Introduction

Flavor is among the most important quality attributes for commercial acceptance of roasted peanuts (Arachis hypogaea L.) as snacks or peanut butter. Relatively little research has been published on flavor and other sensory attributes of peanut cultivars under development in the USA, mainly because breeding efforts have been directed at developing cultivars with increased yield, grade and disease resistance, the traits with the most economic impact on peanut production. Traits such as peanut flavor, an important attribute for consumers, but one with little direct and measurable economic value, have received little weight in selecting lines for release to commercial producers. Isleib et al. (2001) suggested that there is greater variation in peanut flavor among cultivars and breeding lines developed and/or released during the past 10 years than there was in cultivars released earlier, in part due to the incorporation of exotic parents into breeding programs in order to introduce genes for disease resistance. Recently manufacturers of products such as snack foods or peanut butter have demanded increased emphasis on maintenance or improvement of peanut flavor in new releases.

To date, only two cultivars have been released that trace their immediate ancestry to diploid wild species of genus Arachis: COAN and NemaTAM (Simpson and Starr, 2001; Simpson et al., 2003). Because of changes in the U.S. peanut price support program, growers are demanding greater levels of host plant resistance in new cultivar releases, and use of wild species-derived resistances is likely to become more common in the future. The peanut genetics program at N.C. State Univ. has been actively developing peanut lines with multiple disease resistance using diploid Arachis species as sources of resistance. Several germplasm lines derived from crosses between A. hypogaea (2n  =  4x  =  40) and A. cardenasii Krap. & Greg. (2n  =  2x  =  20), a species with high levels of resistance to several pathogens and insect pests of peanut, have been released (Stalker and Beute, 1993; Stalker and Lynch, 2002; Stalker et al., 2002a,b). These germplasm lines are being used as parents in several U.S. peanut breeding programs. At N.C. State and Texas A&M Univ., additional populations have been derived from the diploid species A. diogoi Hoehne, A. correntina (Burk.) Krap. & Greg., A. stenosperma Greg. & Greg., and A. batizocoi Krap. & Greg. (Tallury and Stalker, unpublished data; Simpson et al., 1993). These new germplasm lines and other interspecific hybrid selections have been hybridized with commercial cultivars. Several advanced populations are being evaluated in field tests for yield, grade, and resistance to the diseases tomato spotted wilt virus (TSWV), leaf spots [caused by Cercospora arachidicola Hori and Cercosporidium personatum (Berk. & Curt.) Deighton], Cylindrocladium black rot (CBR) (caused by Cylindrocladium parasiticum Crous, Wingfield, & Alfenas), and Sclerotinia blight (caused by Sclerotinia minor Jagger). Preliminary yield and disease resistance data suggest that several lines are promising candidates for commercial cultivation in the Virginia-Carolina production area (Tallury et al., unpublished). However, no sensory evaluations have been made on these materials. The overall objective of this research was to evaluate sensory attributes of interspecific hybrid-derived breeding lines for peanut flavor to determine if transfer of disease resistance from wild species was associated with concomitant changes in flavor.

Materials and Methods

Plant Material

An array of 16 wild species-derived breeding lines (Table 1) were grown as entries in the Leafspot Advanced Test during 2005 (Sprayed) and 2006 (Sprayed and Unsprayed) at the Peanut Belt Research Station at Lewiston, NC. The lines traced to five Arachis species: A. batizocoi, A. cardenasii, A. correntina, A. diogoi, and A. stenosperma. Lines designated “HTS” were developed by H.T. Stalker; those designated “SPT” were developed by S.P. Tallury. Parentage of the wild species-derived lines was complex and included U.S. virginia-type parents Florigiant (Carver, 1969), NC 5 (Emery and Gregory, 1970), NC 6 (Campbell et al., 1977), NC 7 (Wynne et al., 1979), NC 12C (Isleib et al., 1997), Perry (Isleib et al., 2003), runner-type parents Southern Runner (Gorbet et al., 1987) and NC 3033 (Beute et al., 1976), and A. hypogaea plant introductions PI 261942, PI 270806, and PI 337396 (USDA-ARS, Nat. Genetic Resources Program. Germplasm Resources Information Network). The virginia-type cultivar NC 7 was included as a performance and flavor standard. The tests were conducted in a randomized complete block design with 2 replications. Each plot was comprised of two rows 7.3 m in length spaced 91 cm apart. Seed spacing at planting was 25 cm. Plots were planted on 11 May 2005 and 11 May 2006, dug 30 Sept. 2005 and 2 Oct. 2006, and harvested by combine on 5 Oct. 2005 and 5 Oct. 2006. Standard cultural practices, including irrigation and a full program of chemical control of leaf spots, were applied to the plots except that leaf spot fungicides were not applied to the “unsprayed” test in 2006.

Table 1

Wild species-derived lines for sensory evaluation using the notation Purdy et al., (1968).

Results and Discussion

Variation among environments was primarily attributable to the difference between the 2005 and 2006 seasons (Table 2). This observation is consistent with earlier studies where year-to-year variation was shown to be a major part of the total variation in peanut sensory quality (Pattee et al., 1994, 1997, 1998, 2004). Although significant variation among entries was found for the roasted peanut, sweet, and bitter sensory attributes, in no case was the contrast between NC 7 and the mean of wild species-derived lines significant (Tables 2, 3). There was a difference between the means of the HTS and SPT lines for roasted peanut [4.62 vs. 4.35 flavor intensity units (fiu), P = 0.0038] and sweet attributes (3.57 vs. 3.80 fiu, P = 0.0041), but not for bitter (2.45 vs. 2.49 fiu, P = 0.5924). Significant variation was also observed among the HTS lines for sweet and among the SPT lines for bitter (Table 2). For roasted peanut, five of the 16 species-derived lines scored as great as or numerically greater than NC 7 for sensory intensity, although none was significantly greater (Table 3). Two lines, SPT 04-01 and SPT 04-12, had significantly lower roasted peanut intensity scores than NC 7. For sweet attribute intensity, the mean of SPT lines was significantly greater than that for NC 7 (3.80 vs. 3.42 fiu, P = 0.0264), and four individual SPT lines scored significantly greater than NC 7. One line, SPT 04-06, also scored significantly less in the bitter attribute. There was very little environment-by-genotype interaction (Table 2).

Table 2

Mean squares from analysis of variance of sensory attributes measured on wild species-derived peanut breeding lines developed by H.T. Stalker (“HTS” lines) and S.P. Tallury (“SPT” lines) and on virginia market-type flavor standard NC 7.

Table 3

Adjusted means of sensory attributes measured on wild species-derived peanut breeding lines developed by H.T. Stalker (“HTS” lines) and S.P. Tallury (“SPT” lines) and on virginia market-type flavor standard NC 7.

These results are positive in the sense that, except in two cases, introduction of disease and pest resistance traits from the Arachis species did not result in degradation of the flavor profile relative to NC 7, the long-time flavor standard for the virginia market-type. This has not always been the case in breeding for disease resistance because large-seeded virginia-type cultivars developed for resistance to CBR (NC 8C, NC 10C, NC 12C, and Perry) had inferior flavor profiles (Isleib et al., 2001). In the case of those cultivars, their resistance to CBR was derived from sources within A. hypogaea. As a result of these observations, it appears that flavor of wild species-derived germplasm will not prevent its use either as parents in peanut breeding programs or as cultivars. Variation observed among wild species-derived lines for sensory quality is consonant with the variation observed among lines derived exclusively from A. hypogaea ancestry. However, with these lines and as additional Arachis species are utilized for germplasm enhancement, it will be necessary to monitor flavor profiles in lines deriving resistance from them.

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