Genetic Differences In Growth Research Articles

Effect of water stress on growth and dry matter distribution of four dryland species used in tree planting in the Sahel

AbstractWater stress is the most important factor limiting early survival and growth of seedlings in arid and semi-arid zones. Many woody species develop adaptive mechanisms in response to water stress. This study assesses survival rate, growth and dry matter distribution in response to water stress in four dryland species (Senegalia dudgeonii, Senegalia gourmaensis, Vachellia nilotica and Vachellia tortilis). A total of 240 seedlings (60 per species) were grown using a completely randomized block design with three replicates in each of three water treatments (control = 100 percent of field capacity; moderate water stress = 50 percent of field capacity; severe water stress = 25 percent of field capacity) with a 7 day watering frequency. Data were collected on seedling survival, height, collar diameter, leaf production and dry matter distribution. Survival rate of the four species was not affected by water stress. However, the morphological responses to water stress were significantly different between species. Water stress resulted in significant reductions in height and collar diameter, higher below-ground biomass and significant increase in shedding of leaves. Under water stress, S. dudgeonii, S. gourmaensis and V. tortilis invested more in root growth. The allocation pattern from above-ground to below-ground parts was found to be the main adaption to drought. In contrast, V. nilotica gave preference to above-ground development, which could be an indication that the seedlings are adapted to grow under severe water stress. The results confirm the interspecific genetic differences in growth and dry matter distribution among species. These variations in water stress response may be used as criteria for species selection for degraded land reforestation.

Changes in reproductive investment with altitude in an alpine plant

In perennial species, the allocation of resources to reproduction results in a reduction of allocation to vegetative growth and, therefore, impacts future reproductive success. As a consequence, variation in this trade-off is among the most important driving forces in the life-history evolution of perennial plants and can lead to locally adapted genotypes. In addition to genetic variation, phenotypic plasticity might also contribute to local adaptation of plants to local conditions by mediating changes in reproductive allocation. Knowledge on the importance of genetic and environmental effects on the trade-off between reproduction and vegetative growth is therefore essential to understand how plants may respond to environmental changes. We conducted a transplant experiment along an altitudinal gradient from 425 to 1 921 m in the front range of the Western Alps of Switzerland to assess the influence of both altitudinal origin of populations and altitude of growing site on growth, reproductive investment and local adaptation in Poa alpina. In our study, the investment in reproduction increased with plant size. Plant growth and the relative importance of reproductive investment decreased in populations originating from higher altitudes compared to populations originating from lower altitudes. The changes in reproductive investment were mainly explained by differences in plant size. In contrast to genetic effects, phenotypic plasticity of all traits measured was low and not related to altitude. As a result, the population from the lowest altitude of origin performed best at all sites. Our results indicate that in P. alpina genetic differences in growth and reproductive investment are related to local conditions affecting growth, i.e. interspecific competition and soil moisture content.

The effect of genotype, location and their interaction on early growth and branching in apricot trees

SummaryThe purpose of this study was to identify relevant variables and appropriate stages in tree development to determine, as early as possible, genetic differences in growth and branching of apricot trees. Quantitative growth and branching traits of young trees were studied in four genotypes planted at three locations in the French growing area. Over the first three years of growth, the organisation of ten limbs was described for each genotype location combination using ‘AMAPmod’ methodology. From the first year, the length, diameters, volume and sylleptic branching of limbs were influenced by genotype. In the second and third years, genetic variability was more clearly detected when cumulative variables, rather than annual variables, were considered on the cumulative components of limbs. At all three locations, the diameters, volume and number of long laterals were greatly affected, in particular, by genotype when the data were accumulated over the first 2 years. In addition, the abortion of short laterals developed on the first annual shoot was influenced by genotype. In contrast, from the second year, location clearly affected the length and number of “growth units” of limbs. As regards branching, location influenced the number of sylleptic shoots in the first year, then the number of long lateral shoots in the second year. Finally, the study showed that genetic differences in growth and branching need at least 3 years to be expressed on appropriate parts of the limbs and could be used to assess early breeding criteria for tree vigour and form.

Genetic differences in growth among wild populations of the yabby, Cherax destructor (Clark)

Before commencing a breeding programme on a new aquaculture species, it is prudent to identify populations or strains with superior characteristics for commercial production. Information on the comparative performance of populations allows informed decisions to be made on the starting genetic base for the programme. As a precursor to a breeding programme in the decapod species, Cherax destructor (Clark), five geographically isolated populations were evaluated for the traits weight at age, abdomen length and abdomen width over a period of 9 months. Mean weight at age was found to vary among the populations by up to 42%, whereas mean abdomen length was similar among four out of the five populations. No differences were found in abdomen width. This study emphasizes that rapid genetic gains can be made simply by starting a breeding programme based on faster growing populations.

Genetic differences in growth of an invasive tree species

Invasive plants are often more vigorous in their introduced ranges than in their native ranges. This may reflect an innate superiority of plants from some habitats or an escape from their enemies. Another hypothesis proposes that invasive plants evolve increased competitive ability in their introduced range. We present the results of a 14‐year common garden experiment with the Chinese Tallow Tree (Sapium sebiferum) from its native range (Asia), place of introduction to North America (Georgia) and areas colonized a century later (Louisiana and Texas). Invasive genotypes, especially those from recently colonized areas, were larger than native genotypes and more likely to produce seeds but had lower quality, poorly defended leaves. Our results demonstrate significant post‐invasion genetic differences in an invasive plant species. Post‐introduction adaptation by introduced plants may contribute to their invasive success and make it difficult to predict problem species.

Growth and survival of Arcto-Norwegian and Norwegian coastal cod larvae (Gadus morhuaL.) reared together in mesocosms under different light regimes

To evaluate genetic differences in growth and survival potential as a function of light regime, cod larvae from two stocks (CC: coastal cod and AC: Arcto-Norwegian cod, spawning at latitudes of 60°N and 69°N respectively) were co-reared in mesocosms. The experiment was carried out with two artificially illuminated light regimes, corresponding to the natural photoperiod at peak spawning of the respective stocks (CC: 7–8 h distinct dark period, AC: ‘mid-night sun’ as continuous light with 2–3 h reduced light intensity). One additional regime with ambient natural light analogous to 60°N was used. At termination on day 36 post-hatch, larvae of the co-reared stocks were distinguished from each other by a genetic marker in the CC stock. Stock-specific differences in growth rate and survival were indicated, with CC larvae growing and surviving better than AC larvae. This is in agreement with earlier comparisons of larval growth in these stocks. The 69°N light regime did not enhance growth for any of the two stocks. However, natural light greatly increased growth rate of both stocks, indicat ing important mechanisms in regulation of larval feeding relative to light quality or intensity. The results may be important for choice of stock and illumination in intensive aquaculture of this species.

Evidence of differences in growth and food intake regulation in different genetic strains of channel catfish

Norris and USDA‐103 strains of channel catfish Ictalurus punctatus were compared for growth rate and food conversion ratio under satiation feeding and restricted feeding (1% body weight day−1) regimes. At the start of the experiment Norris fish weighed 2·8 g, USDA‐103 fish weighed 14·0 g. Therefore, a regression of the loge of specific growth rate against the loge of mean body size with an empirically derived fixed slope of ‐0·37 was used to compare growth rates. Under both feeding regimes the USDA‐103 strain had faster specific growth rates and more efficient food conversion. In subsequent studies, voluntary food intake of size matched fish (60 g average) from these two strains was compared using a radiographic method. Fish were acclimatized to tank conditions for 3 weeks prior to voluntary food intake measurement. Half of the groups were deprived of food for 2 days prior to food intake measurement, while the remaining groups were fed 1% body weight day−1. The USDA‐103 strain fish ate significantly more food and grew faster than the Norris strain fish. Previously fasted Norris fish subsequently ate more than their fed counterparts, whereas the fed USDA‐103 fish consumed more food than the fasted USDA‐103 group. When the USDA‐103 strain fish were deprived of food for 4, 2 or 0 days, all groups subsequently consumed between 4·5 and 5·0% of body weight in one meal. The USDA‐103 fish, unlike the Norris fish were not stimulated to consume more after short‐duration fasting. Taken together, these results suggest that there are genetic differences in growth, food conversion ratio and regulation of food intake between Norris and USDA‐103 strains.

Genetic testing of common carp in cages. 2. Influence of variation in initial weight on weight gain

Three tests are described, in which common carp were stocked into net cages. A positive association was found between weight gain and initial weight, both for individual carp and means of four to five fish. This association cannot be due to direct interactions among the groups, since different test groups were stocked separately. In the last test, seven genetic groups were stocked into separate cages. Their observed weight gains were corrected for the biassing effect of variation in initial weight, with the aid of multiply-nursed samples. This resulted in a reduction of the standard deviation of weight gain, a reduction in the association between initial weight and weight gain, and a change of ranking among the genetic groups tested. We conclude that reliable estimation of genetic differences in growth requires amending observed weight gains for variation in initial weight in separate testing cages. This has been previously demonstrated for communal pond testing.

Feed efficiency changes accompanying selection for body weight in chickens and quail

Feed efficiency data for growth selected and unselected and also stocks divergently selected for body weight were reviewed with special emphasis on changes immediately after hatching. Examination of feed efficiency differences between genetically diverse stocks from hatch to market age normally reveal only small differences in the efficiency of feed utilization. On the other hand, differences in feed intake appear to be the dominant factor in growth-related changes of these genetically diverse stocks. However, when data were segmented into periods which allowed investigation of differences at early ages, especially immediately after hatching, major differences in feed efficiency between genetically diverse groups were observed.These data indicate that feed efficiency plays a more important role in explaining genetic differences in growth than indicated by previous investigations. The appearance of the greatest differences between genetically diverse stocks immediately after hatching indicates that early feed efficiency changes may allow for greater subsequent feed intake. Therefore, it appears that changes in early feed efficiency along with changes in feed intake both play major roles in explaining genetic differences in growth. The role of feed efficiency is apparently obscured by the maintenance requirements associated with large body sizes of selected stocks when measurements are obtained at older ages.

Genetic differences in growth within and between Lycopersicon species

Growth analyses were carried out on 88 accessions of five Lycopersicon species. Experiments were conducted in a climate room at 19/14° C day/night temperature which was irradiated at 20 W/m2 for eight hours per day. Large differences in plant weights between wild species and the cultivated tomato were observed from 44 to 84 days after sowing. The increase in plant dry weight could be described by a second order polynomial function. When compared at a standardized plant weight of one gram, the relative growth rates (RGR) of the wild and cultivated accessions ranged from 5.3 to 11.8% and 8.5 to 12.2% per day respectively, limiting the use of wild species as sources for strong growth. When expressed at plant weights of one and three g large differences in decrease of the RGR were observed within L. esculentum. The modern hybrid tomato cultivars were among the fastest growing genotypes, with a relatively slow decrease in RGR.

Direct and Maternal Genetic Differences between Lines of Mice Selected for Body Weight and Litter Size: Traits of Offspring2

Genetic differences in growth and body composition were estimated from linear contrasts among two selected lines of mice, reciprocal F1′s, F2′s and backcrosses. Line W had been selected for increased 6-wk body weight and line L for large litter size. Genetic differences estimated were direct average (gD), direct heterosis (hD), maternal average (gM), maternal heterosis (hM) and recombination loss (rD). Litters were not standardized at birth. For body weights and gains, gD or gM was the most important genetic difference at all ages, and W was the line favored. At birth, 12 d and 21 d, gM was the only significant genetic difference, but gD was more important than gM at 42 d. The only significant genetic difference for gain from 21 to 42 d was gD. Average maternal differences were due to the more favorable environment resulting from the smaller litter size of W dams. Direct heterosis was not significant at any age. However, differences in litter size had suppressed a direct heterotic advantage for weight at 21 and 42 d and for postweaning gain. At 21 d, the larger litter size of crossbred dams prevented expression of their better maternal influence on progeny weight. Maternal heterosis for 42-d weight was actually negative as a result of the negative environmental impact of increased litter size. These selection criteria have resulted in up to 9 and 10% direct and maternal heterosis, respectively, on body weight, but standardization of litter size would be required for it to be expressed. Recombination loss was not significant for weight at any age. For weight of ash, fat, moisture and protein at 42 d, differences in gD and gM were similar and favored line W. Direct heterosis was observed for all constituents except fat. When expressed as a percentage of the whole body, only fat and protein exhibited a genetic difference. For gD, line W had a higher percentage fat, but L had a higher percentage protein. Significant differences in 21 to 42 d feed consumption were found for gD, gM and hM, the former two favoring W and the latter being negative. Efficiency of postweaning gain showed differences in gD and gM. Line W was favored only for the former. Efficiency of protein gain from 21 to 42 d did not show any genetic differences.

Genetic differences in growth and survival between strains and hybrids of rainbow trout ( Salmo gairdneri) stocked in aquaculture lakes in the Canadian prairies

Several thousand small, shallow, highly productive lakes across the Canadian prairies are used by farmers for commercial and recreational production of rainbow trout. This report summarizes the results of evaluations of genetic differences between strains of trout from 1972 to 1978. Strains of fish were obtained from the wild and from private and government hatcheries in Canada, the U.S.A., and Europe. Matched plantings of different strains were made in several experimental lakes annually and growth and survival were determined. The relative effects of strains (genetic effect), lakes (environment effects) and strain × lake interactions were determined in each study. Significant hybrid vigour for both growth and survival was observed for some but not all crosses.

Post Embryonic Growth in Relation to Egg Weight

THE close dependence of chick hatching weight on egg weight has been reported by many investigators (Upp, 1926; Galpin, 1938; Kosin et al., 1952). It has been generally conceded however, that the initial influence of egg size on chick size is short-lived and has no important effect on subsequent growth and could for all practical purposes be ignored. Goodwin (1961) however, has described the initial effect of egg weight on subsequent growth as being cumulative and has suggested that the influence of hatching egg size on market weight is of sufficient magnitude to be of practical importance in the broiler industry. To the extent that egg size effects on growth are environmental (e.g., due to age or season) the adequacy of random sample broiler tests and even experimental breeding and research investigations designed to reveal genetic differences in growth might also be questioned.Since further information on these egg size…

The Growth of Inbred and Hybrid Chicken Embryos

INTRODUCTIONSTUDIES dealing with genetic differences in the rate of post-embryonic growth in the chicken have been numerous; while those dealing with differences in embryonic growth have been comparatively few. Moreover, studies that have dealt with genetic differences in avian embryonic growth have yielded conflicting results. Some workers have concluded that the genotype of the chicken embryo has no effect on its growth rate. Others have concluded that genetic differences in growth rate do exist.Byerly (1930), using Rhode Island Reds. White Leghorns, and the reciprocal crosses between the two, found slight but inconsistent differences in the size of embryos of the same age. He later reported (1932) that the growth rate of the chicken embryo was a function of its food supply. McNally and Byerly (1936) found they could explain such differences as they obtained in the rate of early embryonic growth in terms of differences in egg weight… .