Incomplete Diallel Cross Research Articles

Additive‐genetic relationships of growth and morphometrics to meat yield traits in Macrobrachium nipponense (De Haan, 1849)

AbstractBased upon mixed linear model and incomplete diallel cross between different strains of Macrobrachium nipponense, the additive‐genetic correlations of growth and morphometrics with meat yield traits in M. nipponense were estimated using the minimum norm quadratic unbiased estimation procedure. Path analysis method was utilized to investigate the overall additive‐genetic determinations of growth and morphometric traits on the meat yield traits. Results indicated that growth and morphometrics were genetically positively correlated with abdominal meat weight (p < 0.01), but were not genetically correlated with abdominal meat percentage (p > 0.05) in both sexes. Growth and morphometrics were genetically positively correlated (p < 0.01). Abdominal meat weight was genetically positively correlated with abdominal meat percentage (p < 0.01). In terms of the overall additive‐genetic determination, body weight had the greatest impact on abdominal meat weight in both sexes. In contrast, abdominal meat weight, abdominal length, and body weight were most influential on abdominal meat percentage in both sexes. The genetic relationships of growth and morphometrics to meat yield traits were elucidated in M. nipponense for the first time, contributing to formulation of sound improvement plan for the meat yield traits in this commercially important prawn species.

Combining Ability Analysis of Maize Inbred Lines Suitable For Machine Harvest

Using self selected maize inbred lines and hybrid combinations as test materials, the combining ability of maize hybrids suitable for machine harvest was analyzed. Ten maize inbred lines were selected as female parent (P1) and three inbred lines as male parent (P2). The experiment design of incomplete diallel cross was adopted in this study. The combining ability of 10 agronomic characters such as plant height, ear height, ear grain weight, ear length, ear diameter, number of rows per ear, number of grains per row, 100- grain weight, number of branches in male ear and water content at harvest were analyzed. The present findings revealed that in terms of general combining ability, JM39 was the best in ear length, grain number per row, 100-grain weight, branch number of male ear and water content at harvest, followed by JM35, JM26 and JM28. In terms of specific combining ability, the combination with better performance were JM39×JF167, JM39×JF200 and JM35×JF167. Moreover, JM26, JM28, JM35 and JM39 could be used directly, and the other inbred lines could be improved and reused. Plant height, number of rows per ear, number of grains per row and 100-grain weight should be selected in the early generation, while ear height, ear diameter, number of branches in male ear and water content at harvest should be selected in the late generation. Bangladesh J. Bot. 51(4): 889-895, 2022 (December) Special

Combining Ability of Some Agronomic Characters of Sweetwaxy Double Recessive Maize Inbred Lines

The present study was undertaken to explore more excellent sweet-waxy maize germplasm resources and provide a theoretical basis for the rational application of sweet-waxy maize inbred lines. Eight sweetwaxy maize inbred lines VB. RN1621, RN1423, RN1432, RN1636, RN1441, RN1443, RN1457 and RN1669 were selected as female parents (P1) and three sweet-waxy maize inbred lines e. g. LN505, LN506 and LN515 were taken as male parents (P2). Using incomplete diallel cross NCII design, 24 combinations were configured to analyze the combining ability of eight agronomic characters such as plant height, ear height, ear grain weight, ear length, number of grains per row, hundred-grain weight, peel residue rate and amylopectin content. It was obaerved that the order of general combining ability was RN1669, RN1636 and LN506. The combination with the highest effective value of special combining ability was RN1641 × LN506, RN1621 × LN506 followed by RN1657 × LN506 which ranked third. Plant height, panicle grain weight and bark residue rate should be selected in the early generation. The ear height, ear length, 100-grain weight and amylopectin content may be selected in the late generation, which can be used for sweet-waxy maize breeding. Bangladesh J. Bot. 51(4): 849-854, 2022 (December) Special

Analysis Of Agronomic Traits Combining Ability Of Sweetwaxy Double Recessive Corn Inbred Lines

Sweet-waxy corn is a kind of fresh corn which is harvested, processed and eaten in the milk ripening period. It is one of the most popular special corns in the fresh corn market. In order to screen and evaluate the breeding value of sweet-waxy corn inbred lines, 10 selected sweet waxy double recessive corn inbred lines i.e JT111, JT113, JT116, JT120, JT124, JT128, JT131, JT135, JT139 and JT145 were used as female parents (P1), and 3 waxy corn inbred lines namely JN44, JN55 and JN88 were used as male parents (P2), and NC II design of incomplete diallel cross was used to analyze combining ability of 10 agronomic characters, including plant height, ear height, grain weight per ear, ear length, ear diameter, rows per ear, grains per row, 100-grain weight, skin residue rate and amylopectin content. Results showed that in general combining ability, JT124 had the best performance in ear length, grain number per row, 100-grain weight, skin residue rate and amylopectin content, and the better inbred lines were JT120, JT111 and JT113. In the special combining ability, JT124×JN55, JT124×JN88 and JT120×JN55 were the best crossing combinations. JT124, JT120, JT111 and JT113 could be used directly, and other inbred lines could be improved and reused. Plant height, row number per ear, grain number per row and 100-grain weight should be selected in early generation, while ear height, ear diameter, skin residue rate and amylopectin content should be selected in late generation. According to this, one can select the breeding target and the suitable parent inbred line. Bangladesh J. Bot. 51(4): 923-929, 2022 (December) Special

The Relation between Genetic Difference for Parents of Hybrid Rice and Heterosis

Exploring the indica-japonica differentiation in parents of hybridization can provide theoretical bases for utilizing inter-subspecific heterosis. In this study, 5 sterile lines and 18 self-bred restorer lines were used as female parents and male parents respectively. Then 90 combinations were constructed by incomplete diallel cross followed by relationship analysis between parental Cheng’s index difference value and Euclidean distance and heterosis. The results showed a significant correlation between several phenotype values, super male parent heterosis and control heterosis and Euclidean distance or Cheng’s index difference value. However, it was no significant correlation for yield. Further analysis found a common interval, 3.41 - 3.46 for Euclidean distance and 3 - 4 for cheng’s index difference value of parents, which was significant or high significant positive correlated with phenotype value, super male parent and control heterosis of main yield traits. This illustrates that the larger the genetic difference of parents was, the stronger the heterosis combinations were, when the genetic differences of parents were in an appropriate range.

Transcriptome Analyses Indicate Significant Association of Increased Non-Additive and Allele-Specific Gene Expression with Hybrid Weakness in Rice (Oryza sativa L.).

The heterosis in hybrid rice is highly affected by the environment and hybrid weakness occurs frequently depending on the genotypes of the hybrid and its parents. Hybrid weakness was also observed in our field experiments on nine rice hybrids produced by 3 × 3 incomplete diallel crosses. Among the nine hybrids, five displayed mid-parent heterosis (MPH) for grain yield per plant, while four showed mid-parent hybrid weakness (MPHW). A sequencing analysis of transcriptomes in panicles at the seed-filling stage revealed a significant association between enhanced non-additive gene expression (NAE) and allele-specific gene expression (ASE) with hybrid weakness. High proportions of ASE genes, with most being of mono-allele expression, were detected in the four MPHW hybrids, ranging from 22.65% to 45.97%; whereas only 4.80% to 5.69% of ASE genes were found in the five MPH hybrids. Moreover, an independence test indicated that the enhancements of NAE and ASE in the MPHW hybrids were significantly correlated. Based on the results of our study, we speculated that an unfavorable environment might cause hybrid weakness by enhancing ASE and NAE at the transcriptome level.

Coordinating High Yield and Superior Eating Quality of Rice: A Case Study of Hybrid Varieties Derived from Longke638S and Jing4155S

The planting area of hybrid rice (Oryza sativa L.) has continuously decreased in recent years partially because of the low eating quality. Longke638S and Jing4155S are two elite male sterile lines, which are used for developing many hybrid varieties with large planting areas in China. Here, 21 hybrid rice varieties of an incomplete diallel cross population with Longke638S and Jing4155S as female parents were planted under field conditions for two consecutive years, aiming to investigate the physiological and transcriptomic characteristics that is required for coordinating high yield and superior eating quality. As a result, grain yield ranged from 7.15 to 9.23 t ha−1 in 2019 and from 7.49 to 9.23 t ha−1 in 2020, and a negative relationship was identified between yield and quality-related traits. Hybrid varieties with Longke638S as the female parent (LLY) had higher yield but lower eating quality than those with Jing4155S as the female parent (JLY). The higher yield of LLY over JLY was due to higher biomass production and N uptake as well as higher yield stability across planting years, while their lower grain quality can be mainly ascribed to lower amylose content and alkali spreading value. Male parents significantly affected yield-related traits of LLY and eating quality-related traits of JLY. Candidate genes involved in grain starch biosynthesis were differentially expressed between LLYHZ, JLYHZ, and JLY1212, such as Wx and ALK. Overall, this study examined the relationship between grain yield and eating quality and identified the physiological and molecular traits that limited grain yield or eating quality of LLY and JLY hybrid varieties.

Analysis of combining ability for stem-related traits and its correlations with lodging resistance heterosis in hybrid wheat

With the application of hybrid wheat, lodging is becoming one of the major factors limiting high yield in its production. However, few studies have focused on combining ability and heterosis analysis of stem-related traits. In this study, 24 crosses were made according to NCII genetic design, using the three (photo-sensitive male sterile lines)×eight (restorer lines) incomplete diallel crosses. The length of basal second internode (LBSI) and breaking strength of basal second internode (BSBSI) as well as other stem-related traits were used to perform the principal component analysis (PCA), combining ability and heterosis analysis. The PCA results showed that the variables could be classified into two main factors, which were named as the positive factor (factor 1) and the negative factor (factor 2), and accounted for 52.3 and 33.2%, respectively, of the total variance in different variables, combined with the analysis for index weight indicated that the factor 1-related traits play positive roles in lodging resistance formation of hybrids. Combining ability variance analysis indicated that its genetic performance was mainly dominated by additive gene effects, and the hybrid combinations with higher lodging resistance can be selected by using of 14GF6085 (R1), 14GF6343-2 (R4), 14GF6937 (R6), 14GF7433-1 (R7), and BS1086 (M3), which are with the features with lower general combining ability (GCA) effects of factor 2-related traits whereas higher GCA effects of factor 1-related traits. The heterosis analysis showed that the wide range of heterosis varied with the traits and combinations, and GCA or specific combining ability (SCA) effects of factor 1-related traits except wall thickness of basal second internode (WTBSI) were positively and closely related to the heterosis of lodging resistance. Generally, the correlation coefficients of heterosis to GCA effects of sterile lines (GCAm) of factor 1-related traits are significantly higher than that to GCA of restorer lines (GCAr) and SCA, combined with the higher GCAm variance values of factor 1-related traits compared to GCAr, the GCAm of factor 1-related traits should be particularly considered when breeding hybrid combinations. The heritability analysis showed that the narrow-sense heritability of the diameter of basal second internode (DBSI) and the center of gravity height (TCGH) were obviously lower (<60%) than other traits, suggesting that these two traits were suitable for selection in higher generation for parental breeding. These could provide a theoretical basis for parental breeding and heterosis utilization of lodging resistance.

Transcriptome Reveals Allele Contribution to Heterosis in Maize.

Heterosis, which has greatly increased maize yields, is associated with gene expression patterns during key developmental stages that enhance hybrid phenotypes relative to parental phenotypes. Before heterosis can be more effectively used for crop improvement, hybrid maize developmental gene expression patterns must be better understood. Here, six maize hybrids, including the popular hybrid Zhengdan958 (ZC) from China, were studied. Maize hybrids created in-house were generated using an incomplete diallel cross (NCII)-based strategy from four elite inbred parental lines. Differential gene expression (DEG) profiles corresponding to three developmental stages revealed that hybrid partial expression patterns exhibited complementarity of expression of certain parental genes, with parental allelic expression patterns varying both qualitatively and quantitatively in hybrids. Single-parent expression (SPE) and parent-specific expression (PSE) types of qualitative variation were most prevalent, 43.73 and 41.07% of variation, respectively. Meanwhile, negative super-dominance (NSD) and positive super-dominance (PSD) types of quantitative variation were most prevalent, 31.06 and 24.30% of variation, respectively. During the early reproductive growth stage, the gene expression pattern differed markedly from other developmental stage patterns, with allelic expression patterns during seed development skewed toward low-value parental alleles in hybrid seeds exhibiting significant quantitative variation-associated superiority. Comparisons of qualitative gene expression variation rates between ZC and other hybrids revealed proportions of SPE-DEGs (41.36%) in ZC seed DEGs that significantly exceeded the average proportion of SPE-DEGs found in seeds of other hybrids (28.36%). Importantly, quantitative gene expression variation rate comparisons between ZC and hybrids, except for transgressive expression, revealed that the ZC rate exceeded the average rate for other hybrids, highlighting the importance of partial gene expression in heterosis. Moreover, enriched ZC DEGs exhibiting distinct tissue-specific expression patterns belonged to four biological pathways, including photosynthesis, plant hormone signal transduction, biology metabolism and biosynthesis. These results provide valuable technical insights for creating hybrids exhibiting strong heterosis.

Phenotypic and genetic dissection of cadmium accumulation in roots, nodes and grains of rice hybrids

Rice accumulates higher levels of cadmium (Cd) in grain than other cereals, and hybrid rice varieties cover around half of the total rice area in China. Therefore, understanding the phenotypic and genetic characteristics of Cd accumulation in rice hybrids is vital for food safety. An incomplete diallel cross design was used to analyse the heritability and combining ability of Cd accumulation in rice hybrids growing in soil contaminated with Cd. The quantitative real-time PCR was used to detect the gene expressions that related to Cd uptake and transport. The Cd contents in brown rice, nodes and roots were detected by ICPOES, and the Cd contents in xylem sap were detected by ICPMS. Additive effects dominated the Cd accumulation in brown rice, upper nodes, and the Cd translocation efficiency from roots to nodes of hybrids. The Cd accumulation in brown rice was positively correlated with Cd accumulation in upper nodes and translocation efficiency from roots to nodes. Regarding the general combining ability, the restorer lines R2292 and R2265, and the male sterile lines KeBX58S, Ke20A, Ke76-1BS and Ke244-1BS were found to be potential elite parental lines for developing hybrid rice with low Cd accumulation. Hybrid rice with low Cd accumulation in brown rice can be derived from parental lines with low general combining ability for Cd content in brown rice.

Heterosis of plant gross weight and heterotic group classification of inbred lines in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Heterotic groups have been well studied in hybrid breeding of grain crops, such as maize. However, little such information is available for Chinese cabbage. Plant Gross Weight (PGW) is one of the most important yield traits of Chinese cabbage. In this work, 48 F1 hybrids were obtained by incomplete diallel cross (6 × 8) of 14 Chinese cabbage inbred lines, then all parents and F1 hybrids were cultivated to evaluate heterosis performance on the PGW trait in two growing seasons (2017 and 2018) at Yangling, China. A total of five methods were used to determine the heterotic groups of tested inbred lines, which include 1) SCA method based on specific combining ability effect, 2) SCA-Y method based on SCA effect by Yang's method, 3) HSGCA method based on heterotic group specific and general combining ability, 4) HGCAMT method based on general combining ability of multiple traits. Besides, the 14 parental lines also clustered by 5) SSR method based on similarity of a core set of 28 simple sequence repeat (SSR) markers. The result showed that heterosis is obvious on the PGW trait in most F1 hybrids, with the mean value of Mid-parent heterosis (MPH) and Better-parent heterosis (BPH) is 111.17 % and 82.03 % respectively. PGW and MPH of F1 hybrids were used as final indexes to evaluate the efficiency of these five methods on heterotic group classification. The result revealed that HSGCA method and SCA method are most optimal to classify the heterotic groups in Chinese cabbage with identical division results. SSR method based on the core set of 28 SSR markers is also an effective way to predict heterosis in advance which can be used as the basis of field cross design. The 14 inbred lines of Chinese cabbage were classified into five heterotic groups based on common results of HSGCA method and SCA method. Furthermore, five inbred lines were selected as testers for further determining heterotic groups of other new inbred lines. This work is expected to raise the breeding efficiency of Chinese cabbage hybrid breeding and provide reference for classifying heterotic groups in other vegetable crops.

Combining ability analysis on rhizomatousness via incomplete diallel crosses between perennial wild relative of rice and Asian cultivated rice

Compared with annual cultivated rice, perennial rice had great advantages of soil erosion control, labor saving, water and fertilizer management, etc. As the key organ for perenniality, rhizome can help grasses to achieve rapid expansion to occupy more environmental resources, and withstand the harsh environmental conditions. Oryza longistaminata, a perennial wild relative of rice with vigorous rhizomes, is an ideal donor for transferring perenniality to Asian cultivated rice (Oryza sativa). However, some hybrid F1 between O. longistaminata and cultivated rice didn’t have rhizomes. Obtaining rhizomatous hybrid progeny becomes a prerequisite for the rhizomes study. In this work, four varieties of O. sativa and three accessions of O. longistaminata were used to carry out an incomplete diallel cross experiment. It was found that most F1 hybrids had rhizomes with varying length and numbers. Data analysis showed that the general combining ability (GCA) of the female parents had significant effect on rhizome-related trait of the F1s. Nevertheless, the GCA of the male parents and special combining ability of the hybrid combination played minor effect. And we speculated that the appropriate choice for female parents is more crucial to obtain rhizomatous hybrid. As the first incomplete diallel cross between O. longistaminata and O. sativa, this work would be benefit to appropriate parent selection for genetic research and breeding of perennial rice.

Genetic determination of processing traits in the red swamp crayfish, Procambarus clarkii (Girard)

The additive genetic correlations of processing traits (two traits, abdominal meat weight and yield) with growth (body weight) and morphometrics (seven traits, chela length, chela width, cephalothorax length, cephalothorax width, abdominal length, abdominal width and abdominal depth) in red swamp crayfish (6 months old) were first estimated within two sexes based upon the additive-dominance genetic model under two rearing environments. Three geographic broodstocks of Procambarus clarkii (Guantan, Dapu and Yanghe) were used. The genetic mating design was incomplete diallel cross, in which three mating combinations (Guantan ♂ × Dapu ♀, Guantan ♂ × Yanghe ♀, and Dapu ♂ × Yanghe ♀) were produced. Path analysis method was then used to ascertain the overall genetic determinations of growth and morphometric traits on processing traits. The objective of this study is to recommend feasible strategy for improvement of processing traits in P. clarkii. The results indicated that body weight was highly positively correlated with processing traits; chela traits were negatively correlated with abdominal meat weight and positively correlated with abdominal meat yield, but very small in magnitude; negative genetic correlations occurred between cephalothorax dimensions and processing traits; abdominal dimensions were positively correlated with processing traits. Upon pursuing indirect selection for processing traits, body weight should be the primary candidate for direct selection, and at the same time smaller cephalothorax or larger abdominal dimensions also should be taken into consideration.

GWAS for resistance against black point caused by Bipolaris sorokiniana in wheat

Black point is a severe wheat grain disease caused by complex pathogens, of which Bipolaris sorokiniana is dominant. Analysis of effective resistance genes/quantitative trait loci (QTL) is an essential prerequisite for breeding by marker-assisted selection (MAS). In this study, we aimed to identify the loci resistant to black point caused by B. sorokiniana in 10 wheat genotypes by performing a genome-wide association study with an incomplete diallel cross population. Twenty-three major marker-trait associations (MTAs) resistance to B. sorokiniana black point were identified, which could explain more than 11% of the phenotypic variations. They were located on 1B, 1D, 2B (2), 2D, 3A (2), 3B (2), 3D, 4A, 5A (2), 5B (2), 6B (3), 6D, 7A (2), and 7D (2), respectively. The average number of major MTAs in the 10 resistant lines was 20.2, whereas that in the susceptible lines was 9.8. All the major MTAs in the parents were detected in the F1 hybrids. Three PCR markers were developed for detecting two MTAs using two recombinant inbred line populations. These PCR markers linked to black point resistance and accessions with a larger number of resistance alleles can be used to improve wheat resistance by QTLs pyramiding via MAS.

Bayesian hierarchical modeling of yield in incomplete diallel crosses of the Pacific oyster Crassostrea gigas

Identifying elite inbred parent lines that produce high-performing hybrid Pacific oyster seed requires diallel or factorial test crosses among lines, each acting as both a male and a female parent. Previously, we used the generalized linear model with fixed effects (i.e. GLM) to partition variance in yield, among hybrid families produced by a diallel cross, into causal genetic components—principally, general combining ability (GCA), specific combining ability (SCA), and reciprocal effect (R). However, GLM is extremely sensitive to missing information, which arises from loss of hybrid families for random environmental causes or from variation in the reproductive success of parent lines. To resolve this issue, we apply a Bayesian hierarchical model, which partitions yield variance into the familiar causal genetic components, while providing Bayesian shrinkage estimates incorporating the uncertainty of missing data. Our study suggests that correlation between observed yields and those predicted by the Bayesian model is high (r2 ≥ 0.99), for observed offspring, regardless of diallel completeness. Additionally, in analyses of complete diallel crosses, line-specific GCA rankings from GLM and Bayesian models are consistent for parent lines. Finally, comparing simulated complete and incomplete diallel datasets, we show the accuracy of predicted yield for families that are present and of parent-line ranking by GCA and the reliability of parent-line selection for double-cross hybrids, especially when non-parental lines (i.e. the four hybrid parents used to predict the yield of double-cross hybrids) are present. Our study demonstrates that the Bayesian hierarchical model performs as well as GLM in analyzing complete diallel crosses and can properly deal with incomplete diallel crosses for which GLM does not work. Therefore, the Bayesian hierarchical model is powerful in diallel analysis to select superior parent lines for producing high-yielding, hybrid, Pacific oyster seed.

Estimates of heritability based on additive-dominance genetic analysis model in red swamp crayfish, Procambarus clarkii

Heritability has been proven as an effective means for assessing the genetic variation harbored in populations of aquaculture species. In order to make an overall genetic evaluation, heritabilities of twelve traits in red swamp crayfish, Procambarus clarkii (5 months old), including growth, body dimension and processing traits, were estimated in this study. The estimation was based on the additive-dominance genetic analysis model using the incomplete diallel cross between three geographic populations of the species under two rearing environments. Results indicated that all heritabilities for mature females (n = 1312) and males (n = 1109) were low to medium in magnitude (P < .05), ranging between 0.06 (±0.02) and 0.32 (±0.05). All traits were controlled by additive effect, dominance effect, additive × environment, dominance × environment interactions and other environmental effects to varying degrees, depending on traits in question. Body length, abdominal length, total weight and processing traits were primarily controlled by additive effect, dominance effect, A × E and D × E interactions, while other body size traits were mainly controlled by dominance effect and D × E interaction. With the effects of non-additive genetic and environmental sources removed, estimates of heritability obtained were more accurate. It is anticipated that better genetic gain for improvement of economically important traits, especially processing traits, would be achieved via mass selection in P. clarkii.

GENERAL AND SPECIFIC COMBINING ABILITY OF INITIAL PARENTAL FORMS IN TOMATO FOR COMPLEX OF ECONOMICALLY VALUABLE TRAITS TO DEVELOP HYBRIDS F1 OF CHERRY AND COCKTAIL TYPES

Results of estimation of general and specific combining ability of male and female parental tomato forms were given for complex of traits. The estimation was carried out according to incomplete diallel crosses 15x15. Such varities as ‘Trapeza’, Rosovaya kapelka’, ‘Seniorita’, ‘Ocharovanie’, ‘Tigris’ ‘Vishnya Zheltaya’ (Gavrish), ‘Denezhnoye Derevo’ (national breeding), and lines: ‘46/06’, ‘49/09’, ‘295/09’, ‘336/11’, ‘354/11’, ‘357/11’, ‘388/09’ (nor), ‘498’ (selection of TARI) were used as intial breeding accessions, differing in bush type (determinate and indeterminate), duration of vegetative phase (ultraearly, early, medium early, middle-ripening), fruit shape (rounded, oval), fruit color (red, pink, black, orange, tiger and with the gene nor), fruit weight (10 g. and more), brush structure (dense, friable). As a results, ‘Trapeza’, ‘Vishnya Zheltaya’, ‘Ocharovaniye’, ‘Seniorita’, and lines: ‘295/10’, ‘49/09’, ‘498’, ‘357/11’, ‘354/11’, ‘388/09’ (nor) were selected and recommended to be used in breeding program for development of heterotic hybrids with high fruit setting and generative bush type. The promising hybrids F 1 with high constants of specific combining ability for a complex of economically valuable traits have been observed. Because of different lines and accessions were used in crossings, these hybrids varied in internode length of cluster type, classical or shorten; rounded or oval fruit shape; fruit color, red (F 1 combinations ‘354/11’ х ‘Seniorita’, ‘Trapeza’ х ‘L.49/09’, L. ‘49/09’ х L.354/11), pink (F 1 combination ‘Rosovaya Kapelka’ х ‘L.354/11’), yellow (F 1 combination ‘Ocharovaniye’ х ‘Vishiya Zheltaya’), deep brown (F 1 combination ‘L.357/11’ х ‘L.354/11’).

Inheritance analysis of anther dehiscence as a trait for the heat tolerance at flowering in japonica hybrid rice (Oryza sativa L.)

We analyzed the heredity of anther morphology in rice (Oryza sativa L.) using incomplete diallel crosses of six japonica restorer lines and eight cytoplasmic male-sterile (CMS) lines, and 48 F1 combinations resulting from these crosses. We analyzed four traits: the length of dehiscence formed in the apical (ADL) and basal (BDL) parts of the anther and the respective widths, ADW and BDW. The ratios of V gca (variance of general combining ability) to V sca (variance of specific combining ability) were 8.0 for BDL, 1.4 for BDW, 3.0 for ADL, and 2.8 for ADW. Narrow-sense heritability (H N 2 ) was 76.5 % for BDL, 37.9 % for BDW, 66.0 % for ADL, and 65.9 % for ADW. The effects of GCA (general combination ability) for BDL ranged from −67.0 to 68.9 μm (CMS lines) and from −33.4 to 43.0 μm (restorer lines); those for ADL were −46.7 to 44.0 μm (CMS lines) and −29.5 to 34.0 μm (restorer lines). We conclude that BDL and ADL have high heritability, and we can modify the size of apical and basal dehiscence by selecting suitable CMS and restorer lines.

Parental selection of hybrid breeding based on maternal and paternal inheritance of traits in rapeseed (Brassica napus L.).

Parental selection is crucial for hybrid breeding, but the methods available for such a selection are not very effective. In this study, a 6×6 incomplete diallel cross was designed using 12 rapeseed germplasms, and a total of 36 hybrids together with their parental lines were planted in 4 environments. Four yield-related traits and seed oil content (OC) were evaluated. Genetic distance (GD) was estimated with 359 simple sequence repeats (SSRs) markers. Heterosis levels, general combining ability (GCA) and specific combining ability (SCA) were evaluated. GD was found to have a significant correlation with better-parent heterosis (BPH) of thousand seed weight (TSW), SCA of seeds per silique (SS), TSW, and seed yield per plant (SY), while SCA showed a statistically significant correlation with heterosis levels of all traits at 1% significance level. Statistically significant correlations were also observed between GCA of maternal or paternal parents and heterosis levels of different traits except for SS. Interestingly, maternal (TSW, SS, and OC) and paternal (siliques per plant (SP) and SY) inheritance of traits was detected using contribution ratio of maternal and paternal GCA variance as well as correlations between GCA and heterosis levels. Phenotype and heterosis levels of all the traits except TSW of hybrids were significantly correlated with the average performance of parents. The correlations between SS and SP, SP and OC, and SY and OC were statistically significant in hybrids but not in parents. Potential applications of parental selection in hybrid breeding were discussed.

English

The genetic effect of grain yield plant-1 and its correlation with yield components were investigated in a 7 &times; 7 incomplete diallel cross of seven wheat parents during the crop season of 2009 to 2010. Mean square of general combining ability (GCA) effect was 2.90 for grain yield plant-1, which was highly significant (P&lt;0.01), indicating that additive effect played important role in the inheritance of the trait. Specific combining ability (SCA) effect was highly significant (P&lt;0.01) for grain yield plant-1 (0.68), suggesting that the trait was also controlled by non-additive effect. The estimates of GCA showed that the best combiner for grain yield plant-1 was Ningmai 9. The additive-dominance model was partially adequate for grain yield plant-1 and it was controlled by the over dominance type of gene action. Ningmai 8 possessed maximum dominant genes, whereas Yangmai 9 had maximum recessive genes. Grain yield plant-1 might be controlled by two groups of genes and exhibited moderately high value of narrow sense heritability (h2N=69.51%). The statistical analysis revealed that grain yield plant-1 was positively and significantly correlated with tillers plant-1 (rp=0.584, rg=0.595) and number of grains spike-1 (rp=0.528, rg=0.507) at phenotypic and genotypic levels. The information obtained from the study might be helpful for wheat breeders trying to develop new varieties with high-yielding potential. &nbsp; Key words: Combining ability, diallel cross, grain yield, inheritance, Triticum aestivum L.