Cytogenetics of a new trispecies hybrid in cotton: [(Gossypium hirsutum L. × G. thurberi Tod.)2 × G. longicalyx Hutch. & Lee]

A three‐species hybrid named HTL including Gossypium hirsutum L. [2n = 4 x = 52, (AD)₁ genome] was created using the pseudophyletic introgression method with G. longicalyx Hutch. & Lee (2n = 2x = 26, F₁ genome) as donor parent and G. thurberi Tod. (2n = 2x = 26, D₁ genome) as bridge species. The new hybrid was totally self‐sterile and its interspecific status was confirmed using simple sequence repeat markers and cytogenetic analysis. Cytogenetic studies showed that its chromosome configuration was 2n = 52 = 14.13 I + 15.10 II + 1.03 III + 0.9 IV + 0.03 V + 0.13 VI (where I, II, III, IV, V and VI are univalents, bivalents, trivalents, tetravalents, pentavalents and hexavalents, respectively). Prospects for successfully exploiting the HTL hybrid in breeding programmes are discussed.     

Validation of a set of informative simple sequence repeats markers for variety identification in Pak‐choi (Brassica rapa L. ssp. chinensis var. communis)

A core set of 21 simple sequence repeats (SSR) markers was developed for Pak‐choi (Brassica rapa ssp. chinensis var. communis) variety identification. We initially selected 74 SSR markers which exhibited high polymorphism and reproducibility in SSR detection from 2129 SSRs. Using the 74 SSR‐based dendrogram for 45 inbred lines as calibration, 21 core SSRs were selected out. The utility of this core set SSRs was firstly tested in 45 inbred lines and finally verified in 102 commercial varieties. We also constructed a molecular ladder for each core SSR as a reference standard. Diversity analysis of this core SSR panel in 102 varieties demonstrated that each marker generates 2–3 alleles (averaged 2.33), with polymorphism information content values ranging from 0.01 to 0.56 (averaged 0.31). The averaged values of Shannon information index, observed heterozygosity, expected heterozygosity and Wright's fixation index were 0.59, 0.43, 0.38 and −0.09, respectively. Furthermore, the 21 SSR‐based classifications for 102 varieties were consistent with traditional classification based on morphology. This core SSR panel represents an effective tool for genetic variation analysis in Pak‐choi.     

The resistance to leaf rust and powdery mildew of recombinant lines of barley (Hordeum vulgare L.) derived from H. vulgare × H. bulbosum crosses

A set of 23 recombinant lines (RLs) of barley ( Hordeum vulgare L.) derived from H. vulgare  ×  H. bulbosum L. crosses was inoculated with barley leaf rust ( Puccinia hordei ) and powdery mildew ( Blumeria graminis f.sp. hordei ) at the seedling stage to identify their levels and mechanisms of resistance. Eight RLs were studied further in glasshouse and field tests. All three barley parents ('Emir', 'Golden Promise' and 'Vada') were highly susceptible to powdery mildew and leaf rust isolates. Several RLs showed partial resistance expressed as high relative latency periods and low relative infection frequencies against leaf rust. This high level of partial resistance was due to a very high level of early aborting colonies without host cell necrosis. Several RLs showed hypersensitive resistance to some or all isolates. For powdery mildew, one RL was completely resistant to the CC1 isolate and had a hypersensitive resistance to the CO-02 isolate. Three RLs derived from 'Emir' were completely resistant to both powdery mildew isolates, and three more RLs tested in the field had higher levels of partial resistance than their parents. The results indicate that H. bulbosum contains major and minor gene(s) for resistance to leaf rust and powdery mildew that can be transferred to cultivated barley.     

Meiosis and fertility in interspecific hybrids of Nicotiana tabacum L. ×N. glauca Grah. and their derivatives

Nicotiana glauca is of potential interest to breeders as it carries resistance to black root rot of tobacco. Cytological investigations of sexual interspecific hybrids of N. tabacum T′T′TT (2n = 4x = 48) cv. ‘Wiślica’ × N. glauca GG (2n = 2x = 24) were carried out. The analyses of chromosome association at diakinesis and metaphase I in the PMCs of amphihaploid F₁ T′TG (2n = 3x = 36) revealed low variable pairing with 0–5 bivalents. The sterile amphihaploids F₁ were converted into partial female fertile amphidiploids T′T′TTGG by chromosome doubling. Among 36 mature plants obtained, 15 were found to have chromosome numbers (2n = 6x = 72) and were verified as amphidiploids, 9 had (2n = 6x = 70 or 71) chromosomes while the remaining 12 were haploid. True amphidiploids, in spite of quite high chromosome pairing during meiosis, were very different in pollen fertility, ranging from 0% to 85%. Male fertility disturbances did not correlate with the degree of female fertility upon pollination with N. tabacum. Sesquidiploids T′TG (2n = 5x = 60) obtained from backcrossing the amphidiploids to parental tobacco showed more than 22 bivalents, 10–12 univalents and occasional multivalents that indicated the possibility of interchange events between N. tabacum and N. glauca genomes.     

A new,useful flowering characteristic in Beta vulgaris L.

In a culture of Beta vulgaris L., Czechoslovak semi-sugar-beet variety Choovka, one plant was found of which all flowers came into flower simultaneously; they were distributed with regular density; all glomerules—even at the twig tips—were of the same size and ripened at the same time. These properties which are of a great economic value were fixed by further cultivation.     

Chromosome pairing and fertility of interspecific hybrids between Trifolium repens L. and T. occidentale Coombe

Trifolium occidentale is a diploid wild relative with the potential to improve the drought and salt tolerances of white clover (Trifolium repens). Previous work has shown that it is possible to efficiently produce large T. repens × T. occidentale breeding populations using colchicine‐doubled (4×) T. occidentale. For effective introgression (backcross) breeding, it is also essential that interspecific chromosome pairing and recombination occur. In this study, it was apparent that chromosome pairing was occurring not only between T. occidentale and T. repens subgenomes, but also between the ancestral subgenomes of T. repens. Thus, interspecific hybridization has the potential for major genome recombination and opens the way for introgression of traits from T. occidentale into white clover.     

Breeding for increased nitrogen‐use efficiency: a review for wheat (T. aestivum L.)

Nitrogen fertilizer is the most used nutrient source in modern agriculture and represents significant environmental and production costs. In the meantime, the demand for grain increases and production per area has to increase as new cultivated areas are scarce. In this context, breeding for an efficient use of nitrogen became a major objective. In wheat, nitrogen is required to maintain a photosynthetically active canopy ensuring grain yield and to produce grain storage proteins that are generally needed to maintain a high end‐use quality. This review presents current knowledge of physiological, metabolic and genetic factors influencing nitrogen uptake and utilization in the context of different nitrogen management systems. This includes the role of root system and its interactions with microorganisms, nitrate assimilation and its relationship with photosynthesis as postanthesis remobilization and nitrogen partitioning. Regarding nitrogen‐use efficiency complexity, several physiological avenues for increasing it were discussed and their phenotyping methods were reviewed. Phenotypic and molecular breeding strategies were also reviewed and discussed regarding nitrogen regimes and genetic diversity.     

Mapping polygenes for tuber resistance to late blight in a diploid Solanum phureja × S. stenotomum hybrid population

Potato tuber blight is a disease caused by the oomycete Phytophthora infestans (Mont.) de Bary. Due to the significant economic impact of this disease, introgression of durable resistance into the cultivated potato is one of the top priorities of breeding programmes worldwide. Though numerous resistance loci against this devastating disease have already been mapped, most of the detected loci are contributing towards foliar resistance while specific information on tuber resistance is limited. To identify the genetic components of tuber resistance and its relationship to foliar resistance and plant maturity we have investigated the host‐pathogen interaction in a segregating diploid hybrid Solanum phureja × S. stenotomum family. Mature tubers from this mapping family were inoculated with a sporangial suspension of P. infestans (US‐8 clonal lineage) and evaluated for lesion expansion. No significant correlation was detected between late blight resistance in foliage and tubers, and between plant maturity and tuber resistance. Four chromosomal regions were significantly associated with tuber resistance to the disease. The largest effect was detected near the marker locus PSC (LOD 10.7) located on chromosome 10. This locus explained about 63% of the total phenotypic variation of the trait. The other three resistance‐related loci were mapped on chromosomes 8 (GP1282, LOD 4.4), 6 (CP18, LOD 4.0) and 2 (CP157, LOD 3.8). None of the four tuber resistance loci coincides with the foliage resistance loci detected in this same family. Tuber blight resistance quantitative trait loci (QTL) on chromosomes 2, 8 and 10 are distinct from the maturity QTLs and have an additive effect on tuber resistance. These results indicate that different genes are involved in foliar and tuber resistance to P. infestans in the present family and that some of the resistance genes might be associated with late maturity.     

Pollen viability and meiotic behaviour in intraspecific hybrids of Hydrangea aspera subsp. aspera Kawakami group x subsp. sargentiana

Pollen viability and male meiosis in intraspecific hybrids of Hydrangea aspera subsp. aspera Kawakami group (2n = 2x = 36) and subsp. sargentiana (2n = 2x = 34) were investigated. Although it had been assumed that they were sterile, pollen viability was observed; it varied from 2.5% to 12.1%. The production of gametes with different chromosome numbers was implied by the analysis of the dispersion of the diameter distribution of pollen grains. Analysis of male meiosis made it possible to identify the origins with two major categories of meiotic aberrations: abnormal chromosome distribution (early chromosome migration at metaphase, lagging chromosomes at anaphase, micronuclei at telophase), leading to the formation of unbalanced tetrads and/or ones with supernumerary microspores; and abnormal spindle orientation in metaphase II (tripolar, fused and parallel spindles), leading to the formation of dyads or triads. The mode of 2n pollen formation is of the First Division Restitution type. The high level of parental heterozygosity that is normally associated with them should facilitate the transfer of a polygenic trait in breeding programme.     

Transfer of new dwarfing genes from the weed species Avena fatua into cultivated oat A. byzantina

New sources of dwarfing genes were identified from accessions of Avena fatua in Japan and Korea. The dwarfing genes were transferred from backcrossed and self‐pollinated relatives to the cultivated oat ‘Kanota’. In the cultivated form, the dominant dwarfing gene Dw8 showed a relatively lower transmission rate than recessive, semi‐dominant and nondwarfing genes and was characterized by a distinct link with wild gene cluster. This was also supported by the high transmission rate of wild specific SSR alleles. Four dwarf inbred lines (L153, L169a, L169b and L812) were identified as involving a single recessive dwarfing gene(s). The recessive dwarfing genes that showed normal and stable transmission rates in BC₁F₃ were first reported in hexaploid oats. The L169 segregated two different recessive dwarf lines in BC₁, which were selected as semi‐ (L169a) and extreme‐ (L169b) dwarf lines. The L169a was a good genotype with a high grain yield. L288 is a semi‐dwarf line conditioned by a semi‐dominant dwarfing gene, with a unilateral panicle, large florets and good grain quality due to strong resistance to lodging. L342 had a short peduncle, making the panicle compact, and its phenotype was similar to the dwarfness controlled by Dw7, but the dwarfing genes were different.     

Development of drought‐tolerant breeding lines derived from Helianthus annuus × H. argophyllus interspecific crosses

Helianthus argophyllus is a wild species known as “silver sunflower”, which possesses several traits, including morphological traits that increase drought tolerance. Therefore, introgressions between chosen cultivated lines and two H. argophyllus accessions were made, and segregating generations were established. Important agronomic traits including single heading, high pollen fertility, silver canopy (indicating more cuticular wax), and content of cuticular waxes and oil were selected over six segregating generations. The resulting F₆ lines showed introgression of water saving traits, as they had lower excise leaf water loss, with comparable yield to standard checks. However, these F₆ lines were late maturing and showed poor flowering synchronization between the cultivated and introgressed lines. Introgressed line “D‐22” was particularly promising as a breeding line, with superior agronomic and drought resistance traits. This line had the potential to be used as an inbred parental line for introgression of drought resistance traits into elite sunflower germplasm. Combining ability analysis of the introgressed lines further showed their potential for heterosis breeding or to be used as parental lines in breeding programme.     

Molecular cytogenetic characterization and phenotypic evaluation of new wheat–rye lines derived from hexaploid triticale ‘Certa’ × common wheat hybrids

Hexaploid triticale contains valuable genes from both tetraploid wheat and rye and plays an important role in wheat breeding programmes. In order to explore the potential of hexaploid triticale ‘Certa’ in wheat improvement, two crosses were made using ‘Certa’ as female parent, and common wheat cultivars ‘Jinmai47’ (JM47) and ‘Xinong389’ (XN389) as male parents. The karyotyping of BCF_4:5 lines from Certa/JM47//JM47 and F_5:6 lines from Certa/XN389 was investigated using sequential fluorescence in situ hybridization (FISH). One 1B(1R) substitution line and five 1BL.1RS whole‐arm translocation lines were identified, one of which was found lacking ω‐secalin locus. Many structural alterations on wheat chromosomes were detected in the progeny. Great morphologic differences resulting from genetic variations were observed, among which the photosynthetic capability was increased while grain quality was slightly improved. Compared with both parents, the stripe rust resistance at adult stage was increased in lines derived from Certa/JM47//JM47, while it was decreased in lines derived from Certa/XN389. These newly developed lines might have the potential to be utilized in wheat improvement programmes.     

津田芜菁BrSIZ1基因克隆、定位及表达

SIZ1是植物细胞蛋白质翻译后修饰SUMO化的E3连接酶,参与植物蛋白相互作用、定位和抗逆反应等。为研究BrSIZ1在津田芜菁中的表达特性,本研究克隆了津田芜菁SIZ1基因全长cDNA序列,命名为BrSIZ1 (GenBank登录号为KY441465),该基因全长2754 bp,其ORF全长2571 bp,编码856个氨基酸残基的多肽。构建了BrSIZ1-GFP表达载体进行亚细胞定位研究,结果显示BrSIZ1-GFP定位于细胞核内,可能在细胞核中发挥其功能。利用荧光定量PCR检测表明,该基因表达量在叶子中最高,幼苗和红色根皮中次之,表达具有组织特异性。而且BrSIZ1在芜菁根皮中的表达受长波紫外线(UV-A)诱导,在4°C、37°C胁迫的幼苗中,表达量增加。     

Optimizing embryo age and media for enhancing hybrid seedling recovery in sour orange (Citrus aurantium) × Sacaton citrumelo (C. paradisi × Poncirus trifoliata) crosses through embryo rescue

In citrus, development of new hybrids is difficult due to failure of the germination of zygotic embryos. Hence, this study was conducted to standardize embryo age and media for maximizing the germination and subsequent seedling growth in sour orange × Sacaton citrumelo crosses followed by the identification of simple sequence repeats (SSR) markers for distinguishing the hybrids. A factorial experiment in complete randomized design was conducted with two each embryo age (110–120 and 130–140 days after pollination) and culture media (G‐B5 supplemented with 1.5 mg/L GA₃ plus malt extract and G‐B5 plus malt extract) for in vitro embryo culture of sour orange × Sacaton citrumelo progenies. Older embryos germinated well in both media, though highest on M1 medium (100%). In fact, M1 medium gave higher plantlet survival in both age groups. The seedling growth of older embryos had highest root length (37.80 mm) and shoot length (24.20 mm) in M1 medium at 60 days after inoculation (DAI). Three SSR markers (TAA45, CAC15 and CAC39) showed polymorphism between female and male parents and were able to identify their hybrids.     

Inheritance of aroma compounds in a model population of Fragaria × ananassa Duch.

The inheritance of important aroma compounds is demonstrated by the use of a model population of Fragaria  ×  ananassa . Two cultivars were chosen for the crossing, 'Mieze Schindler' and 'Elsanta', which differ strongly in pedigree, phenotype, and fruit traits, including flavour. Two hundred seedlings of this cross-combination were randomly selected from a population of 438 seedlings and propagated, with three plants per seedling. Aroma analysis was performed by automated headspace solid phase micro-extraction in combination with non-targeted data analysis (pattern recognition). This method can assist breeding programmes by the preparation and analysis of hundreds of samples by a simple procedure. The method was backed up by the substance identification using gas chromatography/mass spectrometry. Data processing of 78 detectable volatile compounds by Chromstat^TM in the F₁ population showed very high variability of the volatile patterns. The ester methyl anthranilate (MA) is a discriminative key compound, being present only in the mother cultivar 'Mieze Schindler', and not detectable in 'Elsanta'. Methyl anthranilate was detectable in one fourth of the F₁ population. This low degree of inheritance shows that this important compound is easily lost in the breeding process, which could explain why all investigated modern cultivars do not contain MA. The results are valuable for the choice of breeding partners and for selection in seedling populations.