 and 5.17 Mg ha−1), whereas protein concentration in grain was 2% greater for the OPC relative to hybrid cultivars (94.6 and 92.4 g kg−1). Endosperm modification score and tryptophan concentration in protein were similar for all cultivar types. Genotype × environment interactions and sums of squares for deviations from linear regression S2d for grain yield and protein concentration in grain were largest (indicating least stability) for single‐cross hybrids, followed by three‐way, double‐cross, and open‐pollinated cultivars (OPCs), successively. The reverse trend was observed for endosperm modification score, suggesting that more homogeneous cultivars had greater stability for this trait. Additive main effects and multiplicative interactions (AMMI) analysis indicated that genotype × environment interaction effects for grain yield and endosperm modification score were different for hybrids than OPCs; certain environments favored either hybrids or OPCs. In conclusion (i) protein quality and endosperm modification score were always within expected values for QPM and (ii) tryptophan concentration in protein was the most stable trait, followed by protein concentration in grain, then endosperm modification score and finally grain yield.