Annual Crop Species Research Articles

Influence of Host Plant Species and Fertilization Regime on Larval Performance and Feeding Preference of the Redbacked Cutworm and the Pale Western Cutworm (Lepidoptera: Noctuidae).

The redbacked cutworm, Euxoa ochrogaster (Guenée), and the pale western cutworm, Agrotis orthogonia (Morrison), are generalist pests that cause sporadic economic damage to several annual crops in the Canadian Prairies. Early larval instars feed on foliage, whereas mature larvae eat into the stem and sever crop seedlings. Here, we evaluate the influence of annual crop species and host fertilization on the larval performance and feeding preference of both cutworm species. Performance is the ability of an insect to reach its maximum growth potential. The first set of experiments evaluated larval development and preference on canola (Brassica napus L. [Capparales: Brassicaeae]), field peas (Pisum sativa L. [Fabales: Fabaceae]), and spring wheat (Triticum aestivum L. [Cyperales: Poaceae]). The redbacked cutworm had higher performance on canola and peas, while the pale western cutworm had higher performance on wheat. In multiple-choice feeding experiments, the redbacked cutworm consumed more canola, whereas the pale western cutworm consumed more spring wheat. The third set of experiments evaluated larval development on fertilized and unfertilized seedlings of canola and spring wheat seedlings. When fed unfertilized seedlings, the redbacked cutworm had better performance on canola than spring wheat, whereas pale western cutworm had better performance on spring wheat than canola. Fertilizer application enhanced the performance of both cutworms regardless of the crop species. Despite their generalist feeding behavior, both cutworm species have a larval feeding preference for the host plant on which they achieve high performance. Canola-cereal cropping is a common crop rotation schedule in the region; however, this tactic will not negatively impact cutworm performance.

Current knowledge and future research opportunities for modeling annual crop mixtures. A review

Growing mixtures of annual arable crop species or genotypes is a promising way to improve crop production without increasing agricultural inputs. To design optimal crop mixtures, choices of species, genotypes, sowing proportion, plant arrangement, and sowing date need to be made but field experiments alone are not sufficient to explore such a large range of factors. Crop modeling allows to study, understand and ultimately design cropping systems and is an established method for sole crops. Recently, modeling started to be applied to annual crop mixtures as well. Here, we review to what extent crop simulation models and individual-based models are suitable to capture and predict the specificities of annual crop mixtures. We argued that: 1) The crop mixture spatio-temporal heterogeneity (influencing the occurrence of ecological processes) determines the choice of the modeling approach (plant or crop centered). 2) Only few crop models (adapted from sole crop models) and individual-based models currently exist to simulate annual crop mixtures. 3) Crop models are mainly used to address issues related to crop mixtures management and to the integration of crop mixtures into larger scales such as the rotation, whereas individual-based models are mainly used to identify plant traits involved in crop mixture performance and to quantify the relative contribution of the different ecological processes (niche complementarity, facilitation, competition, plasticity) to crop mixture functioning. This review highlights that modeling of annual crop mixtures is in its infancy and gives to model users some important keys to choose the model based on the questions they want to answer, with awareness of the strengths and weaknesses of each of the modeling approaches.

Rhamnolipids From Pseudomonas aeruginosa Are Elicitors Triggering Brassica napus Protection Against Botrytis cinerea Without Physiological Disorders.

Rhamnolipids (RLs) are amphiphilic molecules naturally produced by some bacteria with a large range of biological activities. Although some studies report their potential interest in plant protection, evaluation of their effects and efficiency on annual crops of worldwide agronomic interest is lacking. The main objective of this work was to investigate their elicitor and protective activities on rapeseed crop species while evaluating their physiological effects. Here we report that RLs from Pseudomonas aeruginosa secretome trigger an effective protection of Brassica napus foliar tissues toward the fungus Botrytis cinerea involving the combination of plant defense activation and direct antimicrobial properties. We demonstrated their ability to activate canonical B. napus defense responses including reactive oxygen species production, expression of defense genes, along with callose deposits and stomatal closure as efficient physical protections. In addition, microscopic cell death observations and electrolyte leakage measurements indicated that RLs trigger a hypersensitive response-like defense in this plant. We also showed that foliar spray applications of RLs do not induce deleterious physiological consequences on plant growth or chlorophyll content and that RL protective properties are efficient on several grown cultivars of rapeseed. To our knowledge, this is the first report of RLs as an elicitor that suppresses fungal disease on tissues of an annual crop species under greenhouse conditions. Our results highlight the dual mode of action of these molecules exhibiting plant protection activation and antifungal activities and demonstrate their potential for crop cultures as environmental-friendly biocontrol solution.

Trait-based responses of seven annual crops to elevated CO2and water limitation

AbstractBy potentially disrupting crop production, climate change has been implicated as a threat to global food security. We focus on two elements of climate change: elevated atmospheric carbon dioxide concentration, or e[CO2], and reduced water availability, as caused by drought. Both variables have been shown to have effects on crop physiology, although there is considerable evidence of interactions and moderation by species-specific differences. Measuring traits helps scale environmental effects up to functional responses, and we focused on traits connected to photosynthesis, which has a close association with crop yield. We measured the response of four physiological traits—quantum photosynthetic yield, chlorophyll content, root:shoot ratio and leaf area—across a diverse set of seven annual crop species grown under three levels of e[CO2] (450, 575 and 700 ppm) and two levels of water availability (minimum ~45 and ~15% VWC) in a growth chamber. Species included barley, durum wheat, maize, oats, sorghum, pinto bean and sunflower. Our regression analysis focused on testing for interactions between e[CO2] and water limitation and determining relative effect sizes of climate change impacts across species, data that can be used for species-specific modeling or determining appropriate levels of environmental variables in free-air CO2enrichment studies designed to extend small-scale experimental results to the field. Across all species and all traits, the strongest effect of e[CO2] occurred from 450 to 575 ppm, with only marginal differences from 575 to 700 ppm. We found substantial declines in leaf area across all species as a result of e[CO2] and wide variability in leaf area responses to water limitation. Other traits showed weak and variable responses to both e[CO2] and water limitation. While our data confirm that elements of global change, especially increased atmospheric CO2concentration, do affect traits related to photosynthesis, we found no discernible pattern to suggest which crops might be more resistant to e[CO2].

Crop Biomass Not Species Richness Drives Weed Suppression in Warm-Season Annual Grass–Legume Intercrops in the Northeast

Intercropping with functionally diverse crops can reduce the availability of resources that could otherwise be used by weeds. An experiment was conducted across 6 site-years in New York and Maryland in 2013 and 2014 to examine the effects of functional diversity and crop species richness on weed suppression. We compared four annual crop species that differed in stature and nitrogen acquisition traits: (1) pearl millet, (2) sorghum sudangrass, (3) cowpea, and (4) sunn hemp. Crops were seeded in monoculture and in three- and four-species mixtures using a replacement design in which monoculture seeding rates were divided by the number of species in the intercrop. Crop and weed biomass were sampled at ~45 and 90 d after planting. At the first sampling date, intercrops produced more crop biomass than monocultures in all but 1 site-year; however, weed biomass in intercrops was lower than monocultures in only 1 site-year. By the second sampling date, crop biomass was consistently greater in the intercrops than in the monocultures, and weed biomass was lower in the intercrops than in monocultures in 2 site-years. Although we observed several negative relationships between crop species richness and weed biomass, crop biomass was a more important factor than species richness for suppressing weeds. Despite the weak weed suppression from the two legumes compared with the two grasses, legume crops can provide other benefits, including increased forage quality, soil nitrogen for subsequent crops, and resources for pollinators if allowed to flower. On the other hand, if weed suppression is the top priority, our results suggest that monocultures of high biomass–producing grasses will provide more effective suppression at a lower seed cost than functionally diverse intercrops that include low biomass–producing legumes in warm-season intercrops.

What Agriculture Can Learn from Native Ecosystems in Building Soil Organic Matter: A Review

Over the last century, researchers and practitioners with diverse backgrounds have articulated the importance of improving soil organic matter (SOM) contents in agricultural soils. More recently, climate change scientists interested in CO2 sinks, and agroecologists interested in ecological intensification have converged on the goal of building SOM stocks in croplands. The challenge is that agriculture itself is responsible for dramatic losses of SOM. When grassland or forest ecosystems are first converted to agriculture, multiple mechanisms result in SOM declines of between 20% and 70%. Two of the most important mechanisms are the reduction in organic matter inputs from roots following the replacement of perennial vegetation with annual crop species, and increases in microbial respiration when tillage breaks open soil aggregates exposing previously protected organic matter. Many agricultural practices such as conservation tillage and integration of cover crops have been shown to achieve some degree of SOM improvement, but in general adoption of these practices falls short of accumulating the SOM stocks maintained by grasslands, forests or other native ecosystems that agriculture replaced. Two of the overarching reasons why native terrestrial ecosystems have achieved greater soil organic matter levels than human agroecosystems are because they direct a greater percentage of productivity belowground in perennial roots, and they do not require frequent soil disturbance. A growing body of research including that presented in this review suggests that developing perennial grain agroecosystems may hold the greatest promise for agriculture to approach the SOM levels that accumulate in native ecosystems. We present calculations that estimate potential soil organic carbon accumulation rates in fields converted from annual to perennial grains of between 0.13 and 1.70 t ha−1 year−1.

Diversity of agricultural plants on Lesvos Island (Northeast Aegean, Greece) with emphasis on fruit trees

Historical evidence concerning the island of Lesvos has revealed the cultivation of cereals, olive trees, vines, figs and vegetables. Although the island's agricultural economy has been based almost exclusively on olive tree cultivation since the 18th century (ce.), wide diversity of other crops has significantly contributed to the growth of the local economy. Two consecutive inventories and collection expeditions of crop landraces on the island of Lesvos were conducted in 2011 and 2012. The first expedition focused mainly on annual species, while the second one focused exclusively on fruit trees and grapevine landraces. Both expeditions included visits to nearly 50 villages and contacts with amateur and professional farmers, directly related to landraces. During the first expedition a total of 63 donors contributed 309 accessions of 37 annual crop species and genera, mainly vegetables followed by pulses and cereals. A large variation of fruit trees and grapevine landraces has been recorded during both expeditions, including 143 landraces’ names of 13 different species, with the greatest variability observed in pears, figs, apples and cherries as well as in grapevine. Results of the study revealed the substantial plant genetic wealth of cultivated species on the island of Lesvos. The urgent need to collect, conserve and promote this biodiversity is highlighted, since it constitutes invaluable plant material both for scientific purposes as well as for the economic sustainable development of the island.

Identification of genomic sites for CRISPR/Cas9-based genome editing in the Vitis vinifera genome.

BackgroundCRISPR/Cas9 has been recently demonstrated as an effective and popular genome editing tool for modifying genomes of humans, animals, microorganisms, and plants. Success of such genome editing is highly dependent on the availability of suitable target sites in the genomes to be edited. Many specific target sites for CRISPR/Cas9 have been computationally identified for several annual model and crop species, but such sites have not been reported for perennial, woody fruit species. In this study, we identified and characterized five types of CRISPR/Cas9 target sites in the widely cultivated grape species Vitis vinifera and developed a user-friendly database for editing grape genomes in the future.ResultsA total of 35,767,960 potential CRISPR/Cas9 target sites were identified from grape genomes in this study. Among them, 22,597,817 target sites were mapped to specific genomic locations and 7,269,788 were found to be highly specific. Protospacers and PAMs were found to distribute uniformly and abundantly in the grape genomes. They were present in all the structural elements of genes with the coding region having the highest abundance. Five PAM types, TGG, AGG, GGG, CGG and NGG, were observed. With the exception of the NGG type, they were abundantly present in the grape genomes. Synteny analysis of similar genes revealed that the synteny of protospacers matched the synteny of homologous genes. A user-friendly database containing protospacers and detailed information of the sites was developed and is available for public use at the Grape-CRISPR website (http://biodb.sdau.edu.cn/gc/index.html).ConclusionGrape genomes harbour millions of potential CRISPR/Cas9 target sites. These sites are widely distributed among and within chromosomes with predominant abundance in the coding regions of genes. We developed a publicly-accessible Grape-CRISPR database for facilitating the use of the CRISPR/Cas9 system as a genome editing tool for functional studies and molecular breeding of grapes. Among other functions, the database allows users to identify and select multi-protospacers for editing similar sequences in grape genomes simultaneously.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0787-3) contains supplementary material, which is available to authorized users.

The effect of late fall seeding time on the seed production of Italian ryegrass

Coulman, B., Loeppky, H. and Entz, M. 2015. The effect of late fall seeding time on the seed production of Italian ryegrass. Can. J. Plant Sci. 95: 641–645. Italian ryegrass (Lolium multiflorum Lam.) is a cool-season grass, which behaves as an annual in the Great Plains region of western Canada and is used as a grazing crop. Italian ryegrass requires vernalization for reproductive development to occur. Late fall (dormant) seedings, which have been used for annual crop species, have often resulted in earlier developing seedlings in the spring and higher yield than spring seedings. For Italian ryegrass, dormant seedings may result in vernalization of early-spring-germinating seedlings, allowing seed production without having to overwinter established plants. The objective of this study was to compare the seed yield and stand establishment of late fall (dormant) and spring seedings of Italian ryegrass at three locations in the Great Plains region of western Canada. Stand establishment was assessed by measuring tiller density in the month of June, and these densities were greater for spring than late fall seedings. Most spring seedings had no reproductive development and, thus, no seed yield; however, most late fall seedings produced seed the following year, indicating that vernalization of early-developing seedlings did occur. There were significant differences in seed yield among the four cultivars tested and among sites. Based on the high variation in seed yield among cultivars and sites and the relatively low yield levels obtained, late fall seedings of Italian ryegrass cannot be recommended in the Great Plains region of western Canada.

Construction of a reference genetic map of Raphanus sativus based on genotyping by whole-genome resequencing.

This manuscript provides a genetic map of Raphanus sativus that has been used as a reference genetic map for an ongoing genome sequencing project. The map was constructed based on genotyping by whole-genome resequencing of mapping parents and F 2 population. Raphanus sativus is an annual vegetable crop species of the Brassicaceae family and is one of the key plants in the seed industry, especially in East Asia. Assessment of the R. sativus genome provides fundamental resources for crop improvement as well as the study of crop genome structure and evolution. With the goal of anchoring genome sequence assemblies of R. sativus cv. WK10039 whose genome has been sequenced onto the chromosomes, we developed a reference genetic map based on genotyping of two parents (maternal WK10039 and paternal WK10024) and 93 individuals of the F2 mapping population by whole-genome resequencing. To develop high-confidence genetic markers, ~83 Gb of parental lines and ~591 Gb of mapping population data were generated as Illumina 100 bp paired-end reads. High stringent sequence analysis of the reads mapped to the 344 Mb of genome sequence scaffolds identified a total of 16,282 SNPs and 150 PCR-based markers. Using a subset of the markers, a high-density genetic map was constructed from the analysis of 2,637 markers spanning 1,538 cM with 1,000 unique framework loci. The genetic markers integrated 295 Mb of genome sequences to the cytogenetically defined chromosome arms. Comparative analysis of the chromosome-anchored sequences with Arabidopsis thaliana and Brassica rapa revealed that the R. sativus genome has evident triplicated sub-genome blocks and the structure of gene space is highly similar to that of B. rapa. The genetic map developed in this study will serve as fundamental genomic resources for the study of R. sativus.

Foliar Silicon and Titanium Applications Influence Growth and Quality Characteristics of Annual Bedding Plants

This study investigated the effects of foliar Si and Ti applications on annual bedding plant growth and quality in soilless media. The five annual plant species selected were geranium (Pelargonium x hortorum 'Elite Cherry'), impa- tiens (Impatiens walleriana 'Accent White'), pansy (Viola x wittrockiana 'Delta Premium Marina'), petunia (Petunia x hybrid 'Celebrity White') and snapdragon (Antirrhinum majus 'Montego Purple'). Sodium silicate (NaSiO3) supplied fo- liar treatments of 0, 50, 100, 150 and 200 mg Si·L -1 and Ti-ascorbate (Tytanit ® ) supplied foliar treatments of 0, 25, 50, 75 and 100 mg Ti·L -1 . Silicon treatments affected plant height for all five species, while Ti treatments only affected plant height for geranium, petunia and snapdragon. Snapdragon plant height increased linearly in response to Si and Ti treat- ments. Plant height increased, then decreased quadratically for geranium with Ti treatments and pansy with Si treatments. The number of days to flower for petunias exhibited a linear decrease with Ti treatments while impatiens exhibited a lin- ear increase with Si and Ti treatments. Geranium responded with a quadratic decrease, then increase for the number of days to flower with increasing Ti treatments. The chlorophyll SPAD content of impatiens exhibited a linear decrease in response to Ti treatments, while geranium had the same response to Si treatments. Silicon and Ti supplementations were found to affect growth and quality characteristics of annual bedding plants. However, this response was species specific and further research is needed to assess the specific impacts of Si and Ti on additional annual crop species and varieties grown in soilless media.

Comparison of the penetration of primary and lateral roots of pea and different tree seedlings growing in hard soils

Establishment and survival of tree seedlings in hard soils depends on production of deep root systems. This study evaluated the primary and lateral roots of an annual crop and several tree species growing in soils of varying strength. We grew peas and acacias by direct seeding, plus three eucalypts by direct seeding and transplanting, and measured various root characteristics. At all levels of soil compaction, the primary roots of acacia were thicker and they elongated faster than did those of the eucalypts. However, lateral roots of transplanted eucalypts elongated faster than their primary roots, and the rate of root elongation was negatively correlated with soil penetration resistance, especially for Eucalyptus camaldulensis. The primary root diameter of all plants increased with increasing penetration resistance, but acacia roots continued to elongate faster than pea roots. Pea plants produced most of their roots in the top 5 cm, whereas tree roots were more uniformly distributed with depth. Although not statistically significant at P = 0.05, the relative rate of root elongation in very hard soil correlated modestly (P = 0.11) with the maximum root growth pressure of four tree species. These variations in root growth behaviour can be related to the intrinsic variability of root characteristics for each plant species and the natural abundance of each species in different environments.

Differences in soil water content between perennial and annual forages and crops grown under deficit irrigation and used by the dairy industry

Water for irrigated agriculture is becoming increasingly scarce worldwide and this has led to interest in deficit irrigation (DI) as a means of reducing forage and crop water requirements. While perennial ryegrass (Lolium perenne L.) dominates the forage base on Australian dairy farms, its ability to extract water from the soil profile under DI compared to other species has not been documented under best practice management. Changes in soil water content (SWC) of twenty two perennial and annual forage and crop species were evaluated over three years to assess the ability of these forages to extract water from the soil profile compared to perennial ryegrass under DI on a brown Dermosol, over three years at Camden, Australia. Seven perennial and three annual forage species created a greater (P<0.001) soil water deficit (SWD) to 150cm than perennial ryegrass. Paspalum (Paspalum dilatatum Poir.) created the largest SWD to 150cm of 226mm, which was 78mm greater than perennial ryegrass for the same year. Estimated plant root depth was greater than 150cm for 11 of 12 perennial forage species, but less than 150cm for seven of 11 annual forage species. This study showed that there were large differences between values of maximum extractable water for the range of forage species evaluated, which has implications for reducing irrigation requirements and reducing recharge.

The Potential for Pyroxasulfone to Selectively Control Resistant and Susceptible Rigid Ryegrass (Lolium rigidum) Biotypes in Australian Grain Crop Production Systems

The widespread evolution of resistance in rigid ryegrass populations to the highly effective, in-crop, selective herbicides used within southern Australian grain-crop production systems has severely diminished the available herbicide resource. A new PRE grass-selective herbicide, pyroxasulfone, may offer Australian grain producers a new option for rigid ryegrass control in wheat crops. The efficacy and level of selectivity of rigid ryegrass control with pyroxasulfone was investigated for a range of annual crop species in potted-plant, dose–response studies. In comparison with other currently available PRE herbicides, pyroxasulfone provided effective control of both resistant and susceptible rigid ryegrass populations. Additionally, control of these populations was achieved at rates that had little or no effect on the growth and survival of wheat. This crop was also the most tolerant of cereal species, with triticale, barley, and oat being more injured at higher pyroxasulfone rates than wheat was. In general though, pulse-crop species were found to be more tolerant of high pyroxasulfone rates than cereal-crop species. There were subtle effects of soil type on the efficacy of pyroxasulfone, where higher rates were required to achieve effective control on soils with higher clay or organic matter contents. The ability of pyroxasulfone to selectively control resistant and susceptible rigid ryegrass populations as identified in these studies clearly indicate the potential for widespread use and success of this herbicide in Australian cropping systems.

Interactive effects of HIV/AIDS and household headship determine home garden diversity in the Eastern Region of Ghana

Home gardens are important for enhancing food and nutritional security for HIV/AIDS-afflicted rural households through dietary diversity. Female-headed households may depend on home gardens more than average households to supply and supplement the household's diet when labour is constrained for field cropping. This paper compares household characteristics, dietary diversity, labour allocated to crop husbandry and home garden biodiversity amongst 22 HIV/AIDS-afflicted female-headed households, 15 non-HIV/AIDS-afflicted female-headed, 10 HIV/AIDS-afflicted dual-headed and 33 non-HIV/AIDS-afflicted dual-headed households in rural communities in the Eastern Region of Ghana. Information on household characteristics and labour allocation to home garden management was obtained through a cross-sectional survey and in-depth interviews. Dietary diversity score was estimated for each household based on a 24-hour qualitative dietary recall. Plant species in each home garden were recorded. HIV/ AIDS affliction did not affect home garden diversity but afflicted households had more on-farm sources of income and a higher dietary diversity and allocated more adult labour to home garden activities than non-afflicted households. Dual-headed households had more diversity in the home garden and allocated more adult male labour to the home garden than female-headed households. Statistically significant interactions between HIV/AIDS affliction and headship were observed for Shannon-Wiener index, number of crop species, number of annual crop species and number of root and tuber crop species in the home gardens: there were no headship effects when households were afflicted whereas dual-headed households had higher values than female-headed households in non-afflicted households. HIV/AIDS-afflicted households had significantly more annual crop species and more root and tuber crop species than non-afflicted households for female-headed households, whereas there were no significant differences for dual-headed households. Faced with confinement to the homestead in caregiving and by the obligation to ensure household food and nutritional security, HIV/AIDS-afflicted households spent more (female] labour on home garden management than non-afflicted households to produce crops for sustenance and dietary diversity.

The transpiration response by four topographically distributed Eucalyptus species, to rainfall occurring during drought in south eastern Australia

Vegetation covers a substantial proportion of the terrestrial Earth surface and where removed from human influence has evolved influenced mainly by climatic and edaphic constraints. Over the past 200 years, substantial tracts of the wheat‐sheep belt of southern Australia has been cleared of native vegetation and replaced by annual crop and pasture species. As a consequence, there has been a change in the water balance of many catchments as now more water leaks beneath the roots of introduced plants, contributing to groundwater rise and expansion in the amount of land affected by salinization. In an attempt to arrest root zone leakage, scientists and managers acknowledge the need for new agricultural practices which mimic the ecohydrological behaviour patterns of remnant vegetation.In this paper, we examine the water use characteristics of four woodland Eucalyptus species growing in different topographic and edaphic environments in south eastern Australia. Eucalyptus sideroxylon and E. rossii were the sub‐ and dominant species inhabiting the stony ridges, while in the adjacent valleys E. macrorhyncha and E. albens were the sub‐ and dominant species, respectively. At the two locations, sub‐dominant species were highly responsive to episodic rainfall events both during and following drought, and exhibited distinct seasonality in daily transpiration rate; while the dominant species at each location was less responsive to rainfall and water use appeared to be less seasonally dependent. Analysis of the water use response indicated that the two sub‐dominant species had shallower roots while the major of roots of the dominant trees were likely to be located deeper in the substratum. This suggested that the stony ridges may store water deeper in the substratum than previously thought, to sustain some remnant vegetation over the dry summers, and ultimately, contribute less recharge to groundwater.

Molecular Population Genetics of Herbivore-induced Protease Inhibitor Genes in European Aspen (Populus tremula L., Salicaceae)

Plants defend themselves against the attack of natural enemies by using an array of both constitutively expressed and induced defenses. Long-lived woody perennials are overrepresented among plant species that show strong induced defense responses, whereas annual plants and crop species are underrepresented. However, most studies of plant defense genes have been performed on annual or short-lived perennial weeds or crop species. Here I use molecular population genetic methods to survey six wound-inducible protease inhibitors (PIs) in a long-lived woody, perennial plant species, the European aspen (Populus tremula), to evaluate the likelihood of either recurrent selective sweeps or balancing selection maintaining amino acid polymorphisms in these genes. The results show that none of the six PI genes have reduced diversities at synonymous sites, as would be expected in the presence of recurrent selective sweeps. However, several genes show some evidence of nonneutral evolution such as enhanced linkage disequilibrium and a large number of high-frequency-derived mutations. A group of at least four Kunitz trypsin inhibitor genes appear to have experienced elevated levels of nonsynonymous substitutions, indicating allelic turnover on an evolutionary timescale. One gene, TI1, has enhanced levels of intraspecific polymorphism at nonsynonymous sites and also has an unusual haplotype structure characterized by two divergent haplotypes occurring at roughly equal frequencies in the sample. One haplotype has very low levels of intraallelic nucleotide diversity, whereas the other haplotype has levels of diversity comparable to other genes in P. tremula. Patterns of sequence diversity at TI1 do not fit a simple model of either balancing selection or recurrent selective sweeps. This suggests that selection at TI1 is more complex, possibly involving allelic cycling.

Agrobacterium-mediated in vitro transformation of wood-producing stem segments in eucalypts.

The genetic manipulation of perennial woody tree species presents a range of additional challenges compared to that of annual weedy crop species. These include long generation times and reproductive cycle, the heterogeneity of plants under investigation and, when investigating wood properties, a number of physical and biochemical limitations to microscopical and molecular experimentation. The use of in vitro wood formation systems for molecular studies and Agrobacterium-mediated introduction of transgenes overcomes many of these obstacles. Using a commercially relevant Eucalyptus species as model organism, we demonstrate here that in vitro wood formation systems can be readily employed to introduce transgenes into growing wood-producing tissue, initially leading to frequent transient gene expression in a range of cell types. Stable transformation events were observed as sectors of transformed tissue derived from primary transformation events in individual cells. The usefulness of such systems for the analysis of gene function during the process of wood formation and wood quality determination, as well as for constructing developmental fate maps of cambial derivatives, is discussed.

The effect of improved pastures and grazing management on soil water storage on a basaltic plains site in south-west Victoria

Soil salinity of non-irrigated farmlands in Australia has been largely attributed to tree clearing and their replacement by annual pasture and crop species. This paper deals with the effects of sowing perennial ryegrass and greater inputs of fertiliser, and the effect of grazing management, on water use and the potential to improve recharge control on a gravelly soil derived from basalt.In 1991, neutron access tubes were inserted into plots on a project established in 1989 to examine the impact of upgrading the pasture on sheep productivity. These plots were subdivided in 1996 to examine the impact of grazing management (tactical v. set-stocking) and pasture type (pastures dominated by annual species v. upgraded pastures) on productivity. Neutron probe readings were taken periodically from tubes in each plot, at depth intervals of 25 cm (December 1991–March 1995) or 20 cm (August 1995–April 1999) to 170 cm. There was no effect of treatment on soil moisture. Data for 2 wet years (1995 and 1996) indicate that the effective soil-water storage capacity to 170 cm depth for these pastures was a mean of 125 mm of water. This represents the potential buffer before winter rainfall exceeds the water use by the pasture, fills the soil profile to capacity and then either runs off or allows deep drainage to occur.We did not achieve a significant reduction in soil-water storage, and therefore potential recharge of groundwater, by re-sowing the pasture with perennial ryegrass and applying more fertiliser, or by altering the grazing management to a form of rotational grazing. Compared with set-stocked annual pasture, the impact of such treatments was to reduce soil-water storage to a depth of 170 cm in autumn by less than 20 mm/year. There was no association between total herbage production and soil-water storage, however an increased percentage of perennial ryegrass in the pasture was associated with a small reduction in soil-water storage in 1 year. Greater use of soil-water may depend upon using deeper-rooted perennials or maintaining a higher proportion of perennial species in the sward (the perennial ryegrass in the re-sown pastures declined from 53% in October 1996 to 4% in October 1998).

Parent Selection in Breeding for Roasted Peanut Flavor Quality1

Abstract The sensory attributes that make up roasted peanut flavor quality are important traits to evaluate in the development of new cultivars. Recent publications have characterized the variation in sensory attributes in U.S. peanuts (Arachis hypogaea L.), however, no estimates of the effects of lines as parents in a breeding program have been calculated. Best linear unbiased prediction (BLUP) is a method for predicting the breeding value of a parent based on the performance of its relatives. Commonly used in animal and tree breeding, the method is rarely applied in annual crop species. The method was applied to a set of data collected on the three sensory attributes roasted peanut, sweet, and bitter for 250 peanut genotypes evaluated in 53 environments. BLUP solutions computed using different estimates of narrow-sense heri-tability (h2) were highly correlated (r &amp;gt; 0.9), suggesting that precise estimates of h2 are not necessary. Correlations of values predicted by BLUP with observed values were moderate (0.63 &amp;lt; r &amp;lt; 0.71) for individual lines, but strong (0.85 &amp;lt; r &amp;lt; 0.92) for means of crosses. BLUPs of breeding value can be used to predict means of crosses, but segregation within crosses affords additional opportunity for progress from selection. BLUPs of breeding value were superior to midparent values in predicting cross means. The previously reported flavor relationships between the runner and virginia market types were predicted by the breeding values of some commonly used parents. Specific lines with superior breeding values for flavor quality included runner-types Florunner, its components and sibling lines, and high-oleic derivatives of Sunrunner; virginia-types Altika, White's Runner, NC Ac 18457, and X90053; and spanish-type Pearl. Jenkins Jumbo, Florigiant, NC7, and CBR-resistant lines had inferior breeding values for flavor quality.