Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
(N/A)
Non Technical Summary
Insect pests cause significant profit loss for peanut growers and shellers in the Southeast, especially foliage feeding caterpillars (FFCs) and peanut burrower bug (PBB). The proposed project aims to identify novel sources of resistance to FFCs in peanut; introgress new or under-utilized sources of FFC resistance; and develop methods by which resistance to PBB can be reliably evaluated and quantified to begin screening material for resistance. Some work has been done to identify sources of FFC resistance in wild peanut species; little has been done to introgress them into commercial peanut cultivars. To date, several sources of resistance to fungi, viruses, and nematodes have been identified and introgressed into cultivated peanut from wild relatives. We seek to follow the same rationale for improving resistance to insects. Ultimately, our hope is to deploy resistance to insect pests into the commercial peanut market to strengthen profitability, reduce reliance on pesticides, and increase resilience of the southeastern farming communities that depend so heavily on peanut production.We propose to accomplish the following objectives:1. Screen peanut wild species, and wild species-derived lines to identify genotypes with high levels of resistance to FFCs that will serve as optimum targets for introgression of resistance.2. Screen previously-developed mapping populations and chromosome segment substitution lines to identify quantitative trait loci conferring resistance to FFCs.3. Develop a greenhouse or lab assay for measuring PBB damage in a reliable, quantifiable manner to facilitate improved genetic studies of resistance to PBB and begin screening germplasm for resistance.
Animal Health Component
40%
Research Effort Categories
Basic
30%
Applied
40%
Developmental
30%
Goals / Objectives
Insect pests cause significant profit loss for peanut growers and shellers in the Southeast, especially foliage feeding caterpillars (FFCs) and peanut burrower bug (PBB). The proposed project aims to identify novel sources of resistance to FFCs in peanut; introgress new or under-utilized sources of FFC resistance; and develop methods by which resistance to PBB can be reliably evaluated and quantified to begin screening material for resistance. Some work has been done to identify sources of FFC resistance in wild peanut species; little has been done to introgress them into commercial peanut cultivars. To date, several sources of resistance to fungi, viruses, and nematodes have been identified and introgressed into cultivated peanut from wild relatives. We seek to follow the same rationale for improving resistance to insects. Ultimately, our hope is to deploy resistance to insect pests into the commercial peanut market to strengthen profitability, reduce reliance on pesticides, and increase resilience of the southeastern farming communities that depend so heavily on peanut production.We propose to accomplish the following objectives:1. Screen peanut wild species, and wild species-derived lines to identify genotypes with high levels of resistance to FFCs that will serve as optimum targets for introgression of resistance.2. Screen previously-developed mapping populations and chromosome segment substitution lines to identify quantitative trait loci conferring resistance to FFCs.3. Develop a greenhouse or lab assay for measuring PBB damage in a reliable, quantifiable manner to facilitate improved genetic studies of resistance to PBB and begin screening germplasm for resistance.
Project Methods
Methods by Objective (abbreviated - see proposal for full methods)Screen peanut wild species, wild species-derived lines, and synthetic allotetraploids derived from wild species that are interfertile with cultivated peanut, to identify genotypes with the highest levels of resistance to FFC and begin introgression breeding effortsScreen previously developed recombinant inbred mapping populations to identify quantitative trait loci (QTL) conferring resistance to FFCs.Develop a greenhouse or lab assay for measuring PBB damage in a reliable, quantifiable manner to facilitate improved genetic studies of resistance to PBB.Objective 1. Screen peanut wild species, wild species-derived lines to identify genotypes with the highest levels of resistance to FFCs and that will serve as optimum targets for introgression of resistance.We will focus on previously developed introgression lines and synthetically derived wild species allotetraploids for resistance screening in Objective 1, some of which have been previously documented as having some resistance to FFCs. Germplasm lines that were previously developed with introgressed segments from A. cardenasii include GP-NC WS 7 though GP-NC WS 10 (Stalker et al., 2002), GP-NC WS 16, and GP-NC WS 17 (Tallury et al., 2013). Synthetic allotetraploids that have been developed within our lab (Table 1) will also be screened. Because many of these allotetraploids are not well-suited for production agriculture, in vitro studies such as this one are very effective. Additional introgression lines have been developed within our lab that include introgressed segments from A. ipaënsis, A duranensis, A stenosperma, A batizocoi, and A valida.Screening for resistance to FFCs will be done based on antibiosis, as demonstrated previously (Levinson et al., 2020). One neonate will be transferred onto the leaflets using a paint brush. At third instar onwards, tweezers will be used to manipulate the larvae and pupae. Petri dishes will be sealed with Parafilm to prevent escapes. Parameters to be recorded will include Larval survival; larval stage duration (the number of days from first-instar larva stage to pupal formation); pupal weight; pupal stage duration (the number of days from pupal development to adult emergence); % adult emergence. At least 20 replications will be done per genotype.Once genotypes with strong resistance are identified, more in-depth studies can be done to establish the mechanism of the resistance. For instance, studies on non-preference. Also, anatomical (such as leaf thickness, leaf hair or trichome density) and biochemical (eg. anthocyanins, phenols, and quinones) studies (War et al. 2012) can be carried out to better understand resistance. Several sources of resistance will need to be evaluated to ensure there are no unintended pleiotropic effects on critical traits like peanut flavor, seed composition, plant vigor, etc. We will begin making crosses and start the introgression breeding effort as soon as we begin identifying lines with strong resistance.Objective 2. Screen previously developed recombinant inbred mapping populations to identify QTL conferring resistance to FFCsUsing the same screening method in Objective 1, mapping populations and CSSLs that have been previously developed or are currently under development will also be evaluated for resistance to FFCs. As part of another research project, we have been developing several mapping populations derived from crossing elite A. hypogaea cultivars with A. magna x A. diogoi synthetic allotetraploids, which have several beneficial characteristics including resistance to some viruses. However, these populations could serve as valuable potential mapping populations if resistance is identified in the parents. Thus far, we have an F4 population derived by crossing A. hypogaea runner type peanut cultivar 'IAC 321' (Sempre Verde, Godoy et al., 2022) with synthetic tetraploid (A. magna / A. diogoi)4x; F1 hybrids derived from crossing elite cultivars Georgia-12Y and TifNV-HG with the allotetraploid, (A. magna / A. diogoi)**.Also previously developed in our lab is a group of CSSLs derived from crossing A. hypogaea with a synthetic allotetraploid, BatSten1 (Table 1), which combines wild species A. stenosperma and A. batizocoi (Bertioli et al., 2021). These 37 CCSL lines are comprised mostly of cultivated peanut genome, with small segments derived from the synthetic allotetraploid, in this case, BatSten1 (Fig. 5). If resistance is identified in any of these lines, it makes identification of the causal QTL region much easier due to the small segments of BatSten1 genome. These lines were selected so that the maximum amount of BatSten1 genome could be represented in as few CSSL lines as possible. If strong resistance is identified in these lines, the best genotypes will be used to begin the introgression breeding effort.Objective 3. Develop a greenhouse or lab assay for measuring PBB damage in a reliable, quantifiable manner to facilitate improved genetic studies of resistance to PBB.Screening for PBB susceptibility in the field is challenging due to the sporadic and unpredictable nature of infestations. A greenhouse-based screen utilizing PBB from a culture currently maintained at the UGA Peanut Entomology Laboratory would provide a reliable method for quantifying pest injury and facilitate improved genetic studies of resistance to PBB. The work described here is designed to develop a greenhouse-based screening protocol for PBB.Two peanut cultivars, one known to be susceptible to PBB such as Georgia-06G, and one that has shown marginal levels of resistance such as Georgia-12Y, will be grown in pots in the Peanut Entomology greenhouse at the UGA Tifton Campus. Plants will be direct-seeded and grown in a medium that consists of 50% field soil and 50% potting mix that has been steam treated to ensure that it is free of arthropods. Potted plants (20 per cultivar) will be placed individually in BugDorm insect rearing cages prior to seedling emergence. Third instar PBB nymphs (N= 20) from a culture maintained at UGA will be introduced to the soil in each cage at 100 days after planting. Cages will be monitored 2x each week for the presence of adult PBB. Following adult emergence, plants will be removed from the soil and all pods will be collected and evaluated for PBB injury. Injury will be determined by shelling each pod, removing the testa (seed coat) and visually examining each seed for feeding scars. Pods will be classified by physiological development stage, and the presence and severity (number of feeding scars) of PBB feeding injury will be quantified for each seed. We expect to see feeding injury on seed from caged plants that is characteristic of that observed in the field. We hope to identify measurable differences between the highly susceptible cultivar and the less-susceptible cultivar. This result would suggest that the described method can be used to screen peanut genotypes for susceptibility or resistance to PBB injury with a high level of precision.Once a suitable method is determined, screening wild and wild-derived germplasm will begin. If lines with strong resistance are identified, they will enter the crossing program to begin the introgression breeding effort.