Relationships among seed weight components, seedling growth traits, and predicted field breeding values in slash pine

Dry weights of seed components (seed coat, gametophyte, and embryo), germination vigor (peak value and days to 50% germination), and three seedling growth traits (total height, stem dry weight, and shoot dry weight) under regimes of low (5 ppm) and high (50 ppm) nitrogen were measured for 64 open-pollinated families of slash pine (Pinus elliottii Engelm.) that have been field tested for 5- and 15-year volume growth. There were moderate to strong relationships among the seed components using the 64 family means (r = 0.80 between gametophyte weight and embryo weight; r = 0.68 between seed-coat weight and embryo weight; r = 0.50 between seed-coat weight and gametophyte weight). Seed-coat, gametophyte, and embryo weight, expressed as a percentage of total seed weight, were approximately 44, 50, and 6%, respectively, and those percentages were similar for small, medium, and large seed size classes. Family mean correlations between seed weight components and seedling growth traits were generally high at 12 weeks and decreased at 24 and 40 weeks, depending on the trait; however, most correlations remained statistically significant throughout the 80-week measurement. Correlations between seed components and seedling traits were generally higher in the high regime at 12 weeks, but by the 40- or 80-week measurements, correlations were generally higher in the low-N regime. Among the seed weight components, embryo weight consistently had the strongest relationship with seedling growth traits. Family mean correlations between germination vigor indices and seedling growth traits were high at 12 weeks, but declined significantly thereafter. Correlations between seed weight components and predicted field breeding values for 5- and 15-year volume growth were significantly greater than zero, and indicated that embryo weight in particular may be useful in genetic selection for volume growth