Heterotic Effects Research Articles

Estimates of Heterosis for Morphological and Flavor Attributes in Tomato

Existing tomato (Solanum lycopersicum L.) cultivars may not retain the ability to yield at desired levels. Twenty-eight tomato hybrids were studied to determine effects of heterosis on vine length, internode length, stem diameter, pH of tomato juice, total soluble solids, and reducing sugar from eight parental diallel excluding reciprocal crosses (half diallel) to quantify heterotic effects. Differences among parents indicated genetic diversity, and varying degrees of heterotic effects occurred for traits among hybrids. Maximum heterosis in the desired direction was for vine length, internode length, stem diameter, pH of tomato juice, total soluble solids, and reducing sugar over the mid-parent as well as the better parent. Hybrids P30 × P45 and P45 × P54 were best for most traits and could be potential sources for improved tomatoes for morphological traits; hybrids P30 × P45, E-02 × P28, and P54 × P59 might be used to improve tomato flavor attributes.

GENETIC SYSTEM CONTROLLING THE YIELD AND ITS COMPONENTS IN THREE BREAD WHEAT (TRITICUM AESTIVUM, L.) CROSSES

This investigation was carried out at El. Gemmeiza Agric. Res. Station , A.R.C, Egypt, during the three successive seasons, 2009/2010, 2010/2011 and 2011/2012 to study genetic variance, gene action, heterosis, inbreeding depression, heritability and genetic advance for grain yield and its components and some agronomic characters. Six populations (P1, P2, F1, F2, Bc1 and Bc2) for three crosses were used in this study coming from (P1x P3), (P2 x P4) and (P3 x P4). Analysis of variance showed significant differences among the studied generations' means for all studied traits. Scaling test showed that most studied characters were significant indicating the presence of non-allelic interaction.. Additive type of gene effect was significant either positive or negative for no .of spikes / plant, 100-kernel weight and grain yield /plant in the first and second crosses. Meantime, dominance gene effects was significantly positive for all studied traits except plant height, no. of spikes /plant and grain yield /plant in the second cross .Additive x additive and additive x dominance type of gene actions were significantly positive or negative for all studied traits in the three crosses except for no .of spikes / plant in the first and second crosses and 100- kernel weight in the second and third crosses. On the other hand dominance x dominance type gene effect was found to be significant for all studied traits except plant height and 100-kernel weight in the first and third crosses, respectively. Heritability for days to heading in narrow sense was high and nearly equal to its corresponding in broad sense. High estimates for hertibility in broad sense were accompanied bymoderate value of narrow sense for no. of kernels /spike, 100 –kernel weight and grain yield plant in the three crosses.The third cross gave the highest heterotic effect towards earliness for number of days to heading and number of days to maturity with moderate heritability in narrow sense and with genetic advance being 1.59 and 1.98 days for both characters , respectively .Significant positive heterotic effects relative to better parent was obtained for no . of kernels / spike , 100 kernel weight and grain yield in the second and third crosses .

Partial Decomposition of the Genetic Correlation between Forage Yield and Fiber Using Semihybrids

ABSTRACTVoluntary intake potential of a forage crop is generally considered to be the most important feed characteristic regulating animal performance. Efforts to develop forage crops with increased intake potential have been associated with reduced plant fitness, prompting a need to modify breeding objectives and methods. The objective of this study was to determine if semihyrids could be used to restore all or a portion of the forage yield lost to drift during selection for low neutral detergent fiber (NDF) in smooth bromegrass (Bromus inermis Leyss.). A total of 48 semihybrids were created by pair crossing within four base (original) populations, four high‐NDF populations, and four low‐NDF populations. Genetic variation declined progressively with increased NDF concentration. Midparent heterosis was positive and significant for four of six semihybrids at the low‐NDF level. Two of these semihybrids also had positive and significant heterosis for NDF, reflecting the typical positive genetic correlation between yield and NDF. However, two of these semihybrids had no heterotic effect for NDF, resulting in partial decay of the genetic correlation due to a combination of linkage and drift acting on alleles that independently control these two traits. Because about one‐third of this genetic correlation is malleable by manipulation of linkage and drift, there is potential to produce low‐NDF smooth bromegrass populations without sacrificing forage yield potential.

Genetic divergence among Nellore breed herds raised in the South Region of Brazil

The objective of this study was to evaluate the genetic divergence among Nellore breed animals raised in 45 farms in the Southern Region of Brazil. The characteristic studied was weaning weight adjusted to 205 days of life (P205), from 10,874 animals sired by 425 bulls and 7,629 cows, collected between 1976 and 2001, and distributed in the states of Rio Grande do Sul (1,499), Santa Catarina (2,332) and Paraná (7,043). The animals were distributed by cluster analysis in eight genetic divergent groups, enabling this technique to be applied to organize the matings in order to obtain heterotic effect. The herd/farm groups were formed through the hierarchical Ward method, using the direct (VGD) and maternal (VGM) breeding values predicted by the REML method. The VGD of the animal accounted for 90% of the differences among herds, and the remaining 10% was attributed to differences in the VGM. On average, the P205 for the animals from inter-group mating was 1.4kg higher than those from intra-group mating, representing 2.4% of heterosis.

Entering the second century of maize quantitative genetics.

Maize is the most widely grown cereal in the world. In addition to its role in global agriculture, it has also long served as a model organism for genetic research. Maize stands at a genetic crossroads, as it has access to all the tools available for plant genetics but exhibits a genetic architecture more similar to other outcrossing organisms than to self-pollinating crops and model plants. In this review, we summarize recent advances in maize genetics, including the development of powerful populations for genetic mapping and genome-wide association studies (GWAS), and the insights these studies yield on the mechanisms underlying complex maize traits. Most maize traits are controlled by a large number of genes, and linkage analysis of several traits implicates a 'common gene, rare allele' model of genetic variation where some genes have many individually rare alleles contributing. Most natural alleles exhibit small effect sizes with little-to-no detectable pleiotropy or epistasis. Additionally, many of these genes are locked away in low-recombination regions that encourage the formation of multi-gene blocks that may underlie maize's strong heterotic effect. Domestication left strong marks on the maize genome, and some of the differences in trait architectures may be due to different selective pressures over time. Overall, maize's advantages as a model system make it highly desirable for studying the genetics of outcrossing species, and results from it can provide insight into other such species, including humans.

Caracterização e dissimilaridade entre populações de cenoura

Verificou-se a efetividade de caracteres fenotípicos na caracterização e dissimilaridade, bem como a distância genética entre populações melhoradas e cultivares de cenoura. Os experimentos foram conduzidos na Embrapa Hortaliças, Distrito Federal. Seis genótipos de cenoura, sendo três populações melhoradas (712467, 712473 e 712464), e três cultivares (Brasília, BRS Esplanada e BRS Planalto) pertencentes ao grupo Brasília, foram avaliadas nas safras de verão de 2007/2008, 2008/2009, 2009/2010. Os experimentos foram instalados em delineamento de blocos ao acaso com duas repetições e parcelas de 1 m² de área útil. Aos 100 dias após semeio, foram colhidas 25 raízes por parcela e avaliadas individualmente para diâmetro do xilema da raiz, e para caracteres que fazem parte dos descritores mínimos para registro e proteção de cultivares de cenoura. Foram realizadas estimativas de repetibilidade e número de avaliações necessárias para caracterizar as populações, a dissimilaridade fenotípica e genotípica entre as populações, e os coeficientes de determinação (R²) de acordo com diferente número de avaliações. Verificou-se que, com exceção do caractere formato de ponta da raiz, os demais caracteres estudados, que fazem parte dos descritores mínimos de cenoura, não são eficientes para ambos os processos de caracterização e discriminação de populações de cenoura pertencentes ao grupo Brasília. Não são esperados grandes efeitos heteróticos ao serem cruzados os genótipos de processamento BRS Esplanada e 712464. Para as populações de mesa avaliadas, é possível obter efeitos heteróticos apenas quando utilizada a cultivar Brasília nos cruzamentos.

Cautions of Using Allele-Based Tests Under Heterosis

:In genetic studies, heterotic effects are commonly assessed as dominant, additive, or recessive effects for a given genetic marker. However, the distorting effect of heterosis on statistical tests is non-trivial. An inheritance model needs to be carefully chosen to achieve highest testing power. We assess this through simulations via allele- and genotype-based tests. Chi-square test statistics for different inheritance models are formulated as a function of relative risks and allele frequencies. The results indicate that testing power from the commonly used allele-based tests can be substantially diminished by heterosis. Assessing the existence of heterosis is thus recommended to avoid false negative findings.

IDENTIFICATION OF DROUGHT TOLERANT MOLECULAR MARKERS IN RICE (Oryza sativa L.) I- ASSESSMENT OF F1 GENOTYPES UNDER NORMAL AND DROUGHT CONDITION

The present study was carried out at the Experimental Farm of the Rice Research and Training Center (RRTC), Sakha, Kafer EL-Shiekh, Egypt, during three successive rice growing seasons 2010, 2011 and 2012 aiming to establish combiners that may have drought tolerance characters by hybridization between local sensitive and imported tolerant rice cultivars which will be subjected to aggressive Simple Sequence Repeat (SSR) molecular technique. So, eight genotypes namely; Moroberekan, IET1444, Azucena, IRAT170, GZ530-20-10, Giza177, Giza 178 and Sakha101 were chosen for line by tester cross. The hybrid grains were grown in 2011 as F1 and transplanted in a randomized complete block design (RCBD), with three replications, (each F1 cross transplanted between its parents). All the genotypes (eight parents and 15 F1 crosses) were planted under both normal and imposed drought conditions. The obtained results exhibited that, the parents Moroberekan, IET 1444, Giza 178 and Sakha 101 and the F1 crosses involved these parents, in particular the crosses Moroberekan x Giza177 and IET 1444 x Sakha 101 showed the most favorable mean performances values for root, yield and physiological characters, under stress conditions. Moreover, under drought stress, the following F1 crosses; IET 1444 x Giza177, IRAT 17 x Sakha101 show remarkable increase in the mean performance of average panicle length, average number of panicles per plant, average grain yield per plant as well as harvest index. However, insignificant heterotic effects were recorded for average root volume (RV) with the F1 combiner; GZ350-20-10 x Giza178. Neverthless, root to shoot ratio (R:S) did not show insignificant heterosis effects under drought condition. The most desirable crosses under normal and drought stress were; Moroberekan x Giza177, Moroberekan x Sakha101, IET 1444 x Giza178, IET 1444 x Sakha101. Since these crosses maintained the most favorable shoot, root, yield and physiological characters under both normal and drought stress conditions. The vigorous growth of F1 rice hybrids may partially attributed to the development and function of the root system. Also, it was found that F1 hybrid surpassed parents in the total root length, number. of root per plant. As a result, the root system of F1 hybrids was not only greater in volume, but also longer in length. Additionally, root to shoot ratio showed higher values than that of parents. Signficant GCV estimates were recorded for all the studied traits except the parents IET 1444 for average root volume per plant and the parent Giza 178 for root to shoot ratio under normal condition and Giza 177 for average number of roots per plant for number of roots per plant. Also, signficant GCV estimates were recorded for all the studied traits except the parents IRAT 170, Giza 177 and Giza 178 for average relative water content.

Estimation of Heterosis and Combining Ability in Petunia (Petunia hybrida Hort.)

Combining ability and heterosis were estimated for ornamental and vegetative traits of four petunia (Petunia hybrida Hort.) inbred lines viz. L5 (P1), L8 (P2), L11 (P3) and L17 (P4) and their diallel hybrids in horticultural research farm of Ferdowsi University of Mashhad, Iran in 2011. The measured traits were plant height at first flower, number of leaf to first flower, flower diameter, flower tube length, internode length, stem diameter, plant height at flowering stage, plant spreading, number of branches per plant, leaf length and width. The results of combining ability for all studied traits revealed that both additive and non-additive gene effects contributed to the inheritance of the traits. Estimates of general combining ability effects showed that parent P3 was a good general combiner for most of the studied traits. For flower diameter, hybrid combination P1 × P2 had the highest significant positive specific combining ability effects. Reciprocal effects were significant for all traits and hybrid combination P1 × P2 had the highest significant positive reciprocal effects for flower tube length and plant height. Heterosis was found significant relative to both the mid parent and batter parent for all traits. For flower diameter, the highest positive values of heterotic effects were recorded in hybrid combination P2 × P3 both relative to the parental mean (37.3%) and relative to the better parent (33.9%). It is obvious that heterotic effects represent an important resource in hybrid breeding of petunia.

Effects of Heterosis and Direction of Crossing on Production Performance of F 1 Offspring of Dominant Black Strain and Fulani Ecotype Chickens.

The objectives of this study were to determine the mode of gene action of determinants of performance (i.e. positive or negative heterosis) in F chickens produced by mating  Fulani Ecotype (FE) and Dominant Black strain (DB) chickens, and whether the direction of crossing (DBxFE or FExDB) influenced the mode of gene action. Analysis of all F data  irrespective of cross direction (combined) showed that the effect of 1percentage heterosis was positive but weak for Weight Gain (WG) = 0.04, Feed Intake (FI) = 3.83, Body Weight at First egg (BWF) = 0.76, Egg Weight (EW) = 11.28, and 0 for Egg Number (EN) and Mortality (M) during the laying period. The combined heterotic effects were negative for Hen Day Production (HDP), Feed efficiency (FEf), Age at Sexual Maturity (ASM), and mortality from day old to 21 weeks of age (-0.16, -4.33, -9.15 and -67.74% respectively). Positive but low heterosis was obtained for BWF (0.76), and EW (11.28) and WG, FEf, EN, ASM, HDP and M showed negative heterosis (-100.00 to - 0.28) in the DBXFE cross bred. The mean performance of the FEXDB showed positive heterosis ranging from 1.08 to 100% in WG, FI, BWF, EW, EN, HDP and M during the laying period, while negative heterosis; -67.74, -4.54 and -8.22 was observed for M (0- 21days), FEf and ASM. The reciprocal effects showed F FEXDB were superior in ASM, 1 BWF and EW, while F DBxFE were superior in EN, HDP and M. 1Key words: Exotic laying strain, Fulani Ecotype chicken, Heterosis, Reciprocal effects.

Heterosis of qualitative and quantitative characteristics in sweet gourd (Cucurbita moschata duch.ex poir)

The heterotic effects and genetic components of variation for qualitative and quantitative characters were estimated in sweet gourd. The phenotypic coefficients of variation were higher than genotypic coefficient of variation for all the characters indicating that environment played a considerable role on the expression of these characters. High heritability coupled with high genetic advance found in parents and hybrids for number of fruits per plant, individual fruit weight and fruit yield suggested that improvement would be effective through phenotypic selection. Both positive and negative heterosis was observed for different qualitative and quantitative characters in F1 hybrids of sweet gourd. None of the hybrids exhibited maximum heterosis for all the traits, but significant and desirable level of heterosis over mid parent and better parent was obtained in several hybrids for the different traits. For node number of first female flower, two hybrids, OP 10×OP 24 and OP 10×OP 20 recorded the highest significant positive mid and better parent heterosis, respectively. The highest significant (p<0.05) positive mid and better parent heterosis for female flowers per plant was exhibited by the hybrid OP 20×OP 02. Significant (p<0.05) and desirable level of mid and better parent heterosis was exhibited by six and four hybrids, respectively, for fruits per plant and fruit yield per plant. The hybrids OP 10×OP 20 and OP 20×OP 02 showed the highest significant (p<0.05) positive mid parent and better parent heterosis for % reducing sugar, respectively. None of the hybrids showed significant (p>0.05) heterosis over mid and better parent for brix content. The hybrids OP 10×OP 02 and OP 04×OP 02 showed significant mid parent heterosis for carotene content. Four hybrids, OP 10×OP 20, OP 20×OP 02, OP 10×OP 02 and OP 04×OP 02 exhibited significant (p<0.05) positive heterosis for majority of the characters studied and were identified as promising for commercial cultivation. We concluded that performance of these hybrids needs to be further evaluated in multi location or on farm trial prior to commercial use.

Heterosis for litter size and growth in crosses of four strains of Iberian pig

Data collected from a complete diallel cross scheme with four ancient lines of Iberian pigs have been analyzed in order to estimate genetic line and heterotic effects on litter size and growth traits. Records of the number of piglets born alive (NBA) and total number of piglets born (TB) from 2768 litters of 817 dams were analyzed using different animal models fitting crossbreeding parameters. Estimated values of genetic correlations between NBA or TB records at early and later parities were close to 0.60. Significant differences in litter size at first and second parities were observed between some dam lines, but not at the third and later parities. Negligible progeny specific heterotic effects on litter size traits were estimated in early parities, but they were significant at the third and later parities (ranging from +0.5 to +1.0 alive piglets and from +0.6 to +0.9 born piglets). All these results reinforce the evidence supporting the hypothesis of a partially different genetic basis of litter size at early and later parities. Growth performance in the final fattening period (100–160kg) of purebred and crossbred pigs was analyzed with a Bayesian procedure modeled by a linear growth function. Data consisted of 2103 weight records from 579 pigs of 352–493 days of age. Relevant heterotic effects on weight at 420 days of age (intercept of the growth function) were inferred for the different crosses with mean values ranging from +12.7 to +17.7kg. Heterotic values for daily growth rate (slope of the linear function) were not significantly different from zero for five out of the six combinations of lines but an important heterosis (+66g/d) was estimated between the remaining combinations. The implications of this remarkable heterosis between Iberian pig lines on breeding schemes are discussed in the context of the current breeding structures of this breed.

Net Carbon Exchange Rate of Fragaria Species, Synthetic Octoploids, and Derived Germplasm

The net carbon exchange rate (NCER) of Fragaria species, synthetic octoploids [SO (interspecific hybrids)], F1 (SO × cultivar), and first outcross [OC1 (F1 × cultivar)] hybrids were evaluated in both field and greenhouse conditions. Plants were grown in a field trial at the Elora Research Station in Ontario, Canada, for one season and then plants were dug and moved into a greenhouse where the trial was repeated during the next season. Single leaf photosynthesis measurements and light response curves were generated at different stages of plant development. Photosynthetic capacity of the species was related to the ecological background of the species with sun-adapted species having higher rates compared with the shade-adapted species. The Fragaria species and introgressed hybrids (F1 and OC1) had significantly higher NCERs compared with the cultivars with rates 28% and 23% higher, respectively. Species and hybrids also appear to have increased adaptability to both high and low light conditions. These increases in NCER may be a heterotic effect because NCER of the hybrids were consistently higher compared with the midparent values and in some cases, they were higher than the high parent. These results suggest that the introgression of lower-ploidy Fragaria species into the cultivated strawberry (Fragaria ×ananassa) may lead to increased NCER and light adaptability.

Adaptation to Aridity in the Malaria Mosquito Anopheles gambiae: Chromosomal Inversion Polymorphism and Body Size Influence Resistance to Desiccation

Chromosomal inversions are thought to confer a selective advantage in alternative habitats by protecting co-adapted alleles from recombination. The frequencies of two inversions (2La and 2Rb) of the afro-tropical malaria mosquito Anopheles gambiae change gradually along geographical clines, increasing in frequency with degree of aridity. Such clines can result from gene flow and local selection acting upon alternative karyotypes along the cline, suggesting that these inversions may be associated with tolerance to xeric conditions. Since water loss represents a major challenge in xeric habitats, it can be supposed that genes inside these inversions are involved in water homeostasis. To test this hypothesis, we compared the desiccation resistance of alternative karyotypes from a colonised 2Rb/2La polymorphic population of A. gambiae from Cameroon. The strain included only the molecular form S, one of the genetic units marking incipient speciation in this taxon. Day-old mosquitoes of both sexes were assayed individually for time to death in a dry environment and the karyotype of each was determined post-mortem using molecular diagnostic assays for each inversion. In agreement with expectations based on their eco-geographical distribution, we found that 2La homokaryotypes survived significantly longer (1.3 hours) than the other karyotypes. However, there was weak support for the effect of 2Rb on desiccation resistance. Larger mosquitoes survived longer than smaller ones. Median survival of females was greater than males, but the effect of sex on desiccation resistance was weakly supported, indicating that differential survival was correlated to differences between sexes in average size. We found weak evidence for a heterotic effect of 2La karyotype on size in females. These results support the notion that genes located inside the 2La inversion are involved in water balance, contributing towards local adaptation of A. gambiae to xeric habitats, beyond the adaptive value conferred by a larger body size.

Analysis of gene action in diallel crosses among some Faba bean (Vicia faba L.) genotypes under Maryout conditions

Seven genotypes of faba bean (Vicia faba L.) were used in carrying out half diallel cross, 21 F1 hybrids and 21 F2 progenies evaluated under well watered and rainfed conditions at the Maryout Agriculture Experimental Station of Desert Research Center. Mean squares of genotypes in F1 and F2 generations showed that the differences due to genotypes were significant for all characters studied under well watered and rainfed conditions. The four parental genotypes; P2, P4, P5 and P6 were the earliest in days to 50% flowering and recorded values raging from 30.88 to 47.98days under well watered and rainfed conditions and the two crosses; P1×P3 and P2×P7 in both generations under the two treatments. The parental genotype P2 recorded the highest number of branches per plant (7.85 and 6.94 branches) under well watered and rainfed treatments, respectively. While, the two crosses; P2×P4 and P2×P6 recorded the highest number of pods per plant in both generations under well watered and rainfed treatments. For 100-seed weight the parent Aquadulce (P4) recorded the highest values under well watered and rainfed conditions (95.62 and 71.72g, respectively). As well as the two crosses; P2×P5 and P2×P6 recorded the highest values for seed yield per plant. Significant positive heterosis and heterobeltiosis were detected for different traits; With respect to seed yield per plant, the seven crosses; P1×P7, P2×P5, P2×P6, P4×P6, P5×P6, P5×P7 and P6×P7 had significant positive heterotic effects relative to mid and better parents under the two irrigation treatments. Mean squares of both GCA and SCA estimates were highly significant or significant in both generations for all the studied traits under well watered and rainfed conditions. Variances due to GCA were larger than those for SCA and exceeded the unity were detected for days to 50% flowering in F1 generation under rainfed conditions, No. of branches per plant, No. of pods per plant in both treatments and generations except for F1 generation under rainfed condition, 100-seed weight in both treatments and generations except for the F1 generation under well watered conditions and seed yield per plant in both treatments and generations except for the F2 generation under well watered and rainfed conditions, revealing that the largest part of the total genetic variance associated with different traits being the result of additives types on gene action. General combining ability results showed that the three parental genotypes (P1 (G.461), (P2 (NBL2) and P4 (Aquadulce)) were good combiners for improving most studied traits. Such combinations might have desirable transgressive segregations, provided that the additive genetic system is present in different crosses for increasing plant yield and its components under targeted well watered and rainfed conditions. For SCA, the desirable inter-and intra-allelic interactions were presented in the cross P6×P7 in the two generations under both treatments along with P1×P2 in the F2 generation under both treatments, P1×P5 in F1 and F2 generations under well watered and rainfed conditions respectively, P1×P6, P2×P5 and P4×P6 in F1 under both treatments and the three crosses; P1×P7, P3×P4 and P3×P5 in F1 generation under well watered conditions showed significant positive effects for 100-seed weight. Moreover, seven F1′ P1×P7 in both generations and under the two treatments, P1×P4 in the F1 generation under well watered conditions, P2×P5, P2×P6, P4×P6 and P5×P7 under F1 generation under both treatments and P6×P7 in the F2 generation under rainfed conditions possessed significant positive effects for seed yield per plant. These crosses might be of interest in breeding programs to produce pure lines while most of them involve at least one good combiner for the trait in view.

Gene Action for Yield and Morpho-Physiological Traits in Maize (Zea mays L.) Inbred Lines

The present study was carried out to investigate the genetic structure of 28 hybrids generated by crossing 8 diverse and new maize inbred lines in a half diallel fashion. The estimated value of average degree of dominance (H1/D)0.5 revealed that non-additive genetic effects was more pronounced in the inheritance of days to 50 per cent maturity, anthesis-silking interval and grain yield per plant. On contrary, additive genetic effects was evident for days to 50 per cent tasseling and days to 50 per cent silking. The distribution of positive and negative genes were not too distant for the traits viz., days to 50 per cent tasseling, days to 50 per cent silking and grain yield per plant. Dominance to recessive genes ratio [4DH1]0.5 + F / [4DH1]0.5- F ranged from one to two, indicating that excess of dominant genes against one recessive genes were not much higher. The results indicated that most traits were under the genetic control of non-additive (over dominance) type of gene action, therefore the material can easily be exploited for heterotic effect.

Production of Heterotic Hybrid in Rohu (Labeo rohita) Through Strain Crossing

As a genetic means of aquaculture development, hybridization can increase production quickly in fishes because of heterotic effect. At the backdrop of reports on the decline of growth and reproduction of the hatchery population of Labeo rohita in Bangladesh, a 3 months study was undertaken to see the heterotic effect by intra-specific crossing among the Padma, Jamuna and Hatchery strains of rohu. Six reciprocal crosses and 3 pure crosses were obtained. The fertilization and hatching rates of the developing embryos were found better in the parental crosses than the reciprocal intra-specific hybrids. The growth performance of reciprocal crosses showed significant differences (P< 0.05) over the parental crosses. The best growth performance was observed in Padma ? X Jamuna ? hybrids; providing 72% positive heterosis. Since the growth rate of strain crossed hybrids were reasonably high, this technique can be profitably applied for the production of fast growing seed to ensure higher fish production and more profit.DOI: http://dx.doi.org/10.3126/ijls.v5i1.5035 International Journal of Life Sciences Vol.5(1) 2011 32-38

Chemical and Morphological Characterization of Costa Rican Papaya (Carica papaya L.) Hybrids and Lines with Particular Focus on Their Genuine Carotenoid Profiles

Papaya (Carica papaya L.) F1 hybrids and inbred lines grown in Costa Rica were screened for morphological and nutritionally relevant fruit traits. The qualitative composition of carotenoids showed great similarity, being mostly composed of free and esterified β-cryptoxanthins accompanied by β-carotene, lycopene, and biosynthetic precursors. High levels of (all-E)-lycopene and its isomers were distinctive for red-fleshed hybrids, whereas yellow-fleshed fruits were virtually devoid of lycopenes. Because carotenoid levels among the investigated hybrids and lines differed significantly, this study supports the hypothesis of an exploitable genetic variability, and a potential heterotic effect regarding carotenoid expression may be instrumental in papaya-breeding programs. Due to significantly higher levels of provitamin A carotenoids and coinciding high levels of total lycopene, particularly red-fleshed hybrids might represent prospective sources of these compounds. Furthermore, the nutritional value of some genotypes was boosted by substantial amounts of ascorbic acid (up to 73 mg/100 g of fresh weight), which correlated to total soluble solids (R(2) = 0.86).

Heterotic Effects in Half-Diallel Crosses of Modern and Obsolete Egyptian Cotton Varieties

Heterotic Effects in Half-Diallel Crosses of Modern and Obsolete Egyptian Cotton Varieties

Expression of genes involved in energy homeostasis in the duodenum and liver of Holstein-Friesian and Jersey cows and their F1 hybrid

Differences in feed intake and production efficiency in lactating Holstein-Friesian (HF), Jersey (JE), and JE × HF (F(1)) dairy cows have been reported. The liver-gut axis is important in the regulation of energy homeostasis, appetite behaviour, and production efficiency. The objectives of this study were to determine: 1) the effect of dairy cow genotype on the expression profiles of genes involved in energy homeostasis in duodenal and hepatic tissue, and 2) the association between the expression of these genes across both tissues and with economically important production efficiency traits. The expression of 27 candidate genes involved in energy homeostasis, feed intake, and energy storage was measured by qPCR. Duodenal expression of the pro-opiomelanocortin (POMC), glucagon-like peptide 1 receptor (GLP1R), and insulin-like growth factor 1 (IGF1) genes was highest in HF. In contrast, hepatic expression of the leptin receptor (LEPR), insulin-like growth factor 1 receptor (IGF1R), protein kinase, AMP-activated, beta 1 (AMPKB1), and POMC genes was highest in the F(1) cross. In the duodenum, positive correlations were observed between mRNA expression of anorectic peptides (POMC and GLP1R), whereas a negative correlation was detected between orexigenic (ghrelin) and anorectic (peptide YY) gene expression. A negative correlation was observed between duodenal POMC gene expression and both residual feed intake and milk production efficiency traits, while GLP1R gene expression was negatively correlated with milk production efficiency traits. A heterotic effect was observed in hepatic expression of AMKPB1, IGF1R, LEPR, POMC in the F(1) genotype, possibly mediating improved feed efficiency in cross-bred cows. In conclusion, key genes involved in energy homeostasis and appetite behaviour are differentially expressed due to cow genotype in a tissue-dependent fashion. POMC and GLP1R are potential candidate genes for the identification of single nucleotide polymorphisms regulating energetic efficiency in the dairy cow, which may be incorporated into future breeding programmes.