Incomplete Diallel Research Articles

GENERAL (GCA) AND SPECIFIC (SCA) COMBINING ABILITY FOR QUANTITATIVE CHARACTERS OF ORNAMENTAL VALUE IN F1 INTERSPECIFIC MORNING GLORY HYBRIDS

ISHS XXII International Eucarpia Symposium, Section Ornamentals, Breeding for Beauty - Part II GENERAL (GCA) AND SPECIFIC (SCA) COMBINING ABILITY FOR QUANTITATIVE CHARACTERS OF ORNAMENTAL VALUE IN F1 INTERSPECIFIC MORNING GLORY HYBRIDS

Relationship Between Differential Gene Expression and Heterosis During Ear Development in Maize ( Zea mays L.)

Maize ( Zea mays L.) is one of the most important crops because of the remarkable properties of its hybrid, which is responsible for the high commercial value of hybrid maize. The genetic basis of heterosis (hybrid vigor) is not well understood. A differential display technique was performed to identify genes with differential expression across twelve maize inbred lines and thirty-three hybrids during ear development. An incomplete diallel design was used to investigate the relationship between the global framework of differential gene expression and heterosis. It was found that the genes belonging to MONO pattern (i.e., genes expressed in both parental lines and in hybrid) was the highest in percentage among the total five patterns and illustrated that the properties of differentially expressed genes are not entirely responsible for heterosis. Furthermore, a larger number of differentially expressed genes in hybrid, which serves as a major reservoir for generating novel phenotypes that exhibit heterosis of certain agronomic traits during early development and differentiation of maize ear. Moreover, there were some silent genesin hybrids that are responsible for the arrest or abortion of spikelets and for the increase in kernels weight.

THE SEGREGATION OF TREE HABIT ON PEAR SEEDLINGS IN SIX HYBRID COMBINATIONS

Trees habit is an important trait in pear breeding and pear culture (1, 2, 3). The segregation for trees habit of F1 pear hybrids belonging from six combinations was analysed. The seedlings originate in incomplete diallel cross, effectuated with four genitors (Comtesse de Paris, Milenium, Virgiliu Hibernal, Cluj 89-1-81 selection), were framed in six classes of growth (after UPOV Guidelines), respectively architectural ideotype: 1. Fastigiate; 2. Upright; 3. Semi-upright; 4. Spreading; 5. Drooping; 6. Weeping. In each combination, the majority of F1 hybrids had spreading habit (between 57% in Comtesse de Paris x Milenium and 81% in Milenium x Cluj 89-1-81). The occurrence of high percentages of spreading habit seedlings in all combinations (see the table) suggests that this ideotype of tree growth is easy to obtain in pear breeding. Because a valuable type of tree habit for modern plantation is with a spurred growth habit and strong apical control, it can be appreciated that Milenium (a relative new cultivar created at Fruit Research Station Cluj-Napoca) can be used as genitor for this trait. Especially used as mother genitor in cross with Virgiliu Hibernal (another new cultivar obtained at FRS Cluj), Milenium gave birth to the highest percentage of upright seedlings (16%), and with fastigiate habit (3%)

Heterosis for yield and crossbreeding of the Pacific oyster Crassostrea gigas

Hybrid vigor or heterosis for growth and survival was demonstrated in experimental crosses of inbred Pacific oysters by Hedgecock et al. [Hedgecock, D., McGoldrick, D.J., Bayne, B.L., 1995. Hybrid vigor in Pacific oysters: an experimental approach using crosses among inbred lines. Aquaculture 137, 285–298.]. Substantial evidence for the pervasiveness of heterosis accumulated since then suggests a role for crossbreeding in commercial improvement. Here, we summarize evidence for yield heterosis in juvenile (seed) and adult oysters resulting from four diallel mating experiments. In pair crosses of parental inbred lines, we quantify heterosis by potence, hp=Q/L>1.0, where Q is twice the deviation of a hybrid from the mid-parent value and L is the absolute difference between the mean trait-values of the two parental inbred lines, these contrasts being estimated from ANOVA. For larger incomplete diallel crosses, in which partially inbred parental lines were not reared, we present estimates of Griffing's [Griffing, B., 1956. Concept of general and specific combining ability in relation to diallel crossing systems. Aust. J. Biol. Sci. 9, 463–493.] general and specific combining abilities (GCA, SCA) and, where possible, reciprocal hybrid effects (R). GCA is significant in two of four crosses analyzed, while SCA is significant in all four crosses, particularly at the seed stage, and R is significant in all three crosses, in which reciprocal comparisons were possible. The reciprocal effect is partitioned into maternal (extra-nuclear) and non-maternal (extra-nuclear×nuclear interaction) effects; the latter are significant in 4 of 5 cases, while maternal effects are significant in only 2 of 5 cases. Improvement of commercial oyster seed can be achieved by a combination of selection among inbred lines and crossbreeding of elite inbred lines; pervasive differences between reciprocal hybrids may constrain the direction of interline crosses. Because correlation of seed and adult yield is positive but weak, we propose to retain top inbred parent lines based on seed yield and to re-test the most promising crosses on a much larger production scale.

Analysis of Genotype × Environment Interaction Effects for Starch Pasting Viscosity Characteristics in Indica Rice

Milled rice ( Oryza sativa L.) is composed of approximately 90% starch. The properties of starch have considerable effects on cooked rice palatability and consumer acceptability. Starch pasting viscosity parameters serve as important indices in the estimation of eating, cooking, and processing qualities of rice. In the present study, four cytoplasmic male-sterile (CMS) lines and eight restorer (R) lines have been used in an incomplete diallel cross to analyze seed effects, cytoplasmic effects, maternal gene effects, and their genotype × environment (GE) effects on the following starch pasting viscosity parameters: breakdown (BD), consistency (CS), and setback (SB). The results demonstrated that the total main genetic variances ( V G ) accounted for over 64% of the total genetic variance ( V G + V GE ) for the three traits, indicating that these traits were mainly controlled by the main genetic effects in addition to the GE interaction effects. The estimated total narrow-sense heritability were 67.8%, 79.5%, and 79.5% for BD, CS, and SB, respectively. The general heritability ( h 2 G ) accounted for over 75% of the total heritability ( h 2 G + h 2 GE ), indicating that early selection would be effective for those traits and the selection efficiencies were relatively stable in different environments.

Selection of Interspecific Hybrids for Anther Culture of Indica Rice

The low percentage of callus induction and green-plant regeneration has limited the application of anther culture techniques in indica rice breeding programmes. The aim of this work was to investigate the inheritance of the two characters and to determine whether good combinations with high-frequency callus induction and green-plant regeneration could be selected by sexual hybridization of suitable parents. So, a 3 × 4 incomplete diallel crosses were conducted between 7 parental lines. Three of them were believed to possess relatively high callus induction capacity and the other four relatively high green-plant regeneration capacity, based on our previous studies. Analysis of combining abilities and heritabilities revealed that both additive and non-additive effects were found to be important in the genetic control of callus induction. In case of green-plant regeneration, non-additive effects were predominant. Broad sense heritability values of 0.92 for callus induction and 0.98 for green-plant regeneration suggested that more than 90% of the observed variation was due to genetic effects, with just less than 10% attributed to non-genetic or environmental effects. In addition, the moderate narrow sense heritability values of 0.49 for callus induction, 0.29 for green-plant regeneration showed that the potential to introduce high responding ability into low lines was moderate. It was therefore conceivable that the frequency of anther culture response might be improved by suitable hybridization and selection strategies. A hybrid combination of code no. 67/107 incorporating high callus induction and high green-plant regeneration ability was selected in which genotype with high values of general combining ability (GCA) and positive effects of specific combining ability (SCA).

Genetic analysis of endosperm, cytoplasmic and maternal effects for histidine and arginine in indica rice (Oryza sativa L.) across environments

Genetic main effects and genotype x environment (GE) interaction effects for amino acids histidine (His) and arginine (Arg) in milled rice were analyzed by using the genetic models for quantitative traits of triploid endosperm. Nine cytoplasmic male sterile lines as females and five restoring lines as males were included in an incomplete diallel cross in two environments. Results indicated that the His content and Arg content were mainly controlled by genetic main effects, whereas the ratios of His content to protein content (RHP) or Arg content to protein content (RAP) were mainly affected by GE effects. Since genetic variances involved were found significantly for all traits, the genetic controlling of these two amino acids could be simultaneously affected by the endosperm, cytoplasm and maternal genetic effects. For genetic main effects, the cytoplasm and maternal additive effects for these two amino acids possessed high percentage of 60.2-70.9%, which indicated that selection for these amino acids based on maternal performance could be more effective than that based on single seed. The total narrow-sense heritabilities were high for Arg and RAP with 82.4% and 82.3%, and low for His and RHP with 46.4% and 18.2%, respectively. Since general heritabilities for these two amino acids were found to be much larger than GE interaction heritability, the selection advance for these traits could be expected at different environments. Most cytoplasmic and maternal additive correlations were significantly positive and dominance interaction correlations were also important among all the pairwise traits. Indirect selection of these two amino acids applied in rice breeding was discussed.

Spectrum and inheritance of resistance to the root‐knot nematode Meloidogyne hapla in Rosa multiflora and R. indica

AbstractThe spectrum and inheritance of resistance to the root‐knot nematode Meloidogyne hapla was studied in the diploid species Rosa multiflora and R. indica. The host suitability of seven rose rootstocks, namely five R. multiflora (K2, K1, Floradale, CE63 and CE65) and two R. indica (CE35 and Maroc) clonal accessions, was evaluated using four geographic isolates of M. hapla. Plants grown under greenhouse conditions were tested at high and durable inoculum pressure of nematodes and rated for nematode infestation five months after inoculation on a 0–5 gall index. Different host suitabilities to M. hapla were demonstrated depending on the nematode isolates: in R. multiflora, the clone K2 had a resistant (R) response to all isolates; the clone K1 ranged from intermediate (I) (isolate ‘Canada’) to resistant (other isolates), Floradale was shown to be intermediate, whereas CE63 and CE65 were moderate to good hosts (H). In R. indica, both rootstocks were good to excellent hosts for the isolate Canada but resistant to all three other isolates, thus expressing an isolate‐specific resistance. A study on the genetics of resistance in R. multiflora to the M. hapla isolate Canada was then conducted using an incomplete diallel cross involving all previous clones except Floradale. A total of 120 hybrid individuals belonging to several progenies representing the cross combinations R × I, R × H, I × H and H × H were evaluated. Individuals of each progeny generally ranged into a monomodal distribution that suggests polygenic inheritance of resistance. In the family Rosaceae, the differences in the resistance genetics to the meiotic species M. hapla and to the mitotic species, M. arenaria, M. incognita and M. javanica are discussed in relation to the reproductive status of the nematodes.

Estimation of variances of the effects of incomplete diallels using a matrix approach

A matrix approach is described for assessing the variance of effects in incomplete diallels designs. The method is illustrated by reference to simulated complete and incomplete diallels using different combinations of constraints, average degree of dominance and, for the incomplete diallel, number of hybrids. Our results showed that caution should be taken in working with incomplete diallels under conditions of overdominance because there were changes in the rank of the genotypes when the excluded hybrid had parents with a low frequency of the favorable allele (i.e. the allele which increases expression of a character). The expression described in this paper is a rapid and safe approach to estimate variances and covariances of the effects of contrasts of incomplete diallels.

Avaliação de nove linhagens de milho em cruzamentos dialélicos quanto à tolerância ao alumínio

Avaliaram-se nove linhagens endogâmicas de milho e seus cruzamentos quanto à tolerância ao alumínio (Al), em um dialelo incompleto. Foram utilizados os índices fenotípicos de comprimento relativo de raiz seminal (CRRS), comprimento líquido de raiz seminal (CLRS) e coloração por hematoxilina, determinados após sete dias de crescimento em solução nutritiva contendo 222 mimoles L-1 de Al. Os resultados dos cruzamentos dialélicos demonstraram que os efeitos aditivos foram mais importantes que os efeitos não-aditivos para os três índices avaliados. As linhagens L13, L724, L723 e L16 seriam as mais indicadas para a obtenção de híbridos visando tolerância ao Al, por apresentarem os melhores valores de capacidade geral de combinação e por participarem dos cruzamentos de melhor capacidade específica de combinação. Uma correlação de 0,76 foi observada entre os índices CLRS e a coloração por hematoxilina, de 0,63 entre CLRS e CRRS e de 0,27 entre CRRS e coloração por hematoxilina. A coloração por hematoxilina demonstrou ser uma valiosa ferramenta para programas de melhoramento de milho que visam a seleção de genótipos com maior tolerância ao alumínio.

Inbreeding depression: tests of the overdominance and partial dominance hypotheses.

The two principal theories of the causal mechanism for inbreeding depression are the partial dominance hypothesis and the overdominance hypothesis. According to the first hypothesis, inbreeding increases the frequency of homozygous combinations of deleterious recessive alleles thereby decreasing fitness, whereas the overdominance hypothesis posits that inbreeding increases homozygosity and thus reduces the frequency of the superior heterozygotes. These two hypotheses make different predictions on the effect of crossing inbred lines: the overdominance hypothesis predicts that trait means will be restored to the outbred means, whereas the partial dominance hypothesis predicts that trait means will exceed those of the outbred population. I tested these predictions using seven inbred lines of the sand cricket, Gryllus firmus. Fourteen generations of brother-sister mating resulted in an inbreeding depression of 20-34% in four traits: nymphal weights at ages 14 days, 21 days, 28 days, and early fecundity. An incomplete diallel cross of these lines showed genetic variation among lines and an increase in all trait means above the outbred means, with three being significantly higher. These results provide support for the partial dominance hypothesis and are inconsistent with the overdominance hypothesis.

INBREEDING DEPRESSION: TESTS OF THE OVERDOMINANCE AND PARTIAL DOMINANCE HYPOTHESES

The two principal theories of the causal mechanism for inbreeding depression are the partial dominance hypothesis and the overdominance hypothesis. According to the first hypothesis, inbreeding increases the frequency of homozygous combinations of deleterious recessive alleles thereby decreasing fitness, whereas the overdominance hypothesis posits that inbreeding increases homozygosity and thus reduces the frequency of the superior heterozygotes. These two hypotheses make different predictions on the effect of crossing inbred lines: the overdominance hypothesis predicts that trait means will be restored to the outbred means, whereas the partial dominance hypothesis predicts that trait means will exceed those of the outbred population. I tested these predictions using seven inbred lines of the sand cricket, Gryllus firmus. Fourteen generations of brother-sister mating resulted in an inbreeding depression of 20–34% in four traits: nymphal weights at ages 14 days, 21 days, 28 days, and early fecundity. An incomplete diallel cross of these lines showed genetic variation among lines and an increase in all trait means above the outbred means, with three being significantly higher. These results provide support for the partial dominance hypothesis and are inconsistent with the overdominance hypothesis.Corresponding Editor: P. Jarne

Model of experimental clonal seed orchard for the production of Serbian spruce sPicea omorika /Panc./Purkyne) intraspecific hybrids

The presented model for the establishment of an experimental clonal seed orchard of Serbian spruce was designed based on the results of the analysis and assessment of the genetic potential of Serbian spruce seedling seed orchard at Godovik. Based on the results of the analyses, eight superior half-sib lines of Serbian spruce were selected, of which 24 genotypes were selected. Their hybridisation, by the model of incomplete diallel cross resulted in 21 combinations at the level of half-sib lines, i.e. 48 combinations at the level of parent genotypes. The applied study methods identified the potentially valuable genotypes-cone producers i.e. pollinators, which will be fixed by cloning in the seed orchard of the second generation for the production of the promising hybrids.

Genetic variation within and between populations of Pinus sylvestris L. (Scots pine) for susceptibility to Melampsora pinitorqua Rostr. (pine twist rust).

The genetic variability of Scots pine (Pinus sylvestris L.) for twist rust susceptibility and the consequences for genetic improvement of the species were evaluated after artificial inoculation of 1-year-old seedlings in greenhouse tests. Wind-pollinated progenies, factorial and incomplete diallel mating designs were used to compare two natural populations of Scots pine (Haguenau, France, and Taborz, Poland) and their hybrids (Haguenau x Taborz). Families from Taborz were significantly (P < 0.001) less susceptible to twist rust than those from Haguenau. Inter-population hybrids were as susceptible as the Haguenau population. No clear relationship between severity of infection, shoot length and phenological stage at time of inoculation was observed in intra- and interpopulation crosses. Differences observed between the two natural populations for their response to twist rust are suggested to be the consequence of local adaptation simultaneously for climatic conditions and pathogen pressure. Within each of the two populations, the effects of general combining abilities (GCA) for rust susceptibility were predominant, although estimation of individual heritabilities remained at a moderate level (0.30-0.54). In interpopulation crosses, GCA effects of Haguenau and Taborz populations were still predominant. Moreover, hybrid performance could be predicted with confidence based on the intrapopulation GCA values of parents. Genetic gain on twist rust resistance could be achieved quickly through intrapopulation mass or backward selection based on wind-pollinated progeny tests.

Analyses for inheritance and combining ability of photochemical activities measured by chlorophyll fluorescence in the segregating generation of sugarcane

General and specific combining abilities for chlorophyll fluorescence parameters in leaves of seven sugarcane lines widely used as parents in China were estimated from seedlings of the 12 crosses mated in an incomplete diallel cross-design and of two reciprocal crosses. Results indicated that potential quantum yield of PSII, measured as F v/ F m, was highly inherited and depended on nonadditive gene effects, however, the inheritances of the photosynthetic activities estimated by Rfd and the pool size of the electron acceptors on the reducing side of PSII as measured by T 1/2 depended on additive gene effects. Heritability of T 1/2 was less than that of the other fluorescence parameters. The high general combining ability of YN73-204, CP67-412 as female parents and Ya73-512, Ya71-374 as male parents identified those lines as parents with high photosynthetic efficiency. The performances of F 1 progenies derived from YN73-204 × Ya73-512 and CP67-412 × Ya73-512 were the most desired cross-combinations for high photosynthetic efficiency.

Genetic control of paste viscosity characteristics in indica rice (Oryza sativa L.)

Paste viscosity parameters play an important role in estimating the eating, cooking and processing quality of rice. Four cytoplasmic male-sterile (CMS) lines and eight restorer (R) lines were employed in an incomplete diallel cross to analyze seed effects, cytoplasmic effects and maternal gene effects on the viscosity profiles of indica rice. The results indicated that the viscosity profiles of rice were controlled by the direct effects of the seed, by the cytoplasm and by maternal plant. The seed-direct effects (VA+VD) accounted for over 51% of the total genetic variances (VA+VD+VC+VAm+VDm) for all the traits, suggesting that seed direct effects were more important than maternal effects and cytoplasmic effects. The additive variances (VA+VAm) were much larger than the dominance variances (VD+VDm), which revealed that additive genetic effects were the major contributors of genetic variation for the paste viscosity profiles, and that selection could be applied for viscosity traits in the early generations. Significant cytoplasmic variance (VC) was detected for hot paste viscosity (HPV), cool paste viscosity (CPV) and consistency viscosity (CSV). The cytoplasmic effects for these three traits can, therefore, not be neglected in rice breeding. It was also shown that seed heritabilities (h2o) tended to be larger than maternal heritabilities (h2m) and cytoplasmic heritabilities (h2c). Prediction of the main genetic effects for 12 parents showed that CMS lines had highly positive effects on all the traits except for the breakdown viscosity (BDV), and that R lines had both positive and negative effects on the paste viscosity characteristics.

Pre-zygotic breeding barriers between the wild diploid potato species Solanum maglia and S. kurtzianum from Argentina

Solanum maglia Schldl. is a wild tuber-bearing species from the Quebrada de Alvarado (Mendoza, Argentina) and the Valparaiso area (Chile). Only diploid cytotypes are known from Argentina, while diploids and triploids are found in Chile. Five diploid accessions from Argentina did not produce seeds upon intercrossing. Thus, the basis of this behaviour and the crossability relations of this species with S. kurtzianum, Bitt. et Wittm., another diploid species that grows in its vicinity were investigated. After checking pollen viability, intraspecific and interspecific pollinations were carried out following an incomplete diallel mating design. Five emasculated flowers were pollinated per each one of 135 different combinations of genotypes (crosses); three flowers were fixed in FAA and analyzed under fluorescent microscopy, whereas the remaining two were left on the plant for fruit and seed set. Pollen tube growth was arrested in the first third of the style and no seeds were obtained in intraspecific S. maglia crosses. In interspecific crosses and according to their direction, pollen tubes either grew normally to the base of the style or were arrested in the last third, producing no fruits or fruits with a variable number of seeds in each. It is concluded that the five S. maglia accesions are, possibly, one clone and, thus, the gametophytic auto-incompatibility system prevents seed formation upon intercrossing. On the other hand, the incompatibility reaction observed in the interspecific crosses might be controlled by one or more genes independent of the S-locus.

Fusarium resistance in Gladiolus: Selection in seedling populations

AbstractA test to select Fusarium resistant seedlings of Gladiolus is described. Seedlings of 37 populations, obtained from an incomplete diallel between eight parents with different levels of Fusarium resistance, were used. Significant differences in Fusarium infection between and within populations were detected. Most of the descendants selected had a resistant G. dalenii genotype as one of the parents. The resistance level of the parents was associated with the general combining ability for Fusarium resistance based on the seedling test. Implications for resistance breeding are discussed.

Genetic and heterosis analysis for cooking quality traits of indica rice in different environments

Genetic effects and genotype×environment (GE) interaction effects on the cooking quality traits of indica rice (Oryza sativa L.) were analyzed based on a genetic model for quantitative traits of triploid endosperm in cereal crops. Nine cytoplasmic male-sterile lines as females and 5 restoring lines as males were used in an incomplete diallel cross over 2 years. The cooking quality traits studied were observed to be mainly controlled by genetic effects, but GE interaction effects, especially for amylose content (AC) and alkali spreading score (ASS), were also indicated. Among the genetic effects, seed direct effects and maternal effects were the main components of AC and ASS, respectively; cytoplasmic effects were the main components of gel consistency (GC). Among the GE interaction effects, AC and ASS were mainly affected by maternal interaction effects and GC by direct interaction effects. Additive effects and/or additive interaction effects were the main factors controlling the performance of rice cooking quality traits except for GC which was affected by dominant interaction effects. For AC and GC, there were seed heterosis and/or maternal heterosis. The predicated genetic effects indicated that four parents were better than the others in improving the rice cooking quality traits of the progenies. It was shown that genetic heterosis and GE interaction heterosis were important, especially for amylose content trait in early season indica rice.

Heterosis and combining ability for plant height and its components in hybrid wheat with Triticum timopheevi cytoplasm

The heterosis and combining ability for plant height and its components of hybrid wheat were investigated in an incomplete diallel experiment including 5 CMS lines and 4 restorer lines. The results showed that heterosis (HS) and heterobeltiosis (HBS) occurred in plant height (PH) and length of the first internode (LFI), second internode (LSI), third internode (LTI), basal internode (LBI) and the spike (LS) of hybrids, but their values varied among crosses and characters; the HS and HBS of LBI were larger than those of other characters, the HS and HBS of LSI and LTI contributed a lot to those of PH. There were significant relationships between internode lengths and PH for specific combining ability (SCA) and general combining ability (GCA), and among lengths of the adjacent internodes for SCA and/or GCA effects. However, the relationships of LS with the lengths of internodes and PH were insignificant for GCA, SCA, HS and HBS. The SCA effects were more important than GCA effects for LFI, the reverse was true for LSI, LTI, LS and PH, and the SCA effects was nearly equal to the GCA effects for LBI. So, LFI was mainly influenced by non-additive effect of genes, while LSI, LTI, LS and PH were mainly controlled by additive gene effects, LBI was controlled equally by additive and non-additive effects of genes. The genes that control the length of specific internode not only affect PH, but also the length of the adjacent internode. The genetic system in charge of lengths of internodes and plant height is independent of that for length of spike. Thus, it is possible to develop new wheat cultivars or hybrid combinations having long spike but dwarf plant height.