Stephen S. Jones

Increased food and ecosystem security via perennial grains

Perennial grains hold promise, especially for marginal landscapes or with limited resources where annual versions struggle. Despite doubling of yields of major grain crops since the 1950s, more than one in seven people suffer from malnutrition (1). Global population is growing; demand for food, especially meat, is increasing; much land most suitable for annual crops is already in use; and production of nonfood goods (e.g., biofuels) increasingly competes with food production for land (2). The best lands have soils at low or moderate risk of degradation under annual grain production but make up only 12.6% of global land area (16.5 million km2) (3). Supporting more than 50% of world population is another 43.7 million km2 of marginal lands (33.5% of global land area), at high risk of degradation under annual grain production but otherwise capable of producing crops (3). Global food security depends on annual grains—cereals, oilseeds, and legumes—planted on almost 70% of croplands, which combined supply a similar portion of human calories (4, 5). Annual grain production, though, often compromises essential ecosystem services, pushing some beyond sustainable boundaries (5). To ensure food and ecosystem security, farmers need more options to produce grains under different, generally less favorable circumstances than those under which increases in food security were achieved this past century. Development of perennial versions of important grain crops could expand options.

Breeding for organic and low-input farming systems: An evolutionary-participatory breeding method for inbred cereal grains

Organic and low-input farmers often plant seed varieties that have been selected under conventional practices, traditionally including high inputs of artificial fertilizers, crop protection chemicals and/or water. In addition, these crops are often selected in environments that may or may not represent the local environment of the farmer. An evolutionary participatory breeding (EPB) method emphasizes the utilization of natural selection in combination with site-specific farmer selection in early segregating generations of a heterogeneous crop population. EPB is a combination of two specific breeding methods, evolutionary breeding and participatory plant breeding. Evolutionary breeding has been shown to increase yield, disease resistance, genetic diversity and adaptability of a crop population over time. It is based on a mass selection technique used by farmers for over 10,000 years of crop improvement. Participatory plant breeding programs originated in developing countries to meet the needs of low-input, small-scale farmers in marginal environments who were often overlooked by conventional crop breeders. The EPB method is an efficient breeding system uniquely suited to improving crop varieties for the low-input and organic farmer. The EPB method utilizes the skills and knowledge of both breeders and farmers to develop heterogeneous landrace populations, and is an effective breeding method for both traditional and modern farmers throughout the world.

Decentralized selection and participatory approaches in plant breeding for low-input systems

Heterogeneous environments make it difficult to apply consistent selection pressure because often it is difficult to identify a single or a few superior genotypes across all sets of conditions. However, when the target system is characterized by heterogeneity of environmental stress, varieties developed in high-yielding conditions may fail to satisfy farmers’ needs. Although this type of system is often found in marginal environments of developing countries, heterogeneous environmental conditions are also a feature of organic and low-external-input systems in developed countries. To meet the needs of these systems, breeding programs must decentralize selection, and although decentralized selection can be done in formal breeding programs, it is more efficient to involve farmers in the selection and testing of early generation materials. Breeding within these target systems is challenging, both genetically and logistically, but can identify varieties that are adapted to farming systems in marginal environments or that use very few external inputs. A great deal has been published in recent years on the need for local adaptation and participatory plant breeding; this article reviews and synthesizes that literature.

Perennial wheat: The development of a sustainable cropping system for the U.S. Pacific Northwest

Perennial wheat offers a new solution to the long-standing problems of soil erosion and degradation associated with conventional annual small-grain cropping systems in the Pacific Northwest region. Using classical breeding methods, new types of wheat have been developed that maintain the key characteristics of annual wheat, but continue to grow after harvest. Following dormancy in the winter, growth is initiated from the roots or crowns in the spring, allowing a crop to be harvested every fall. By retaining constant soil cover over multiple years, wind and water erosion would be dramatically reduced. In addition, the costs associated with annual seeding and tillage would be minimized, and unlike many reduced tillage systems, it is expected that standard seeding equipment would be suitable for stand establishment. Other potential benefits of perennial wheat include improved wildlife habitat, more efficient use of available water, provision of a potent carbon sink, and the possibility of integrating straw retrieval into a small grains cropping system. Past attempts in the first half of the last century failed to develop perennial wheat as a viable crop, primarily because of low yields, and the research was ultimately abandoned. Perennial wheat production may now be viewed as acceptable for highly erodible land or for obtaining carbon sequestration credits. This paper presents an overview of solutions to the obstacles encountered by previous researchers, introduces some of the newly developed perennial wheat lines, and discusses considerations for management practices.

Partial Characterization of Glutathione S-Transferases from Wheat (Triticum spp.) and Purification of a Safener-Induced Glutathione S-Transferase from Triticum tauschii

Hexaploid wheat (Triticum aestivum L.) has very low constitutive glutathione S-transferase (GST) activity when assayed with the chloroacetamide herbicide dimethenamid as a substrate, which may account for its low tolerance to dimethenamid in the field. Treatment of seeds with the herbicide safener fluxofenim increased the total GST activity extracted from T. aestivum shoots 9-fold when assayed with dimethenamid as a substrate, but had no effect on glutathione levels. Total GST activity in crude protein extracts from T. aestivum, Triticum durum, and Triticum tauschii was separated into several component GST activities by anion-exchange fast-protein liquid chromatography. These activities (isozymes) differed with respect to their activities toward dimethenamid or 1-chloro-2,4-dinitrobenzene as substrates and in their levels of induction by safener treatment. A safener-induced GST isozyme was subsequently purified by anion-exchange and affinity chromatography from etiolated shoots of the diploid wheat species T. tauschii (a progenitor of hexaploid wheat) treated with the herbicide safener cloquintocet-mexyl. The isozyme bound to a dimethenamid-affinity column and had a subunit molecular mass of 26 kD based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme (designated GST TSI-1) was recognized by an antiserum raised against a mixture of maize (Zea mays) GSTs. Amino acid sequences obtained from protease-digested GST TSI-1 had significant homology with the safener-inducible maize GST V and two auxin-regulated tobacco (Nicotiana tabacum) GST isozymes.

Perennial Wheat Germ Plasm Lines Resistant to Eyespot, Cephalosporium Stripe, and Wheat Streak Mosaic

A perennial wheat cropping system on the Palouse Prairie of eastern Washington may provide an alternative to the Federal Conservation Reserve Program and reduce soil erosion while providing a harvestable crop for growers. Twenty-four perennial wheat germ plasm lines resulting from crosses between wheat and wheatgrass were evaluated under controlled environment conditions for resistance to Wheat streak mosaic virus (WSMV), Cephalosporium gramineum, and Tapesia yallundae (anamorph Pseudocercosporella herpotrichoides var. herpotrichoides). Perennial wheat lines SS452, SS103, SS237, MT-2, and PI 550713 were resistant to all three pathogens. Eight lines (33%) were resistant to WSMV at 21°C and 25°C; AT3425 was resistant to WSMV at 21°C but not at 25°C. Thirteen lines (54%) were highly to moderately resistant to C. gramineum. Thirteen lines (54%) were resistant to T. yallundae in each experiment, but the reactions of four lines differed between experiments. The wheatgrasses Thinopyrum intermedium (PI 264770) and Thinopyrum ponticum (PI 206624) are reported as new sources of resistance to T. yallundae. Perennial wheat must have resistance to these diseases in order to be feasible as a crop in the Pacific Northwest.

Resistance to stripe rust and eyespot diseases of wheat in Triticum tauschii

A collection of 279 Triticum tauschii (syn. Aegilops squarrosa) accessions was evaluated for resistance to stripe rust (Puccinia striiformis) and eyespot (Pseudocercosporella herpotrichoides) diseases. Seedlings were inoculated with four different races of P. striiformis that represent all known virulences in the Pacific Northwest, and a genetically modified strain of P herpotrichoides expressing β-glucuronidase. Seventeen percent (44) of the T. tauschii accessions were resistant to all Pacific Northwest races of stripe rust, and 45% (115) were resistant to eyespot. Thirty-nine of the 279 accessions were resistant to the stripe rust races and the eyespot pathogen. Accessions resistant to stripe rust were mainly from the Caspian Sea region of Iran and Azerbaijan, with the majority belonging to T tauschii subsp. strangulata and T. t. subsp. meyeri. There was no clear association between resistance to eyespot and geographical origin or taxonomic subgroup.

Identification of Resistance to Pseudocercosporella herpotrichoides in Triticum monococcum

Cadle, M. M., Murray, T. D., and Jones, S. S. 1997. Identification of resistance to Pseudocercosporella herpotrichoides in Triticum monococcum. Plant Dis. 81:1181-1186. Eyespot is an important disease of wheat in the United States Pacific Northwest. Genes Pch1, located on chromosome 7D, and Pch2, located on chromosome 7A, are the only known sources of eyespot resistance in hexaploid wheat. A core collection of Triticum monococcum, a close relative of the A-genome donor of bread wheat, consisting of 118 accessions from 26 countries was screened for resistance using a β-glucuronidase-transformed strain of the pathogen. Fiftytwo (44%) accessions from 15 different countries were resistant. More than half of the accessions collected in Turkey (26 of 42) were resistant. Two accessions were more resistant than resistant cultivars Cappelle Desprez (Pch2) and Madsen (Pch1). Screening these accessions for the isozyme marker Ep-A1b, which is linked with Pch2 in hexaploid wheat, revealed variation but no association with resistance. These results indicate T. monococcum is a new source of resistance to Pseudocercosporella herpotrichoides that potentially contains more effective resistance to P. herpotrichoides than that conferred by either Pch1 or Pch2.

Evaluation of Dasypyrum villosum Populations for Resistance to Cereal Eyespot and Stripe Rust Pathogens

Resistance to Pseudocercosporella herpotrichoides (cause of eyespot) and Puccinia striiformis(cause of stripe rust) was evaluated in a germ plasm collection of Dasypyrum villosum (syn. Haynaldia villosa) and a set of disomic addition lines, a substitution, and a translocation line of D. villosum chromosomes in a wheat background. Three races of P. striiformis and a β-glucuronidase-transformed strain of Pseudocercosporella herpotrichoides were used to inoculate plants and evaluate disease reactions. Of the 115 D. villosum accessions tested, 33 (28.6%) were resistant to one or more races of Puccinia striiformis and 8 accessions were resistant to all races. All 219 accessions of D. villosum tested were resistant to Pseudocercosporella herpotrichoides and 158 (72%) of the accessions had lower β-glucuronidase activity than the resistant wheat line VPM-1. Most of the accessions of D. villosum resistant to the stripe rust pathogen originated from Greece; however, there was no distinction among origins for resistance to the eyespot pathogen. Chromosome 4V was confirmed to carry the gene for resistance to P. herpotrichoides. At least one gene for resistance to Puccinia striiformis was located on the short arm of chromosome 6V of D. villosum in the 6VS/6AL-translocation line; this gene was named Yr26.

Nutritional and quality characteristics expressed in 31 perennial wheat breeding lines

Soil erosion due to annual cropping on highly erodible farmland is a major ecological concern in the wheat growing regions of Washington State. In response to requests from farmers, the winter wheat breeding program at Washington State University has been developing perennial wheat selected from crosses between wild wheatgrass species and commonly grown annual wheat cultivars. In 2005/06, we conducted field trials of the most promising perennial wheat breeding lines derived from interspecific crosses between tall wheatgrass ( Thinopyrum elongatum ) and bread wheat ( Triticum aestivum ). Thirty-one perennial breeding lines and two annual winter wheat cultivars were evaluated for nutritional value in the form of grain mineral concentration, multiple baking and milling quality traits, and ease of grain threshability. The objective of this study was to identify the strengths and weaknesses of these post-harvest traits in the perennial wheat lines derived from these interspecific crosses. Mineral nutrient concentrations in the perennial lines were 44, 40, 24, 23, 32, 30 and 33% higher than the annual control cultivars for calcium, copper, iron, magnesium, manganese, phosphorus and zinc, respectively. The annual cultivars had a higher grain mineral content per unit area of land than the perennial lines, due primarily to the higher grain yields of the annual cultivars. Compared to the annual wheat cultivars, the perennial lines produced grain with smaller seed size, lower test weight and reduced flour yield, mix time and loaf volume. Protein content was 3.5–4.5% higher in the perennial lines than in the annual cultivars. The threshability index (TI) ranged from 0.63 to 0.89 in the perennials (μ=0.75); significantly lower than the mean TI of the annual cultivars (μ=0.97). The significant genotype×location interaction found for TI suggests that the variation in annual precipitation positively influenced some perennial lines to express greater threshability. In addition to transferring traits important to the perennial growth habit in wheat, the wild wheatgrass species also introduced beneficial characteristics (i.e. increased protein and mineral concentration) and deleterious traits (poor threshing grain and inferior baking qualities). This research gives researchers a platform from which to direct further research and selection in the development of perennial wheat.