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Enset [Ensete ventricosum (Welw.) Cheesman] is a poorly known costaple crop for 
7 to 10 million of the population of South and Southwest Ethiopia. During the last decades, enset-based farming systems have become endangered due to population pressure, market developments, and occurrence of diseases. This has compromised the role of enset as a major food source. To rationalize conservation efforts, morphological and molecular characterization studies have been initiated. Negash et al. (p. 1105–1111) describes the application of amplified fragment length polymorphisms to assess clonal diversity, and is the first study using molecular markers in enset. In line with farmers' classification, it identifies a set of accessions that may be deleted from the ex situ collections.
Return Clippings to Lower N Fertilizer Requirement
Information is lacking on the effect of returning grass clippings on turfgrass growth and quality. In this study, Kopp and Guillard (p. 1225–1231) determined the effects of returning grass clippings in combination with varying N fertilization rates on growth, N utilization, and quality of turfgrass managed as a residential lawn. Returning clippings increased clipping yield, total N uptake, N recovery, and N use efficiency. The practice of returning clippings was found to improve the growth and quality of turfgrass while reducing the need for N fertilization.
Anion Exchange Membranes Measure N in Turf Soils
The potential of anion exchange membranes (AEMs) for determining available N status of soils for turfgrass use has not been researched extensively. In this study, Kopp and Guillard (p. 1232–1240) characterized the relationship of desorbed NO3-N from AEMs to clipping yield and turfgrass quality using quadratic response plateau and Cate-Nelson models. Critical levels of desorbed NO3-N from AEMs for optimizing dry matter yield and turfgrass quality were developed, indicating the potential of AEMs as a tool for N management of turfgrass.
Night Temperatures and Grain Filling in Maize
Maize (Zea mays L.) leaf photosynthesis during the grain-filling period is affected by low night temperatures. Ying et al. (p. 1164–1172) examined the effect of (i) duration of cold exposure during the night, (ii) acclimation of the leaves to high temperature prior to exposure to light, and (iii) level of incident photosynthetic photon flux density following cold exposure. Studies were carried out with plants grown hydroponically under both field and controlled-environment conditions. Results showed that all three factors affected the reduction in leaf photosynthesis after cold exposure in the dark. In contrast, dark-adapted chlorophyll fluorescence was affected by duration of cold exposure but not by acclimation, indicating that the reduction in photosynthesis due to low night temperature is not associated with photoinhibition.
Low Red to Far-Red Ratios on Sunflower Stems Reduce Yield
The low red (R) to far-red (FR) ratios typical of dense crops increase stem growth and could reduce the resources available for yield. Libenson et al. (p. 1180–1185) investigated this possibility by reducing with selective filters the R/FR ratio reaching the stem of sunflower (Helianthus annuus L.) plants grown at very low densities. Low R/FR ratios increased stem length and dry matter, and reduced grain yield due to a negative effect on grain number. Grain yield of sunflower crops could be improved by selecting against responses to R/FR ratio with negative impact on yield.
Pigeonpea as a Forage in the Southern Great Plains
A primary goal of grazing-based forage production systems is to provide high-quality forage year-round, reducing costs of using harvested, stored, or purchased feeds. The primary forage resources for livestock production in the southern Great Plains are winter wheat and warm-season perennial grasses. Wheat forage is available during winter and early spring. Warm-season perennial grasses are productive only during the late spring and early summer, and their quality declines during mid- and late summer. No high-quality forage is available in late summer and fall. Pigeonpea [Cajanus cajan (L.) Millsp.] is a summer legume with excellent drought tolerance that is used extensively in Asia for both human food (grain) and for forage. Rao et al. (p. 1259–1263) evaluated seasonal forage production patterns and nutritive value of three pigeonpea cultivars. Forage yields were high relative to alternative grasses and legumes, ranging from 1120 kg ha-1 in July to 12600 kg ha-1 in the first week of October. Nitrogen content and dry matter digestibility also compared favorably with other alternatives. On the basis of its excellent production and quality in late summer when other forages are unproductive, pigeonpea may have potential for filling the summer/fall gap in a year-round supply of high-quality forage.
Remote Sensing Estimates Green Leaf Area Index and Dry Weight in Alfalfa
The percentage of sunlight reflected from alfalfa (Medicago Sativa L.) canopies in the near-infrared region (810 nm) was measured by Guan and Nutter (p. 1264–1273) using a hand-held, multispectral radiometer as a means to estimate the effects of alfalfa leafspot pathogens on the growth and development of alfalfa. Compared with single-point defoliation measurements, percentage reflectance explained 15 and 4% more of the variation in alfalfa dry weight and green leaf area index (GLAI), respectively. Area under the curve reflectance models explained 28 and 32% more of the variation in dry weight and GLAI compared with area under the percentage defoliation curves, respectively. This study conclusively demonstrated that percentage reflectance measurements in the near-infrared region (810 nm) had a better relationship with alfalfa dry weight and GLAI than destructive and more labor-intensive percentage defoliation assessments.
Estimation of Daily Growth and Nutritive Value of Tall Fescue
The implementation of intensive grazing strategies require information about pasture daily growth rate and the associated nutritive value of the pasture canopy. Small plot management studies generally report only annual dry mater yields and mean estimates of nutritive value. Burns et al. (p. 1274–1284) provide a method to estimate plant daily growth rate and the associated nutritive value of the new growth and present season-long curves for both the growth and its nutritive value from eight defoliation intensities of tall fescue (Festuca arundinacea Schreb.).
Leafhopper-Resistant Alfalfa in New York
Potato leafhopper (PLH) is a damaging pest of alfalfa (Medicago Sativa L.). In plot trials (Hansen et al., p. 1155–1163), glandular-haired alfalfa (resistant) was compared with susceptible alfalfa. Resistant populations had significantly lower damage scores from PLH, and fewer nymph and adult PLH than susceptibles. However, resistant populations yielded more than susceptibles only in one of four trials. Resistant populations had higher crude protein concentrations and matured earlier than did susceptibles. Seeding year damage reduced yields in the first harvest of the following year. Insecticides increased forage yields. Resistant populations provide benefits such as higher crude protein and less hopperburn, but do not provide complete protection against yield loss from PLH damage.
Chilean vs. African Alfalfa Chromosomes
Alfalfa (Medicago Sativa L.) chromosomes are very small (2–3 µm in length), they are similar in appearance, and 2n = 4x = 32; thus it is very difficult to identify each individual chromosome and make comparisons between germplasm sources. Bauchan at al. (p. 1291–1297) utilized C-banding techniques, computerized image analysis, and cluster and multiple correspondence analysis of C-banding patterns to discriminate between chromosomes from two alfalfa germplasm sources, Chilean and African. Abundant variability in the number, intensity, and location of constitutive heterochromatic DNA was noted; however, this variability was not sufficient to preclude recognition of homologous chromosomes. Aneuploids (2n = 4x + 1 = 33 or 2n = 4x - 1 = 31) were discovered that had either the presence or absence of a chromosome with a satellite. The cluster and multiple correspondence analysis demonstrated that C-band polymorphisms were effective in separating the two germplasm sources with the exception of two individuals from each germplasm source which clustered together.
Improving Sunflower Yield in Late Plantings
Developing strategies for improving sunflower (Helianthus annuus L.) yield in late plantings is needed. In this study, de la Vega and Hall (p. 1202–1210) used genotypes differentially adapted to normal and late planting in an attempt to identify physiological bases of the sowing date (S), genotype (G), and G x S interaction effects. Both S and G x S interaction effects on yield mostly involved the variation of attributes and processes expressed postanthesis. Harvest index was the dominant determinant of the G x S interaction. Canopy stays green proved to be a reliable selection criterion for use in breeding for adaptation to late plantings.
Subspecies Heterosis in Alfalfa Agronomic Field Traits
Heterosis has been found between Medicago sativa L. subsp. sativa and subsp. falcata for forage yield. Riday and Brummer (p. 1081–1087) attempted to determine if subspecies heterosis was present for agronomic field traits. They crossed genotypes between and within the subspecies and measured winter injury, spring regrowth, vigor, growth habit, maturity, height, midseason regrowth, and autumn regrowth. Sativa–falcata heterosis was calculated in several ways. On average, vigor, winter injury, spring regrowth, height, and maturity showed positive heterosis, while autumn regrowth showed negative heterosis, and midseason regrowth and growth habit displayed no heterosis. Agronomic trait heterosis was not as high as forage yield heterosis measured on the same material. Heterotic performance of various agronomic traits, except autumn regrowth, should not greatly hinder the development of sativa–falcata hybrids.
Forage Quality of Inter- vs. Intrasubspecific Crosses of Alfalfa
Medicago sativa L. subsp. sativa and subsp. falcata represent a heterotic pattern that could be used in a semihybrid breeding system to increase yields, but the forage quality of intersubspecific crosses in relation to intrasubspecific crosses is unclear. Riday et al. (p. 1088–1093) compared stem forage quality and leaf/stem ratio of inter- and intrasubspecific crosses of subsp. sativa and falcata. The quality traits analyzed included in vitro dry matter digestibility, neutral detergent fiber, acid detergent fiber, acid detergent lignin, crude protein, hemicellulose, and cellulose. Intersubspecific hybrids had slightly decreased stem forage quality compared with the expected quality based on the average of the intrasubspecies cross means. For many forage quality traits, the decreased quality was equivalent to the level of the poorer performing intrasubspecies cross mean. The magnitude of the forge quality negative heterosis is small enough that it will have little impact on sativa–falcata hybrids.
Dwarfing Genes and Gibberellic Acid Response in Oat
The incorporation in cereals of dwarfing genes for reduced plant height can provide resistance to lodging, but the presence of such genes may also result in reduced yield and grain size. Milach et al. (p. 1147–1154) investigated in cultivated hexaploid oat (Avena sativa L.) the effects of three dominant dwarfing genes on plant height components and gibberellic acid (GA) response. The three genes differentially affected lengths of various internodes and node number. Lines carrying the genes were responsive to exogenous applications of GA. A knowledge of these properties is valuable in attempting to use these genes to develop reduced height oat cultivars.
Related articles in Crop Science:
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