Genetic Variation In Growth Traits Research Articles

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.

Genetic variation in growth traits and yield of rubber trees (Hevea brasiliensis) growing in the Brazilian state of São Paulo

Analysis of variance and covariance was preformed on growth traits (stem girth, bark thickness, total height gain and rubber yield) of 22 open-pollinated progenies of the rubber tree Hevea brasiliensis from an Asian Hevea collection introduced to Agronomic Institute (Instituto Agronomico, Campinas, Sao Paulo, Brazil; IAC) in 1952. This progeny trial was replicated at three sites in Sao Paulo state and it was found that at three years from sowing there was statistically significant variation for girth, bark thickness, height and rubber yield. An individual test sites, values of individual plant heritability for girth ranged from h= 0.36 to h= 0.89 whereas values for heritability for progeny means ranged from h= 0.77 to h= 0.87. These moderate and high heritabilities suggest that a combination of progeny and within-progeny selection would be effective at increasing girth in this population at individual sites. Across sites, values of individual-plant heritability for girth ranged from h= 0.36 to h= 0.47, whereas values for heritability of progeny means girth ranged from h= 0.77 to h= 0.87. There were high positive genetic correlations between increased girth and bark thickness suggesting that breeding aimed at increasing girth would also increase bark thickness and possibly height.

Genetic Variation in Growth Traits in a Quercus robur L. Open-Pollinated Progeny Test of the Slavonian Provenance

Abstract The study presents evaluation of an open-pollinated progeny test of 21 selected plus trees from Slavonian pedunculate oak provenance in Croatia (in the central part of Drava river valley). The test was established in 1992 with two-year-old seedlings. Heights were measured at 5 to 13 years and diameters at breast height (DBH) at 10 to 13 years after sowing. Variances caused by the population within provenance effect were not significant during the studied period. In contrast, variance components caused by family effect were statistically significant, and ranged from 11.1 to 18.6% and from 2.2 to 10.6% for height and DBH respectively. Statistically significant variances caused by the family effect indicate that most of genetic variation of productive traits was within the studied populations. The estimated family mean narrow sense heritabilities varied from 0.62 to 0.78 and from 0.28 to 0.65, while individual heritabilities ranged from 0.48 to 0.80 and from 0.09 to 0.46 for height and DBH, respectively. Realised gain from the test and expected genetic gains by two possible methods of selection for the measured traits have been calculated for: i.) realised gain i.e. superiority of selected plus trees progenies over control plants (bulks from unselected trees within the provenance) ii.) individual within provenance mass selection of first generation plus trees at the same ages as those represented in studied trial and iii.) backward selection among first generation plus trees after open-pollinated testing. Estimated genetic gains indicate that the highest gain could be expected by backward selection among first generation plus trees after open-pollinated progeny testing (9.7 to 22.3% and 6.8 to 17.3% over control means). These results indicate that due to significant within population variation and high additive variances, improvement for productive traits in the studied oak populations could be achieved by use of seeds and plants from selected plus trees (especially from already established clonal seed orchard), at least in younger ages.

Genetic variation in the growth traits of straight-bred and crossbred black bream (Acanthopagrus butcheri Munro) at 90 days of age

The current slow growth rate of black bream (Acanthopagrus butcheri Munro) impedes their widespread commercial aquaculture across inland southern Australia. We report initial estimates of genetic variation for growth traits at 90 days of age from a diallel cross using two black bream populations. Standard length, total length, and wet weight varied significantly among lines and among half-sib groups within lines. Differences among half-sib groups explained 6.8% of the total variance in standard length, 8.3% in total length, and 7.1% in wet weight, giving estimated heritabilities over all lines of 0.27 ± 0.11 for standard length, 0.33 ± 0.13 for total length, and 0. 28 ± 0.12 for wet weight. There was no evidence for heterosis in any traits when straight-bred and crossbred lines were compared. There were high phenotypic (r P = 0.95-0.98) and genetic (r G = 0.63-0.69) correlations among all growth traits.

Comparison of growth traits of eight beef cattle breeds in the Czech Republic

Abstract. Eight beef cattle breeds, Angus (A), Blonde d' Aquitaine (BA), Charolais (C), Czech Pied (CP), Hereford (H), Limousin (L), Piemontese (P) and Simmental (S), were analysed for the following calf traits: birth weight (BW), 210- and 365-day weight ( 210W, 365W) and average daily gains from birth to 210 days (ADG1), from 210 to 365 days (ADG2) and from birth to 365 days (ADG3). Phenotypic parameters were estimated by linear model procedures including the fixed effects of year of birth (1992–1998), herd, sex (male, female), calf number (single, twin), parity and random sire effects. Literature values of heritability estimates were used to derive genetic standard deviations and genetic range for comparison of genetic variation within and between breeds. The means of Blonde d' Aquitaine were highest for all growth traits except for BW, followed by Charolais and Simmental, then Angus, Czech Pied and Limousin with intermediate values and Piemontese and Hereford with lowest growth except for BW in Piemontese and ADG1 in Hereford. Blonde d' Aquitaine also showed high standard deviations for most growth traits except for BW, whereas for Limousin and Piemontese low standard deviations were estimated and for other breeds no consistent pattern was observed. Coefficients of variation were generally high for Hereford and low for Angus. Hypothetical frequency curves were used for comparison of genetic variation within breeds and between breeds. Comparison of extreme and average breeds showed ranges of genetic levels between 79 and 154 % of the average breed level thus indicating the large overall genetic variation for growth traits in beef cattle. Between-breed selection with immediate impact, but steady erosion by time, as well as within-breed selection with slow but steady increase and renewed variation should both be applied for optimal exploitation of genetic resources in the beef industry.

PLASTICITY AND GENETIC DIVERSITY MAY ALLOW SALTCEDAR TO INVADE COLD CLIMATES IN NORTH AMERICA

Two major mechanisms have been proposed to explain the ability of intro- duced populations to colonize over large habitat gradients, despite significant population bottlenecks during introduction: (1) Broad environmental tolerance—successful invaders possess life history traits that confer superior colonizing ability and/or phenotypic plasticity, allowing acclimation to a wide range of habitats. (2) Local adaptation—successful invaders rapidly adapt to local selective pressures. However, even with bottlenecks, many introduced species exhibit surprisingly high levels of genetic variation and thus the potential for evolutionary increases in invasive traits and plasticity. Here we assess the invasive potential of Tamarix ramosissima, by examining the degree of genetic differentiation within and among populations from the latitudinal extremes of its introduced range. Using growth chamber experiments we examined ecologically important variation in seedlings, both in trait means and their reaction norms across temperature environments. Although we found no genetic variation for gas exchange traits, within or among populations, we did find significant genetic variation for growth traits, both in the trait means and in the degree of plasticity in these traits. Northern ecotypes invested more in roots relative to southern ecotypes but only under low temperatures. Both ecotypes increased shoot investment in warm temperatures. Increased root investment in cold temperatures by northern ecotypes may increase their first winter survival. Genetic differences in seedling root investment may contribute to the ability of this species to successfully tolerate and invade a broader latitudinal range. Our data support a model in which both plasticity and adaptive evolution can contribute to the invasive potential of introduced species.

Genetic variation and use of provenances of Pinus sylvestris in Spain: application of Allué’s. Phytoclimatic models

This paper presents the application of the diagnosis and idoneity methods developped by Allué (1990, 1997) to the study of the relatioship between climate and genetic variation and recomendation for the use of forest reproductive material of Scots pine respectively. Growth phenology of Scots pine provenances, from Spain and Germany, have been studied in a provenance tests located in northern Spain, during two years. Siginificant differences have been found in growth rate and total growth. Differences among Spanish provenances are related to the phytoclimate of origin. Origins from close stands, but different phytoclimate, present different performance in terms of growth phenology. The relationship among genetic variation in growth traits and climate, suggest the use of climatic methods for establishing recommendations for the use of forest reproductive material (FRM) of the species. The Idoneity method is of easy applicability and allow us to differentiate among areas for using the different regions of provenance. A map showing the recommendations of each provenance region in the different regions for FRM use and identification defined in Spain is presented.