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ARS Home » Pacific West Area » Pullman, Washington » Grain Legume Genetics Physiology Research » Research » Research Project #423174

Research Project: Genetic Improvement of Cool Season Food Legumes

Location: Grain Legume Genetics Physiology Research

2014 Annual Report


Objectives
In the United States, pea, lentils and chickpeas are grown primarily in the Pacific Northwest and Northern Plains. Over the past five crop seasons (2007-2012), these crops have been grown on an average of 1,260,000 acres in the US with an average harvest value of over $320 million. These crops also contribute to the success of the US wheat and barley industry by serving as useful rotation crops in small grain production systems. This research project has three objectives that focus on developing new and improved varieties of cool season food legumes (peas, lentils, and chickpeas) and effective integrated disease control strategies for these crops. 1) Develop and release new varieties and germplasm of peas, lentils, and chickpea that have higher seed mineral concentrations; improved host-plant resistance to Aphanomyces root rot, Sclerotinia wilt and Ascochyta blight; and higher yields than existing commercial varieties. 2) Identify genetic markers closely associated with superior yield, optimal plant height for harvest, seed mineral concentration, resistance to Aphanomyces root rot, and improved cold tolerance for autumn-sown peas, and validate their utility for marker-assisted plant breeding. Sub-objective 2A: Identify molecular markers in adapted pea populations that are associated with important traits including concentrations of minerals in seed, resistance to Aphanomyces root rot, and winter hardiness. Sub-objective 2B: Identify molecular markers in adapted chickpea populations that are associated with seed size and early maturity. 3) Develop efficient techniques to screen peas, lentils, and chickpeas for host-plant resistance to Ascochyta blight and Sclerotinia wilt, and characterize genetic and physiological factors responsible for the virulence of these pathogens. Sub-objective 3A: Develop efficient techniques to screen peas, lentils and chickpeas for resistance to Ascochyta blight and Sclerotinia white mold. Sub-objective 3B: Determine genetic factors responsible for pathogenicity of Sclerotinia sclerotiorum using a variety of genetic and genomic tools. Sub-objective 3C: Determine the role of solanapyrone phytotoxins produced by A. rabiei during the development of Ascochyta blight disease in chickpea. This research will result in several products, including new varieties of peas, lentils, and chickpeas along with improved methods for controlling diseases of these crops.


Approach
New varieties and germplasm will be developed from pure lines selected from among segregating populations of peas, lentils, and chickpeas. Cyclical hybridization will be conducted to combine favorable alleles for traits of interest. Parental lines will include adapted germplasm, commercial cultivars and accessions from the various international breeding programs. Promising breeding lines will be released as either germplasm or varieties based on a rigorous comparison of their performance relative to that of commercial check varieties. Linkage analysis and the detection of associations between markers and different traits will be done using simple sequence repeats (SSRs), expressed sequence tagged- SSRs, and single nucleotide polymorphisms (SNPs). Pea recombinant inbred line (RIL) populations will be developed from a cross between Aragorn and Kiflica to identify markers associated with seed mineral concentrations. RILs from a cross between the pea cultivars Medora and Melrose will be used to identify markers associated with cold tolerance. Molecular markers associated with seed size and early maturity in chickpea will be detected using a RIL population developed from an interspecific cross between C. arientinum line Flip 90-27 and PI599072 (C. reticulatum). Associations between markers and quantitative trait loci (QTL) conditioning traits of interest will be detected by composite interval mapping. Improved methods will be developed to screen chickpea for reaction to Ascochyta blight. Toxins will be purified from liquid cultures of A. rabiei. Toxins will be adjusted to various concentrations and applied to detached chickpea leaflets. Leaflets treated with water will be used as controls. The speed of lesion development and final lesion size will be used to compare the reactions of different chickpea genotypes. The relationship between field disease scores of the chickpea genotypes and their sensitivity to the toxin will be determined. Studies to develop more efficient methods to screen peas and lentils for reaction to Sclerotinia white mold will initially examine resistant and susceptible materials reported in prior studies. Plants will be grown in the greenhouse and inoculated with agar plugs containing mycelia of S. sclerotiorum. Disease reaction will be scored by measuring the length of the lesion produced by the fungus over different time points. Two approaches will be taken to investigate the genetic factors responsible for pathogenicity and virulence of S. sclerotiorum. One approach will be to use Agrobacterium mediated transformation (AMT) to generate random mutations that will be screened to detect mutants with reduced virulence. The other approach will be to identify genes of S. sclerotiorum that are differentially expressed during the processes of infection and disease development.


Progress Report
This research project is focused on developing improved germplasms and varieties of peas, lentils, and chickpeas that are adapted to existing and emerging areas of production in the U.S., advancing basic knowledge on plant-pathogen interactions, and improving methods to control diseases of these crops. These areas of research are addressed through a combinatorial approach that includes plant breeding and genetics, plant pathology, and molecular biology. Advanced yield trials for peas, lentils, and chickpeas are in progress at several locations in Washington and Idaho. Breeding lines, commercial varieties, and populations are also being evaluated in field nurseries for reaction to several diseases including Ascochyta blight, Fusarium wilt, and Aphanomyces root rot. Seed supplies are being increased for several promising lines from the ARS breeding program. A spring green pea breeding line, PS05100736, is being evaluated for the fifth year in 2014. PS05100736 has consistently had top yields in the USDA-ARS trials and the Washington State Variety Trials, the Idaho State Variety Trials and the Western Regional Trials. The line, which is resistant to both Pea Enation Mosaic Virus (PEMV) and Bean Leaf Roll Virus (BLRV), has been provisionally named ‘Hampton’. Approximately 200 lbs of breeder seed of Hampton was sent to New Zealand in October of 2013, for foundation seed increase, resulting in over 5 tons of seed. Among the ARS lentil breeding lines, there is a large lentil (line designation LC01602300R) that is especially promising. The line has been provisionally named ‘Avondale’ and is broadly adapted to the Palouse region of Idaho and Washington and to NE Montana. Avondale is highly resistant to Stemphylium Blight, a serious disease in Montana. It is slightly taller (38.7cm) at harvest than ‘Richlea’ (37.4cm), a popular large lentil variety, and is similar to Richlea in the time it needs to mature. One especially important advantage Avondale has over Richlea is that it produces larger seed than Richlea. Foundation seed was produced near Pullman in 2013 and a second increase of foundation seed was sent to New Zealand in October 2013, which resulted in over 3 tons of seed. An application for a Plant Variety Protection (PVP) Certificate was submitted in October of 2013. Foundation seed of two new chickpea varieties are being produced in 2014 in Idaho. These two varieties have been provisionally named ‘Royal’ and ‘Nash’. Both varieties consistently produce higher yields and larger seed than Sierra. Applications for Plant Variety Protection Certificates for both of these varieties were submitted in June, 2014. Several ARS chickpea breeding lines appear to be promising candidates for future release as improved germplasm or new cultivars. During 2013, we produced breeder seed for the first time of three lines, CA0790B0042C, CA0790B0043C, and CA0790B0549C, which have average yields over the past four years that are more than 15% greater than Sierra, the most popular chickpea variety in the U.S. A second increase of breeder seed of CA0790B0043C and CA0790B0549C is currently being performed in Pullman, Washington. Efforts continued in improving the nutritional qualities of chickpeas. The seed concentrations of six saturated fatty acids and three non-saturated fatty acids were determined for six chickpea varieties and 22 ARS chickpea breeding lines. Several ARS breeding lines were identified that had high levels of the nutritionally beneficial fatty acids linoleic acid and linolenic acid. These results, in conjunction with our previous efforts to identify chickpeas that have high seed concentrations of several minerals, are assisting us in deciding what chickpeas can be used as parents to develop new varieties that have both improved agronomic traits, such as yield and seed size, coupled to enhanced nutritional characteristics. The ability of legumes to produce their own nitrogen fertilizer through interactions with beneficial bacteria is one of the primary factors that make legumes very desirable crops for use in rotations with small cereal grains including wheat and barley. Considerable progress has been made in examining how these beneficial bacteria interact with plant pathogens, which cause diseases, in peas and chickpeas. Greenhouse procedures were developed so that peas could be inoculated with both beneficial bacteria (Rhizobium leguminosarum) and a fungus (Aphanomyces euteiches) that causes root rot disease. A distinct procedure was also developed in the greenhouse to inoculate chickpeas with both beneficial bacteria (Mesorhizobium ciceri) and a different fungus (Fusarium oxysporum) that causes root rot disease of chickpea. We have observed in both peas and chickpeas that when disease is present, plants that have disease resistance are more capable of supporting colonization by the beneficial bacteria than plants that are susceptible to disease. These results highlight the need to continue our focus on improving disease resistance in legumes in order to insure that legumes can continue to contribute to the sustainability of small grain cropping systems. Chickpea growers typically treat their seed before planting with the fungicide Metalaxyl in order to get protection from disease. During the 2014 growing season, we visited several fields where chickpeas appeared to be suffering from a disease. From these fields we consistently isolated a disease causing fungus (Pythium ultimum) that was resistant to the fungicide Metalaxyl. The discovery of strains of the fungus with resistance to fungicide suggests that this common method of disease control may not remain effective, and has led us to begin a program where we will screen chickpeas for resistance to root rot diseases caused by Pythium.


Accomplishments
1. Release of ‘Avondale’ lentil. The Grain Legume Genetics and Physiology Research Unit, located in Pullman, Washington, released the medium green, market class lentil ‘Avondale’ (Experimental designation LC01302300R). In the U.S., lentils are grown primarily in Montana, North Dakota, Washington and Idaho and are an important rotational crop in dryland, cereal-based cropping systems. Avondale is especially adapted to the northeastern corner of Montana, where it was tested for four years and had an average yield of 1632 kg/ha compared to 1549 kg/ha for CDC Richlea. Avondale is resistant to Stemphylium Blight, an important foliar fungal pathogen in Montana, and will provide growers in Northeast Montana a new, high yielding, disease resistant variety that will confer economic and rotational benefits to their production systems. The Washington State Crop Improvement Association has applied to license Avondale and is producing Foundation and Registered seed in 2014.

2. Solanapyrone toxins are not essential for pathogenicity in Ascochyta blight. The fungal pathogen Ascochyta rabiei causes chickpea blight and produces toxins called ‘solanopyrones’ in culture. Although these toxins were considered to be important in causing disease, their roles in the creation of disease have never been confirmed. ARS scientists at the Grain Legume Genetic and Physiology Research Unit located in Pullman, Washington, produced mutants of the fungus that could not make these toxins. They observed that the mutants caused disease as well as the non-mutant fungus, which indicated that the toxins are not essential in causing Ascochyta blight. This knowledge will assist researchers that are trying to identify what factors in the fungus are responsible for causing chickpea blight.


Review Publications
Saha, G.C., Vandemark, G.J. 2013. Stability of expression of reference genes among different lentil (Lens culinaris) genotypes subjected to cold stress, white mold disease, and Aphanomyces root rot. Plant Molecular Biology Reporter. 31:1109-1115.
Vandemark, G.J., Brick, M., Osorno, J., Kelly, J., Urrea, C. 2014. Edible grain legumes. In: Smith, S., Diers, B., Specht, J., and Carver, B., editors. Yield gains in major U.S. food crops. Madison, WI:CSSA Press. p. 87-123.