The effect of interplant distance on the effectiveness of honeycomb selection. II. Results of the second selection cycle

Summary For a second consecutive generation, the efficiency of the honeycomb selection procedure was observed at low and at high density, i.e. interplant distance being 100 cm and 15 cm respectively. Progress due to selection was determined for each of the two plant densities applied by comparing the performance of offspring from selected plants with that of offspring from plants taken at random. The relation between selection intensity and selection response was observed to study the relation between competing and yielding ability in presence and in absence of interplant competition.Compared to results obtained in a previous generation, it is now dared to be more positive about the perspectives of selection in absence of interplant competition. It is tentatively concluded that single plant selection for yield at wide spacing gives a higher progress and allows a better identification of outstanding genotypes. However, the superiority of selection at low density is not confirmed neither by any estimator of a quantitative genetic parameter nor by the correlation between single plant yield and plot yield of their offspring. The disturbing factors found already in the former generation, namely variation in seed quality and a biased sample of random plants, exerted a less important role in the estimation of the progress. Nevertheless, it is believed that only when they can be reduced more reliable results can be achieved.     

The effect of interplant distance on the effectiveness of honeycomb selection in spring rye. III. Accumulated results of five selection cycles

The effect of interplant distance on the efficiency of mass selection was studied by performing five cycles of honeycomb selection at two interplant distances (d), i.e. d = 100 cm (low plant density, implying absence of interplant competition) and d = 15 cm (high plant density, implying presence of intergenotypic competition). The offspring of plants selected either at low or at high plant density were compared, both at high plant density and at low plant density, with the original population (in fact: offspring of plants taken at random from this population). At high plant density offspring of plants selected at high density performed better than the original population for most of the characters recorded on a per plant basis. At low plant density offspring of plants selected either at high or at low density performed better than the original population for the characters recorded on a per plant basis. The selections differed, however, significantly from each other: the offspring of plants selected at low density performed better. As the latter did not occur at high density genotype × density interaction was indicated. It is concluded that mass selection should be applied at the plant density used in commercial practice. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of competition and selection pressure on yield response in winter rye (Secale cereale L.)

Summary Three intensities of mass honeycomb selection (14.3,5.3 and 1.6%) applied to an unselected rye population gave respectively an annual yield response of 0.28, -3.69 and -5.20% at 15 cm spacing, and of 4.07, 5.39 and 8.99% at 90 cm spacing. The negative response with competition was explained by strong negative correlation between competing and yielding ability which causes positive skewness because of transposition of low yielders and strong competitors from the left to the right tail of the distribution. The positive response in the absence of competition was mainly due to the increased genotypic differentiation which allowed effective discrimination between high and low yielding genotypes. The efficiency of the selection in the absence of competition was further improved by using the honeycomb designs which adjust soil heterogeneity and application of very high family and individual selection pressures.Two cycles of mass honeycomb selection increased the population yield by 29.4%, one cycle of mass plus one cycle of pedigree honeycomb selection did so by 34.5%. The results are discussed in relation to the selection response and to the efficiency of various breeding schemes.Part of senior author's doctoral thesis     

A comparison of several procedures for mass selection in winter rye I. The relative quality of the procedures

Summary The HS-family offspring from each of 463 plants occurring in a population of winter rye were grown in a randomized complete block design. According to 4 sets of requirements, 4 groups of HS-families were created. The HS-families belonging to a certain group were considered to be superior with regard to the specified requirements.Independently from this, selection among the 463 parental plants was simulated. The selection was according to 3 methods (truncation selection, grid selection and honeycomb selection) applied with regard to a single plant trait or with regard to two plant traits. Altogether 9 different single-trait and two-trait criteria were studied for each selection method.The quality of some selection procedure or the other, i.e. a combination of a selection method and a selection criterion, was measured on the basis of the frequency of plants giving rise to a superior HS-family among all plants selected by the procedure.It is concluded that grid selection and honeycomb selection are more effective than truncation selection. Further it is tentatively concluded that honeycomb selection is more reliable than grid selection.     

A comparison of several procedures for mass selection in winter rye. II. What are the merits of adjusting phenotypic values?

Summary To get an improved impression of the genotypic value of individual plants the literature suggests to adjust their phenotypic values according to a moving mean correction or by means of an analysis of covariance, where the mean phenotypic value calculated across neighbours is used as the concomitant variable. In the present paper it is shown that the theoretical merits of these adjustments are promising: they eliminate the contribution due to the trend in soil fertility from the phenotypic value. In an experimental verification actual merits did, however, not show up.It is concluded that interplant competition is the main cause for the failure of the studied adjustments. These may be effective in virtual absence of intergenotypic competition. Thus, in case of single plant selection an extremely low plant density would be required, whereas selection among lines or families would require evaluation by means of multi-row plots.     

Honeycomb selection for yield in early generations of spring wheat

Summary The effectiveness of the honeycomb selection method for yield in spring wheat (Triticum aestivum L.) was evaluated using progenies from two wheat crosses, Glenlea x NB131 and Glenlea x Era. Honeycomb selection was carried out in the F₂ and F₃ generations, grown at the University of Manitoba in the summers of 1980 and 1981, respectively. In both generations, divergent selection was made for both high and low yield. Plants selected in the F₃ generation were entered in an F₄ yield test in the summer of 1982. Results of the experiment showed that honeycomb selection for yield in the F₂ and F₃ generations was effective in identifying parents of high- and low-yielding lines. F₃ plants from highyielding F₂ selections gave higher yields than those from low-yielding F₂ selections by 11.5% and 13.0% for Glenlea x NB131 and Glenlea x Era crosses, respectively. The F₄ yield test showed that high yielding selections from both crosses significantly outyielded by 8.9% low yielding selections and by 14.4% the unselected composite lines. It is concluded that the honeycomb selection method can be used for early generation selection in spring wheat.     

A recurrent selection programme for grain yield in winter barley

Summary The effect of a recurrent selection procedure was evaluated in a winter barley (Hordeum vulgare L.) population. Cycle zero (C₀) was initiated by crossing six high yielding winter barley cultivars with the short straw cv Onice. The F₁'s were crossed according to a diallel scheme without reciprocals. A total of 750 S₀ plants were derived and evaluated; 329 S₀ plants were selected and their progenies (S₁ lines) tested. Fifteen S₁ lines were chosen and used as parents of cycle 1 (C₁), by producing 105 F₁ hybrids which simulated a random mating offspring. One hundred and three randomly chosen S₁ lines belonging to C₀, and 103 S₁ lines belonging to C₁, were evaluated at two locations.For grain yield a significant difference between cycles was observed. From C₀ to C₁ the grain yield increased with 307 g/m². This increase was due to a higher number of seeds per m². For plant height, heading date and 100-kernel weight no differences between cycles were observed.The positive results obtained in this study indicate the potential usefulness of recurrent selection for developing parents or lines superior for grain yield, with little change in other important agronomic traits.     

A comparison of yield and yield component selection in winter wheat

Summary Three populations of winter wheat were formed by crossing Avrora to Sage, TAM W-101, and Danne. Approximately 10% of the F₂ plants from these crosses were selected for high and low levels of number of tillers per plant, number of kernels per spike, 1000-kernel weight, and grain yield. Forty-eight solid seeded F₃ lines obtained from the selected F₂ plants were then selected for high and low expressions of yield components and grain yield. Realized heritabilities were estimated. Indirect responses of yield to yield component selection and direct response to selection for grain yield were measured. Heritabilities were low for tiller number, number of kernels per spike and kernel weights but were high or intermediate for grain yield when selection occurred in the F₂ generation. When selection was practiced in the F₃ generation, heritabilities for tiller number and yield were low, but were intermediate to high for number of kernels per spike and kernel weight and high heritabilities were found for kernel weight. Selection for kernel weight often increased grain yield; however, direct selection for grain yields was usually as effective.Journal article no. J-4488 of the Oklahoma Agri. Exp. Stn., Stillwater, Oklahoma 74074.     

Biometrical analysis of alternative plot types for selection in rye

Summary Maximizing the efficiency of selection for yield and baking quality of winter rye (Secale cereale L.) requires reliable knowledge on the pertinent population parameters. This study reports estimates of variances, heritabilities and genetic correlations from a) large (5 m²) drilled (LD) plots, b) micro drilled (MD) plots, and c) one-row plots of 4 spaced plants (SP). Thirty eight single crosses of rye were grown at two locations for two years in LD, MD and SP plots replicated 2, 4, and 6 times, respectively. Genotypic differences were significant in all plot types for all agronomic and quality traits, although estimates of genetic variances were smaller in LD than MD or SP plots for grain yield, 32-spike weight, and kernels per spike. Heritabilities on an entry mean basis (0.62 to 0.95) were similar among plot types, but on a single plot basis estimates were lower for SP than for MD or LD plots. Genetic correlations were high between all three plot types, with correlations between LD and SP plots being approximately 1.0 for falling number, thousand-kernel weight, and bloom date, 0.90 for grain yield, kernels per spike, test weight and height, and 0.70 for tiller number. Based on the high heritabilities achieved in small plots and the close agreement between MD- or SP- with LD-plot performance we conclude that greater use should be made of small plot types when selecting for yield and quality in winter rye.     

Simultaneous selection for early maturity, increased grain yield and elevated grain protein content in spring wheat

High grain yield and grain protein content, and early maturity are important traits in global bread wheat ( Triticum aestivum L.)-breeding programmes. Improving these three traits simultaneously is difficult due to the negative association between grain yield and grain protein content and the positive association between maturity and grain yield. We investigated the genetic relationship between maturity, grain yield and grain protein content in a population of 130 early maturing spring wheat lines in a high latitude (52–53°N) wheat-growing region of Canada. Grain protein content exhibited negative genetic correlation with maturity (−0.87), grain fill duration (−0.78), grain fill rate (−0.49), grain yield (−0.93) and harvest index (−0.71). Grain yield exhibited positive genetic correlation with maturity (0.69), rate (0.78) and duration (0.49) of grain fill, and harvest index (0.55). Despite the positive association between maturity and grain yield, and negative association between grain yield and grain protein content, higher yielding lines with medium maturity and higher grain protein content were identified. Broad-sense heritabilities were low (<0.40) for rate and duration of grain fill, grain protein content, spike per m², grains per spike, harvest index and grain yield, and medium to high (>0.40) for grain weight, days to anthesis and maturity, and plant height. Selection for longer preanthesis and shorter grain fill periods may help circumvent the negative association between grain yield and grain protein content. Selection for shorter grain fill periods and higher grain fill rate may be a useful strategy for developing early maturing cultivars with acceptable grain yields in northern wheat-growing regions.     

Selection in tetraploid rye. III. Frequency and performance of aneuploids

Summary Aneuploidy was studied in populations selected for high seed-set with regular meiosis and low-seedset with irregular meiosis and an unselected population of the same origin. The frequency of aneuploids was significantly reduced in the high population that was characterised by increased bivalent frequency. In spite of a similar quadrivalent frequency in euploid plants of the low and the unselected population, the former population had a significantly higher frequency of aneuploids. However, there was no significant difference in the performance of aneuploid plants from the three populations. The results indicated that hyperaneuploid gametes were less functional than hypoaneuploid gametes but no significant difference was found in the performance of hypo- and hyperancuploids.     

Transfer of the recessive crossability allele kr1 from Chinese Spring into the winter wheat variety Martonvásári 9

Summary The recessive of crossability allele kr1 was transferred from the spring wheat variety Chinese Spring (CS) into the winter wheat variety Martonvásári 9 (Mv9) by backcrossing the Mv9 × CS hybrids with Mv9. The Mv9 variety possesses dominant Kr1 alleles and is heterogeneous at the kr2 locus, so that some individual plants carry recessive kr2 alleles. The selection of plants possessing the recessive kr alleles from the (Mv9 × CS)Mv9 BC₁ generation was carried out according to the seed set achieved when pollinated with rye (Secale cereale L. cv. Mercator). The partial dominance of the Kr alleles made it possible to differentiate between plants heterozygous at the Kr1 locus and Kr1Kr1 homozygous dominant plants. Two selfed consecutive progenies were tested by pollination with rye to select the homozygous recessive kr1kr1kr2kr2 plants and to check the result of the selection after each backcross.As a result of three backcrosses with Mv9 and two selfings after each backcross the selected progenies had 61.6% seed set with rye tested on sixty individual plants. These data confirm that after the third backcross the selected Mv9 kr1 line carries necessive crossability alleles Kr1 and Kr2, but the genotype is 93.75% Mv9.     

The crossability percentages of 96 bread wheat landraces and cultivars from Japan with rye

Summary Crossability of bread wheat (Triticum aestivum L.) from Japan with rye (Secale cereale L.) was investigated by controlled pollination. No normal seeds were produced, but numbers of shrivelled and small seeds with embryos were used to estimate crossability amongst the 96 accessions, viz: 0–10% (29), 10–30% (23), 30–50% (11), 50–90% (33). The investigation for the pedigrees of varieties with more than 50% crossability percentages showed that the kr alleles of some accessions derived from common ancestors.     

Cytological identification of 1B/1R wheat-rye translocations in winter wheat breeding lines

Summary The incorporation of rye (S. cereale L.) chromatin into winter wheat (T. aestivum L.) cultivars is often achieved via hybridization of unadapted wheat-rye translocation lines with adapted wheat germplasm. Identification of progenies possessing the translocated chromosome has traditionally involved phenotypic screening for the desired rye characteristics. In this study, the Giemsa N-banding technique was evaluated as a potential screening tool for detection of 1B/1R wheat-rye translocations. Five breeding lines were examined from the pedigree Aurora/2^*TAM W-101. The differential banding patterns of chromosome 1B contributed by TAM W-101 and chromosome 1B/1R contributed by Aurora allowed unequivocal identification of translocation genotypes. Three of the lines were found to be heterogeneous, whereby plants were homozygous for either the normal 1B or the translocated 1B/1R chromosome. The remaining two lines were observed to be homozygous and homogeneous for the translocated 1B/1R chromosome. The implication of N-banding chromosomal analyses to wheat breeding is presented.Contribution No. J-5172, Department of Agronomy, Oklahoma Agriculture Experiment Station, Oklahoma State University, Stillwater, OK74078.     

Maternal induced haploids in rye (Secale cereale L.)

Summary An inbred line of rye named P8 was found to possess haploid plants in their diploid stock. Phenomenon of spontaneous haploidy was examined in this line. Fifty families derived from this inbred line were screened to determine their ploidy level by mitotic chromosome count taking root tips. Seven families were found to contain haploid plants. Among these seven families, plants from two families which were diploid were crossed reciprocally with the standard out breeding cultivar Conrah. As all of the tested plants of P8 were found aa allele for 6-Phosphogluconic dehydrogenase (6-PGD) isozyme, therefore, only those Conrah plants which have bb alleles for the same isozyme were used in crossing programme.F1 seedlings were screened with the same isozyme marker and out of 1741 F1 seedlings tested, 51 were found to be non-hybrid phenotype for 6-PGD enzyme. Among these, only five plants were found haploid and the rest were diploid. Haploid plants were obtained only from those crosses where P8 was female which indicates that haploids in this line was maternally induced.     

Optimal regimes of selection for grain yield and harvest index in spring wheat

Summary Alternative strategies of multi-site testing of advanced lines in the northern wheat belt of New South Wales have been evaluated, using genetic parameters for large plot grain yield and hill plot harvest index estimated from dryland and irrigated trials at regional sites during 1975–1981. The average pairwise genetic correlation of large plot grain yields recorded at different sites within years was 0.45±.03, with a mean repeatability within trials of 0.56±.05. Harvest index measured in 20-grain hill plots in 1978 showe genetic correlations of 0.98±.08 with plot yield at the same site, and 0.39±0.06 with plot yield assessed at other sites in the same year.The genetic correlation between harvest index in hill plots and total biological yield in large plots at the same site was 0.84±.13, the relationship showing no evidence of curvilinearity. Selection for harvest index in hill plots is therefore expected to lead to an increase in biological yield as well as grain yield in the breeding populations studied. Quantitative genetic theory suggests that the response to selection for grain yield can be increased by approximately 40% with an initial screening using hill plot harvest index at three sites instead of one, and reallocation of resources in the first stage of large plot yield assessment to include 6–8 sites, rather than dryland and irrigated trials at a single location.     

Crossability of some bread wheat landraces and improved cultivars from western Himalayas with rye

Summary Crossability of 62 bread wheat accessions (14 landraces from Himachal Pradesh and 48 others) was examined with rye. The 3 rye cultivars did not differ in their relative crossability with 4 of the wheat accessions studied. On the other hand, the wheat cultivars differed greatly among themselves in their crossability with rye. Most of the wheat cultivars showed poor (<10%) crossability. Two of the 14 landraces from Himachal Pradesh were found to be free from the crossability inhibitors as they showed very high (>50%) crossability, whereas none of the other 48 cultivars studied was so.     

Reduction of micro-environmental variation in a selection field of rye

Summary With mass selection it is impossible to adjust single plant performance for variation in purely private growing conditions (including instability of development). This was demonstrated by using the character initial kernel weight when honeycomb selection is applied. Further, it was investigated whether reduction for variation for kernel size, depth of sowing and orientation of the kernel at sowing results in reduced phenotypic variation for the mature plant characters on which the selection is based. The conclusion is that with mass selection it is very rewarding to apply a precision drill and to use sieved seed when sowing a selection field. The orientation of the kernel may be neglected.     

Relationship between relative water content during reproductive development and winter wheat grain yield

Summary Water is often the most limiting factor to winter wheat (Triticum aestivum L.) production in the southern Great Plains of the U.S.A., yet the lack of reliable screening criteria has precluded direct selection for drought resistance in breeding programs. Previous work showed that leaf relative water content (RWC) was highly heritable when measured under field-drought conditions, but its adoption as a screening tool for yield improvement requires further investigation of the genetic relationship between grain yield and RWC. Plants representing high and low yield potential under drought stress, and a random group of plants, were selected from an F₂ population having the pedigree, TAM W-101/Sturdy. Two sets of entries, each comprised of the two parents and 24 F₂-derived lines, were evaluated under a rainshelter in the F₃ (1986) and F₄ (1987) generations to determine differences in leaf RWC during reproductive development. One set of entries did not receive any water after the jointing stage, and the other set was grown under well-watered conditions. A positive relationship was observed between grain yield and RWC measured during anthesis and mid-grain fill, as the high-yield selections maintained a significantly higher RWC than the low-yield selections. Grain yield and RWC were also positively associated among random selections segregating for both traits. Subsequent adjustment of genotype means for differences in reproductive development at time of sampling underscored the need to consider differences in maturity when RWC is the selection criterion.     

Estimates of combining ability for resistance of winter rye to Fusarium culmorum head blight

Summary Head blight caused by Fusarium culmorum and F. graminearum is damaging in all winter rye (Secale cereale L.) growing areas. For hybrid breeding, the relative magnitude of general (GCA) and specific combining ability (SCA) is a crucial parameter for developing appropriate selection procedures. Forty single-cross hybrids were produced by crossing six and seven inbred lines of the Petkus and Carsten gene pool, respectively, in a factorial design. Hybrids were evaluated in two years with artificial F. culmorum inoculation. Resistance traits were head blight rating and grain weight relative to the non-inoculated control. Both resistance traits were closely correlated across both years (r-0.8, P=0.01). Significant genotypic variation was found for both traits with medium to high estimates of heritability (h²=0.6-0.8). Components of variance for GCA were, across years, 10 and 6 times larger than those for SCA for head blight rating and relative grain weight, respectively. Significant SCA effects were found for 15 to 20% of all cross combinations across both traits in each year. SCA effects were, however, inconsistent over years leading to a high SCA-year interaction. In conclusion, resistance to Fusarium head blight among the interpool hybrids tested was conditioned mainly by additive gene action that could be utilized by recurrent selection in multi-environment trials.Abbreviations GCA general combining ability - SCA specific combining ability