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Dep. Plant Path. and Micro., Texas A&M Univ. College Sta., TX 77834
* Corresponding author (c-simpson{at}tamu.edu)
‘COAN’ (Reg. no. CV-68, PI 610452) is a runner market-type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) (2n = 4x = 40) cultivar with a high level of resistance to root-knot nematodes [Meloidogyne arenaria (Neal) Chitwood and M. javanica (Treub) Chitwood]. The new cultivar was tested as TP262-3-5 and was released by the Texas Agricultural Experiment Station on 25 March 1999. COAN is the first peanut cultivar to have root-knot nematode resistance and is the first to have an identifiable gene transferred from a wild species of Arachis.
COAN was derived from a backcross introgression pathway (Simpson, 1991) involving a complex interspecific amphiploid hybrid (2n = 4x = 40), utilizing Florunner (A. hypogaea subsp. hypogaea var. hypogaea) as the recurrent parent. The amphiploid was formed by first crossing A. cardenasii Krapov. and W.C. Gregory/A. diogoi Hoehne, and then crossing the 50% pollen fertile F1 hybrid with A. batizocoi Krapov. and W.C. Gregory. The resulting tri-species hybrid (2n = 20) was <1% pollen stained and produced no fruit. The chromosome number was doubled with colchicine to form TxAG-6 (Simpson et al., 1993). TxAG-6 is about 89% pollen stained and is highly fertile, both selfed or when crossed with A. hypogaea. The fertile amphiploid was crossed with Florunner, and five backcrosses produced the designated breeding line, TP262-3-5. In each backcross cycle, selection was made for agronomic characters similar to Florunner and resistance to root-knot nematodes (Nelson et al., 1990; Starr et al., 1990).
COAN has a smaller vine size than Florunner (17% by measurement of main stem and cotyledonary laterals). The smaller canopy has a rounded appearance in mature plants, and the main stem is not apparent in most locations and seeding rates. The lateral branching is profuse, like Florunner, with an alternate pattern, but not uniformly 2 x 2. Leaf color is light green like Florunner. Pods of COAN are similar in size and shape to Florunner, mostly two-seeded (
one in 400, three-seeded). The constriction between the kernels is slightly greater than Florunner (4%). Seed size and color is almost identical to Florunner.
COAN averaged numerically less in yield than Florunner and Tamrun 96 in 19 tests from 1996 to 1998 in Texas but was not statistically different (P = 0.10) than the two check cultivars. In six tests with damaging levels of root-knot nematode present, COAN was 225% higher in pod yield hectare-1 than Florunner with no nematicide application.
Resistance of COAN to root-knot nematodes is expressed as a reduction in nematode reproduction. COAN typically has <10% of the final nematode population density at crop maturity in relation to nematode development on susceptible Florunner (Starr et al., 1995). Nematodes invade the roots of COAN but either fail to develop or develop at a much reduced rate. Resistance to the nematode species was confirmed in the third and fourth self-pollinated generations of TP262-3-5 (Starr et al., 1995).
In shelling tests, COAN was not different (P = 0.10) from Florunner in percentage of jumbo, medium, or No. 1 seed size distribution. Splits, other kernels, damaged kernels, and oilstock were equal to Florunner, and 100 seed weight was equal to Florunner at 57 g 100-1.
Quality analyses varied some by location but indicated no significant difference between COAN and Florunner. Oleic to linoleic fatty acid (O/L) ratio was 1.2:1.4. Oil content was 46:47%, and protein 24%. Flavor and blanchability were both equal to Florunner.
From the BC5 F2:3, 137 of 300 individual plants were selected for uniform phenotype. Ten seeds per selection were screened for nematode resistance and 127 progeny rows which had no susceptible plants (among the 10 seeds tested) were grown in Puerto Rico for winter increase in 1997–1998. The increase resulted in 468 kg of Breeder seed, which were planted near Dilley, TX, for Foundation seed increase in the summer of 1998.
Foundation seed of COAN will be maintained by Foundation Seed Services, Texas Agric. Exp. Station, Texas A&M Univ., Agric. Res. & Ext. Ctr., Vernon, TX. Application (PVP no. 9900338) has been made for U.S. Plant Variety Protection. The cultivar must be sold as a class of Certified seed by variety name only. Small samples of seed for research purposes may be obtained from the corresponding author for a period of five years.
NOTES
Appreciation is expressed to the Texas Peanut Producers Board for their generous support of this research from 1988 to the present time. Registration by CSSA.
Accepted for publication October 31, 2000.
REFERENCES
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