Components of a Cytoplasmic Male Sterility System in Resynthesized and Cultivated Forms of Oilseed Rape (Brassies napus L.)

Male sterile Brassica napus L. plants were found in breeding material which was used for the development of yellow-seeded oilseed rape. The genetic studies indicated that the male sterility was conditioned by the presence of maintamer genes in the nuclear backgrounds of two newly resynthesized B. napus lines, No7076 and No7406, in combination with a male sterility-inducing cytoplasm (S) which is frequently found in cultivated forms of B. napus. Test crosses with nap maintainer and restorer lines support the conclusion that the observed male sterility is of nap type. Furthermore, the Eco RI restriction pattern of mitochondrial DNA of the (S) cytoplasm was identical to that of the nap cytoplasm. Hence, we conclude that we have uncovered a new source of maintainer lines for the nap system which could potentially lead to the production of a better maintainer/restorer system for use in hybrid oilseed rape breeding programmes. However, more work is needed to reduce the glucosinolate content of the maintainer lines and to determine the factors controlling the phenotypic expression of the system.     

Genotype-Environment Interactions and Stability Analysis for Herbage and Seed Yields of Forage Peas Under Rainfed Conditions

Twenty-five genotypes of forage peas (Pisum sativum L.) were evaluated under rainfed conditions for two years at four locations in Syria and one in Lebanon. Since local climatic variation is significant, each location in each year was treated as a separate environment, to give ten environments. Genotype-environment interactions (GXE) were analysed using linear regression techniques. There was considerable variation in herbage and seed yields within both genotypes and environments. Genotype-environment interactions were present for both herbage and seed yields; a large proportion of these interactions was accounted for by the linear regression. Although the non-linear component was also significant, its magnitude was smaller than that of the linear component. The highest and most stable herbage yields were obtained from accessions 46/61, 135/175, 3211/323, 99/103 and 88/335. The highest and most stable seed yields were produced by accessions 4/166, 2428/240, 424/242 and 88/335. Accession 88/335 from Germany, F.R. was the only genotype to combine high herbage and seed yields with wide adaptation and stability and could thus be considered the most widely adapted genotype. Other stable genotypes were identified as suitable for poor environments. Yield of the locally collected genotype, though often high, was found to be unstable. The importance of genotype-environment interactions in future breeding strategies is discussed.     

Studies on the inheritance of five qualitative characteristics in clusterbean (Cyamopsis tetragonoloba (L.) Taub)

Summary The inheritance of five characteristics namely branching behaviour, clustering pattern, growth habit, leaf size and hairiness was studied in clusterbean. All the traits were controlled by single pairs of genes except branching behaviour which exhibited digenic inheritance. Complementary gene effects were involved in the expression of branching in the F₁ and F₂ generations; the F₂ showing a ratio of 9:7 for branched to unbranched genotypes in the cross FS 277 × NC 70 where both the parents were single shooted. The alleles governing branching, discontinuous clustering, indeterminate growth habit, small leaf size and hairiness were dominant over the alleles controlling non-branching, continuous clustering, determinate growth habit, broad leaf and glabrous leaf and stem.     

Transfer of resistance to race 2 of Plasmodiophora brassicae from Brassica napus to cabbage (B. Oleracea spp. Capitata). IV. A resistant 18-chromosome B1 plant and its B2 progenies

Summary The somatic karyotype and meiotic chromosome behavior were studied in an 18-chromosome B₁ plant derived from backcrossing a triploid (Brassica napus x B. oleracea ssp. capitata) F₁ hybrid to cabbage. It is considered that cabbage chromosomes no. 1 and no. 7 were substituted by two shorter B. napus chromosomes. Meiotic disturbances were more apparent during the late stages of second division. Seed fertility of this plant was largely restored in the second backcrosses with both cabbage and broccoli. 18-chromosome B₂ plants resistant to race 2 of Plasmodiophora brassicae were recovered among the progenies.Contribution no. J. 725 from the Research Station, Research Branch, Agriculture Canada, St-Jean, Québec J3B 6Z8.     

Indentification of true genetic dwarfing sources in foxtail millet (Setaria italica Beauv.)

Summary True genetic dwarfs hither-to not reported have been located in foxtail millet. The dwarfs as a group distinguished themselves from the talls in having altered constellation of characters. The morphological differences were highly significant for plant height, internodal length, and tillering potential. The talls had elongated internodes compared to dwarfs while there was no difference for node number on the main stem suggesting that short internodal length was primarily responsible for dwarfism. The dwarfs also showed slightly higher leaf number per plant, leaf area and harvest index compared to talls. The dwarfs were insensitive to exogenous GA₃ application indicating that GA₃ synthesis is not impaired. This suggests that dwarfing gene sources presently identified are true genetic dwarfs and their behaviour is similar to dwarfs derived from Norin 10 in wheat and Dee-geo-woo-gen in rice. The superior morphological frame makes these dwarfs ideal as far as plant type is concerned and offers immense potentialities in breeding high yielding foxtail millets.     

Reselection of a Pearl Millet Cultivar Utilizing Residual Variability for Downy Mildew Reaction*

‘BJ 104’ was the most widely grown pearl millet hybrid in India until it became susceptible to downy mildew (DM) in 1984—85. Residual variability for resistance was found in both parental lines, 5141 B (maintainer of 5141 A) and J 104, and through four generations of pedigree selection under intense disease pressure in the DM nursery, two lines, IC-MA841 (from 5141 B) and ICMP 84814 (from J 104), were selected resulting in a reconstituted DM resistant hybrid (‘ICMH 84814’) which was equal in yield to the original ‘BJ 104’. The reconstituted hybrid, though phenotypically similar, can be distinguished from “BJ 104” being slightly taller, flowers later, has heavier heads, and 1000-seed weight, but tillers less. A similar exercise was attempted on Tifton 23 B, the female parent of the first widely grown hybrid (‘HB 3’— the male parent was also J 104), but no variability for resistance to DM was found.     

Novel complementary genes for adult plant leaf rust resistance in a wheat stock carrying the 1BL-1RS translocation

The wheat-rye translocation (IBL-IRS) that carries the tightly linked genes Lr26/Sr31/Yr9, has been widely exploited in the development of wheat cultivars worldwide. This resistance, however, has become ineffective owing to the evolution of new pathotypes of Puccinia recondita that neutralize the resistance of Lr26. Inheritance studies on ‘Federation4′/‘Kavkaz’ revealed complementary genes derived separately from ‘Federation’ and ‘Kavkaz’ for adult plant resistance. This previously undescribed source of resistance appears to be widely effective and could therefore be used to broaden the genetic base for resistance in India. Its effectiveness in other geographical areas is unknown.     

Yield and quality components of silage maize in killed and live cover crop sods

In sloping areas with high precipitation, planting maize into live winter cover crop sods may help to alleviate the environmental problems associated with clean-tillage production systems of maize. The present study evaluates the performance of silage maize (Zea mays L.) under several cultivation methods: CC (conventional cropping system, i.e., maize was sown into the bare, autumn-ploughed soil); LGS/CK (maize was planted into a living Italian ryegrass (Lolium multiflorum Lam.) sod which was subsequently herbicidally killed); and LGS/MR (similar to LGS/CK, but the ryegrass was mechanically regulated). The research was conducted in the midlands of Switzerland on a fertile sandy loam under humid conditions during three cropping seasons. With 110 kg N ha⁻¹ (fertilizer nitrogen plus mineral nitrogen of the soil at maize planting), the CC system was much more productive than were the LGS/CK and LGS/MR systems in terms of dry matter and nitrogen yields of maize. Increasing the nitrogen supply to 250 kg N ha⁻¹ considerably reduced the yield advantage of CC over the LGS/CK and LGS/MR systems, indicating that nitrogen was the most limiting factor for maize yield in the mulch seeding systems. With 250 kg N ha⁻¹, the LGS/CK and LGS/MR systems produced greater total yields of digestible organic matter (maize plus ryegrass) than did the CC system, whereas the total nitrogen yield was similar for all cropping systems. The whole-shoot concentrations of nitrogen were highest under CC, irrespective of the level of nitrogen supply. With 110 kg N ha⁻¹, concentrations of phosphorus and magnesium were clearly higher for the mulch seeding systems. There were only minor differences among the cropping methods in the concentrations of potassium and calcium in the whole shoot. When 250 kg N ha⁻¹ were applied, there were no significant variations among the cropping systems in the concentrations of minerals. Changes in the botanical composition of the cover crop sod and in the time and method of cover crop control may help to reduce the competition for nitrogen between maize and the living mulch.     

Genetic variation among European maize inbreds for resistance to the European corn borer and relation to agronomic traits

The univoltine European corn borer (ECB) has become a major limiting factor for maize (Zea mays L.) production in central Europe. The objective of this study was to survey the genetic variation for ECB resistance in European elite maize germplasm. Eighteen flint and 23 dent inbreds were screened under artificial ECB infestation at two locations in 1993 and 1994. Resistance was assessed by damage rating of broken plants, measurement of tunnel length in dissected stalks, and yield reduction in infested plots relative to insecticide-protected control plots. Flint lines showed significantly greater means for damage rating than dent lines with grain yield reduction of 35% and 24%, respectively. Significant genotypic variances among lines and high heritabilities were found for agronomic traits and damage rating. Heritabilities were intermediate for tunnel length and relative grain yield. Significant associations of days to silking, ear dry matter content, and dry matter yield of the whole plant with damage rating and tunnel length suggested a better resistance in late-maturing, high-yielding inbreds. Genotypic correlations of relative grain yield with tunnel length and damage rating ranged between ?0.46 and ?0.72. Partial correlations, eliminating the effect of flowering time, confirmed these associations. Damage rating of stalks is the most suitable trait for evaluation of ECB damage owing to its high heritability and easy recording. Tunnel length below the primary ear is a useful trait for assessing antibiosis because it is not correlated with days to silking. Inbreds with extreme resistance and susceptibility were identified which can be used as parents for establishing breeding and QTL mapping populations.     

Relationship between morphological variation and geographical origin or selection history in Lupinus pilosus

Patterns of morphological diversity were examined in Lupinus pilosus in relation to geographical origins or selection history of accessions. There was significant variation among accessions for most architectural and reproductive characters in a field experiment in Perth, Western Australia. Late flowering was associated with resetted early growth, profuse branching and collection in higher rainfall sites. High yield and profuse podding on the main stem was associated with large pods and leaves, many seeds per pod, greater height to the first main-stem pod, and collection in higher altitude sites. Ten groups of accessions, identified by hierarchical cluster analysis, accounted for 79% of genotype and 69% of genotype x character sums of squares. One group, possibly taxonomically distinct from the others, consisted exclusively of wild types from northern Israel with poor pod set and low seed yield, poor nodulation, pale foliage, and small leaves. Wild types from Turkey and Crete had rosetted early growth and were late flowering, and the Turkish group had extremely rapid mid-season growth. Ornamental types from Europe or Australia with pink, purple or white flowers clustered together in an early flowering group with vigorous early growth. A smooth-seeded type of L. pilosus was discovered in a group of short, late flowering and rough-seeded types from Syria.