Late Leaf Spot Severity and Yield of New Peanut Breeding Lines and Cultivars Grown Without Fungicides

Abstract

Peanut (Arachis hypogaea) cultivars with resistance or tolerance to Cercospora arachidicola and/or Cercosporidium personatum, the causes of early and late leaf spot, respectively, are needed for organic production in the southeastern U.S. To determine the potential of new breeding lines for use in such production systems, field experiments were conducted in Tifton, GA, in 2014 and 2015 in which nine breeding lines and two cultivars, Georgia-06G and Georgia-12Y, were grown without foliar fungicide applications. In one set of trials, cultivar Georgia-12Y and most of the breeding lines evaluated had early season vigor ratings, early-season canopy width measurements, final plant populations, and pod yield that were greater than those of standard cultivar Georgia-06G. In those trials, final late leaf spot Florida scale ratings were lower and canopy reflectance measured as the normalized difference vegetation index (NDVI), was higher all the breeding lines than those of Georgia-06G. In another set of trials, two of those same breeding lines had final late leaf spot ratings similar to those of Georgia-12Y in 2014, whereas in 2015, six of those breeding lines had final leaf spot ratings that were lower than those of Georgia-12Y. Yields were similar for Georgia-12Y and all the breeding lines in the Gibbs Farm trials. Across years and breeding lines at the Lang Farm, the relationship between visual estimates of defoliation and NDVI was described by a two sector piecewise regression with NDVI decreasing more rapidly with increasing defoliation above approximately 89%. The utility of NDVI for spot comparisons among breeding lines appears to be limited to situations where there are differences in defoliation. Georgia-12Y and multiple breeding lines evaluated show potential for use in situations such as organic production where acceptable fungicides available for seed treatment and leaf spot control are limited.

Late Leaf Spot Defoliation, Microclimate Modification, and Southern Stem Rot Development in Peanut (Arachis hypogaea L.) in South Carolina

“…Georgia-06G, Georgia-12Y, and Georgia-13M, on the other hand, have an intermediate runner decumbent growth habit (Branch, 2007). Moreover, a cultivar such as Georgia-12Y has been frequently reported to have rapid canopy closure compared to other Runner type peanuts (Jordan et al, 2017;Jordan et al, 2019;Plumbee et al, 2018). Taking this into account, while Georgia-13M had greater LLS defoliation and/or AUDC than TUFRunner 511 in some instances observed in our study, the nature of TUFRunner 511 canopy may still have created a more open system compared to Georgia-13M and in turn may have offset the effect of LLS defoliation on microclimate conditions.…”

Comparison of Trimble GreenSeeker and Crop Circle (Model ACS-210) Reflectance Meters for Assessment of Severity of Late Leaf Spot

“…A field trial was conducted at the University of Georgia Gibbs Farm. The trial included a total of ten treatments consisting of nine advanced breeding lines (Jordan et al 2017) and cultivar Georgia-12Y (Branch 2013). There were three replications.…”

“…A field experiment was conducted in which 13 treatments consisted of nine advanced breeding lines, planted without seed treatment, and cultivars Georgia-06G and Georgia-12Y. Each of Georgia-06G and Georgia-12Y were planted with and without seed treatment (Jordan et al 2017). Seed treatment was same as that described previously.…”

First draft genome and transcriptome of Cercosporidium personatum, causal agent of late leaf spot disease of peanut

“…ELS and LLS cause severe losses in peanut costing Georgia farmers $ 44 million a year [ 1 ] as consequence of reduced yield and expensive multiple fungicide applications [ 2 – 4 ]. Although the search for LLS resistance in peanut is a persistent effort [ 2 , 5 , 6 ], little is known about the population genetics of the pathogen, which is necessary to attain durable host resistance [ 7 ]. The availability of a C. personatum genome will enable such studies.…”