Showing papers on "Heterosis published in 1982"
TL;DR: Prospects of developing hybrid rice varieties elsewhere appear bright especially in countries that have organized seed production, certification and distribution programs and where hybrid seed can be produced at a reasonable cost.
Abstract: Studies conducted at the International Rice Research Institute (IRRI) during 1980 and 1981 have shown up to 73% heterosis, 59% heterobeltiosis and 34% standard heterosis for yield in rice. The latter was estimated in comparison to commercial varieties: IR36 and IR42 (yield 4–5 t/ha in wet season trials and 7–8 t/ha in dry season trials). Generally speaking, absolute yield was lower and extent of standard heterosis was higher in wet season than in dry season with some exception. Yields up to 5.9 t/ha (22% standard heterosis) in the wet season and 10.4 t/ha (34% standard heterosis) in the dry season were obtained. Most of the hybrids performed better in some season while some performed better in both seasons. Hybrids showed better lodging resistance although they were 5–10 cm taller. F1 hybrids had significant positive correlations with the parental traits viz., yield (r = 0.446), tillering (r = 0.746), height (r = 0.810) and flowering (r = 0.843). Selection of parents among elite breeding lines on the basis of their per se yield performance, diverse origin and resistance to insects and diseases should give heterotic combination. Yield advantage of hybrids was due primarily to increase in number of spikelets per unit area even though tiller number was reduced. Grain weight was either the same or slightly higher. High yielding hybrids also showed significant heterosis and heterobeltiosis for total dry matter and harvest index. For commercial utilization of heterosis in rice, effective male sterility and fertility restoration systems are available and up to 45% natural outcrossing on male sterile lines has been observed. Consequently, F1 rice hybrid have been successfully developed and used in China. Prospects of developing hybrid rice varieties elsewhere appear bright especially in countries that have organized seed production, certification and distribution programs and where hybrid seed can be produced at a reasonable cost.
162 citations
114 citations
Journal Article•
TL;DR: For most of the characters greater variabil ty in F2 was observed in those crosses having moderate to highly diverse parents, and maximum heterosis was displayed by those crosses in which parents were moderately diverse.
Abstract: Twenty F1 crosses and their 17 F2 populations involving highly diverse, moderately diverse and less diverse parents were evaluated to find out the relationship between genetic divergence of the parents and heterosis in F1 generation and genetic variability in F2 generation in soybean. It was observed that, in general, dive.gent crosses showed high heterosis for most of the characters but the maximum heterosis was not observed in most divergent crosses. Maximum heterosis was displayed by those crosses in which parents were moderately diverse. The tntra-cluster crosses were less heterotic. For most of the characters greater variabil ty in F2 was observed in those crosses having moderate to highly diverse parents. The F2 population derived from ‘UPSM 726 x Type 49’ cross, which involved moderately diverse parents, produced most variable progeny for primary branches, pods per plant and seed yield.
47 citations
41 citations
39 citations
29 citations
TL;DR: The evidence of a possible heterotic threshold indicates that more sophisticated methods such as cell fusion and bilateral sexual polyploidization may not be necessary to exploit the full potential of the hybrid approach in the potato, and a simple and direct “2-way” hybridization approach may be optimal.
Abstract: Complex hybrids containing genomes from three different Solanum tuberosum Groups were synthesized (3-way hybrids), utilizing 2n gametes in 4x−2x crosses. Ten such families were compared to nine analogous two-Group (2-way) hybrid families and nine (1-way) families representing conventional Gp. Tuberosum breeding materials. The three types of crosses, representing three descending levels of heterozygosity, were placed in four field trials. The 3-way hybrids were never significantly superior to the 2-way hybrids for vigor, yield, or tuber type. When yields were adjusted for maturity differences, the 3-way hybrids tended to be inferior to the 2-way hybrids for yield. This suggests that there may be a heterotic threshold in the cultivated potato, beyond which point more heterozygosity does not result in greater vigor or more yield. While the 2-way and 3-way hybrids did not significantly differ from each other, they both dramatically surpassed the conventional 1-way crosses for vigor and yield (42%). The evidence of a possible heterotic threshold indicates that more sophisticated methods such as cell fusion and bilateral sexual polyploidization may not be necessary to exploit the full potential of the hybrid approach in the potato. A simple and direct “2-way” hybridization approach may be optimal, or at least would seem comparable with other hybrid approaches, and is a technology ready for immediate and widespread implementation.
27 citations
21 citations
21 citations
TL;DR: It is suggested that a multiplicative interaction between the heterotic leaf area and photosynthesis rate could possibly explain heterosis in dry matter production in heterotic hybrids.
Abstract: Heterotic hybrids of sorghum produced more dry matter than their respective parents. Therefore, an analysis of leaf are development, rate of photosynthesis and activities of RuBP carboxylase and PEP carboxylase was made to determine whether the superior dry matter production in the hybrids could be attributed to any of these characteristics. Heterosis in leaf area was maintained at all stages in plant growth. Heterosis in photosynthesis was observed only during grain development in certain hybrids. At all other stages, the photosynthesis rate in hybrids were either intermediate or similar to one of the parents. No heterotic effect was observed in enzyme activity at any stage of growth. It is suggested that a multiplicative interaction between the heterotic leaf area and photosynthesis rate could possibly explain heterosis in dry matter production in heterotic hybrids.
TL;DR: The fasciata genes themselves were found to be the most probable cause of these cases of recessive epistasis, which explain most of the quantitative distinctions between the different hybrids.
Abstract: Dominant genes are the main cause of the heterosis induced by fasciated mutants of different lines of Pisum sativum. Most of these cases were originally interpreted by different authors as examples of monogenic overdominance. Several not-closely-linked genes appear to have mutated simultaneously in most of the fasciated lines. Although fasciation itself is recessive, other mutant characters, such as lateness, increased stem length (number and length of internodes) and, in part, seed production per plant, show dominant inheritance. The latter two features are, however, to a considerable extent suppressed in the fasciated lines by unfavourable gene-interactions (epistasis). Crossing these lines with non-fasciated ones shows that the epistatic genes are recessive and the dominant genes are then no longer hindered in their action. By eliminating the epistatic genes from the genomes of fasciated lines by recombination, the heterosis phenomenon has been fixed on six independent occasions for different lines. The fasciata genes themselves were found to be the most probable cause of these cases of recessive epistasis. The question whether different kinds of fasciation affect heterosis differently is examined. Recessive epistasis and dominance explain most of the quantitative distinctions between the different hybrids. In addition, one example of heterosis between non-fasciated lines is given and the possible meaning of the overall results for plant breeding and population genetics is mentioned.
01 Jan 1982
TL;DR: It was suggested that the heterotic potential of H x L crosses could be successfully exploited to create a broader genetic base.
Abstract: Two sets of diallel crosses involving diverse parents were evaluated for heterosis and combing ability for 15 characters measured at seedling, flowering, and harvest phases. The utility of Spanish x Spanish, Valencia x Valencia, Virginia Bunch x Virginia Bunch and Virginia Runner x Virginia Runner crosses along with the infra-specific ones in breeding programs is emphasized. A high range of heterosis was shown by a few crosses. Parents of the diallels were classified as High (H) or Low (L) on the basis of their gca over the 15 characters spanning the entire growth phase of the plant. It was suggested that the heterotic potential of H x L crosses could be successfully exploited to create a broader genetic base.
TL;DR: It is indicated that without the introduction of new germplasm, haploidization followed by repolyploidization can only be expected to result in tetraploids with heterozygosity equal to or below that of their parents.
Abstract: Solanum tuberosum Group Tuberosum haploids (2n = 2x = 24) were inter-mated using bulk pollen. Nearly half of the resulting progeny were tetraploid, arising from bilateral sexual polyploidization. Subsequent yield trials indicated that the diploid progeny did not yield significantly more than the original haploids, but the tetraploid progeny did yield significantly more than their diploid sibs and the original haploids. Tetraploid cultivars and conventional tetraploid breeding families significantly out-yielded the haploid-derived tetraploids. These results and the theoretical considerations which are presented indicate that inter-mating haploidsper se does not increase heterozygosity. More importantly, these results indicate that without the introduction of new germplasm, haploidization followed by repolyploidization can only be expected to result in tetraploids with heterozygosity equal to or below that of their parents.
01 Jan 1982
Journal Article•
TL;DR: Reciprocal recurrent selection is recommended as the suitable breeding methodology for genetic upgrading of this crop for the purposes of oil yield and component characters.
Abstract: The type of gene action has been studied for oil yield and component characters in two crosses of sunflower involving two selections from the variety ‘Peredovick’ and a dwarf selection from variety ‘Smena’. Simple scaling tests, joint scaling tests and interaction models employing six primary generations have been used to assess the occurrence and relative contribution of different components of epistasis. Epistasis has been found to occur for all the characters in both the crosses. The type of epistasis is compared with the occurrence of heterosis. It is found that complementary or duplicate type of epistasis is not as important in the expression of heterosis as are the relative signs and magnitude of additivt, dominance and interaction parameters. Keeping in view the fact that all types of gene action, i.e., additive, dominance and epistatic have been observed in the material, reciprocal recurrent selection is recommended as the suitable breeding methodology for genetic upgrading of this crop.
TL;DR: Combining ability analysis was done on a diallel cross of a random sample of four different cultivated diploid potato populations (Solanum tuberosum Group Andigena haploid, Gp. Phureja and Gp Stenotomum) to determine the amount of heterosis and the gene action involved in the inheritance of tuber yield, fresh vine yield, total plant accumulation (tuber+vine) fresh and dried, dry vine yield and density as discussed by the authors.
Abstract: Combining ability analysis was done on a diallel cross of a random sample of four different cultivated diploid potato populations (Solanum tuberosum Group Andigena haploid, Gp. Tuberosum haploid, Gp. Phureja and Gp. Stenotomum) to determine the amount of heterosis and the gene action involved in the inheritance of tuber yield, fresh vine yield, total plant accumulation (tuber+vine) fresh and dried, dry vine yield and density (specific gravity). The analyses of variance on data from two locations demonstrated significant general combining ability for most traits, indicating a preponderance of additive gene action. Specific combining ability was not significant for any of the traits. Heritabilities for the more important traits such as tuber yield and density were large enough to ensure progress from selection.
Journal Article•
TL;DR: Heterosis for yield in the material was mostly associated with hybrid vigour in number and/or weight of capitula, and the results suggest tremendous potential of hybrids in safflower for raising per hectare yields and oil out-turn.
Abstract: The nature and magnitude of heterosis for plant yield, seed oil percent and a number of other variables related to fitness and productivity in cultivated safflower were assessed in the F1 generation of 8 x 8 full diallel in 1978 and 10 x 10 in 1979. Hybrids displayed substantial differences in their heterotic responses for various characters. Averaged over 146 crosses from both the diallels, heterosis was very high for yield per plant (55%), high for capitulum weight (26%), moderate for capitula number (19.5%) and number of primary branches/plant (13.5%), low for capitulum diameter (6 8%) and negligible or absent for plant height, flowering time, seed weight and percent oil. Hybrids outyielded their superior parents in 76 cases and the best adapted check in 28 cases out of 146 examined. The highest yielding hybrid in the material excelled its superior parent by 119% and the bast standard check by 70% across reciprocal crosses. Hybrids between genetically diverse parents manifested more hybrid vigour than those from closely related ones. A number of top yielding crosses involved either one or both the parents otherwise low or medocire in yield potential. Ranking of crosses based on their heterotic effects over mid or superior parents showed relatively poor agreement with the actual per se performance of crosses. Heterosis for yield in the material was mostly associated with hybrid vigour in number and/or weight of capitula. Reciprocal differences were, in general, low or absent in safflower. No undesirable heterotic responses in maturity duration, plant height and oil percent were detected in crosses that manifested significant positive heterosis for yields. The results suggest tremendous potential of hybrids in safflower for raising per hectare yields and oil out-turn
Journal Article•
TL;DR: Heterosis over better parent ranged from 27.28 per cent for grains per pod (Selection-436 x Chafa) to 111.31% for pods per plant (Phule G-5 x Annegiri) and hybrids showing high heterosis also showed high inbreeding depression.
Abstract: Heterosis over better parent ranged from 27.28 per cent for grains per pod (Selection-436 x Chafa) to 111.31 per cent for pods per plant (Phule G-5 x Annegiri). Maximum beneficial heterosis for grain yield was observed in Phule G-5x Annegiri (72. 11%). In general, hybrids showing high heterosis also showed high inbreeding depression.
Journal Article•
TL;DR: The study supported the importance of harvest index for improving maize yield and provided a genetic background in which expressivity of both harvest index and biological yield can be simultaneously improved.
Abstract: Gene effects and nature of heterosis were determined in eight, early-maturing varieties of maize for grain yield, harvest index and four ear characters by the procedure of Gardner and Eberhart (1966). Additive genetic effects were predominant for grain yield, ear length, ear girth, cob girth and number of grain-rows. The study supported the importance of harvest index for improving maize yield. Early maturing varieties of maize provide a genetic background in which expressivity of both harvest index ard biological yield can be simultaneously improved.
01 Jan 1982
TL;DR: Combining ability, components of genetic variance and graphic analysis revealed that nodulation in the cultivars of Chickpea was predominantly under the control of non-additive gene action although substantial additive effect was also present.
Abstract: Combining ability, components of genetic variance and graphic analysis revealed that nodulation in the cultivars of Chickpea (Cicer arietinum L.) under study, was predominantly under the control of non-additive gene action although substantial additive effect was also present. The crosses giving high specific combining ability effects also manifested highly significant positive heterosis. The parents F-61, Giza and Annegiri possessed mostly dominant alleles while Phule G-5, NEC-249 and N-31 possessed mostly recessive alleles having positive effect on nodule weight.
TL;DR: A general linear model for obtaining fixed parameters in crossbreeding experiments using the principle of minimum average square error is described and the estimability of the parameters is shown.
Abstract: The present paper describes a general linear model for obtaining fixed parameters in crossbreeding experiments. The principle of minimum average square error is used for choosing the « best model for prediction. The effect of ignoring some parameters in general is given. Application of the model to different types of crossbreeding experiment is discussed. In this connection, the estimability of the parameters is shown.
TL;DR: There were significant differences in the absorption and transport of Rb among the cultivars, and between the rainfed and irrigated ones, and this suggests that several ion uptake parameters have to be examined while looking for the phenomenon of heterosis in hybrid plants.
Abstract: The uptake patterns of Rb were examined in four popular sorghum hybrids along with their parents, employing excised roots and intact seedlings with a view to identify heterosis in the absorption or transport processes. The cultivars consisted of two types, generally grown under irrigated or rainfed conditions. The results revealed that there was heterosis in the absorption by excised roots in the rainfed hybrid CSH‐8; and in the trans‐location of Rb to the shoot in the irrigated hybrids, CSH‐5 and CSH‐6. There were significant differences in the absorption and transport of Rb among the cultivars, and between the rainfed and irrigated ones. This suggests that several ion uptake parameters have to be examined while looking for the phenomenon of heterosis in hybrid plants and it should not be restricted to one or two features.
TL;DR: Highly significant positive heterosis was found for root length, diameter and fresh weight in F, hybrids derived in a seven-parent diallel cross of commercially available cultivars of Brassica napus L.sica nupus L., and the inheritance of these three traits is thought to be conditioned by additivity at the majority of loci and partial dominance at the remaining ones.
Abstract: Highly significant positive heterosis was found for root length, diameter and fresh weight in F1 hybrids derived in a seven-parent diallel cross of commercially available cultivars of Brassica napu...
TL;DR: Formulae are derived for predicting the performance of crosses among populations in terms of effects defined in the F2 populations of single loci and interaction effects among two or more loci, arguing that the latter is of limited value in prediction or interpretation of crossbred data.
Abstract: Formulae are derived for predicting the performance of crosses among populations in terms of effects defined in the F2 populations of single loci and interaction effects among two or more loci. The difference between the Fl and mid-parent mean includes dominance (D) additive X additive (AA) and dominance X dominance (DD) effects, that between the Fl and F2 only D and DD effects, and that between the F2 and first backcross mean only AA effects. This parametrization is compared with that in terms of recombination loss, and it is argued that the latter is of limited value in prediction or interpretation of crossbred data. The traditional explanations of heterosis (dominance, overdominance, epistasis) agree with genetic models referring to qualitative and quantitative modes of enzyme activity caused by allelic differences. The proposed models are illustrated in three figures. Heterosis has been defined for various two-way crossbred animal populations in terms of genetic components. Complementarity has been analyzed and for non-linearity and position effects general formulas have been derived.