Inheritance in seed size of alfalfa: Quantitative analysis and response to selection

Seed size in alfalfa (Medicago saliva L.) has been positively correlated with seedling vigour and early growth, but there were few published reports on inheritance or selection for this trait. The objective of this research was to estimate components of genetic variance for inheritance of alfalfa seed size and determine the most efficient selection method. Components of genetic variance were estimated on seed and pollen plants of ‘BIC-7-WH’ and their progeny arranged in a North Carolina Design II mating design under controlled environmental conditions. Three selection methods, differing in parental control and selection pressure, were used to determine selection response. The seed parent genotype had a major role in determining alfalfa seed size, but the genotype of the seed had no influence. For genetic studies, pollen and seed parent effects on seed size should be measured on seed harvested from progeny plants. Seed size was controlled by additive and non-additive components of genetic variance. Heritability for seed size was 41.3%. Selection for seed size was effective and a significant shift for larger and smaller seed was attained after one cycle of selection.     

Increasing 2n gamete production in diploid alfalfa by cycles of phenotypic recurrent selection

Two cycles of selection (3rd and 4th) were carried out in a diploid population of alfalfa to improve the frequency of 2n gametes. All the plants produced unreduced gametes, except one in the 2n egg population. The average seed set, used as a measure of 2n gametes production, increased significantly in the 2n pollen selection. Conversely, the increase was not significant in the case of 2n eggs. The improvement in 2n pollen production was confirmed cytologically. These results, like those of the first two cycles of selection, suggest that 2n pollen production is controlled by few major genes while 2n egg production is controlled by one recessive major gene and influenced by minor genes. The mutants selected have been utilized for producing heterotic tetraploid progenies through Bilateral Sexual Polyploidization (BSP).     

Field resistance of perennial glandular-haired Medicago strains and alfalfa cultivars to the alfalfa weevil

Summary Field plots planted in 1986 to four, perennial, glandular-haired Medicago strains and four alfalfa cultivars were evaluated for alfalfa weevil, [Hypera postica (Gyllenhal)], abundance and feeding damage as well as plant height from 23 April through 21 may 1987 and from 25 April through 26 May 1988. The plots were located near Mead, Nebraska and both sweep and stem sampling methods were utilized. In 1987, M. glandulosa had the fewest larvae present in sweep samples on 1, 9, and 15 May, although on the last date it did not differ significantly from three other entries. The glandular-haired M. glandulosa also was among those entries having the fewest number of larvae present in stem samples on 9 May, 1987. Significant differences in the number of damaged stem tips were observed on 9 and 21 May, 1987, when M. glandulosa was among those entries having the least amount of damage. The other three glandular-haired strains had larval infestations and damage similar to those for the cultivars. Weevil abundance and damage were generally low in 1988. Medicago glandulosa was shortest of the glandular-haired strains, which were shorter than the cultivars.     

Thermal dependence of glutathione reductase in one tetraploid and its near-isogenic diploid alfalfa

Summary A more thorough understanding of the biochemical basis of superior performance of one alfalfa (Medicago sativa L.) genotype compared to another would expedite improvement in agronomically useful genotypes. Information on thermal dependence of glutathione reductase (GR, E.C. 1.6.4.2) in different ploidy levels of alfalfa is lacking. Our objective was to investigate the thermal dependency of GR in two genetically comparable populations of alfalfa at diploid and tetraploid levels. Thermal stability was similar for the enzyme from both populations, whereas variation was found for: i) the minimum apparent Km (0.53 and 4.14 M NADPH), ii) the temperature at which the minimum apparent Km was observed (15 and 25° C), and iii) the thermal kinetic windows (TKW) (the temperature range over which the apparent Km is within 200% of the observed minimum Km, 5 and 20° C width) in diploid and tetraploid alfalfa, respectively. The TKW data suggest that the diploid can perform optimally under a narrower (i.e. smaller TKW) and lower range (i.e. the temperature at which the lowest Km was observed) of temperatures, whereas the tetraploid can perform optimally under a wider range (i.e. larger TKW) of temperatures. This finding is in agreement with previously published growth data on near-isogenic populations of diploid and tetraploid alfalfa.Abbreviations GR glutathione reductase - TKW thermal kinetic window - Km apparent Km This work was supported by USDA Specific Cooperative Agreement No. 58-7MN1-8-143 from the Plant Stress and Water Conservation Unit, USDA-ARS, Lubbock, Texas. Joint contribution of the Texas Tech University, USDA-ARS, Lubbock, TX and University of Wisconsin, Madison, WI. TTU Journal No. T-4-306.     

Selection for increased forage yield in alfalfa at different NaCl levels

Summary Alfalfa (Medicago sativa L.) forage yield may be reduced by moderate levels of salinity. Increasing forage yield in saline environments through plant breeding could partially ameliorate this problem. However, prior indirect selection either in cell culture, at germination, or during seedling growth has not resulted in agronomically relevant levels of salt tolerance. This study was conducted to determine whether mean forage yield of alfalfa grown in saline environments could be increased. To reduce the number of possible selection schemes, forage yield data for five harvests from Sonora and its parental cultivar African grown in a greenhouse and irrigated with 0, 30, 60, or 80 mM NaCl were used to simulate one cycle of selection at each NaCl environment. Greatest gains in forage yield were expected under non-saline conditions with decreased gains under saline conditions. Selection based on yield in regrowth harvests was also predicted to be more efficient than that based on seedling harvest. Experimental populations were developed from Sonora and African at each NaCl level using phenotypic selection for increased mean forage yield for harvests 3 to 5. After each of two cycles of selection, forage yield from selected, control (plants selected randomly under non-saline conditions), and parental populations was evaluated at 0, 30, 60, and 80 mM NaCl. Gains in forage yield were observed in African when the selection and evaluation environments were the same, but in Sonora this was observed only at 0 NaCl. Selection at 0 NaCl did not increase forage yield at 60 or 80 mM NaCl in either germplasm source. This suggests that selection for increased forage yield may be successful at low to moderate NaCl levels in germplasm with ample variation for yield when grown in saline environments, while selection for increased forage yield in non-saline conditions may be ineffective.     

Single plant versus clonal line performance in alfalfa

Summary Single plants and clonal lines of fifty-six alfalfa clones were compared in a field trial. The error coefficient of variation was much higher for single plants than for clonal lines. Unreplicated single-plant and clonal-line performance were inadequately related. Replicated single-plant performance approached closely the performance of unreplicated clonal lines. Correlation between yield and height was low.     

Diallel analysis of tolerance to aluminium in alfalfa

Summary Acid soils having high levels of aluminium (Al) can drastically reduce yields in alfalfa and the most economically viable solution to the problem appears to be the development of Al-tolerant cultivars. To assist with the choice of a breeding method, a six-parent alfalfa diallel (crosses and reciprocals included but not parents) was evaluated in Al-toxic nutrient solution in terms of height (HT) and dry weight (DW). General combining ability was significant for both traits and constituted the majority of the genetic variation. Specific combining ability was significant only for HT and reciprocal effects were significant only for DW. Tolerance appeared to be at least partially dominant to sensitivity. Results indicate that a mass selection scheme, such as recurrent phenotypic selection, may be effective in increasing levels of tolerance in at least some alfalfa populations and that minor grains may also be achieved through exploiting non-additive genetic variation.     

Inheritance of trichome density in Ethiopian mustard leaves

A pubescent mutant of Ethiopian mustard (Brassica carinata A. Braun), N2-9531, was developed from the glabrous line C-101. The objective of this research was to study the inheritance of trichome density in this mutant. Plants of N2-9531 and C-101 were reciprocally crossed and F₁, F₂, and BC₁F₁ generations were analysed for trichome density. The average trichome density differed in the reciprocal F₁ and F₂ generations, indicating partial cytoplasmic effects. The trichome density of F₁ plants was lower than the midparent value, revealing a partial dominance of absence over high trichome density. Segregation in the F₂ and BC₁F₁ generations approximated 1:4:6:4:1 and 1:2:1 ratios, respectively indicating that two independent loci (H ₁ and H ₂) acting in an additive manner contributed equally to the expression of trichome density. The proposed genotypes were h ₁ h ₁ h ₂ h ₂ for N2-9531 and H ₁ H ₁ H ₂ H ₂ for C-101. The simple inheritance of this trait should facilitate the transfer of leaf pubescence to other Ethiopian mustard lines. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of resistance to early blight disease in a diploid potato population

Early blight disease, caused by Alternaria solani Sorauer, is a serious disease of potato foliage and tubers that occurs in most potato‐growing regions world‐wide. Developing new potato cultivars with resistance to early blight may reduce losses in the field and in storage, and lessen the need for fungicide applications. A total of 280 clones, derived from 72 maternal half‐sib families from a diploid random‐mated hybrid population of Solarium phureja×Solarium stenotomum were examined for resistance to early blight. The clones that were evaluated in a replicated field trial for 2 years in Pennsylvania, USA, had similar early blight intensity both years. Significant differences were found among families, within families and for the interaction of years × within families. Broad‐sense heritability for resistance, measured as area under the disease progress curve (AUDPC), was estimated as 0.73, with a 95% confidence interval of 0.65‐0.78, and narrow‐sense heritability was estimated as 0.61 ± 0.29 (P = 0.05). The correlation of AUDPC for early blight between years was 0.57 (P < 0.0001). These results suggest that this diploid population is worthy of use in breeding for early blight resistance.     

Estimation of genetic parameters in a recurrent selection program in Apple

Combining ability was estimated for 8 tree and 11 agronomic traits in a multi-location apple genetics population to select individuals for the next cycle of selections. Families more than three standard errors away from the general mean were identified for each trait and extreme individuals (with regard to that trait) from those families were selected. On the whole, 148 individuals were chosen based upon individual traits and, in a few cases a combination of traits, in a way that maintains the original diversity within the population. Narrow-sense heritability estimated separately for each site for fruit ribbing, fruit russet, fruit overcolour amount and fruit weight ranged from 0.0–0.13, 0.05–0.58, 0.34–0.40 and 0.27–0.90 respectively. Phenotypic correlation and additive genetic correlation were small and from small to moderately high respectively, between pairs of traits. The implication of these genetic parameter estimates in apple breeding is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Performance of intersubspecific alfalfa hybrids in sward versus space planted plots

Intersubspecific hybrids between Medicago sativa subsp. sativa and subsp. falcata show biomass yield heterosis in space planted plots. Relative biomass yield of alfalfa is known to differ in space planted versus sward plots, although the magnitude of the difference is variable. The objective of this study was to determine if and how much of the biomass yield heterosis observed in space planted alfalfa hybrids was retained in sward planted plots. Two falcata genotypes (WISFAL-6 and PI502453-1) and three elite sativa genotypes were crossed in a diallel mating design. Progeny were transplanted into space-planted plots and harvested three times per year or drilled into sward plots harvested four times per year. Hybrids of WISFAL-6 with the sativa genotypes produced as much first harvest biomass yield as intra-sativa hybrids in space-planted plots and more in sward plots. Yield in subsequent harvests was lower than intra-sativa hybrids in sward plots only. Hybrids of PI502453-1 with sativa were generally lower yielding than intra-sativa crosses. A moderate correlation was observed between biomass yield in space planted and sward plots. Heterosis expression in swards was lower than that in spaced planted nurseries for progeny of both falcata genotypes. The increased plant-to-plant competition in swards is the likely cause of the loss of heterosis.     

Heterosis and genetic analysis of iron concentration in grains and leaves of maize

Iron (Fe) is a major micronutrient affecting animal and plant health. Maize (Zea mays L.) is an important crop for both food and fodders. The concentration of Fe in grains and vegetative organs, therefore, may exert a direct or indirect influence on human nutrition. Improving Fe nutrition by breeding is a promising way, but little is known about the genetics and heterosis of Fe nutrition in maize. In the present study, nine inbred lines were used to analyse the heterosis, combining ability and genetic ability of Fe concentration in grain and in the leaves supporting the cobs (ear‐leaf) of maize by a diallel mating design. It was showed that heterosis of Fe concentration in grains was very low, indicating that traditional hybrid breeding may not be efficient for improving this trait. Iron concentration of the ear‐leaf was controlled by additive gene effects and heterosis was high, indicating that hybrid breeding can be used to improve Fe nutrition of the vegetative organs of maize.     

Late blight resistance in a diploid full-sib potato family

Late blight, caused by Phytophthora infestans (Mont.) de Bary, is the most destructive disease of potato worldwide. As this pathogen can rapidly overcome major race‐specific resistance genes, identifying the basis for enhanced quantitative resistance has become a crucial element for implementing advanced breeding strategies. A population of 230 full‐sib progeny derived from a cross between two diploid hybrid Solanum phureja × S. stenotomum clones was evaluated for foliage resistance against late blight in replicated trials at multiple locations in Pennsylvania between 1999 and 2002. In field experiments, plants were evaluated visually for per cent defoliation, and area under the disease progress curve (AUDPC) was determined. The two parents and three control cultivars (‘Atlantic’, ‘Kennebec’ and ‘Katahdin’) were included in all trials. In all three experiments, the presence of a significant number of clones exhibiting transgressive segregation were observed. There were significant differences among environments as well as among clones, and the clone × environment interaction was also significant. Stability analysis revealed that 37 clones made a significant contribution to the overall environment × clone interaction. Broad‐sense heritability for resistance, measured as AUDPC, was estimated as 0.67. The overall results indicate the presence in this potato family of a high level of field resistance against late blight. This segregating diploid family appears to be a good candidate for quantitative trait loci mapping to identify and characterize the genetic components of partial late blight resistance.     

番茄果实主要品质性状的配合力及遗传力分析

为了给番茄的品质育种提供理论依据,采用多年来的高自交、纯合的6个性状不同的番茄材料(42、43、44、50、63、69)作为亲本,按照Griffing完全双列杂交(p2),配制成30个杂交组合。并分析了番茄6个亲本和30个杂交组合果实5个品质性状的配合力及遗传力。结果表明：亲本43的番茄红素、糖酸比、可溶性固形物等性状的一般配合力效应值都最高或较高,说明亲本43是个在选育风味品质和营养品质方面理想的亲本材料;亲本42的番茄果重的一般配合力效应值最高,亲本42可作为培育外观品质优良的番茄的理想材料;组合50×43在各品质性状的特殊配合力均比较高,它可以作为选育优良性状综合比较好品种。     

Competition among components of synthetic varieties in alfalfa

Summary Eighteen alfalfa polycross progenies were tested for forage and seed yield in pure stand as well as in competition with the mixture of all progenies included in the test. The type of border affected significantly the forage and seed yield of individual progenies in one third of the cases. In most of these cases competition from the mixture resulted in reduction of the yield of individual progenies. There was no correlation between pure stand forage and seed yield, but there was significant positive correlation between forage and seed yield determined under conditions of competition. It is concluded that polycross progenies should be tested in plots bordered by the mixture of all progenies being tested.     

高粱16个数量性状的相关遗传力分析

运用多元遗传分析法分析了高粱１６个数量性状的相关遗传力参数。结果表明，多数性状间相关遗传力小于性状遗传力。当选择强度相等时，对一级枝梗数表型的选择可以明显提高二级枝梗数和穗粒数。对其他性状的间接选择相对效率都比性状的直接选择效率要低。相关遗传力通径分析表明，穗粒数表型对穗粒重的直接作用最大，其次为千粒重和二级枝梗数。各性状通过穗粒数都有最大的正向间接作用。因此，穗粒数对产量的贡献超过其他性状，是提     

Quantitative genetic analysis of condensed tannins in oilseed rape meal

Condensed tannins (proanthocyanidins, PAs) in the seed meal of oilseed rape can potentially have a negative impact on non-ruminant livestock nutrition, particularly because of their ability to form indigestible, astringent or bitter-tasting complexes with proteins. One option to overcome this problem is the breeding of oilseed rape varieties with reduced condensed tannins in the seed coat. This might be achievable via selection of genotypes with thinner seed coats and consequently reduced condensed tannin accumulation (seed coat structural cell mutants), or alternatively by selection of genotypes with reduced biosynthesis of condensed tannins (flavonoid biosynthesis mutants). Both types of transparent testa (TT) mutants are well-characterised in Arabidopsis; however the genetic basis of the yellow-seed trait in the polyploid genome of rapeseed is still not completely understood. In this study, genetic and chemical analyses of PAs were performed in 166 doubled haploid (DH) rapeseed lines from the segregating Brassica napus doubled haploid population YE2-DH (black seed × yellow seed). Using these analyses, the relationship between seed colour and PA fractions in B. napus was investigated with a view to improving the rapeseed meal quality. Proanthocyanidin contents were estimated by vanillin and HPLC assays and the obtained values were used to identify quantitative trait loci. Closely linked molecular markers that were identified during this study for the target traits (seed colour, condensed tannins) can be valuable tools for breeding of new oilseed rape cultivars with reduced levels of antinutritive PA compounds.     

Population genetic simulation and data analysis with Plabsoft

Computer simulations are a useful tool to solve problems in population genetics for which no analytical solutions are available. We developed Plabsoft, a powerful and flexible software for population genetic simulation and data analysis. Various mating systems can be simulated, comprising planned crosses, random mating, partial selfing, selfing, single-seed descent, double haploids, topcrosses, and factorials. Selection can be simulated according to selection indices based on phenotypic values and/or molecular marker scores. Data analysis routines are provided to analyze simulated and experimental datasets for allele and genotype frequencies, genotypic and phenotypic values and variances, molecular genetic diversity, linkage disequilibrium, and parameters to optimize marker-assisted backcrossing programs. Plabsoft has already been employed in numerous studies, we chose some of them to illustrate the functionality of the software.     

Estimates of genetic variability and heritability for vegetative and reproductive characters of kiwifruit (Actinidia deliciosa)

The results of this study indicated a great deal of genetic variation in a number of characters of horticultural interest in kiwifruit seedling populations, and therefore, a potential to improve kiwifruit by vine selection. High narrow sense heritability was shown for pedicel length(0.62) and flowering duration (0.50) in male vines, and pedicel length (0.67),floral shoot percentage (0.54), leaf length-width ratio (0.64), fruit elongation (0.64) and fruit weight (0.52) in female vines. For these traits, selection of superior seedlings should lead to rapid genetic improvement in these populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic control of alfalfa seed yield and its components

Seed yield is of little agronomic importance in alfalfa (lucerne) but is critical in the marketing of varieties. In order to develop breeding criteria, the quantitative genetics of seed yield components must be studied. The objective of this study was (1) to evaluate combining ability for seed yield and its components and (2) to estimate the genetic control of these same characters. A 7 × 7 diallel mating design, including reciprocals, among parents from different varieties, and a 7 × 7 factorial design within the ‘Flamande’ population were evaluated. In the diallel design, where the progenies were evaluated over two growing seasons, a high genotype effect was found for seed yield and its components while genotype × year interaction was only significant for seed yield per plant. General combining ability (GCA) effects explained most of the variation due to genotype effect. Specific combining ability (SCA) and reciprocal effects were only significant for seed yield per plant. ‘Europe‐1’, ‘Rival‐5’ and ‘Medalfa‐7’ were the most promising parents, conferring the highest GCA for most of the characters evaluated, especially for seed weight per inflorescence. In the factorial design, seed weight per pod was the only character for which the year effect was not significant. Male and female effects were significant for all characters and these effects were larger than the male × female interaction variance for all the characters. These results were stable over the 2 years for most characters. Additive variance was larger than dominance variance, for all traits. This resulted in high narrow‐sense heritabilities, especially for seed yield per plant, seed weight per inflorescence and number of seeds per pod. Seed weight per inflorescence and number of seeds per inflorescence were highly correlated with seed yield per plant among the full‐sib (FS) families, in both experiments. Increase in seed yield potential in alfalfa could be achieved by the use of seed weight per inflorescence as a selection criterion.