Adrienne Gorny

Award will fund 6 individual projects related to Guava Root-Knot Nematode: a)Renovation of Method Road Nematology Laboratory and Greenhouse Range facilities for work with the Guava Root-Knot Nematode (Meloidogyne enterolobii) b)Research Towards a Rapid, Species-specific, Field Deployable Test for GRKN and Advancement of Molecular Diagnostics for Soil and Sweetpotato Samples c)Evaluating Integrated Use of Fumigants, Nematicides, and Rotational Crops for Management of GRKN in Sweetpotato in the Field, Storage, and Pack House d)On-Farm Crop Rotation and Cover Crop Evaluations, and Sweetpotato Clone Evaluations to Manage Guava Root-Knot Nematode d)Breeding Resistance to GRKN and SRKN into a New Generation of High Quality, Marketable Sweetpotato Cultivars for NC Growers e)Guava Root-Knot Nematode: A County Operations Action Plan

This project will develop integrated strategies to address trade barriers for export sweetpotatoes in the United States.

We propose to deploy genomic and phenomic tools as an integrated approach for the development of superior sweetpotato varieties with robust resistance to M. enterolobii and M. incognita, and high storage root yield, shape and quality attributes that command a high market value. Beyond identifying the genetic components underpinning these traits, a breeding approach that accounts for the complex genetics of polyploidy (e.g. allele dose-dependent phenotypes) will be designed for combining multiple desirable traits in a single genetic background (i.e. multi-trait selection). This is particularly important in sweetpotato where a single important trait can break an otherwise remarkable variety. Resistance to GRKN and SRKNwill be studied within the context of a holistic nematode management strategy that maximizes economic and farm sustainability

Meloidogyne enterolobii (syn. M. mayaguensis), commonly known as the Guava Root Knot Nematode (GRKN), is a newly introduced root-knot nematode (RKN) that is highly virulent against widely-used RKN resistant crop varieties. M. enterolobii has been reported in Florida, North Carolina, South Carolina and Louisiana. In North Carolina, it has been detected in fields in Columbus, Johnston, Wayne and Wilson counties. These counties are located in the sweetpotato growing belt in North Carolina and significant damage to sweetpotato production can be caused by GRKN. Resistant sweetpotato varieties need to be developed to help NC sweetpotato growers to win the battle against M. enterolobii. In this research project, we are going to: 1) develop an efficient screening protocol for selection of GRKN-resistant sweetpotato clones from breeding populations; 2) conduct studies to identify DNA markers for M. enterolobii resistance in sweetpotato by screening a genetic mapping population from Tanzania x Beauregard with known resistance to GRKN derive from the African land race cultivar Tanzania; 3) initiate preliminary work to establish DNA marker-assisted selection for GRKN-resistant sweetpotato clones.

Meloidogyne enterolobii (syn. M. mayaguensis), commonly known as the Guava Root Knot Nematode (GRKN), is a newly introduced root-knot nematode (RKN) that is highly virulent against widely-used RKN resistant crop varieties. M. enterolobii has been reported in Florida, North Carolina, South Carolina and Louisiana. In North Carolina, it has been detected in fields in Columbus, Johnston, Wayne and Wilson counties. These counties are located in the sweetpotato growing belt in North Carolina and significant damage to sweetpotato production can be caused by GRKN. Resistant sweetpotato varieties need to be developed to help NC sweetpotato growers to win the battle against M. enterolobii. In this research project, we are going to: 1) develop an efficient screening protocol for selection of GRKN-resistant sweetpotato clones from breeding populations; 2) conduct studies to identify DNA markers for M. enterolobii resistance in sweetpotato by screening a genetic mapping population from Tanzania x Beauregard with known resistance to GRKN derive from the African land race cultivar Tanzania; 3) initiate preliminary work to establish DNA marker-assisted selection for GRKN-resistant sweetpotato clones.

Plant-parasitic nematodes are reported to cause 12.3% annual crop losses worldwide, resulting in economic losses worth $157 billion (USD). Among these soil-borne pests, root-knot nematodes (RKN) are considered the most devastating due to their world-wide distribution, broad host range, and high potential to cause extensive qualitative and quantitative crop loss. Cotton annual yield losses worth nearly $74 million (USD) is attributed to RKN damage, in the U.S. alone. To mitigate the losses caused by these nematodes, especially southern root-knot nematodes (Meloidogyne incognita), host resistance has been bred into several varieties of major agricultural crops, including cotton. However, an aggressive species of RKN, guava root-knot nematode (M. enterolobii), can overcome the host resistance and cause serious damage to the M. incognita-resistant varieties of several crops. Since its first detection in the U.S. in 2001 in Florida, this nematode has spread at an alarming rate and has now been identified in North Carolina, South Carolina, Florida, and Georgia. Compounding the problem further, M. enterolobii has an exceptionally wide host range, including cotton and its common rotational crops The objectives of this research are to: 1. Evaluate the susceptibility of 30 cotton commercial varieties and breeding lines, differing in genetic background and/or susceptibility to RKN, against isolates of M. enterolobii from Georgia, North Carolina, and South Carolina, and an isolate of M. floridensis from Georgia under greenhouse conditions. 2. Evaluate ten cotton varieties and breeding lines differing in their susceptibility to M. eneterolobii under field conditions at the Guava Root-knot Nematode Research Nursery field at the Border Belt Tobacco Research Station in Whiteville, NC.

The general objectives are to search for the presence of GRKN in the southeast United States (the Carolinas, Florida, Georgia), to screen accessions of cucurbit (cucumber and watermelon), pepper and sweetpotato germplasm for resistance, and to demonstrate that GRKN can be managed and contained efficiently and effectively.

The NC SweetPotato Commission Foundation will mitigate the spread of Guava Root-Knot Nematode (GRKN) in packing facilities through a three-fold approach. In cooperation with NC State University, nematode specialist Adrienne Gorny will develop a rapid-response test to identify the presence of GRKN in sweetpotatoes prior to their being packed or stored for later shipment. Second, the project will support the identification and development of best practices to be used at the packing house to reduce the inadvertent transmission of GRKN and to prevent shipping infested product that can result in North Carolina Sweetpotato growers losing market share. Third, we will work with a maximum of six packing houses who agree to be part of a pilot project to determine both the cost effectiveness and the reduction of nematode population as a result of gassing storage facilities prior to moving sweetpotatoes to the packing line for preparation for shipping. Our end goals are to (a) make it easier and more cost effective to identify the presence of the nematode in harvested crop; (b) raise packer awareness of actions they may be inadvertently taking that unknowingly spreads GRKN in fields; and (c) identify additional tools that packers can use to protect the integrity of stored sweetpotatoes.

Guava Root Knot nematode (GRKN) is a pest that poses severe threat to NC agriculture, particularly to the sweet potato industry. Many of our crops are host species to this nematode and solutions are needed to mitigate the incidence and spread of GRKN. Preliminary work by this research group has shown some sesame varieties are resistant or tolerant to GRKN. We propose to study sesame as a rotational alternative to other summer crops in order to reduce GRKN populations and keep sweet potato land in North Carolina productive.

Plant-parasitic nematodes pose a significant limitation to corn production in North Carolina and the Southeastern United States. Several genera of plant-parasitic nematode are yield limiting pathogens of corn, including Southern root-knot (Meloidogyne incognita), stubby-root (Trichodorus and Paratrichodorus spp.), stunt (Tylenchorhynchus spp.), sting (Belonolaimus spp.), and lesion nematodes (Pratylenchus spp.). Management options for plant-parasitic nematodes include crop rotation, cultural practices, and chemical control. However, chemical control options in corn are limited due to the costs of application and the limited economic return with their application. Genetic resistance of the crop to infection by the nematode is the most effective, robust, and economical management tool. However, no genetic host resistance is known or commercially available to these nematodes in maize, which means many corn hybrids commonly grown are susceptible to infection by these nematodes. Therefore, identification and study of naturally occurring genetic resistance is important to support resistance breeding effort and economical corn production across the state. In order to support the longer-term goal of resistance breeding efforts in corn to soilborne nematodes, generating more data on the response of diverse corn lines with diverse genetic makeup is imperative to better understand and characterize the possible sources of resistance available to plant breeders. We propose evaluating corn lines for response to the Southern root-knot nematode (Meloidogyne incognita race 3). The Southern root-knot nematode is endemic and widespread across the Coastal Plains region of North Carolina, and it may rob yields in corn across the state. In the short term, the immediate findings will be used to enhance current nematode management recommendations, with the goal of supporting profitable corn production in North Carolina.