Progress 05/01/07 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) To determine whether factors exudated by potato roots can be identified and used to assist in the control of potato cyst nematode. Approach (from AD-416) Hydroponic potato root exudate will be fractionated, purified by HPLC and analyzed with an ion trap mass spectromter. Documents Reimbursable with APHIS. Log 33763. Solanum sisymbriifolium was evaluated for potential use as a trap crop to aid eradication. Plantlets were made in tissue culture & grown in the greenhouse. Plants were also planted in the field near Parma, ID to evaluate how the plant performed under typical Idaho field conditions. A greenhouse study is currently underway to establish whether two accessions of Solanum sisymbriifolium are immune to the Idaho potato cyst nematode (PCN) population. Approximately 50 plants have been transplanted from tissue culture into pots in the greenhouse & inoculated with 10 cysts per pot. Root exudate from various other crops/plants was tested for hatching activity to determine whether other plants might be potential trap crops. No hatching activity was found in any non- Solanaceous plant examined. Efforts continue to try to purify hatching factors from root exudates & hydroponics were used to generate large amounts of exudate for analysis that are free from confounding factors contributed by the soil or microbes. Eradicating the PCN population in Idaho will require depriving the nematode of its plant hosts over a protracted time period of as long as 30 years. The presence of host weeds of G. pallida can play a significant role in success or failure of the eradication program. Nine weed plant species, one tomato, & three potato varieties were planted in 4-inch clay pots containing sandy loam soil (80% sand, 15% silt, 5% clay, & < 0.5% organic matter), previously fumigated with methyl bromide (Prosser greenhouse soil), & inoculated with 40 cysts that were collected from infested fields in Idaho. Plant species were replicated five times, & randomly placed on greenhouse benches. The trial lasted 3 months, after which cysts were extracted from soil using a Fenwick can. The number of cysts extracted from different replications of each test plant was variable. The cysts that were introduced around the root system of plants were not encased in sachets, & therefore some or all of the recovered cysts could be the original cysts that were introduced. However, those from hairy nightshade (Idaho biotype) & Russet Burbank potato were high enough (> 40) to indicate that they were suitable hosts of Idaho Globodera pallida. The number of cysts on Desiree (known host of G. pallida), & cutleaf nightshades (Idaho & Wash. biotypes) were higher than Sant� potato (known non-host to G. pallida), suggesting that the two cutleaf nightshades may also serve as hosts in the infested fields. In general, due to variability of nematode reproduction, the negative host status of any plant should be verified through further experimentation. Another study is currently underway evaluating the host status of 12 weed species using greenhouse derived cysts for inoculum. Cyst harvest will occur in early September. This project supports objective 1: Identify superior germplasm for potato disease & pest-resistance, phytonutrients, minerals, & determine the extent of natural variation in diverse potato germplasm of select phytonutrients/metabolites & objective 3:Elucidate genetic, molecular & biochemical factors governing host disease resistance. Progress was monitored by phone, email & meetings.
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) To determine whether factors exudated by potato roots can be identified and used to assist in the control of potato cyst nematode. Approach (from AD-416) Hydroponic potato root exudate will be fractionated, purified by HPLC and analyzed with an ion trap mass spectromter. Documents Reimbursable with APHIS. Log 33763. Significant Activities that Support Special Target Populations We are pursuing two different approaches, one which seeks to use hatching factors whether pure or crude, and the other which attempts to identify trap crops. We established that the field cysts are not suitable for our studies because results with them are too variable. However, fresh greenhouse cysts are extremely limiting, so we developed hatching assays that use much smaller amounts of cysts than traditional assays. Given the limitation of cysts, we decided to focus on screening for potential trap crop candidates largely outside of the Solanum family. Out of 40 trap crops evaluated in this study, hatching activity was not evident in lupine, chenopodium or rye. Solanum. sisymbriifolium and eggplant were the only two potential trap crops that had significant hatching. We have also begun fractionation studies of root exudate using a C18 RP HPLC column. Fractions have been identified with activity and we can already exclude about 60% of the compounds found in potato root exudates from being hatching factor candidates. The growth solution from hydroponically grown potatoes has hatching activity and is a potential large scale source of HFs. Interestingly, processing plant waste has not yet shown activity. If this result holds up, it is interesting because there are numerous shared compounds between processing plant effluent and root diffusate. In this case it would help us further narrow the pool of potential hatching factors. We have also generated MS profiles from root exudates from numerous plants, some of which have hatching activity and some of which do not. This type of approach is anticipated to greatly help in narrowing down the list of potential HF candidates. Progress on this project was monitored by the ADODR via numerous conference calls, on- site visits, emails, and a national research review held twice, once at Prosser and once in Portland.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) To determine whether factors exudated by potato roots can be identified and used to assist in the control of potato cyst nematode. Approach (from AD-416) Hydroponic potato root exudate will be fractionated, purified by HPLC and analyzed with an ion trap mass spectromter. Documents Reimbursable with APHIS. Log 33763. Significant Activities that Support Special Target Populations The group has initiated some experiments and begun preparation for others. A limiting factor for most of the groups currently is the wait for new generation Potato Cyst Nematode (PCN) cysts, as the cysts from the field are not suitable for most of our research goals. Thus, obtaining new generation cysts by the Idaho group is where most of the emphasis has been up to this point. Cysts from the infestations done with the juveniles produced from the first shipment of cysts (about 600) from APHIS have been harvested and placed at low temperature to overcome diapause. We anticipate these cysts can be used for experiments starting in fall, 2008. A large shipment of approximately 27,000 additional cysts was received in 2008 and more extensive hatching studies have been initiated to optimize the production of J2 nematodes (comparing root diffusates from various sources, diffusate concentrations, etc.) and to start studies on potential weed hosts for PCN. As for finding ways to cause cysts to hatch, we have found at least some activity from the effluent from potato processing plants, of which each plant generates 10s of millions of gallons per year. We are also in the process of testing the solutions that hydroponic potatoes are grown in for hatching activity. Only potatoes and a few closely related Solanaceous plants secrete PCN hatching factors. We are evaluating compounds found in exudates and have some indications of what classes of compounds are unique to potato and are thus potential candidates to be examined as hatching factors. Plant material is being gathered that will be tested for use as a trap crop that can induce essentially a suicide hatch and not allow any reproduction. Weed trials are underway to test whether any of the weeds found in Idaho are potential hosts. The bulk of activity on this grant will commence once new generation cysts are available.
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