Unique gliadin patterns in Chinese winter wheat cultivars

Cultivated Chinese wheat germplasm has been a valuable genetic resource in international plant breeding. Patterns of gliadin among cultivated Chinese accessions are unknown, despite the proven value and potential novelty. The objective of this work was to analyse the diversity within improved Chinese wheat germplasm. The electrophoretic banding patterns of gliadin in winter wheat cultivars and advanced lines were determined by acid-polyacrylamide gel electrophoresis. For 148 leading commercial cultivars and promising advanced lines used in this study, 48 patterns were identified, 29 corresponding to ω -gliadin, nine to γ -gliadin, five to β -gliadin and five to α -gliadin. The most frequent patterns were A6 in ω ; B in γ ; B in β and A in the region of α . A total of 116 band types appeared in the 148 samples: 94 accessions had unique gliadin types, and 22 gliadin, types while not unique, were found in 54 accessions. The gliadin patterns of Chinese wheat cultivars and lines greatly differed from the patterns of wheat lines from other countries. Three patterns, E, J, H, M, N and O in the ω -zone had not been reported previously. Three wheat zones of China, the Northern Winter Wheat Region, the Yellow and Huai Valley River valleys Winter Wheat Region and the Southwestern Winter Wheat Region, showed different frequencies in their gliadin patterns. This information can be used to monitor genetic diversity with Chinese wheat germplasm.     

Regional patterns of microsatellite diversity in Ethiopian tetraploid wheat accessions

This study was conducted to assess regional patterns of diversity of Ethiopian tetraploid wheat accessions and to identify areas of diversity that can be used as source of new germplasm for developing high yielding and stable varieties. A collection of 133 Ethiopian tetraploid wheat accessions and eight introduced cultivars was analysed using 29 wheat microsatellite markers. A total of 383 alleles were detected with an average value of 13.14 alleles per locus. Relatively more alleles were observed in the B genome than in the A genome. Gene diversity indices ranged from 0.08 to 0.95, with a mean value of 0.72. Accessions collected from the same region were pooled and the number of alleles and gene diversity were calculated over the 29 simple sequence repeats for each region. Higher numbers of alleles were detected in the Shewa region (8.72), followed by Tigray (5.86) and Hararghe (5.76). The highest average gene diversity value was found in Shewa (0.65), followed by Gondar (0.64). No significant correlation was observed between geographic distance and genetic distance. Out of 383 different alleles detected, 93 (24.4%) were observed to be region‐specific. Region‐specific alleles were found across all chromosomes except for Xgwm752, Xgwm155 and Xgwm148. Genetic similarity coefficients were estimated for all the possible 55 pairs of regional comparisons and they ranged from 0.16 to 0.52, with a mean value of 0.50. All provinces were differentiated in the UPGMA cluster diagram.     

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

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

Inheritance and potentials of a mutated dwarfing gene ndf1 in Brassica napus

A dwarf mutant ‘NDF‐1′, approximately 70 cm high, was derived from a 200‐cm high doubled haploid (DH) line ‘3529’ (Brassica napus), seeds of which were jointly treated with chemical inducers and bombardment of fast neutron. The leaves of the ‘NDF‐1’ mutant were wrinkled and thicker compared with the wild‐type control. The mutant had much lower values than its original parents for all agronomic traits, except for its seed weight. A genetic analysis revealed that dwarfism is under the control of a major gene (designated as ndf1) with a mainly additive effect and non‐significant dominance effect. Because of the high level of resistance to lodging, breeding programmes for double low dwarf oilseed rape and heterosis utilization were initiated. Some new dwarf strains with improved agronomic performance were developed. The hybrid of the cross between the tall parent and the dwarf line showed increased harvest index and significantly higher seed yield than the tall parent or the control variety ‘Zhongyou 821’ and presented an estimated heterosis vigour rate as high as 12.5–25.8%. The dwarf trait will be a promising marker for a simple, economic and efficient way to control the purity of F₁ hybrid varieties in hybrid production of B. napus.     

Homozygous transgenic rice lines expressing GNA with enhanced resistance to the rice sap-sucking pest Laodelphax striatellus

Homozygous transgenic rice lines expressing snowdrop lectin, Galanthus nivalis agglutinin (GNA), were investigated for resistance to the rice small brown planthopper (SBPH), Laodelphax striatellus, an important rice sap‐sucking pest causing yield losses and serving as vector for some important rice viruses. Insect bioassay results revealed that both the GNA‐expressing homozygous lines tested significantly inhibited SBPH by decreasing its survival, its overall fecundity and retarding development. This is the first report on homozygous transgenic rice lines expressing GNA conferring enhanced resistance to SBPH. This result suggests that transgenic rice expressing GNA will be useful in rice pest resistance breeding, as an alternative to conventional breeding for the control of SBPH, and potentially alleviating damage caused by the viruses it transmits.     

Effectiveness of selection for quality traits during the early stage in the potato breeding population

Potato cultivars resistant to cold‐temperature sweetening are of major importance to the processing industry producing both chips (crisps) and French fries. When most modern potato cultivars are maintained in cold storage to retard sprouting, the tubers accumulate reducing sugars, and the products become an unacceptable brown colour when fried. Selection for better processing quality during the early generations of a breeding programme could be of considerable advantage. Using a portable ‘sugarmeter’, which requires only a drop of sap from the tuber on a test strip, many samples can be efficiently surveyed for low sugar as early as the F₁ generation. Using seedlings of three test crosses, glucose and specific gravity of field‐grown tubers, minitubers from greenhouses and microtubers from in vitro culture were compared after cold treatment. Although the mean glucose levels of minitubers and microtubers were higher than field‐grown tubers, the correlation between the glucose contents of the three types of tubers was fairly high. A considerable genetic improvement was noted when progenies were grown as minitubers or microtubers, even though the response to selection for low glucose levels in minitubers and microtubers was lower than from direct selection from field‐grown tubers. The specific gravity of field‐grown tubers showed a significant association with freshly harvested minitubers and microtubers. Selection for low glucose content in minitubers can therefore save considerable resources in a breeding programme.     

Genetic analysis of four self-incompatible lines in Brassica napus

Reciprocal hybridization between four self-incompatible lines of Brassica napus: 271, 181, 184 and ‘White Flower’, revealed incompatibility. The reciprocal F₁s obtained by bud pollination showed self-incompatible reactions, and no segregation for self-incompatibility was observed in all the reciprocal F₂ populations, indicating that lines 271, 181, 184 and ‘White Flower’ were genetically identical with regard to self-incompatibility. Observations of self-incompatibility in 17 hybrids from crosses between line 271 and 17 varieties of B. napus showed 10 of the F₁ hybrids to be self-compatible, while four were partially self-compatible and three were self-incompatible. Genetic analysis based on F₂ and BC₁ populations from five self-compatible F₁ hybrids and two self-incompatible F₁ hybrids suggested the existence of at least two loci controlling the self-incompatibility of line 271: one is the S locus, with dominant and recessive relationships between the S alleles, and the other is the suppressor (sp) of the S locus. The sp locus is genetically different from the S locus, and also shows dominant and recessive relationships between the sp alleles.     

Genetic analysis of presence and absence of lint and fuzz in cotton

Cotton fibre mutants that were fuzzless and/or lintless were crossed with each other and a normal genotype (fuzzy, linted) to produce F₂ and BC₁ generations. F₂ segregation ratios from the cross of fuzzless‐lintless × fuzzy‐linted, for fuzzy‐linted, fuzzless‐linted and fuzzless‐lintless were 45 : 15 : 4. From the cross of fuzzless‐lintless × fuzzy‐linted, the F₂ segregation ratios were 9 : 39 : 16 whereas the BC₁F₁ segregation ratios from the F₁ backcrossed to fuzzless‐lintless were 1 : 3 : 4. These data suggest that the presence or absence of lint and fuzz are controlled by the interaction of four gene loci on non‐homologous chromosomes. We designate these loci as N₁, N₂, Li₃ and Li₄, where N₁ N₁ confers the presence of fuzzy, N₂N₂ confers inhibition of fuzzy initiation and development, and duplicate gene pairs, Li₃Li₃ and Li₄Li₄, determine the presence of lint. Homozygosity for li₃li₃ and li₄li₄ might also inhibit fuzz from development. In other words, they were recessive epistatic to fuzz genes.