Genetic studies of several abnormal leaf shapes of the cultivated peanut (Arachis hypogaea L.) have been reported (Hammons, 1973; Wynne and Coffelt, 1982; Murthy and Reddy, 1993). Some of the more aberrant leaf shapes included Krinkle-leaf (Hammons, 1964), Cup, Flop, Ilex, Hedera, and Corduroy-leaves (Loesch and Hammons, 1968), Narrow-leaves (Gopani and Vaishnani, 1970), Flop-leaf (Branch and Hammons, 1981), and Curley-leaf (Branch, 1987).
In 1996, three plants with puckered leaves were found in the spanish-type cultivar ‘Tamspan 90’ (Smith et al., 1991). These plants appeared to exhibit typical leaf puckering symptoms of tobacco thrips (Frankiniella fusca Hinds) injury even following systemic insecticide application at planting. Puckered leaves have a partially wrinkled appearance with some chlorosis along leaf margins. The puckering seems more pronounced on the younger leaves as compared to the old leaves and becomes quite apparent within the first 3–4 weeks after emergence. Individual plants were selected for further testing as Tamspan 90-normal and Tamspan 90-puckered, respectively. Progeny rows from each selection have bred true-to-type for the past seven years.
Subsequent thrips counts from Tamspan 90-puckered and Tamspan 90-normal actually revealed more thrips larvae (53 vs 23) in the leaf terminals of the Tamspan 90-normal as compared to Tamspan 90-puckered (JW Todd, unpublished data). Additional tests conducted to evaluate a possible preplant herbicide × systemic insecticide interaction at varying rates of each pesticide likewise showed no significant effect between either selection (WC Johnson III, unpublished data). The distinct plant type of Tamspan 90-puckered appeared to be under genetic control. The objective of this study was thus to determine the inheritance of the puckered-leaf shape found in Tamspan 90.
Materials and Methods
Reciprocal crosses were made in the greenhouse between the puckered-leaf Tamspan 90 selection and the normal leaf Tamspan 90 selection. Both of these selections would be classified as A. hypogaea subsp. fastigiata var. vulgaris. Reciprocal crosses were also made between the puckered-leaf Tamspan 90 selection and the normal leaf ‘Georgia Browne’ cultivar that belongs to A. hypogaea subsp. hypogaea var. hypogaea (Branch, 1994). Such crossings between and within subspecies should provide for a wider range of genetic diversity and recombination.
Another puckered-leaf mutant genetic stock ICGL 6 (PI 561916) from ICRISAT was obtained and grown in the greenhouse. Plants of both Tamspan 90-puckered and PI 561916 had very similar phenotypes. Cross combinations for allelism tests were made between the puckered-leaf Tamspan 90 selection and the puckered-leaf mutant genetic stock ICGL 6 (PI 561916).
During 1998, 1999, and 2000, the F1, F2, and F3 generations were respectively field grown in space-planted nurseries at the agronomy research farm near the University of Georgia, Coastal Plain Experiment Station, Tifton, GA. Data from visual classification of normal leaf and puckered-leaf among segregating individual plants and progeny rows were analyzed by the CHISQA program (Hanna et al., 1978).
Results and Discussion
The F1 leaf shape was normal for all crosses involving normal leaf × puckered-leaf combinations suggesting that the puckered-leaf trait was recessive. No maternal or cytoplasmic effects were detected among reciprocal crosses.
The F1 leaf shape was puckered from the cross between the puckered-leaf Tamspan 90 selection × puckered-leaf mutant ICGL 6. This finding suggests no allelic difference between these two independently found genotypes for the puckered-leaf shape.
The F2 segregation showed a good fit to a 13 normal leaf: 3 puckered-leaf genetic ratio (Table 1). Total, pooled, and homogeneity chi-square values were all found acceptable at P≥ 0.05. These data suggest two genes control the inheritance of the puckered-leaf shape trait with epistatic interaction. The presence of one homozygous recessive gene with the presence of one homozygous or heterozygous dominant gene is needed for the puckered-leaf shape.
The segregation of F3 progenies from F2 normal leaf plants did not deviate significantly from an expected two gene model of 7 none segregating:6 segregating ratio (Table 2). The segregation of F3 progenies from F2 puckered-leaf plants only fit an expected two gene model of 1 non- segregating:2 segregating ratio. Thus, the F3 findings supported the 13:3 digenic epistatic model found in the F2 generation.
These results agree and independently confirm the previous report involving different genetic lineages for the inheritance of the puckered-leaf shape trait found in the cultivated peanut (Dwivedi and Nigam, 1989). The genotype of this trait had been previously proposed as nl1 nl1 Nl2 Nl2 . (Nigam et al., 1993). However, since the gene symbol nl was first used for narrow leaves (Matlock et al., 1970) and to avoid further confusion in the literature, the gene symbol puc1 Puc2 is being proposed to distinguish puckered-leaf from narrow leaf.
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- Contribution from the University of Georgia, College of Agricultural and Environmental Sciences. [^]
- 2 Prof., University of Georgia, Dept. of Crop & Soil Sciences, Coastal Plain Experiment Station, Res. Agron. USDA-ARS, and Prof. University of Georgia, Dept. of Entomology, Coastal Plain Experiment Station, respectively, Tifton, GA 31793-0748 [^] *Corresponding author (email: firstname.lastname@example.org).