Management of Meloidogyne incognita with resistant genotypes in a sweet sorghum - sugar beet - cotton rotation

Authors: Davis, Richard; Harris-Shultz, Karen; Knoll, Joseph - Joe

Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: A crop rotation experiment was conducted in Tifton, GA to evaluate the effectiveness of resistant genotypes of sweet sorghum, sugar beet (SB), and cotton for suppression of Meloidogyne incognita when those crops were grown in that order. Sorghum treatments were a nematode-susceptible and a resistant genotype; sugar beet and cotton treatments were a resistant genotype, a susceptible genotype, and the susceptible genotype plus fumigant nematicide. Sorghum was planted in June 2016, and nematode levels were barely detectable at planting. At harvest (August 2016), nematode levels were greater under the susceptible than the resistant genotype. SB was planted (October 2016) in a 3×2 factorial arrangement of treatments (3 SB treatments and the 2 previous sorghum treatments). SB galling was greater following susceptible sorghum. Fumigation decreased galling in susceptible SB, but the lowest galling was on resistant SB. The previous sorghum treatment had less effect on galling on resistant SB than on susceptible SB regardless of fumigation (a sorghum × SB interaction). Nematode samples from SB at harvest in May 2017 were consistent with the levels of galling observed. Fumigation of susceptible SB increased sugar content (°Brix), but the previous sorghum treatment had no effect. Cotton was planted in early June 2017 in a 3×3×2 factorial arrangement of treatments (3 cotton treatments, the 3 previous SB treatments, and the 2 previous sorghum treatments). Neither the previous sorghum treatment nor SB treatment affected cotton root galling at harvest. Susceptible cotton had the greatest galling, susceptible cotton with fumigation was intermediate, and resistant cotton had the least. Nematode samples at harvest were generally consistent with observed levels of galling on cotton, although previous sorghum treatment, which did not affect galling, may have affected nematode counts (P = 0.0601). Cotton yield following resistant SB was greater than following susceptible SB regardless of fumigation, and fumigated susceptible cotton had the greatest yield. In general, fumigation and resistance were both effective in reducing galling and final nematode levels for each crop and significantly contributed to reducing galling and nematode levels in the subsequent crop. Although the effects of fumigation and resistance in sorghum were apparent in the SB crop, they were not apparent in the cotton crop.