Fruit of 10 peanut (Arachis hypogaea L.) genotypes differing in botanical type and geographical source were evaluated to establish parameters for making reliable maturity determinations on the basis of internal pericarp color (IPC), and to compare the IPC, kernel density (KD) and arginine maturity index (AMI) methods of estimating peanut maturity.
Kernels from fruits with detectable, non-disease related internal pericarp darkening were significantly lower in density than kernels from fruits without internal pericarp darkening. No difference in density was detected between kernels from fruits differing in intensity of internal pericarp darkening. In general, two-seeded fruits with detectable non-disease related darkening in at least one orbital of the pericarp were mature, whereas fruits with no internal pericarp darkening were immature.
Mature fruit percentages were determined on sample sizes of 25, 50, 75, and 100 fruits. Although standard errors were consistently high for 25-fruit samples, means and standard errors were similar for sample sizes of 50, 75, and 100 fruits, indicating that estimates based on 50-fruit samples were reliable.
Post-harvest stability of IPC was evaluated from determinations made on five dates at 30-day intervals. IPC did not change sufficiently during the 120 day period to affect the maturity estimates.
Kernel samples classified as mature by the IPC method were significantly lower in density and free arginine content than kernels classified as immature. Correlations among maturity estimates using the IPC, KD and AMI methods were highly significant, with all coefficients exceeding 0.95.
The results indicate that peanut samples can be evaluated reliably for maturity by subjective classification of IPC. Maturity estimates on the basis of IPC were as effective as those determined using either the KD or AMI methods. The IPC method requires no sophisticated equipment and it is simple, rapid and nonsacrificial which makes it particularly useful in breeding programs involving large numbers of maturity determinations.
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Keywords: Arachis hypogaea L., kernel density, arginine maturity index.
How to Cite:
Gilman, D. & Smith, O.,
(1977) “Internal Pericarp Color as a Subjective Maturity Index for Peanut Breeding¹”,
Peanut Science 4(2),
30 Jun 1977