Disease resistant cultivars with good quality are needed by U.S. peanut growers to lower production costs. In the Virginia-Carolina (V-C) production area, use of resistant cultivars to reduce leaf spots would be a cost-effective and environmentally safe alternative to chemical applications. Twenty-six interspecific hybrid derived breeding lines with 5
Peanut (
A potential source of disease resistance genes for peanut improvement is the wild species. The genus contains about 80 diploid (2
Experimental material with their genetic background.
The overall goal of our research program is to develop peanut cultivars with resistance to the most common diseases in the V-C production area, which include early leaf spot (ELS), TSWV, Sclerotinia blight (SB) and CBR. The specific goals of the research reported in this paper are 1) to compare tetraploid, interspecific hybrid derived breeding lines with commercial peanut cultivars for their agronomic performance and leaf spot resistance, and 2) to evaluate the potential of tetraploid interspecific hybrid derived breeding lines for commercial cultivation in the V-C peanut production area.
Twenty-six tetraploid, interspecific hybrid derived breeding lines, six
Defoliation ratings were recorded on plots on 2, 14, and 21 Sept. in 2004, on 21 and 27 Sept. in 2005, and on 9 and 21 Sept. in 2006, respectively. The severity of the disease was rated on a proportional scale from 1 = no defoliation (resistant) to 9 = complete defoliation (susceptible). The 3 yrs of data were combined to generate mean disease scores. Pod yield and grade were measured on all plots and combined to generate means. Analysis of variance was performed on defoliation scores, yields and grades. Means were adjusted for block effects in the incomplete block design if block effects were found to be significant by F-test. The means for the 43 entries from each year were used to perform an analysis of variance as if for a randomized complete block design using years as the blocking variable. Means were separated by t-tests. All analyses were performed using the general linear models procedure (PROC GLM) of the SAS statistical software package (
Significant variation among the 43 entries was observed (P<0.05) for both defoliation score and yield (
Means of defoliation score, yield, and selected grade characteristics of susceptible cultivars, resistant
Currently, peanut growers use foliar application of fungicides to control leaf spots, usually beginning in early July and continuing until mid-Sept following a 14-d spray schedule or a weather based spray advisory. This requires five to six sprays during the crop season to control leaf spots with chemical costs of$371–494/ha. The interspecific hybrid derived breeding lines have high levels of leaf spot resistance even under heavy disease pressure, unlike some of the moderately leaf spot resistant V-C peanut cultivars which express severe defoliation symptoms under heavy disease pressure, and are a promising source for the development of leaf spot resistant cultivars for the V-C area.
Although disease-resistant cultivars may reduce fungicidal sprays and lower production costs, the most important traits to a grower are the yield and grade because they determine the price and eventual profits. Large-seeded virginia type cultivars, such as Gregory, Perry, NC 12C, NC-V11, VA 98R and Wilson, dominate the V-C production area. In field tests conducted without chemical control of leaf spots, the mean yields ranged from 2296±313 kg/ha in NC 7 to 3070±363 kg/ha in Brantley, whereas 19 of the 26 interspecific hybrid derived breeding lines produced at least 3000 kg/ha without chemical control of leaf spots (
Overall, the means of the selected grade characteristics of the interspecific breeding lines were slightly inferior to those of the cultivars (
Currently grown cultivars in the V-C area produced less yield with more disease than the interspecific hybrid derived breeding lines. Many interspecific hybrid derived breeding lines yielded 3000 kg/ha without chemical control of leaf spots. This indicates that the interspecific hybrid derived breeding lines evaluated in this study have superior leaf spot resistance combined with high yield. Because the diploid
This research was supported by funds from NC Peanut Growers Association, NC Crop Improvement Association and NC Foundation Seed Producers, Inc. Susan Copeland and Philip Rice helped with field planting and recording data.
1Dept. Crop Science, Box 7629, N. C. State Univ., Raleigh, NC 27695-7629.