Identification of Sweet Potato Germplasm Resistant to Pathotypically Distinct Isolates of Meloidogyne enterolobii from the Carolinas

Abstract

Meloidogyne enterolobii (syn. mayaguensis) is an emergent species of root-knot nematode that has become a serious threat to sweetpotato (Ipomoea batatas) production in the southeastern United States. The most popular sweetpotato cultivars grown in this region are highly susceptible to M. enterolobii. As a result, this pest has spread across most of the sweetpotato growing counties in the Carolinas, threatening the industry as well as other crops in the region. The development and release of new sweetpotato cultivars with resistance to M. enterolobii would help to manage and slow the spread of this pest. To support sweetpotato resistance breeding efforts, 93 accessions selected from the USDA germplasm collection and breeding programs in the United States were screened to identify 19 lines with strong resistance to M. enterolobii. The resistance in these accessions was tested against two M. enterolobii isolates that were collected from sweetpotato production fields in the Carolinas. These isolates were found to have distinct pathotypes, with galling and nematode reproduction differences observed on cotton as well as sweetpotato. This study is the first report of intraspecific pathotypic variation in M. enterolobii and identifies sweetpotato germplasm with resistance against both pathogenic variants of this nematode.

Virulence of Two Isolates of Meloidogyne enterolobii (Guava Root-Knot Nematode) from North Carolina on Cotton Lines Resistant to Southern Root-Knot Nematode (M. incognita) and Reniform Nematode (Rotylenchulus reniformis)

“…In the contiguous United States, M. enterolobii was first reported in Florida, being initially classified as M. mayaguensis, where it was morphologically and molecularly differentiated from other common Meloidogyne spp., e.g., M. incognita and M. arenaria (Brito et al, 2004). In the late 2010s, M. enterolobii was discovered in North and South Carolina, and Louisiana (Ye et al, 2013;Rutter et al, 2019;Philbrick et al 2020). Recently, M. enterolobii was intercepted in Louisiana on sweetpotato storage roots imported from North Carolina, confirming previous suspicions of a link between M. enterolobii spread and sweetpotato planting stock (Thiessen, 2018;Rezende et al, 2022).…”

“…Meloidogyne enterolobii is an emerging pathogen in the cotton production areas of the southeastern U.S. Reports from Brazil indicated that cotton varieties expressing resistance to southern RKN were susceptible to populations of M. enterolobii (Galbieri et al, 2020). Multiple isolates of M. enterolobii have been collected from the Carolinas and evaluated in greenhouse experiments for differences in virulence on a range of sweetpotato genotypes (Schwarz et al, 2020;Rutter et al, 2021). In this study, we evaluated two such isolates regarding their reproduction on cotton germplasm lines having strong resistance to southern RKN, mediated by qMi-C11 and qMi-C14, and/or RN, mediated by the Ren barb2 QTL.…”

“…Meloidogyne enterolobii isolate "NC.1" was received from Dr. William Rutter (USDA-ARS) and isolate "18-5126" from Dr. Eric Davis (North Carolina State University) under APHIS permit number P526P-19-02617. Details describing the isolation and characterization of these isolates can be found in Rutter et al (2021) and Schwarz et al (2021), respectively. A quarantine permit was obtained from the State of Mississippi Department of Agriculture and Commerce that allowed experiments to be conducted in growth chambers at our facility.…”

Genetic diversity, population structure, and selection of breeder germplasm subsets from the USDA sweetpotato (Ipomoea batatas) collection

“…An emerging concern within the United States is the highly virulent guava root-knot nematode ( Meloidogyne enterolobii ), which causes significant damage to a wide range of crops and has become a serious problem in the US sweetpotato industry ( Rutter et al., 2021 ). Although sources of resistance to this introduced nematode species have been identified ( Rutter et al., 2021 ; Schwarz et al., 2021 ), the most popular cultivars grown in the United States are highly susceptible. Identification and introduction of cultivars with resistance will be crucial in efforts to control this emerging pest of sweetpotato.…”

Sustainable sweetpotato production in the United States: Current status, challenges, and opportunities

“…However, these same RKN‐resistant cultivars are highly susceptible to M. enterolobii . Multiple resistant germplasms have been reported in the USDA‐GRIN collection (Rutter et al., 2021; Schwarz et al., 2021). However, no M. enterolobii ‐resistant cultivars have yet been released for the commercial market in the United States.…”