Screening cotton cultivars for resistance to Meloidogyne incognita and Fusarium oxysporum f. sp. vasinfectum race 1 and 2 in the Southern High Plains of Texas

Date

2022-05

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Abstract

Fusarium wilt is caused by the interaction between Meloidogyne incognita (the southern root-knot nematode, SRKN) and Fusarium oxysporum f. sp. vasinfectum (Fov) races 1 and 2. Traditionally, Fusarium wilt in cotton was managed by chemical control of SRKN or using partially SRKN resistant cultivars. However, while SRKN resistance genes have been identified, Fov resistance remains understudied. Thus, this project seeks to evaluate cultivars for resistance to Fusarium wilt. A total of 84 cotton cultivars were screened in the Southern High Plains region of Texas in O’Donnell, Seminole, Turkey, and Whiteface in 2019 and 2020 (5 trials total) to evaluate resistance to Fov and SRKN. Stand loss percentage (mortality), SRKN population densities, and lint yield (kg/ha) were evaluated for cultivars. Four greenhouse trials were also conducted in 2020 and 2021 where cultivars infested with SRKN and Fov were evaluated with the Area Under the Disease Progress Curve (AUDPC), root necrosis percent, and stem necrosis percent. Overall, cultivars with at least partial SRKN resistance had lower nematode populations; however, SRKN resistance alone did not always result in lower plant mortality compared to cultivars with no SRKN resistance. Highly SRKN resistant cultivars PHY 480 W3FE and DP 1747NR B2XF consistently had similar disease ratings with SRKN susceptible cultivars and higher disease ratings than cultivars from BASF with partial SRKN resistance. This demonstrated that SRKN resistance alone is not sufficient to manage Fusarium wilt disease. ST 4946GLB2, a cultivar whose heritage can be traced back to LA 887, which carries partial resistance to both SRKN and Fov, consistently had the lowest disease ratings in all four greenhouse trials. In addition, DNA extraction and sequencing were performed at each location to identify the Fov race present in the field. In 2019, Fov race 1 was present in O’Donnell and Turkey, while Fov race 2 was present in Seminole. In 2020, Fov race 1 was present in Turkey, while Whiteface had both races 1 and 2. These results indicate that both races are present in the region and can be found within the same field.

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Keywords

Disease Management, Fusarium Wilt, Southern Root-Knot Nematode

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