Performance and genetic variation of big-leaf mahogany (Swietenia macrophylla King) in provenance and progeny trials in the Yucatan Peninsula of Mexico
Stocks of the valuable big-leaf mahogany (Swietenia macrophylla King) are declining, and trials for growth and pest resistance are needed to select material for plantations. Seeds were collected from 67 open-pollinated trees from five provenances in the Yucatan Peninsula of Mexico and planted in three provenance/progeny trials in the state of Quintana Roo, Mexico, in order to characterize genetic variation in growth traits and for Hypsipyla resistance or recovery, and to assess the potential for genetic gain. Differentiation among provenances was found only for relative height growth rate (RHGR). The total years of apical attack by Hypsipyla grandella varied by a magnitude of 100% among families but showed little heritability. After 4 years, mean height per family ranged from 328 to 564 cm, 160 to 381 cm, and 253 to 390 cm at each site. Although heritabilities for height were too low for cross-site selection, sufficient heritability (h(I)(2) = 0.26), additive genetic coefficients of variation (AGCV = 22%), and type B genetic correlations (r(b(f)) = 0.74) for RHGR across the two sites with poorer growth indicated that this trait might be used as a surrogate. This would yield an estimated gain of about 17% for the best 15% of trees. At the site with better growth, there was sufficient heritability (h(I)(2) = 0.31) and AGCV (20%) for height at year 5 to obtain an estimated gain of 15% for the best 15% of trees. We suggest a selection strategy using the best germplasm from the best performing trial to exploit the resources on high quality sites, and the best material from the poorer sites for lower quality areas. (C) 2007 Elsevier B.V. All rights reserved.