Heterosis for yield and other agronomic traits of winter triticale F1 and F2 hybrids

Triticale is generally treated as a self‐pollinating crop and line breeding is practised. Hybrid breeding has been discussed for some time, but there is little information for winter triticale. This study investigated heterosis for eight agronomic traits in F₁ and F₂ hybrids grown together with their parents as drilled plots in three environments. On average, grain yield heterosis was 12.5 dt/ha (a relative 10.5%) compared with the mid‐parent value for F₁ hybrids, and 6.2 dt/ha (5.0%) for F₂ hybrids and withawide range of 4.4–17.1 dt/ha for F₁ hybrids. A positive contribution to the heterosis of yield was made by kernels/spike and 1000‐kernel weight, whereas spikes/m² showed negative heterosis. Hybrid plants in F₁ and F₂ were taller than mid‐parents (8.3 cm and 5.3 cm, respectively), with a tendency to earlier heading. The negative heterosis for falling number in F₁ and F₂ hybrids could be a problem for commercial production of triticale hybrids. By selecting parents for combining ability and the identification of heterotic patterns, grain yield heterosis of 20% appears feasible.     

Heterosis and combining ability for grain yield and other agronomic traits in winter triticale

Hybrid breeding is a widely discussed alternative for triticale. Heterosis as well as general (GCA) and specific combining ability (SCA) effects were estimated for eight agronomic traits. The experiment comprised 24 F₁ hybrids, produced by a chemical hybridizing agent, together with their six female and four male parents, grown in drilled plots in two locations. In comparison with the mid‐parent values, hybrids averaged a 6.4 dt/ha (10.1%) higher grain yield, 8.4% more kernels per spike, a 6.8% higher 1000‐kernel weight, 9.7% lower falling number (FN) and 4.4% greater plant height. SCA effects for grain yield were significant and ranged from 4.5 to 6.9 dt/ha for grain yield. Together with GCA x location interactions, they explained most of the variation. For 1000‐kernel weight, GCA effects were predominant. SCA and interactions with location accounted for most of the variation in FN, whereas interactions were negligible for plant height. Correlations between mid‐parent and hybrid performance and between GCA and per se performance of parents were tight for all traits except grain yield, which allows for pre‐selection of parental lines. Although the amount of heterosis in triticale at present is closer to wheat than to rye, by selecting parents for combining ability and identifying heterotic patterns, grain yield heterosis of up to 20% appears sufficiently encouraging to embark on hybrid breeding.     

Heritabilities and genetic variation for preharvest sprouting in progenies of Clark's Cream white winter wheat

Summary Preharvest sprouting resistance is a major breeding criterion in many regions where white wheat (Triticum aestivum L.) is produced. Availability of genetic sources of sprouting resistance should significantly advance this goal. Objectives of the present investigation were to determine heritabilities and genetic variation of sprouting resistance in progeny of six susceptible genotypes and Clark's Cream, a cultivar with excellent sprouting resistance. Sixty-five randomly selected F₂:F₃ lines from the six parental combinations were evaluated in blocks-within-replication designs at two locations during 1984–85. Falling number, -amylase activity, and sprouting percentage in simulated rain were usually more favorable in F₂:F₄ grain than in grain of the susceptible parents and frequently equalled levels in grain of the resistant parent. Broad sense heritability estimates were moderate to high for falling number and -amylase activity, low to moderate for visual sprouting, and inconsistent for embryo germination in ABA. Phenotypic correlations with sprouting were significant most often for falling number and least often for the agronomic traits, days to heading and kernel weight. We concluded that increased preharvest sprouting resistance is an attainable objective when genetic sources of strong resistance and appropriate selection criteria, such as sprouting after simulated rain, are used.     

Hybrid breeding for biomass yield in winter triticale: I. Hybrid performance,trait correlations and heterosis

Triticale (×Triticosecale Wittmack) holds great potential as a source for biomass production for industrial applications in Central Europe and hybrid breeding in particular appears promising owing to the higher vigour of hybrids compared to lines. In this study, a set of 178 winter triticale genotypes, including 91 hybrids, their 10 male and 23 female parental lines, as well as 54 varieties were evaluated for biomass yield and other agronomically relevant traits in 2 years at five locations in Germany. We observed a large variation of dry biomass yield as well as significant genotypic variances and high heritabilities for all traits. For the hybrids, a moderate correlation was observed between biomass and plant height and between biomass and grain yield. Mid‐parent heterosis of biomass yield ranged from ?13.6 to 16.5% with an average of 4.8%, and the maximum commercial heterosis was 9.1%. Taken together, our results illustrate the potential of hybrid breeding of triticale for biomass yield to diversify our portfolio of crops for biomass production.     

Relationship between genealogical distance and breeding behaviour in oats (Avena sativa L.)

Summary Eight oat cultivars and experimental lines from four germplasm sources were crossed in a diallel mating design without reciprocals. F₁ heterosis for grain yield was evaluated in two experiments, and 48 F₂-derived lines from each of the 28 matings were evaluated for bundle weight, grain yield, straw yield, harvest index, height, and heading date in two experiments. Number of transgressive segregates per trait and generalized genetic variance were calculated for each mating. Genealogical distance for each mating was obtained by using coefficient of kinship based on the pedigree of the parents. The relationship between genealogical distance and the three types of breeding behaviour was examined via correlation and regression. Significant correlations occurred only for genealogical distance with numbers of transgressive segregates for height and with generalized genetic variances. Both were positive. Significant heterosis was observed for matings of more distantly related parents. Regressions on genealogical distance, when significant, were linear. Genealogical distance between parents was positive associated with diversity on the basis of breeding behavior.Journal Paper No. J-11874 of the Iowa Agriculture and Home Economics Station, Iowa State Univ., Ames, IA 50011. Project 2447.     

Relationship between heterosis and genetic distance based on morphological traits and AFLP markers in pepper

Genetic diversity is considered as one of the criteria for the selection of parents for hybrid breeding. The present study was undertaken to evaluate genetic divergence among seven pepper cultivars and to assess the relationship between heterosis and parental genetic distance. Twenty‐one F₁ hybrids and seven parents were evaluated for 15 morphological characters in a greenhouse and in the field. The parents were examined for DNA polymorphisms using six amplified fragment length polymorphism (AFLP) primer combinations. Cluster analysis using two genetic distance measures grouped the seven parents differently. Mid‐parent and high‐parent heterosis was observed for most characters. Most hybrids outperformed the parental lines for fruit yield, earliness and plant height. Morphological and AFLP‐based distance measurements were efficient enough to allocate pepper genotypes into heterotic groups. The correlations of morphological distances with mid‐parent heterosis were significant for days to flowering and maturity, suggesting earliness can be predicted from morphological distances of parental lines. However, the correlations of AFLP‐measured genetic distances with mid‐ and high‐parent heterosis were non‐significant for all characters, except for fruit diameter, and proved to be of no predictive value.     

异源细胞质对普通小麦穗发芽抗性影响的初步研究

采用种子发芽法和室内穗上发芽法,分析比较了不同异源细胞质对普通小麦及杂种F_1的穗发芽抗性的影响,结果表明:不同细胞质对穗发芽抗性表现出不同的遗传效应,在小麦抗穗发芽育种及杂种优势利用中有一定参考价值。     

Heterosis in Primary Hexaploid Triticale with Heterozygous Wheat or Rye Genome*)

Twelve primary hexaploid triticale (X Triticosecale Wittmack), synthesized from, three lines of tetraploid wheat (Triticum durum L., T. turgidum L.) and four inbred lines of rye (Secale cereale L.), were used to produce 18 crosses with homozygous wheat and heterozygous rye genome and 12 crosses with heterozygous wheat and homozygous rye genome. Parents and crosses of triticale, wheat, and rye were tested for two years (rye for one year only) in two-replicate block designs with 1 m²-plots. Data were assessed for plant height, grain yield and for yield-related traits. Performance of triticale crosses was considerably lower than that of the wheat and rye crosses. The amount of heterosis varied greatly between years. Positive and mainly significant heterosis was revealed in triticale generations F₁ and F₂. The average values were closer to those in wheat than to those in rye. For most characters a high level of heterosis was retained in tnucalt1 generation F₂. Heterozygosity of the wheat and rye genome both contributed to heterosis in triticale. However, gene action of the rye genome strongly depended on the homozygous wheat background: one wheat line almost completely suppressed and another greatly stimulated the heterotic effect of the rye genome. In the later case, the amount of heterosis was related to that in rye per se. Information from hybrid rye breeding may therefore be used when establishing gene pools for hybrid breeding in triticale.     

黄瓜数量性状遗传距离与杂种优势关系的研究

探讨数量性状遗传距离与杂种优势的关系,为黄瓜新品种的选育提供理论依据。选择5份黄瓜自交系材料作为母本,6份黄瓜自交系材料作为父本,按半双列杂交法配制出29个杂交组合,对11份黄瓜自交系材料的7个数量性状进行杂种优势分析和聚类分析,并研究数量性状遗传距离与杂种优势的关系。研究结果表明,各数量性状均有不同程度的正向杂种优势,其中株高、结瓜数和单株产量的杂种优势最为明显,而单果重、主蔓20节内雌花数、果实长和果实粗的杂种优势比较微弱。11份黄瓜自交系被分为3大类群,地理远近与遗传距离之间并不存在必然的联系。结瓜数的中亲优势指数和杂种优势指数、果实长和果实粗的中亲优势指数及单株产量的超亲优势指数与亲本遗传距离之间存在显著的相关关系,而株高、单株产量的中亲优势指数和杂种优势指数与亲本遗传距离之间存在极显著的相关关系,大部分数量性状的杂种优势都随着遗传距离的增大而增大。在进行黄瓜种质资源评价时,不能以地理关系作为唯一标准;在进行黄瓜杂交育种时,可根据育种目标,适当选择较大的遗传距离来获得杂种优势。     

Heterosis in yield, endotoxin expression and some physiological parameters in Bt transgenic cotton

Although heterosis in cotton has been studied for many decades, very little is known about the performance of hybrids derived from Bt transgenic cotton parents. In order to known better the heterosis performance, yield and endotoxin expression in 20 hybrids (F₁) and their Bt transgenic parents were examined from 2002 to 2003 (Experiment 1), and the dynamics of source, sink and their ratios in a well‐performing hybrid H01 were investigated in 2004 and 2005 (Experiment 2). Results in Experiment 1 showed an average mid‐parent heterosis of 21.3% and an over check heterosis of 7.6% in lint yield. Considerable heterosis was also detected in boll numbers, boll size and Bt protein content. Of the 20 hybrids, H01 (K0215 × K643) exhibited the greatest heterosis in yield and Bt protein content in 2002 and 2003, while lint yields of H01 were increased 12.6% and 9.1% in 2004, and 11.7% and 8.9% in 2005, compared with K0215 and K643 in Experiment 2, respectively. Significant heterosis for dry matter accumulation and dry matter allocation to reproductive organs and ratio of fruiting forms/total plant (w/w) were also detected in H01. Sources (leaf area, leaf area index, leaf dry weight per plant and diurnal performance of photosynthesis), sinks (number of fruiting nodes, fruiting forms and dry weight of fruiting forms per plant) and the flow from source to sink were significantly enhanced in H01 relative to its parents. Both total N and Bt protein in H01 were higher than those in its parents. Significant correlation was also found between total N and Bt protein in the main‐stem leaves (R² = 0.877**). It is concluded that there existed considerable heterosis in yield, yield components and endotoxin expression in some Bt transgenic hybrids. Yield advantage of hybrid cotton (F₁) over parents can be attributed to improved source, sink and flow, while the enforced expression of Bt genes in hybrid cotton appeared to be due to the enhanced nitrogen level in plants.     

Hybrid performance and AFLP- based genetic similarity in faba bean

Successful prediction of heterosis and performance of F₁-hybrids from the genetic similarity of their parents based on molecular markers has been reported in several crops and can be very helpful in hybrid breeding. The relationship between genetic similarities based on amplified fragment length polymorphism (AFLP) of 18 European faba bean lines and their hybrid performance and heterosis was investigated. Parental lines, 62 F₁-hybrids and their F₂-progenies were evaluated in field trials in four environments in Germany for seed yield, 1,000-seed weight and plant height. Results clearly demonstrated a stable superiority of the hybrids over their inbred parents and elite check cultivars, and showed a marked and varying amount of heterosis. Parental seed yield and F₂-hybrid yield were promising as predictors for F₁-hybrids. AFLP analysis of the 18 inbred lines using 26 EcoRI/MseI primer combinations resulted in 1202 polymorphic fragments. Cluster analysis based on genetic similarity estimates unambiguously identified pedigree-related inbred lines. No clear separation of the 18 inbred lines into subgroups was detected. Correlation coefficients between genetic similarity estimates and either heterosis or F₁-hybrid performance were small and not useful. Also correlations between specific genetic similarity and specific combining ability were too small for all traits to be of predictive value. Results showed that AFLP-based genetic similarities are not useful to predict the performance of hybrids or heterosis within the elite European faba bean gene pool.     

Utilization of tom thumb source of pre-harvest sprouting tolerance in a wheat breeding programme

Summary Segegating populations of the cross Tordo (a spring white-grained Tom Thumb derivative) and Tr 454-16 (a spring white-grained Sonora-Gabo derivative) were studied for plant height, apparent -amylase synthesis (AAS) and response to gibberellic acid. Means, variances and heritabilities for these characters were computed and their association was studied by computing correlation coefficients. Plant height showed high heritability while AAS and response to GA₃ showed moderate heritability. Plant height was positively correlated with AAS and response to GA₃. The results pointed out the importance of using Tom Thumb as a source of pre-harvest sprouting tolerance in a wheat breeding programme, particularly in areas where wheat breeding is restricted to evolving white-grained cultivars.     

Heterosis and inheritance of drought tolerance in faba bean, Vicia faba L.

Twelve parental lines of faba beans and 27 F₁ hybrids derived from them were field-tested under a dry and a well-watered treatment, at two German locations (Göttingen, Hohenheim) in two years (1995, 1996). Drought was artificially induced using rain shelters from anthesis until maturity. Data were collected on yield under dry (Yd) and well-watered (Yw) conditions. Drought tolerance was assessed as Yd/Yw. The mid-parent heterosis was significant for Yd and Yw, but not for Yd/Yw. Relative heterosis for Yd (52.0%) was greater than for Yw (39.3%). Parental heritability was greater for Yw (0.86) than for Yd (0.61). However, it was similar for both traits in F₁ hybrids (0.65 and 0.66). Principal component analysis showed that F₁ hybrids exhibited the same pattern of adaptation as their parents. The heritability of drought tolerance was 0.48 in F₁ hybrids and 0.70 in parents. Attention should be paid to its negative correlation with yield. Several hybrids combined high tolerance, a favourable pattern of adaptation and appropriate performance.     

Heterosis,combining ability and genetic effect,and relationship with genetic distance based on a diallel of hybrids from five diverse <Emphasis Type="Italic">Gossypium barbadense</Emphasis> cotton genotypes

The cultivated tetraploid Gossypium barbadense L. cotton produces superior natural fibers for the textile industry in the world. However, the possibility in utilization of heterosis to further increase its lint yield has not been extensively explored. In this study, two commercial US Pima cotton cultivars and three exotic G. barbadense lines, together with all of their possible hybrids in F₁ and F₂ progeny without reciprocals, were tested for lint yield, yield components, and fiber quality traits in four environments in 2005–2007. With a few exceptions, genotype (G), environment (E), and G × E were all significant or highly significant for all the traits studied. General combining ability (GCA) variances for all the traits in both F₁ and F₂ were also significant, while specific combining ability (SCA) variances were detected only for lint yield, fiber length, and micronaire in both generations and boll weight in F₁. GCA × E was also detected for lint percent, seed index, and fiber length in both F₁ and F₂, and boll weight in F₁, but none of the traits had significant SCA × E. As a group, F₁ and F₂ out-yielded the parent group by 20–40% and 6–10%, respectively. Mid-parent heterosis (MPH) for lint yield in F₁ was generally positive, ranging from ?4.7 to 116.4% with an average of 21.2–48.7%, while lint yield MPH in F₂ ranged from ?23.3 to 69.4% with an average of 6.4–12.4%. However, useful heterosis in lint yield was only detected in the hybrid between the two US commercial cultivars Pima S-7 and DP 340. MPH for other traits was low or not detected. MPH in F₂ was lower than that in F₁ but they were generally positively correlated. The genetic distances (GD) of the parents (based on 467 polymorphic RAPD and AFLP markers) between the five parents was not consistently correlated with MPH and SCA of their hybrids and dominant effects for lint yield and other traits. However, significant and positive correlations between GD of parents and the performance of their hybrids were detected for lint yield, lint percentage, and lint index in both F₁ and F₂ in most of the tests. GD of parents was also correlated with their GCA and additive effects in lint yield, lint percent, lint index, micronaire, plant height, and elongation. The results suggest that the close correlation between GD and hybrid performance per se was mainly due to the existence of GCA and additive effects from parents.     

Genetic analysis of rapeseed self-incompatibility lines reveals significant heterosis of different patterns for yield and oil content traits

Self‐incompatibility is one of the most effective approaches to utilizing heterosis in oilseed rape around the world. To evaluate the heterosis of double low self‐incompatibility, the possibility of combining seed yield and oil content, and the genetic effects of parents on their hybrid progenies, a 2‐year field trial using a 3 × 22 NC II mating design was conducted during the 1999‐2001 growing seasons in Wuhan, China. Significant differences in seed yield per plant and seed oil content were observed among the F1 hybrids and between F1 progenies and their parents. However, the heterosis for seed yield per plant was much greater than that for seed oil content. Mid‐parent heterosis and high‐parent heterosis of seed yield per plant ranged from 5.50 to 64.11% and from –2.81 to 46.02%, while those of seed oil content ranged from –1.55 to 7.44% and –3.61 to 6.55%, respectively. Non‐additive genetic effects were a major mechanism that accounted for the yield heterosis in addition to additive effects. In contrast, seed oil content heterosis was mainly dependent on an additive genetic effect. General combining ability (GCA) determined the stability of hybrid cultivars. In hybrid breeding, parental materials might be selected by the sum of GCAs and variances of special combining abilities (SCAs) of female and male parents for traits affected by both additive and non‐additive effects, and by the sum of GCAs of two parents for traits controlled mainly by additive effects. Primary branches and their siliques were the most important yield traits.     

Means and variances for Fusarium head blight resistance of F2-derived bulks from winter triticale and winter wheat crosses

Fusarium head blight (FHB), caused by Fusarium graminearum and Fusarium culmorum, is a devastating disease in cereals. This study was undertaken to estimate progeny means and variances in each of five winter triticale and winter wheat crosses using unselected F₂−derived lines in F₄ or F₅ generation bulked at harvest of the previous generation. Fifty (triticale) and 95 (wheat) progeny per cross were inoculated in two (triticale) or three (wheat) field environments. FHB rating was assessed on a whole-plot basis. Mean disease severities of the parents ranged from 2.3 to 6.4 in triticale and from 3.1 to 6.5 in wheat on a 1-to-9 scale (1 = symptomless, 9 = 100% infected). The midparent values generally resembled the means of their derived progeny. Significant (P < 0.01) genotypic variance was detected within each cross, but genotype × environment interaction and error variances were also high for both crops. Medium to high entry-mean heritabilities (0.6–0.8) underline the feasibility of selecting F₂-derived bulks on a plot basis in several environments. Phenotypic correlation of FHB resistance between generation F_2:4 and F_2:5 was r = 0.87 (P < 0.01) tested across 150 wheat bulks at two locations. Our estimates of selection gain are encouraging for breeders to improve FHB resistance in triticale and wheat by recurrent selection within adapted materials.     

Best linear unbiased prediction of triticale hybrid performance

Predicting single-cross performance is of special interest in hybrid breeding of triticale. We used molecular and phenotypic data of factorial triticale crosses and compared several approaches to predict their single-cross performance. Twenty-three inbred lines and their 76 incomplete factorial crosses were field evaluated for grain yield, plant height, and heading time at five locations in Central Europe. In addition, the parental lines were genotyped with 52 SSR markers. Plant height and heading time were predicted with high accuracy based on mid-parent performance. In contrast, prediction of hybrid performance based on mid-parent value was not accurate for grain yield. Using general combining ability effects led to an enhanced prediction accuracy of hybrid grain yield performance. This accuracy could be slightly improved using best linear unbiased prediction approaches. The prediction accuracy was considerably high even if the number of tested hybrids was small. Consequently, best linear unbiased prediction of hybrid performance is a promising tool for hybrid triticale breeding programs.     

Heterosis performance of yield and fibre quality in F1 and F2 hybrids in upland cotton

Because of the difficulty of producing F₁ hybrid seeds by hand emasculation and pollination, wide use of heterosis in cotton production has been limited in China. The objective of this study was to evaluate the potential of F₂ hybrids for yield and fibre quality. A half diallel involving eight parents and their F₁ and F₂ hybrids was grown in replicated studies at Linqing and Nanjing in 1999 and Nanjing in 2000. Yield and fibre quality was determined for all 64 entries. Fibre quality was also determined for parents and F₁s, but only for Zhongmiansuo 28 (ZMS28), Xiangzamian 2 (XZM2) and Wanmian 13 (WM13) F₂s. These three F₂ hybrids are extensively planted in China and provide experimental controls with which to compare the performance of new hybrids. Average yield heterosis for F₁s and F₂s was 15.9 and 9.2%, respectively. Inbreeding depression for yield varied but some F₂s greatly out‐yielded the best variety. Average F₁ heterosis was 6.7, 6.2 and 2.9%, respectively for number of bolls per unit area, boll weight, and lint percentage. The average F₂ heterosis for the same traits was 4.4, 3.3 and 1.6%, respectively. F₁ heterosis for fibre traits was low. In general, parental average was a good indicator of the yield and fibre quality of F₁ hybrids. These encouraging results suggest there is sufficient heterosis for yield to use F₂s in China.     

Aluminium tolerance in lentil (Lens culinaris Medik.) with monogenic inheritance pattern

The objectives of this study were to determine genetics of Al tolerance and whether the Al tolerance observed is governed by the same gene. The lines ‘L‐7903’ and ‘L‐4602’ have been developed through breeding programme as Al‐tolerant lines. These lines showed maximum root regrowth and minimum accumulation of Al and callose as compared to sensitive genotypes (‘BM‐4’ and ‘L‐4147’). Al tolerance in the parents, F₁, F₂ and backcross generations was estimated using the regrowth of the primary root after staining and scoring of fluorescent signals. The F₁ hybrids responded similarly to the tolerant parents, indicating dominance of Al tolerance over sensitivity. The segregation ratios obtained for Al tolerance and sensitivity in the F₂ and backcross generations were 3 : 1 and 1 : 1, respectively. Test of allelism confirmed the same gene was conferring Al tolerance in both genotypes (‘L‐7903’ and ‘L‐4602’) as the F₁ was also tolerant and no segregation of tolerant : sensitive was recorded. These results indicated that Al tolerance is a monogenic dominant trait that can be easily transferred to agronomic bases through backcross breeding technique.     

Agronomic and qualitative characteristics of ten bread wheat hybrids produced using a chemical hybridizing agent

Summary Ten experimental hybrids derived from the crossing of representative Italian pure-line varieties were grown at three locations in 1984–85. The amount of F₁ seed produced from the crossings ranged from 1.5 up to 4 kg per plot of 20 m². Hybrid purity was on average 88% when estimated through the growout test and 82% when estimated through acid polyacrylamide gel electrophoresis (A-PAGE) of gliadin.All the hybrids showed high-parent heterosis for plant height. Grain yield was higher in the hybrids (71.1 q/ha) than in the female parents (66.5 q/ha); the range of mid-parent heterosis being-10% to +17%. Four hybrids showed standard heterosis (yield advantage). The highest value (+6%) was obtained with the combinations Chiarano x Leopardo and Claudia x Leopardo. Among yield components, the number of spikelets/spike proved to be an important trait and may explain the superiority of the hybrids over the traditional varieties.The bread-making quality appeared intermediate to that of the parents or closer to that of the poorest parental variety.