bluuebunny/crossref_metadata_2025 huggingface dataset:
Canopy Characteristics Associated with Deficient and Excessive Cotton Plant Population Densities
Authors: Heitholt James J.
Published: July 2010

Cotton (Gossypium hirsutum L.) genotypes exhibit variation in leaf types and leaf area index (LAI). The objective of this research was to characterize canopy development and yield of two cotton leaf types grown in varying plant population densities. Field experiments were conducted in 1991, 1992, and 1993 with both the okra‐leaf (low LAI) and normal‐leaf (high LAI) isolines of ‘DES 24‐8ne’ cotton with selected plant population densities (5, 10, and 15 plants m−2). Photosynthetic photon flux density (PPFD) interception (1991–1992) LAI (1991–1993) were determined periodically and final lint yield was determined at maturity. Averaged across years, yields of okra‐leaf in narrow rows were 6 to 7% greater at 10 and 15 plants m−2 than at 5 plants m−2. In 1991 and 1992, early‐season PPFD interception of okra‐leaf at 10 and 15 plants m−2 was greater than at 5 plants m−2. In 1992 and 1993, okra‐leaf at 10 and 15 plants m−2 attained an LAI of 4.0 to 4.5 whereas the 5 plants m−2 density failed to reach 4.0. Therefore, both PPFD interception and LAI limited yield of okra‐leaf at 5 plants m−2. In contrast to okra‐leaf, lint yields of normal‐leaf were 4 to 8% greater at 5 plants m−2 than at 10 and 15 plants m−2. In 1991 and 1992, the lower yields of normal‐leaf at 10 and 15 plants m−2 were apparently associated with late‐season LAI values of 5.0 or greater, whereas the 5 plants m−2 density developed late‐season LAI values ranging from 4.0 to 4.8. These findings indicate that (i) optimal plant density was higher for okra‐leaf than for normal‐leaf and (ii) a maximum LAI between 4.0 and 5.0 was required to maximize cotton lint yields in this environment.
Divergent Selection in Alfalfa for Resistance to Sclerotinia Crown and Stem Rot
Authors: Halimi E. S. , Rowe D. E. , Aung Myint
Published: July 2010

Sclerotinia crown and stem rot (SCSR) caused by Sclerotinia trifoliorum Eriks. is often a serious disease on alfalfa (Medicago sativa L.) during cool, wet periods of the year. No cultivars have been developed with increased resistance to this disease. This research determines the selection responses to one cycle of divergent selection for resistance to SCSR. Plants of four genetically different populations were evaluated for resistance to SCSR using a stem‐tip inoculation technique. Selectious were made at 4 and 8% selection intensities for both resistance and susceptibility. Selections were polyerossed to produce four experimental synthetics (two selected for resistance and two selected for susceptibility). Plants grown from seed of each experimental synthetic and from remnant seed from each source population were evaluated for resistance along with ramets of the parental plants of the synthetics. Experimental synthetics selected for resistance at selection intensities of 4 and 8% had necrotic regions 4.0 and 4.5 cm long, respectively. The experimental synthetics selected for susceptibility at intensities of 4 and 8% had necrotic regions 7.4 and 8,2 cm long, respectively. Means of each of the experimental synthetics were significantly different (P 0.05) from the mean (6.1 cm) of the unselected population. Ileritability was estimated at 0.49 (SE = 0.14) using a regression of offspring parent. Resistance to Sclerotiula is heritable and can be increased or decreased using the stem‐tip inoculation technique.
Recurrent Selection for 2,4‐D Tolerance in Cicer Milkvetch
Authors: Townsend C. E.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.), a long‐lived perennial forage legume, has many attributes that make it well suited for permanent pastures in a sustainable agricultural system. Its relatively poor seedling vigor, however, has reduced its potential. A selective, postemergence herbicide, e.g., 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], could improve establishment by controlling broadleaf weeds. Therefore, this study was conducted to evaluate the use of phenotypic recurrent selection for increasing the tolerance of cicer milkvetch seedlings to 2,4‐D. Seedlings were treated in the greenhouse at the three‐leaf stage of development with a 1.0 kg a.i. ha− rate of 2,4‐D. Five cycles of recurrent selection for regrowth at the apical meristem following treatment with 2,4‐D increased extended seedling height (total length) 38% more than that of the cultivar Monarch (Cycle 0). Seedlings were visually selected for extended height about 4 wk after herbicide application. Selection for extended height reduced root and total seedling dry weights 21 and 13%, respectively, from the Cycle 0 to the Cycle 1 population. For Cycles 1 through 5, however, extended height was significantly correlated with shoot (r = 0.99), root (0.93) total seedling (0.97) dry weights, and apical meristem regrowth score (0.97), but not with crown meristem regrowth score ( − 0.50). Recurrent selection for increased regrowth at the apical meristem following application of 2,4‐D was an effective and inexpensive procedure for increasing the tolerance of citer milkvetch to 2,4‐D.
Stability of Resistance to Leaf Disease in Orchardgrass and Smooth Bromegrass Germplasms
Authors: Berg C. C. , Sherwood R. T.
Published: July 2010

Genetic resistance is the only practical method to control foliar diseases on forage grasses. Once developed, resistance must be transmitted, without selection, through several generations of seed increase. This study was conducted to determine whether disease resistance would be maintained when disease resistant germplasms were advanced two generations without conscious selection for disease resistance. Orchardgrass (Dactylis glomerata L.) germplasm PL‐OGDR1 resistant to purple leaf spot (caused by Stagonospora arenaria Sacc.), and smooth bromegrass (Bromus inennis Leysser) germplasm PL‐BDR1 resistant to brown leaf spot [caused by Pyrenophora bromi (Died.) Drechs.] were used to initiate this study. Plants of the germplasm releases, two populations produced by unselected advance, and three cultivars of each species were rated for disease reaction in two greenhouse inoculation tests. Mean spot size and disease coverage scores were low for all generations of resistant germplasms, and there were no differences among generations. The frequency distribution of disease scores within generations remained relatively constant for generations. Cnltivars were much more susceptible, with disease scores that averaged twofold to threefold higher than resistant germplasms. Results indicated that in the absence of selection pressure, disease resistant populations developed by five cycles of recurrent phenotypic selection for resistance to orchardgrass purple leaf spot or bromegrass brown leaf spot can be advanced for two successive unselected generations without a shift in resistance.
Thermal Dependence of Glutathione Reductase; Thermal Limitations on Antioxidant Protection in Plants
Authors: Mahan James R.
Published: July 2010

Though plants have endogenous systems to prevent and/or repair thermal damage, thermal stresses often limit agronomic yields. The enzyme glutathione reductase plays a role in the detoxification of oxidants that often result from exposure of plants to high or low temperatures. Since thermal limitations on the function of glutathione reductase could limit the ability of a plant to withstand thermal stress, it is important to understand its thermal dependence. Previously, the thermal dependence of maximal velocity and apparent KM have been used to describe the thermal dependence of enzymes and define an optimal thermal range for their function. While both maximal velocity and apparent KM are factors in the thermal response of the velocity of an enzyme reaction, they are not necessarily indicative of the thermal dependence of velocity under physiological conditions. In this study, a computer program was used to develop estimates of the thermal dependence of reaction velocity at a given temperature and substrate concentration. Optimal thermal ranges for the glutathione reductascs from spinach (Spinacia oleracea L.), corn (Zea mays L.), and cucumber (Cucurais sativum L. cv. Ashley) were predicted from the thermal dependence of maximal velocity, predicted velocity, Vmax/KM, and apparent KM. These results suggest that the predicted thermal dependence of velocity may be a useful indicator of the optimal thermal range of plant enzymes.
Humidification of Green Canola Seed Leads to Pigment Degradation in the Absence of Germination
Authors: Johnson‐Flanagan Anne M. , Maret Lol L. D. , Pomeroy M. Keith
Published: July 2010

Mature canola seeds (Brassica napus cv. Westar) exposed to frost during development frequently contain green pigments that discolor extracted canola oil. The green pigments must be removed from the oil by bleaching, which significantly reduces the oil yield. The quantity of pigment remaining in the oil prior to bleaching is a function of the amount of pigment and the proportion of phytylated pigments in the seeds. The objective of this study was to determine whether the quantity and chemistry of the pigments could be altered by seed humidification after harvest without leading to germination. Intact plants with seed moisture in the range of 700 to 500 g kg−1 were exposed to −15°C for 3 h. The seeds were harvested at maturity, and analysed for moisture content, pigment content, storage protein, and triacylglyceroi before and after exposure to 97% relative humidity for 10 d that increased seed moisture content to 230 g kg−1. This treatment led to a 25% reduction in total pigment content and a 35% increase in the percentage of dephytylated pigments. In vitro measurementisn dicated this was the result of chlorophyllase activity. Neither storage proteins nor triacylglycerols were mobilized during humidification. In comparison, unrestricted water imbibition led to changes associated with seed storage protein reserve mobilization within 24 h of initial imbibition. Apparently, humidification treatment has the potential to decrease canola oil pigment content without decreasing seed oil or meal quality and quantity. The recommended humidification procedure attains a seed moisture content of 200 g kg−1, which can be achieved by a 7‐d exposure to 97% RH.
Plant Regeneraton from Callus Cultures of Switchgrass
Authors: Denchev P. D. , Conger B. V.
Published: July 2010

Regeneration from cells or tissues cultured in vitro is a fundamental requirement for most applications of plant biotechnology. The objective of this study was to develop protocols in which plants could be regenerated with ease and in high numbers from tissue cultures of switchgrass (Panicum virgatum L.). Mature caryopses and young leaf segments of the cultivar Alamo were explanted onto agar solidified Murashige and Skoog medium containing 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 6‐benzylaminopurine (BAP). BAP at 45 μM for mature caryopses and at 5 μA/for leaf explants in combination with 22.5 μM 2,4‐D produced high frequency plantlet regeneration by both organogenesis and somatic embryogenesis. The mode of regeneration was documented by light and scanning electron microscopy. One thousand regenerated plants have been established in the field for observation and evaluation.
Forage Yield and Quality of Semidwarf Barley
Authors: Rasmusson Donald C. , Simmons Steve R.
Published: July 2010

Semidwarf barley (Hordeum vulgare L.) with enhanced lodging resistance has been developed for feed grain production. Its potential as a forage crop has not been evaluated. Our objective was to determine forage yield, forage quality, and grain yield of semidwarf barley compared with conventional barley cultivars developed for malting and feed grain production. Three semidwarf experimental barley lines were compared with two conventional height malting barley cultivars in the field at St. Paul, MN, on a Waukegan silt loam (fine‐silty over sandy or sandy‐skeletal, mixed, mesic Typic Hapludoll) and at Crookston, MN, on a Wheatville loam (coarse‐silty over clayey, frigid Aeric Calciaquoll). Semidwarf barleys averaged 24% less stem and 29% greater inflorescence proportion than conventional barleys. Leaf blade and leaf sheath proportion for semidwarf and conventional height barley were similar. Semidwarf barley averaged 11% less whole plant acid detergent fiber (ADF), 8% less neutral detergent fiber (NDF), and 8% less acid detergent lignin (ADL) concentrations than conventional height barley. Whole plant crude protein concentration did not consistently differ for the semidwarf and conventional height barley. Whole plant NDF, ADF, and ADL concentrations were negatively correlated with inflorescence percentage (r2 ? 0.75) and grain yield (r2 ? 0.85) and positively correlated with stem percentage (r2 ? 0.48) and height (r2 ? 0.98). Forage and grain yields of semidwarf and conventional height barley were not consistently different. Lodging resistant, semidwarf barley had superior forage quality compared with conventional height barley and thus has good potential as a forage crop when grown alone or as a companion crop for forage establishment.
Cell Wall Composition of Diverse Clovers during Primary Spring Growth
Authors: Brink G. E. , Fairbrother T. E.
Published: July 2010

Forage digestibility is influenced by plant cell wall composition. We compared changes in cell wall composition of the herbage and plant fractions of four clovers differing in life cycle and growth habit and examined the relationship between digestibility and cell wall composition in these plant fractions. Primary spring growth of berseem (Trifolium alexandrinum L.), red (T. pratense L.), subterranean (T. subterraneum L.), and white (T. repens L.) clover was harvested in each of 2 yr beginning in late March and thereafter every 10 d (eight harvests total). Cell wall, hemicellulose, cellulose, and lignin concentration were determined for leaf, petiole, stem, and reproductive fractions and herbage at each harvest. Herbage cell wall concentration of berseem, red, and white clover increased 3.1, 2.4, and 0.8 g kg−1 d−1, respectively. Maximum herbage cell wall concentrations of annual berseem and subterranean clover herbage were greater than those of perennial red and white clover(500 and 497 vs. 425 and 280g kg−1 respectively). With the exception of subterranean clover, leaf cell wall concentration of all clovers ranged from ≈ 200 to 300g kg−1 Trends for stem cell wall and hemicellulose Concentration of erect‐growing berseem and red clover were similar, while petiole cell wall and hemicellulose trends were similar for annual berseem and subterranean clover. Herbage and plant fraction cell wall concentration were negatively correlated with digestibility due primarily to the inverse relationship between digestibility and cell wall‐ligning cncentration. The minor differences in leaf cell wall concentration during primary spring growth indicate minimal differences exist among these clovers in relation to their value to grazing ruminants.
Importance of the Phyllochron in Studying Development and Growth in Grasses
Authors: Wilhelm W. W. , McMaster Gregory S.
Published: July 2010

The phyllochron, which is defined as the interval between similar growth stages of successive leaves on the same calm, has been used extensively to describe and understand development of grasses. The purpose of this paper is to introduce seven papers presented as part of the symposium Understanding Development and Growth in Grasses: Role of the Phyllochron Concept. Environmental (temperature, water, and day length) factors and genetics affect the duration of the phyllochron. The following seven papers broaden the discussion of these topics and present new concepts about how the environment and genetics impact the relationship between leaf appearance and whole plant development.
The Phyllochron: Where Do we Go in the Future?
Authors: Rickman R. W. , Klepper B. L.
Published: July 2010

This paper integrates, expands, and applies information from seven articles written for a symposium on the use of phyllochron concepts for describing shoot development in grasses. Generally, no one environmental factor is a perfect predictor of plant development rate. Factors that influence development rate include genetics, nutrition, water supply, day length, light, and temperature. Average air temperature, when accumulated in the form of a degree‐day sum, does at times correlate linearly with plant developmental descriptors such as the Haun stage. The interval between visual appearance of successive leaves (the phylloehron) may be approximated as a constant number of degree‐days for such a situation. If not only the visual extension of plant organs but the initiation of both vegetative and reproductive organs at active growing points can be linearly correlated with average temperature sums, an elegantly simple line diagram iliustrates the full season synchronous initiation and development of all plant vegetative and reproductive parts. Development of each organ at the cellular level may be represented. This simple but complete representation of synchronous development based on the phyllochron provides a foundation for describing and improving understanding of the genetic and environmental control of grass development rate.
Anthracnose Resistance of the Cucumber Germplasm Collection in North Carolina Field Tests
Authors: Wehner Todd C. , St. Amand Paul C.
Published: July 2010

The resistance of the entire cucumber (Cucurnis sativus L.) germplasm collection within the U.S. National Plant Germplasm System and of many available cultigens (improved cultivars, breeding lines, land races, feral cucumbers, and plant introductions) to anthracnose [Colletotrichum orbiculare (Berk. and Mont.) Arx] was tested under field conditions in North Carolina and compared with known resistant cultigens. Mean anthracnose leaf ratings for environments ranged from 5.5 to 7.7. Data within an environment were standardized to a mean of 4.5 and a standard deviation of 1 to improve comparisons among cultigens by removing the main effect of environments. The moot resistant 27 cultigens are all of U.S. origin and are improved cultivars or breeding lines. The most resistant cultigens, for which multiple environment data are available, were ‘Dual’, ‘Regal’, ‘Slice’, and Gy 3. The most susceptible cultigens, for which multiplenvironment data are available, were PI 390248, PI 251028, and PI 277741. Thirty‐one cultigens were classified resistant, 100 moderately resistant, and 773 susceptible. No plant introductions were found to be more resistant than the most resistant named cultivars or breeding lines tested. Cultigens found to be resistant in other studies were generally moderately resistant or resistant in this study, except for PI 179676 and PI 183445, which were susceptible in this test.
Powdery Mildew Resistance in Winter Wheat: II. Identity of Resistance Genes
Authors: Chung Y. S. , Griffey C. A.
Published: July 2010

Gene number and mode of inheritance of powdery mildew resistance in 10 wheat (Triticum aestivum L.) lines was determined in a previous report. However, the allelic relationships of these genes to each other and to known genes was not determined. Eight of the 10 powdery mildew resistant wheat lines were crossed with each other and to each of 13 host differential lines that have known genes for resistance to powdery mildew, caused by Blumeria graminis (DC.) E. O. Speer sp. tritici Em. Marchal. In each cross, 300 to 800 F2 seedlings were evaluated for their reaction to isolate 127 of B. graminis f. sp. tritici in the greenhouse to determine the relationship and putative identity of resistance genes in the eight lines. One common gene, Pm4b, was identified in the wheat lines C39, A55‐2, R107, ‘Armada’, and SIS. The three genes in C39 and SI5 were identified as Prm2, Pm4b, and Pm6 based on lack of susceptible progeny from crosses of these lines with the corresponding host differentials. The resistance genes in OK75R3645 and GO4779 differ from each other and from those identified in the other resistant lines. The resistance gene in OK75R3645 most likely is an allele or closely linked to the Pm3 locus. It is probable that the resistance gene in GO4779 is Pml, as no segregation for susceptible progeny was observed in the cross of GO4779 with the differential line Axminster/8*CC(Pml). A single recessive gene, pm8, was postulated for ST1‐25, whose disease reaction was intermediate to isolate 127. Six different genes governing resistance to powdery mildew were identified among the eight wheat lines, and Pm4b was the most common gene.
Plant Height Response of Semidwarf and Nonsemidwarf Wheats to the Environment
Authors: Budak N. , Baenziger P. S. , Eskridge K. M. , Baltensperger D. , Moreno‐Sevilla B.
Published: July 2010

Nonsemidwarf wheats (Triticum aestivum L.) are preferred in drought‐prone dryland agriculture but are difficult to select under higher rainfall environments where early generation breeding nurseries are often located. To determine the importance of genotype differences in height and the genotype × environment interaction, a combined analysis of variance across three ecogeographic zones was performed using genotype plant height. Genotypes were significantly different and the genotype × environment interaction was significant. Similar results were obtained when the genotypes were classified as semidwarf [gibberellic acid (GA)‐insensitive] or nonsemidwarf (GA‐sensitive) wheats. The genotype × environment interaction was also partitioned, and the environment × (semidwarf vs. nonsemidwarf wheat), environment × semidwarf wheat, and environment × nonsemidwarf wheat were all significant. The importance of significant genotype × environment interactions is (i) plant height in the eastern Nebraska poorly predicted plant height in western Nebraska, (ii) nonsemidwarf wheats interacted differently than semidwarf wheats with the environment, (iii) plant height should be measured in each ecogeographic zone or at least the eastern zone and either the central or northwestern zone, and (iv) among nonsemidwarf and semidwarf wheats a variety of responses to the environment were found. With regression estimates of stability, semidwarf genotypes were more stable (lower b values) than nonsemidwarf genotypes. Though nonsemidwarf genotypes were on average taller than semidwarf genotypes, semidwarf genotypes with excellent stability could be identified that were not too tall in eastern Nebraska and retained their height in western Nebraska. Nonsemidwarf wheats with similar environmental responses were not identified.
Effect of S3 Recurrent Selection in Four Tropical Maize Populations on Their Selfed and Randomly Mated Generations
Authors: Vasal S. K. , Dhillon B. S. , Srinivasan G. , McLean S. D. , Crossa J. , Zhang S. H.
Published: July 2010

Maize (Zea mays L.) breeders working with lowland tropical germplasm have experienced difficulties in developing good inbred lines. One limitation is moderate to drastic inbreeding depression (ID) these germplasms. In the present study, two cycles of S3 recurrent selection were conducted in four white maize populations (Pop. 21, Pop. 25, Pop. 29, Pop. 32) with tropical adaptation to improve them as hybrid‐oriented source germplasm, and the effect of selection was examined in the selfed (S1) and randomly mated (Syn‐2) generations. In each population, 200 to 250 S3 progenies were evaluated and 15 to 20 selected and intermated to form improved versions after cycle 1 (C1) and cycle 2 (C2). Selection was practiced for high grain yield, vigor, and other agronomic traits during inbreeding generations and in the S3‐progeny tests. The S1 and Syn‐2 generations of the C0, C1, and C2 of four populations were evaluated in three environments in Mexico, using split‐split plot design with populations in main plots, generations in subplots, and cycles in sub‐subplots. Selection improved the grain yield of the S1 generation, and the linear gain per cycle (Gc) was 12, 9, 4, and 4% in Pop. 21, Pop. 29, Pop. 32, and Pop. 25, respectively, being significant in Pop. 21 and Pop. 29. The C2 of Pop. 21 had the highest grain yield in both Syn‐2 and S1 generations. Generally, selection did not significantly affect grain moisture, days to silk, and anthesis‐silking interval, but it increased plant height in different populations. Combined over populations, however, grain moisture was significantly increased in addition to grain yield and plant height in both S1 and Syn‐2 generations. The linear Gc for grain yield across populations was 7.41 and 3.20% in the S1 and Syn‐2 generations, respectively. The effect of selection on grain yield and plant height was generally lower in the Syn‐2 than the S1 generation of Pop. 25, Pop. 29, and Pop. 32, but was comparable in two generations of Pop. 21. The ID for grain yield across populations decreased from 39% in CO to 35% in C2. The selection was effective in improving grain yield and reducing ID; and the improved populations would serve as better germplasm sources for the extraction of vigorous inbred lines.
Heritability of Resistance to Leaf Spot Caused by Septoria spraguei in Russian Wildrye
Authors: Berdahl J. D. , Krupinsky J. M.
Published: July 2010

A leaf‐spot disease of Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] caused by Septoria spraguei Uecker & J.M. Krupinsky has the potential to reduce forage quality and yield, particularly in subhumid portions of the northern Great Plains region of the USA and Canada. This study was conducted to estimate heritability of resistance to S. spraguei and to measure the correlation between disease ratings in greenhouse and field environments. Twenty‐five parent clones and their respective half‐sib families were inoculated with S. spraguei in a greenhouse environment and subjected to natural infection in a field nursery. In the greenhouse, narrow‐sense heritability (h2) estimates from the regression of half‐sib family means on parent means were 0.57, 0.79, and 0.72, respectively, for lesion number, lesion size, and percentage necrosis ratings on leaf blades. Heritability estimates in the field environment were 0.22, 0.57, and 0.36, respectively, for lesion number, lesion size, and percentage necrosis. Lesion size was the only rating for which the entry × year interaction was nonsignificant in the field for both parents and half‐sib families. The Spearman rank correlation coefficient between greenhouse and field environments for lesion size means of half‐sib families was 0.61**. Recurrent phenotypic selection for small lesion size among half‐sib families inoculated with S. spraguei in a single greenhouse environment should be effective in improving resistance to this leaf‐spot disease in Russian wildrye.
Responses to Selection for Endosperm Hardness and Associated Changes in Agronomic Traits after Four Cycles of Recurrent Selection in Maize
Authors: Cavanaugh K. J. , Zehr B. E. , Nyquist W. E. , Hamaker B. R. , Crane P. L.
Published: July 2010

Increased endosperm hardness of grain in maize (Zea mays L.) is desirable for dry milling, storage, and expert purposes. This study was conducted to evaluate changes in endosperm hardness resulting from four cycles of visual recurrent selection for increased hardness in two dent corn synthetics representative of U.S. Corn Belt germplasm, and to determine associated responses in other agronomic traits. Testcrosses of random S1 lines from each cycle of selection were grown in replicated trials at four locations in each of 2 yr for determination of grain hardness and evaluation of agronomic traits. Evaluation of grain hardness was through measurement of average kernel density and the Stenvert hardness test. Significant increase in endosperm hardness was limited to the first cycle of selection in both synthetics. No significant changes corresponding to altered endosperm hardness were detected for any of five agronomic traits measured in testcross hybrids from S1 lines representing each cycle of selection. Estimated genetic correlation coefficients indicated a negative, nonsignificant trend between grain yield and grain hardness. These results indicate increases in grain hardness can be achieved through selection in dent corn germplasm common to the U.S. Corn Belt. However, continual progress in recurrent selection may require quantification of hardness by measurements such as kernel density and the Stenvert hardness test, rather than simple visual judgment of relative hardness. Genetic correlation coefficients indicate selection progress can be simultaneously made for both grain yield and grain quality.
Evaluation of Rapid Cycle Recurrent Selection for Early Flowering in Oat
Authors: Rooney W. L. , Stuthman D. D. , Sosa‐Dominquez G. , Hellewell K. H.
Published: July 2010

More efficient methods of recurrent selection are important to oat (Avena sativa L.) breeding. Although recurrent selection methods have been utilized successfully for the improvement of a number of traits in oat, rapid‐cycle population improvement methods for moderately to highly heritable traits have not been evaluated. Our objectives were (i) to evaluate effectiveness of rapid‐cycle recurrent selection for early flowering, and (ii) to determine the effect of selection for early flowering on grain yield, maturity, and plant height. Phenotypic recurrent selection for early flowering was practiced for four cycles. The scheme requires one generation per cycle and up to three cycles can be completed in 1 yr. From each of the 30 selected plants in all four cycles, a single F2:4 line was derived for replicated testing. All derived lines and the original parents were evaluated at Rosemount and St. Paul, MN, in 1992 and 1993. Analysis of F2:4 lines from the earliest 12 plants per cycle indicated that selection reduced days‐to‐flowering by 1.25 days per cycle. Grain yield and plant height were reduced by 25 and 8%, respectively. Although the selection was effective, this population resulted in an unacceptably high frequency of aneuploid and phenotypically off‐type progeny. Cytological analysis of the original F1 hybrids indicated the presence of chromosomal interchanges between some of the C0 parents. We hypothesize that the absence of a selfing generation in a closed recurrent selection system enhanced chromosomal interchange differences, resulting in a high frequency of off‐types and aneuploids in later cycles. Therefore, if interchanges are present between breeding lines, recurrent selection without selling in oat may not be a useful method for long‐term selection programs.
Daylength Influence on the Growth and Metabolism of Sainfoin
Authors: Kallenbach R. L. , Matches A. G. , Mahan J. R.
Published: July 2010

Sainfoin's (Onobrychis viciifolia Scop.) poor growth following defoliation and lack of stand persistence have limited producer acceptance. Because sainfoin growth is poorest in the summer when the daylengths are longest, daylength influence on regrowth and persistence was investigated. Forty, 130‐d‐old (±4 d) ‘Renumex’ sainfoin plants were placed in growth chambers under daylengths of 10, 13, and 16 h of light daily. After a 14‐d adjustment period, plants were clipped to 2 cm. Clipped plants were allowed to regrow for 35 d (Harvest 1) clipped again and allowed to regrow for 14 additional days before final harvest (Harvest 2). Plant height, number of blooms, number of leaves, leaf area, and shoot dry mass were measured before each clipping and at final harvest (Harvest 2). Mass of taproots, fine roots and crowns as well as taproot reducing sugars, total sugars, and total nonstructural carbohydrate (TNC) were determined at Harvest 2. Activity of starch degrading enzymes and whole plant metabolism was measured at Harvest 2. Although daylength had some effects on sainfoin growth form (i.e., plant height and reproductive structures), the vegetative growth of sainfoin was otherwise unaltered by daylength (P > 0.05). Fine root mass was 38% (0.33 g plant−1) greater (P < 0.05) in the 16‐h treatment than in the 10‐h treatment. Taproot carbohydrates, starch enzyme activity, and metabolic heat rates were not altered by daylength (P > 0.05). Our results show that factors other than daylength regulate sainfoin growth after defoliation.
Soybean Germplasm Resistant to Races 3, 5, or 14 of Soybean Cyst Nematode
Authors: Young Lawrence D.
Published: July 2010

Soybean, Glycine max (L.) Merr., accessions added to the U.S. soybean germplasm collection since 1980 were evaluated for reaction to Races 3, 5, and 14 of the soybean cyst nematode, Heterodera glycines Ichinohe. Accessions were evaluated in the greenhouse by inoculation with approximately 1000 H. glycines eggs and enumeration of females developing on roots 35 d after planting. Nineteen accessions were resistant to Race 3, 11 accessions were resistant to Race 5, and two accessions were resistant to Race 14. The PI 467312 was resistant to all three races. These resistant accessions may contain new genes for resistance to this nematode.
A PC SAS Computer Program to Generate a Dissimilarity Matrix for Cluster Analysis
Authors: Mumm Rita Hogan , Dudley J. W.
Published: July 2010

Cluster analysis is being used increasingly in plant breeding research to reveal relationships among inbreds, hybrids, or varieties. However, few software programs popular in agricultural research feature a procedure for generating the dissimilarity matrix, which often serves as input to the cluster analysis. The elements of this matrix are estimates of relationship for all possible pairs of subjects, computed using the raw data and expressed in terms of disparity or distance. A computer program we have written in personal computer SAS code is designed to generate a matrix of dissimilarities (distances) between all pairs of subjects based on binary (0, 1) data recorded for each subject. The user can choose among three association coefficients and between two types of distances to express dissimilarities. Data organization and program output are illustrated by example.
Cytoplasmic‐Genic Male‐Sterility in Interspecific Matings of Cajanus
Authors: Ariyanayagam R. P. , Rao A. Nageshwar , Zaveri P. P.
Published: July 2010

The discovery of two stable male‐sterile genes and the prevalence of adequate insect‐aided cross‐pollination led to the development and release of the first pigeonpea [Cajanus cajan (L.) Millsp.] hybrid in India. Commercialization of this hybrid is constrained because of the labor intensiveness of seed production and concerns about seed purity. Cytoplasmic male‐steriles would effectively circumvent these constraints and revolutionize the hybrid seed industry. This paper reports the development of cytoplasmically determined male‐sterility, which was accomplished by two methods: wide hybridization involving conventional backcrossing of Cajanus sericeus van der Maesen and Cajanus cajan and multiple cross genome transfer. In these matings, two forms of reversion to fertility were noticed, one influenced by low temperature and high humidity, and the other probably determined by genetic factors alone. The influence of temperature on fertility restoration as reported for Vicia faba L. is different from that seen in species crosses of Cajanus. The multiple cross genome transfer method resulted in stable cytoplasmic‐genic male sterility maintainable by the pigeonpea genotypes ICPL 85030 and ICPL 90035. These male‐sterile lines are in agronomically desirable backgrounds.
Carbohydrate Levels in Field‐Grown Leafy and Normal Maize Genotypes
Authors: Dwyer L. M. , Andrews C. J. , Stewart D. W. , Ma B. L. , Dugas J.‐A.
Published: July 2010

Photosynthate contribution to grain yield is complex depending, in part, on the translocation of photosynthate within the plant. A 3‐yr field study was conducted to compare the distribution of leaf and stem carbohydrate concentrations of two leafy maize hybrids, both with extra leaves above the ear, vs. a normal hybrid on a loam soil (Typic Eutrochrept) at Ottawa, Canada (45°23′N, 75°43′W). The Leafy hybrid outyielded the Check (both with stay green characteristic), but the Leafy 1 hybrid had yields inferior to the other two. Patterns of leaf and stem carbohydrate concentrations with leaf level varied among hybrids. This genetic variability could be quantified by fitting data to a cubic equation and by calculating mean leaf or stem concentrations for the upper canopy. Patterns in total nonstructural carbohydrates paralleled patterns in sugar concentrations. Leaf carbohydrate concentrations were less than one‐third those of stem concentrations, showed more diurnal variation, and appeared to be directly influenced by photosynthate production. Mean stem carbohydrates for both leafy hybrids and the Check showed a small rise during the first 10 to 12 d after pollination (DAP), followed by a decline before 35 DAP, which was largest in Leafy 2. Between 40 and 60 DAP, concentrations in Leafy 1 fell slightly, while those in Leafy 2 and the Cheek rose. The larger drop in stem carbohydrates in Leafy 2 could be an indication of greater translocation to the grain during early grain fill in this hybrid. The decline in Leafy 1 stem concentrations just before black layer may have provided a later source of carbohydrates to the grain. This study suggests that analysis of canopy carbohydrates may identify the actual photosynthetic contribution of leaf area to grain yield.
Irrigation and Nitrogen Fertilization Effects on White Grub Injury to Kentucky Bluegrass and Tall Fescue Turf
Authors: Crutchfield Berry A. , Potter Daniel A. , Powell Andrew J.
Published: July 2010

Root‐feeding white grubs (Coleoptera: Scarabaeidae) are important pests of cool‐season turfgrasses in the eastern USA. We studied effects of irrigation and N fertilization on Kentucky bluegrass (Poa pratensis L.), and tall fescue (Festuca arundinacea Schreb.) response to grub damage under greenhouse and field conditions. Potted turfgrasses, with or without Japanese beetle (Popillia japonica Newman) grubs (122/0.1 m2), were maintained under two irrigation regimes, with or without supplemental N fertilizer (204 kg N ha−1). Foliar and root yields, and grub survival were measured after 4 wk. In the field, sod was grown in rooting boxes, with or without spring fertilization (146 kg N ha−1) and fall irrigation (2.54 cm wk−1). Half of the plots were infested with southern masked chafer (Cyclocephala lurida Bland) grubs (66 /0.1 m−1) in late August and effects on aesthetic damage, surface temperature, foliar yield, root strength, and grub survival were measured for 9 wk. Grubs severely damaged roots of both grasses regardless of management regime. Within regimes, however, this damage significantly reduced follar yield only in turf that received both N and high irrigation. In the greenhouse, grub‐damaged grasses that received remedial N, nevertheless, had higher foliar yield than did non‐fertilized grasses without grubs. In rooting boxes, fall irrigation following spring fertilization enhanced visual quality of grub‐infested turf and root strength of grub‐damaged Kentucky bluegrass. Survival of grubs did not differ between grass species or fertilization regimes, but more P. japonica survived in pots receiving high irrigation. Irrigation during the fall feeding period, followed by remedial N fertilization, may promote tolerance and recovery of grub‐damaged turfgrasses.
Identification of a Beta maritima Source of Resistance to Root‐Knot Nematode for Sugarbeet
Authors: Yu M. H.
Published: July 2010

Root‐knot nematodes (Meloidogyne spp.) are economically important plant pests that cause root gall symptoms and limit sugarbeet (Beta vulgaris L.) production. With the increasingly restrictive use of nematicides, the development of resistant sugarbeet cultivars becomes urgent. This study was conducted to identify the source of root‐knot nematode resistance and to evaluate transmission of resistance in sugarbeet hybrid progeny. One hundred‐ninety B. vulgaris and 113 sea beet (B. maritima L.) germplasm lines and accessions were evaluated for nematode resistance, via 1000 second‐stage juveniles (J2) per‐plant inoculations, under greenhouse and growth chamber conditions from 1993 to 1994. Beet seedlings developed better root systems in conetainers and pulp pots than in growth pouches for host reaction to the nematode infection assay. From non‐cultivated sea beet, an accession (PI 546387) was identified that segregated for plants free from root gall formation and from reproduction of M. incognita Race 1. Resistance was transmitted to approximately 23% of the F1 progeny when resistant B. martima phenotypes were crossed to sugarbeet. Development of sugarbeet root‐knot nematode resistant cultivars should be facilitated by this identification of a resistance source and the close phylogenetic relationship of the two Beta taxa.
Heritability and Genotype × Environment Interactions for Straighthead in Rice
Authors: Rasamivelona Andre , Gravois Kenneth A. , Dilday Robert H.
Published: July 2010

Straighthead is a physiological disorder of rice (Oryza sativa L.), which is manifested by floret sterility resulting in yield loss. The objectives of this study were to estimate the narrow‐sense beritability (h2) and the relative importance of genotype × environment interactions for straighthead and to suggest an optimum experimental design for straighthead screening. Ten commercial cultivars and 22 randomly chosen experimental lines representing southern USA rice germplasm were tested from 1991 to 1993 at three Arkansas locations: Stuttgart [Crowley silt loam (fine, montmorillonitic, thermic Typic Albaqualf)], Marianna (Loring silt loam [fine‐silty, mixed, thermic Typic Fragiudalf)], and Colt [Calloway silt loam (fine‐silty, mixed, thermic Glossaquic Fragiudalf)]. Straighthead was induced by monosodiumm ethane arsenate [4.48 kg a.i. ha−1] incorporated into the soil before planting combined with a permanentf lood established at the five‐leaf stage and maintained at each location. The genotype × year and the genotype × location interaction variance components were near zero. The three‐way interaction was significant, but its variance component was one‐fourth the magnitude of the genetic variance. The nature of the genotype × environment interaction was explored by determining the number of significant crossover (rank change) interactions. There were 798 significant crossover interactions or 4.5% of the possible 17 856 quadruples. Thus, genotype × environment interactions were minor and due primarily to changes in magnitude rather than to changes in rank. Heritability (single plot basis) was 61%, indicating that selection for resistance to straighthead should be relatively easy in southern U.S. rice germplasm. Two locations with four replications per location should be adequate for screening southern U.S. rice germplasm for reaction to straighthead.
Additional Sources of Tolerance to Cold in Cultivated and Wild Cicer Species
Authors: Singh K. B. , Malhotra R. S. , Saxena M. C.
Published: July 2010

Cold tolerance is an important prerequisite for winter sowing of chickpea (Cicer arietinum L.) in Mediterranean environments. Cold‐tolerant lines identified earlier at ICARDA are sometimes not tolerant enough to tolerate exceptionally cold winters which occur occasionally. The objectives of this study were to identify sources of increased cold tolerance and to ascertain associations of cold tolerance with other plant traits. Cold tolerance of 4284 kabuli and 2137 desi germplasm lines, 857 breeding lines, and 59 lines of seven annual wild Cicer species was evaluated during the five winters from 1987 to 1992 at ICARDA sites at Tel Hadya and Breda in Syria. The susceptible check was killed in all 5 yr, indicating the severity of cold winters. Eleven kabuli but no desi germplasm lines, and 14 breeding lines, were tolerant. Among the cultigens, a germplasm line (ILC 8262), a mutant (ILC 8617), and a breeding line (FLIP 87‐82C) were the best sources of cold tolerance, with a consistent rating of three (1‐9 scale, where 1 = free from damage and 9 = all plants killed) over years and locations. Among wild species, 26 lines of C. reticulation, 10 of C. bijugum, four of C. echinospermum, two of C. pinnatifidum, and one of C. judaicum were cold tolerant. Five lines of C. bijugum and four of C. reticulatum had a rating of two, reflecting their better cold tolerance than the cultigen. Correlation studies on 2970 lines indicated that prostrate growth habit during winter months was positively associated with cold tolerance. Some late‐flowering lines were susceptible, others were tolerant to cold; whereas, all early‐flowering lines were susceptible to cold. Cold tolerance had no association with anthocyanin pigmentation on the stem. Older plants were more susceptible to cold than younger plants.
Photoperiod Shift Effects on Yield Characteristics of Rice
Authors: Volk Gayle M. , Mitchell Cary A.
Published: July 2010

Edible yield must be maximized for each crop species selected for inclusion in the Controlled Ecological Life‐Support System (CELSS) proposed by NASA to support long‐term manned space missions. In a greenhouse study aimed at increasing biomass partitioning to rice (Oryza sativa L.) grain, plants of the high yielding semi‐dwarf rice cultivar Ai‐Nan‐Tsao were started in pots under 8‐h photoperiods at a density of 212 plants m−2. After different periods of time under 8‐h photoperiods, pots were switched to continuous light for the remainder of the cropping cycle. Continuous light did not delay time to first panicle emergence (60 d) or time to harvest (83 d). There was a positive correlation between the length of continuous light treatments and nongrain biomass. Grain yield (1.6 ± 0.2 g plant−1) did not increase in continuous light. Yield‐efficiency rate (grain weight per length of cropping cycle, canopy volume, and weight of nongrain shoot biomass) was used to compare treatments. Small Ai‐Nan‐Tsao rice canopies grown under 8‐h photoperiods were more efficient producers of grain than canopies grown under continuous light for a portion of the rice cropping cycle.
Feeding by Japanese Beetle and Southern Masked Chafer Grubs on Lawn Weeds
Authors: Crutchfield Berry A. , Potter Daniel A.
Published: July 2010

Root‐feeding white grubs (Coleoptera: Scarabaeidae) are among the most injurious insect pests of cool‐season turfgrasses; however, little is known about the influence of common lawn weeds on white grub populations. Greenhouse studies were conducted to evaluate the suitability of six weed species and one turfgrass including white clover (Trifolium repens L.), red clover (T. pratense L.), large crabgrass [Digitaria sanguinalis (L.) Scop.], annual bluegrass (Poa annua L.), buckhorn plantain (Plantago lanceolata L.), dandelion (Taraxacum officinale Weber), and Kentucky bluegrass (Poa pratensis L.) as food for grubs of the Japanese beetle (Popillia japonica Newman) and southern masked chafer (Cyclocephala lurida Bland). Third instars of both species fed upon and reduced root biomass of all weeds tested, and in some cases, reduced foliage yields as well. Survival of both grub species was as high, or higher, on most weeds as on Kentucky bluegrass. Dandelion and white clover appear to be particularly poor hosts for P. japonica and C. lurida, respectively.