Host Suitability and Yield Response of Three Cotton Varieties to Meloidogyne incognita
Feb 11, 2019

WCRC WCRC2 Breeding

ABSTRACT
One susceptible (Deltapine 90) and two resistant (LA 887 and NemX) cultivars were evaluated in field microplots for host suitability and yield loss to an isolate of Meloidogyne incognita. Five replications of seven initial population densities (Pi) of M. incognita (0, 0.5, 1, 10, 50, 100, 500 eggs/500 cm3soil) were established for each cultivar in the 1997 growing season in South Carolina. Deltapine 90 was an excellent host for M. incognita. Severity of galling (G) and reproduction, as measured by the final larvae population density of juveniles in the soil (Pf), responded in a positive linear manner to Pi as predicted by the models G = 1.28 log 10 (Pi + 1) - 0.278, (r 2 = 0.82) and Pf = 822.5 log 10 (Pi + 1) - 253.3, (r 2 = 0.61). NemX and LA 887 were both poor hosts. Severity of galling and Pf for these two varieties responded in a positive linear manner to Pi and could be predicted by the following models: G = 0.239 log 10 (Pi + 1) - 0.013, (r 2 = 0.27) and Pf = 111.78 log 10 (Pi + 1) - 4.80, (r 2 = 0.05) for NemX; G = 0.34 log 10 (Pi + 1) - 0.186, ( r 2 = 0.39) and Pf = 42.62 log 10 (Pi + 1) - 3.51, (r 2 = 0.25) for LA 887. Yield response of the cultivars to Pi did not fit a linear model. In a similar experiment utilizing the same Pi’s, greater yield suppression of DP 90 was observed. The negative linear relationship between Pi and yield fit the model y = - 9.30 log 10 (Pi + 1) + 60.05, (r 2 = 0.13). Generally, LA 887 yielded the highest across Pi’s and had smaller Pf’s at harvest.


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