Correlated effects of exotic pollen‐fertility restorer genes on agronomic and quality traits of hybrid rye

In CMS (cytoplasmic male sterility)‐based hybrid rye (Secale cereale L.) breeding, effective pollen‐fertility restoration is an essential prerequisite for achieving maximum grain yield on the one hand and for minimizing ergot (Claviceps purpurea) infestation on the other. Restorer genes for the CMS‐inducing ‘Pampa’ cytoplasm derived from landraces collected in Iran and Argentina are used by breeders for achieving this goal. Here, restorer genes from four germplasm sources (‘Altevogt 14160’, ‘IRAN III’, ‘Trenelense’ and ‘Pico Gentario’) were analysed by producing three‐way cross hybrids between an elite CMS single cross and pollinators with and without a given restorer gene. Materials were evaluated on large drilled plots for restorer index (RI), grain yield, plant height and other traits in six environments. In experiment 1, a restorer gene from ‘Altevogt 14160’ was used. Seven pairs of marker‐selected carrier and non‐carrier backcross lines served as pollinators. In experiment 2, the pollinators were 17 backcross line pairs from the other three germplasm sources. These lines were grouped as high (RI > 67%) and low restorers (RI < 30%), respectively, using testcrosses with a highly diagnostic CMS tester. Hybrids carrying an exotic restorer gene suffered from a significant grain yield reduction by 4.4% and 9.4% and were 9.3 and 4.8 cm taller in experiments 1 and 2, respectively. Thousand‐kernel weight was reduced, whereas quality traits were only slightly affected. For all traits, significant genetic variance existed among the testcrosses to the presence vs. absence of a given exotic restorer gene. This offers a chance for the breeder to reduce or ultimately overcome the presently observed performance reductions brought about by exotic restorer genes.     

Genome-wide association mapping and genomic prediction of Fusarium head blight resistance,heading stage and plant height in winter rye (Secale cereale)

Rye is a multi-purpose cereal crop grown in Central and Eastern Europe as well as in Western Canada. Fusarium head blight (FHB) is one of the diseases that have a severe negative impact on rye, but knowledge about FHB resistance at the genomic level is totally missing in rye. The objective of this study was to elucidate the genetic architecture of FHB resistance in winter rye using genome-wide association (GWA) mapping complemented by genomic prediction (GP) in comparison with marker-assisted selection (MAS). Additionally, plant height and heading stage were analysed. A panel of 465 S₁-inbred lines of winter rye was phenotyped in three environments (location–year combinations) for FHB resistance by inoculation with Fusarium culmorum and genotyped with a 15k SNP array. Significant genotypic variation and high heritabilities were found for FHB resistance, heading stage and plant height. FHB did not correlate with heading stage, but was moderately correlated with plant height (r = −.52, p < .001) caused by some susceptible short inbred lines. The GWA scan identified 15 QTL for FHB resistance that jointly explained 74% of the genotypic variance. In addition, we detected 11 QTL for heading stage and 8 QTL for plant height, explaining 26% and 14% of the genotypic variance, respectively. A genome-wide prediction approach resulted in 44% higher prediction abilities than marker-assisted selection for FHB resistance. In conclusion, genomic approaches appear promising to improve and accelerate breeding for complex traits in winter rye.     

Prediction of deoxynivalenol and zearalenone concentrations in Fusarium graminearum inoculated backcross populations of maize by symptom rating and near‐infrared spectroscopy

Gibberella ear rot (GER) caused by Fusarium graminearum is a destructive disease in maize of temperate regions resulting in yield reduction and contamination by the mycotoxins deoxynivalenol (DON) and zearalenone (ZON). We wanted to analyse whether prediction of DON and ZON concentrations is feasible either by GER severity ratings or by near‐infrared spectroscopy (NIRS). We analysed 80 and 102 lines developed by backcrossing doubled‐haploid lines from segregating populations to the resistant and susceptible parent, respectively, by artificial infection at three locations in Germany and France. Both backcross (BC) populations differed substantially in their means for all traits with significant (P < 0.01) genotypic variances. DON and ZON concentrations measured by immunotests were significantly (P < 0.01) correlated with each other and with GER severity within each BC population (0.6 ≤ r ≤ 0.9, P < 0.01). DON concentration measured by immunotest and NIRS significantly correlated (r ≈ 0.9, P < 0.01). In conclusion, DON and ZON concentrations could be reliably predicted by GER severity. Additional NIRS analysis of DON concentration might be useful for the positively selected fraction.     

Mycotoxin accumulation and corresponding ear rot rating in three maturity groups of European maize inoculated by two <Emphasis Type="Italic">Fusarium</Emphasis> species

Fusarium graminearum (FG) and F. verticillioides (FV) produce the mycotoxins deoxynivalenol (DON), zearalenone (ZEA) and fumonisins (FUM), respectively, in maize. The EU released limits for these toxins in food. Growing resistant varieties is one alternative to fulfill these limits. Quantification of mycotoxin concentrations is expensive and time consuming. If indirect selection based on cost efficient and fast ear rot rating is feasible, this could increase efficiency of selection. The objective of this study was to analyze correlations between mycotoxin concentrations and ear rot rating by inoculating three maturity groups (early, mid-late, late) each comprising about 50 inbred lines tested in Central and Southern Europe. In the early maturity group flint lines were more susceptible in all instances except ZEA than dent lines. Broad ranges and significant (P < 0.01) genotypic variances were detected, but also genotype × environment interaction variances were significant (P < 0.01). Heritabilities of ear rot rating were similar or higher than those of mycotoxin concentrations (0.61−0.93 and 0.56–0.89, respectively). Although high genotypic correlations between FUM and DON or ZEA were found (0.77; 0.76, respectively), separate testing of FV and FG and corresponding mycotoxins is necessary since genotypes resistant to FV were not necessarily resistant to FG and vice versa. Medium to high heritabilities and high genotypic correlations between ear rot and corresponding mycotoxin concentrations (0.87–0.99) suggest frequent identification of lines with reduced mycotoxin concentrations by ear rot rating. Assuming fixed budgets we conclude that indirect selection by applying cost efficient ear rot rating could increase selection intensity and therefore is more effective than direct selection for reduced mycotoxin concentrations.     

Quantitative-genetic analysis of leaf-rust resistance in seedling and adult-plant stages of inbred lines and their testcrosses in winter rye

Leaf rust is the most frequent leaf disease of winter rye in Germany. All widely grown population and hybrid varieties are susceptible. This study was undertaken to estimate quantitative‐genetic parameters of leaf‐rust resistance in self‐fertile breeding materials with introgressed foreign leaf‐rust resistances and to analyze the relative importance of seedling and adult‐plant resistance. Forty‐four inbred lines and their corresponding testcrosses with a highly susceptible tester line were grown in a field in four different environments (location‐year combinations) with artificial inoculation. Plots were separated by a nonhost to promote autoinfections and minimize interplot interference. Leaf‐rust severity was rated on three leaf insertions at three dates. The testcrosses showed a considerably higher disease severity than the lines. High correlations (r ? 0.9, P = 0.01) existed among the leaf insertions and the rating dates. Large genotypic variation for resistance was found in both the inbred and testcross populations. Genotype‐environment interaction and error variances were of minor importance, thus high entry‐mean heritabilities were achieved. A tight correlation between the inbreds and their corresponding testcrosses was found (r = 0.88, P = 0.01). Heterosis for resistance was significant (P = 0.05), but not very important. In a seedling test with 20—30 single‐pustule isolates, 34 out of 44 inbreds reacted race‐specifically. From the remaining inbred lines, three were medium and seven highly susceptible. In a further greenhouse test with 16 inbreds, seven were susceptible and five were resistant in both seedling and adult‐plant stages. The remaining four lines had adult‐plant resistance. In conclusion, race‐specific leaf‐rust resistance can be selected among inbred lines per se. Lines should also be tested in the adult‐plant stage.     

Production of a desirable Brassica oleracea CMS line using an alloplasmic B. rapa CMS line carrying Diplotaxis erucoides cytoplasm as a bridge plant

In Brassica oleracea, production of F₁ hybrid seeds mainly makes use of the improved Ogura cytoplasmic male sterile (CMS) line. However, reliance on one particular line is a risk, and it would be advantageous to develop other CMS lines. In this study, we transferred Diplotaxis erucoides cytoplasm to B. oleracea cultivars using an alloplasmic B. rapaCMS line as a bridge plant to avoid incompatibility between donor and recipient plants. The new B. oleraceaCMS lines, which were derived by four generations of backcrossing, had small rudimentary anthers with no pollen grain and showed complete male sterility. There was no functional defect in other floral organs, and the ability to receive normal pollen did not appear to be impaired. Moreover, the B. oleraceaCMS lines carrying D. erucoides cytoplasm had larger leaf areas and a normal plastochron. As a consequence, the B. oleraceaCMS lines carrying D. erucoides cytoplasm have the potential to be valuable alternatives for use in commercial B. oleracea hybrid seed production.     

Tagging the dwarfing gene <Emphasis Type="Italic">Ddw1</Emphasis> in a rye population derived from doubled haploid parents

To prevent lodging and sprouting damage in rye, a dominant dwarfing gene, Ddw1, has been incorporated into breeding lines to reduce plant height in Finland. However, the inability to identify heterozygous plants makes it difficult to purify breeding lines. Doubled haploidy (EM-1 × Voima) and bulked segregant analysis were used to search for an efficient PCR-based tool to identify homozygous short plants. In addition, SNP (single nucleotide polymorphism) markers were created from the endosperm-specific β-amylase gene and the microsatellite locus REMS1218 expressed in rye and known to be located near Ddw1. The best marker was a combination of the microsatellite REMS1218 and the SNP created from it, located 13 cM from the QTL corresponding to Ddw1. However, for a rye breeder, the SNP alone is an adequate tool to identify plants homozygous for the EM-1 allele and it can be used in selection for the desirable growth habit in rye.     

Superior CMS (<Emphasis Type="Italic">Ogura</Emphasis>) lines with better combining ability improve yield and maturity in cauliflower (<Emphasis Type="Italic">Brassica oleracea</Emphasis> var. <Emphasis Type="Italic">botrytis</Emphasis>)

Three CMS lines, Ogu1A, Ogu2A and Ogu3A were selected among ten lines after BC₇ based on superior commercial, floral and seed setting traits. Introgression of sterile Ogura cytoplasm in cauliflower nuclear background reduced the flower size but did not affect commercial and seed setting traits drastically. Line × Tester analysis was done by taking these three CMS lines free from floral deformities as female parent with nine diverse lines of snowball cauliflower as tester. The parent Ogu2A exhibited highest GCA effect for curd yield (4.51) and harvest index (1.97) while Ogu1A exhibited highest GCA for earliness (−2.73). The parent, Ogu2A exhibited significant GCA for curd length (0.39) while, none of the CMS lines showed significant GCA for curd diameter and depth. Heterosis for curd yield was highest in the hybrid, Ogu2A × Kt-22 (63.5%) followed by Ogu1A × WF (36.9%) and Ogu1A × Kt-15 was the best hybrid for earliness followed by Ogu3A × Kt-22 with heterosis of −14.4% and −11.7%. However, the number of heterotic hybrids for yield and earliness was low indicating narrow genetic base of the snowball cauliflower.     

Seed storage potential of population varieties and hybrid varieties and their breeding components in rye (Secale cereale L.)*

Seeds of population varieties, hybrid varieties, cytogenetic male sterility (CMS) single cross lines and CMS inbred lines of rye (Secale cereale L.) were stored to determine the respective rates of germination loss with a view to their storage potential. The seeds were stored under controlled conditions at a seed moisture content of 14% and a temperature of 30°C for periods of up to 80 days. The storage potential decreased in the order: hybrid varieties > population varieties > CMS single cross lines > CMS inbred lines. However, the rates of germination loss showed no differences within the respective categories. The inferences drawn for seed storage potential hold for seed vigour potential.     

Responses to selection of S<Subscript>5</Subscript> inbreds for broad-based resistance to ear rots and grain mycotoxin contamination caused by <Emphasis Type="Italic">Fusarium</Emphasis> spp. in maize

Random S₅ inbreds derived from three F₂ maize (Zea mays L.) populations (L1934 × LP918, LP915 × LP2541 and L7310 × L7266) were selected for ear rot resistance after inoculation with a low-fumonisin producing isolate belonging to F. proliferatum. The four less susceptible and the four most susceptible inbreds from each population were crossed and F₁ seeds were pooled. Resistant and susceptible pools from each population were evaluated for disease severity (percentage of the ear visibly diseased) after inoculation with the isolate used for selection, and high toxigenic isolates belonging to F. verticillioides and F. graminearum. Grain mycotoxin concentration was assessed by ELISA. Differences in disease resistance to each fungus were observed between resistant and susceptible pools in most populations and environments indicating that selection after inoculation with a single species might be effective to develop broad-based resistance to Fusarium. Resistant pools exhibited, after inoculation with F. verticillioides, low grain fumonisin concentrations in most populations and years. Positive genotypic correlations between disease severity and fumonisin concentration (0.89 < r_g < 0.98, depending on fungal species and year) indicate that selection for disease severity accounted for most of the variability for field fumonisin accumulation. Selection seemed to be also effective to reduce grain deoxynivalenol and zearalenone concentrations after inoculation with F. graminearum. Ratios between grain deoxynivalenol concentration and disease severity were lower in L7310 × L7266 than those observed in the other populations suggesting that mechanisms affecting mycotoxin accumulation might exist in this population and additional responses should be feasible if including deoxynivalenol concentration as another selection parameter.     

Stability analysis of yield and capsaicinoids content in chili (<Emphasis Type="Italic">Capsicum</Emphasis> spp<Emphasis Type="Italic">.</Emphasis>) grown across six environments

Pearl millet (Pennisetum glaucum) is the most important cereal in crop-livestock production systems in arid and drier semi-arid environments valued for its grain and dry stover. The conventional approach of improving grain yield through greater partitioning of biomass to the grain and decreased stover yield is not a viable strategy for arid regions where biomass also needs to be improved. The current research tested the hypothesis whether biomass can be improved without extending the crop duration. The 232 F₅ lines derived from a cross (J28 × RIB 335/18) were evaluated in their testcross form along with three commercial hybrids under arid zone conditions. Biomass, grain and stover yields, panicle number, grain size and grain number panicle⁻¹ varied 1.8 to 2.7 fold in progeny testcrosses. Variation in duration of flowering time accounted for only 2% of variation in biomass, indicating that considerable scope existed for selection of testcrosses, and by implication, of F₅ progenies with high biomass independent of crop duration. Stover yield accounted for 72% of differences in total biomass with remaining accounted for by grain yield. From among 92 and 132 testcrosses that had flowering time comparable to two early checks, most had significantly higher biomass, grain and stover yields than these early checks but none of the testcrosses had earliness on par with extra-early maturing hybrid HHB 67. Mean superiority of best 5% testcrosses over early checks was 58% for biomass, 68% for stover yield and 53% for grain yield. The results indicated that there are good prospects of improving biomass in arid zone pearl millet without significantly compromising crop duration.     

Genetic variation in testcrosses of European maize inbreds for resistance to the European corn borer and relations to line per se performance

The European com borer (ECB) Ostrinia nubilalis H. is a major pest in World maize Zea mays L. production. Objectives of this study were to (1) investigate the genotypic variance and covariance in testcrosses of European flint and dent inbreds for ECB resistance and agronomic traits, and (2) estimate the correlation between line per se and testcross performance for ECB resistance traits. A total of 16 flint and 24 dent inbreds and their testcrosses with two testers from the opposite germplasm pool were evaluated in four and three German environments, respectively. Using artificial infestation with ECB larvae, resistance was assessed by damage rating of stalks, tunnel length in dissected stalks, and relative yield of infested plots compared with protected plots. Yield losses due to ECB damage in testcross hybrids amounted to 40%. Significant genotypic variances between flint and dent lines and high heritabilities were found for damage rating of stalks for both line per se and testcross performance. Heritabilities were low or intermediate for tunnel length and relative grain yield. Correlations between line per se and testcross performance were tight for the damage rating of stalks and moderate for tunnel length and relative yield in both flint and dent germplasm. For damage rating of stalks, per se performance of lines tested in a few environments can be used to predict their testcross performance. In contrast, assessment of testcross performance for tunnel length and relative yield requires evaluating testcrosses with several testers in multi-environment trials.     

Variation and covariation for quantitative resistance to head blight (Fusarium culmorum) in two testcross series of S2 lines in winter rye

The amount of genetic variation among inbred lines and testcrosses, and covariation between both genetic materials, are of crucial importance for selection efficiency in hybrid breeding. To estimate these quantitative genetic parameters for resistance of winter rye (Secale cereale) to head blight caused by Fusarium culmorum, 88 three-way cross hybrids, produced by crossing each of 44 S₂ Carsten inbred lines with two unrelated Petkus single-cross testers, were evaluated along with the parental lines over 2 years. Resistance traits were head-blight rating and grain weight per spike relative to the non-inoculated control. Significant genotypic variation occurred among lines and in both testcross series. S₂ lines displayed considerably more variation than testcross series. Genotype × environment interaction was more marked among the inbred lines, while estimates of heritability were similar for both genetic materials. Testcrosses showed heterosis for head-blight resistance. No relationship existed between S₂ lines and the two testcross series for any resistance trait. This might be caused by an association between inbreeding and Fusarium-head-blight susceptibility and different inbreeding depression among the S₂ population. The phenotypic correlations between the testcross series were moderate for both traits (r = 0.58, P < 0.01). In conclusion, Fusarium-head-blight resistance has to be selected at the respective heterozygosity levels.     

Effectiveness of Ethrel as a Male Gametocide in Pearl Millet and its Influence on Ergot

In field and greenhouse experiments Ethrel (2-chloroethyl phosphonic acid) was tested for its male garnetocidal effects on pearl millet (Pennisetum americanum) and its subsequent effects on ergot development. Application of Ethrel at 2000 ppm at late boot or early protogyny was the most effective for inducing male sterility in the hybrid, EJ 104. Female fertility in a male sterile line, however, was not affected by Ethrel treatment. Ethrel at 2030 ppm applied at ihe late boot stage resulted1 in partial paniele exsertion, and reduced plant height anc. panide length. In vitro Ethrel (2000 ppm) completely inhibned pollen germination but did not affect germination of conidia of Claviceps fusiformis, the causal agent of ergot of pearl millet. Ergot resistance or susceptibility in pearl millet lines was not affected., probably because Ethrel could not induce complete male sterility.     

Cytoplasmic male sterility with self-incompatibility,a novel approach to utilizing heterosis in rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

The Polima cytoplasmic male sterility (CMS) system has been successfully used in three/two-line hybrid production in rapeseed (Brassica napus L.). However, the sterility of the Polima (pol) CMS lines is sensitive to temperature fluctuations. Also, traces of pollen can cause self-pollination within the CMS lines, which results in reduced levels of F₁ hybrid seed purity and leads to a significant yield loss. Self-incompatibility (SI) is another important approach for hybrid seed production in rapeseed. Despite having a wide range of restorers and being easily selected in a breeding program, SI system has some drawbacks. In this study, SI genes from a self-incompatible line of Brassica napus were transferred to a pol CMS line and S372A, a novel line of combined cytoplasmic male sterility with self-incompatibility was bred. Due to the SI genes, this line produced very few seeds when it was selfed at low temperature and no seeds at high temperature. This suggested that the line with CMS + SI had combined the advantages and overcome the disadvantages of both the pol CMS and SI systems. Furthermore, our results showed that most of the maintainers and all the restorers of the pol CMS system were also maintainers and restorers of the CMS + SI line, respectively. This indicates that the CMS + SI system can be easily used to establish three-line hybrids of rapeseed, and we believe this novel system could be extended to other species of Brassica.     

Development of chloroplast‐specific microsatellite markers for molecular characterization of alloplasmic lines and phylogenetic analysis in wheat

Wheat (Triticum aestivum L.) is strictly a self‐pollinated crop, where hybrid breeding requires well‐characterized cytoplasmic male sterile (CMS) lines. The CMS has mostly been developed by substituting nuclear genome of wheat into the cytoplasm from wild relatives. Molecular characterization of 90 genotypes including 82 CMS lines originating from five different species, namely Aegilops speltoides, Ae. kotschyi, Ae. variabilis, Triticum araraticum and T. timopheevii, and eight popular varieties was carried out. Consequently, a set of 25 microsatellite markers specific to chloroplast (cpSSRs) were designed and successfully validated for specificity of amplification. A total of 15 cpSSRs (60%) were found polymorphic, of which three cpSSRs (TaCM7, TaCM8 and TaCM11) in genic region and twelve cpSSRs were located in intergenic region. Phylogenetic analysis of genotypes using cpSSRs revealed two major groups well in accordance with respective origin. A set of cpSSRs and phylogeny of CMS belonging to different origins developed, which will be helpful for the improvement in CMS system in wheat. The genic cpSSRs can be used for the allele mining and evolutionary studies.     

New insights into genotypic thermodependency of cytoplasmic male sterility for hybrid barley breeding

The cytoplasmic male sterility (CMS) system msm1 in barley is known to be thermosensitive, sometimes resulting in spontaneous fertility restoration in the absence of the corresponding restorer gene Rfm1. Here, we investigated genotypic differences concerning temperature sensitivity and the plant developmental stage at which elevated temperature induces spontaneous fertility restoration in three CMS mother lines. While one line stayed completely male sterile, a significantly higher fertility was observed in two lines after treatment from growth stage DC 41 until maturation. Microscopic analysis revealed that sterile anthers contained neither intact pollen, nor remains of aborted pollen grains, whereas pollen was visible in anthers of potentially fertile plants. We conclude that the barley CMS system affects anther and pollen development prior to meiosis. Elevated temperature during heading and flowering can lead to a spontaneous fertility restoration by reactivating pollen growth. Nevertheless, genotypic variation exists enabling the selection for stable CMS mother lines and the development of F₁ hybrids with high hybridity. As spontaneous fertility restoration due to environmental effects is difficult to phenotype, further investigations will focus on the development of molecular markers for marker‐assisted selection.     

Use of non‐adapted quantitative trait loci for increasing Fusarium head blight resistance for breeding semi‐dwarf wheat

Semi‐dwarf wheat is an important prerequisite for releasing a successful commercial cultivar in high‐yielding environments. In Northern Europe, this aim is achieved by using one of the dwarfing genes Rht‐B1 (formerly known as Rht‐1) or Rht‐D1 (Rht‐2). Both genes, however, result in a higher susceptibility to Fusarium head blight (FHB). We analysed the possibility to use the two non‐adapted FHB resistance quantitative trait loci Fhb1 and Fhb5 (syn. QFhs.ifa‐5A) to counterbalance the negative effect of the dwarfing allele Rht‐D1b in a winter wheat population of 585 doubled‐haploid (DH) lines segregating for the three loci. All lines were inoculated with Fusarium culmorum at four locations and analysed for FHB severity, plant height, and heading date. The DH population showed a significant (p < 0.001) genotypic variation for FHB severity ranging from 3.6% to 65.9% with a very high entry‐mean heritability of 0.95. The dwarfing allele Rht‐D1b reduced plant height by 24 cm, but nearly doubled the FHB susceptibility (24.74% vs. 12.74%). The resistance alleles of Fhb1 and Fhb5 reduced FHB susceptibility by 6.5 and 11.3 percentage points, respectively. Taken all three loci together, Fhb5 alone was already able to reduce FHB susceptibility to the same extent as Rht‐D1b increased it. This opens new avenues for selecting semi‐dwarf wheat by marker‐assisted introgression of Fhb5 without the enhancement of FHB susceptibility.     

Heterosis of purple blotch (<Emphasis Type="Italic">Alternaria porri</Emphasis> (Ellis) Cif.) resistance,yield and earliness in tropical onions (<Emphasis Type="Italic">Allium cepa</Emphasis> L.)

Five open pollinated onion cultivars Red Creole, Kaharda, Koumassa, Sokoto local and Ori were crossed in a complete diallel and their progenies were evaluated in replicated trials, at Sokoto and Talata Mafara, Nigeria, during the 2004/2005 and 2005/2006 seasons. The experiments were randomised as complete block design with three replications. 30 mls of 10⁻¹ cfu of spore suspension of Alternaria porri prepared by serial dilution was poured into the centre of each plot (sunken bed) immediately after irrigation at 2 weeks after transplanting. Combined analysis across seasons and locations indicated significant (P < 0.05) differences between the populations with respect to all the characters under study. Crosses Ori × Koumassa and Koumassa × Ori recorded highly significant (P < 0.01) positive high parent heterosis for bulb diameter. Crosses Ori × Sokoto local and Ori × Koumassa recorded highly significant (P < 0.01) negative high parent heterosis for days to maturity. Cross Sokoto local × Koumassa exhibited highly significant (P < 0.01) positive high parent heterosis for number of leaves/plant. Crosses Red Creole × Kaharda and Kaharda × Red Creeole recorded highly significant (P < 0.01) positive high parent heterosis for disease incidence. Red Creole × Kaharda and Kaharda × Red Creeole also recorded highly significant (P < 0.01) positive high parent heterosis for fresh bulb yield. Cross Kaharda × Ori recorded highly significant (P < 0.01) positive high parent heterosis for bulb weight. The cross Kaharda × Sokoto local recorded significant (P < 0.05) negative high parent heterosis for days to maturity while the cross Red Creole × Kaharda recorded highly significant (P < 0.01) positive high parent heterosis for number of leaves/plant. Bulb diameter and bulb weight recorded highly significant (P < 0.01) and significant (P < 0.05) environmental correlation with days to maturity.     

Interspecific amphiploid‐derived alloplasmic male sterility with defective anthers,narrow disc florets and small ray flowers in sunflower

The cytoplasmic male‐sterility (CMS)/fertility‐restoration system is important for hybrid sunflower (Helianthus annuus L.) seed production. The objective of this study was to characterize two novel alloplasmic CMSs, designated CMS GRO1 and CMS MAX3, with defective anthers, narrow disc florets with no swollen corolla, and short, narrow ray flowers derived from two tetraploid amphiploids (AMPs). Among 26 tested lines, only AMP Helianthus cusickii/P 21 and HA 410 failed to restore male‐fertility. Segregation of CMS, male‐fertile plants and plants with reduced male‐fertility was observed both in the testcross progeny of a six line half‐diallel cross of F₁s with CMS MAX3 and in an F₂ population of CMS GRO1 × RHA 274. Male‐fertility restoration was controlled by at least two dominant genes. Detailed analysis of the mitochondrial genes may provide insight into the differences between these CMSs and other CMS lines. The new CMSs will facilitate the studies of the incompatibility between cytoplasmic and nuclear genes, especially for the alloplasmic CMS involving perennial species, and also provide unique ornamental flower types and CMS sources for hybrid sunflower breeding.