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.     

Effects of selection in tetraploid green gram varieties

A comparative study of the effect of tetraploidy in three varieties of green gram (Phaseolus aureus Roxb.) and selection of plants with high, medium and low vigour showed that the reduced leaflet size and height at the time of flowering can be considerably improved by selection. It appeared that the diploid level can be approached or even exceeded.The reduced fruit setting can also be improved considerably but not the size of fruits and number of seeds per pod. The increased seed weight was further improved in two varieties. The increase in protein content of the tetraploid seeds was greatest in the variety with the lowest protein content at the diploid level.Though for vegetative growth selection alone would suffice to bring the tetraploids up to the diploid level, if not higher, the reduced fruit and seed setting, though responding well to selection, are unlikely to be overcome unless other breeding methods are introduced.     

Recurrent phenotypic selection for forage yield in rye

Summary Cultivars of Cucurbita pepo and other Cucurbita species were characterized by RFLP analysis using different fragments of the ribosomal intergenic spacer (IGS) of Cucurbita pepo as hybridization probes. Several cultivars could be distinguished by a specific rDNA restriction pattern, whereas some cultivars showed an identical RFLP pattern suggesting a closer relationship. Other species of the genus Cucurbita exhibited strong cross-reaction with the C. pepo spacer probes, in contrast to DNA of Cucumis species which did not cross-hybridize.Abbreviations IGS intergenic spacer - ITS internal transcribed spacer - kbp kilo base pairs - rDNA ribosomal DNA - RFLP restriction fragment length polymorphism - rRNA ribosomal RNA     

Results of one cycle of recurrent selection in rye

A sufficiently variable rye population was subjected to one cycle of recurrent selection for combining ability in order to ascertain whether this complex property can be repatterned.Some hundreds of clones derived from this population were toperossed to an other unrelated variety used as tester. Through visual selection, more than half of these clones were rejected. The topcross progenies of the remaining clones were subjected to a comparative test whereby, as was to be expected, a considerable degree of variability was demonstrated. From the best 10% and the poorest 10% that is from those which surpassed the general average by at least 1.5 standard deviation units or remained below that average by at least 1.5 , narrowed populations were built up. This was done with the aid of reserve seed which in the year in which the top cross was made had been obtained from these clones, either through compulsory selfpollination or by allowing the clones to fertilize each other in isolation. The two subpopulations obtained through selection in opposite directions further indicated as high and low were crossed en masse with the same tester variety as the first time. In addition a large number of randomly taken individuals from the high synthetic were cloned and toperossed to this common tester. On testing the top crosses carried out en masse, the high synthetics clearly yielded more than the low ones. In one trial it was even found that the high synthetic surpassed our standard variety Petkus by approximately 20%. It is possible, therefore, to segregate a population into two fractions of different combining ability.The optimistie pieture to be derived from the foregoing trials unfortunately is shaded by the results of the individual test crosses pointing to a shift of the frequency distribution in a negative sense in regard to the original population. The influence of the year may be mentioned as a possible cause of this contrast and also the fact that in the original population a close visual selection had been practised while those obtained from the synthetic resulting after one cycle were derived from individuals which had been taken entirely at random.

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Samenvatting Een voldoende variabele roggepopulatic werd onderworpen aan één ronde van cyclisch herhaalde selectic op combinatie-geschiktheid ten einde na te gaan of deze complexe eigenschap kan worden vervormd.Enige honderden klonen voortgekomen uit deze populatie werden onderworpen aan een top-cross door een als tester gebruikt ander, onverwant, ras. Op grond van visuele selectie werd meer dan de helft van deze klonen afgekeurd. De proefkruisings-nakomelingschappen van de overblijvende klonen werden aan een vergelijkende toets onderworpen waarbij zoals viel te verwachten een aanzienlijke variabiliteit in opbrengstvermogen aan het licht trad. Uit de beste 10% en de slechtste 10%, d.w.z. die welke het algemeen gemiddelde met minstens 1,5 overschreden resp. daar minstens 1,5 beneden bleven, werden vernauwde populaties opgebouwd. Dit geschiedde met behulp van reservezaad dat in het jaar waarin de top-cross werd verricht van deze klonen was gewonnen, hetzij door gedwongen zelfbestuiving, hetzij door de klonen in isolatie aan onderlinge bestuiving over te laten. De op deze wijze verkregen twee in tegenovergestelde richting geselecteerde sub-populaties-aangeduid als high en low-werden en masse gekruist met hetzelfde tester ras als de eerste keer. Bovendien werd een groot aantal willekeurig uit het high syntheticum genomen individuen tot klonen gemaakt en onderworpen aan een top-cross door het zoëven genoemde tester ras. Bij de toetsing van en masse uitgevoerde proefkruisingen bleek de combinatie high x tester duidelijk meer op te brengen dan low tester. In een proef werd zelfs gevonden dat high x tester ons standaardras Petkus met ongeveer 20% overtrof. Het blijkt dus mogelijk een populatie te splitsen in 2 fracties van uiteenlopende combinatie-geschiktheid.Het optimistische beeld dat men uit de zo juist vermelde proeven krijgt wordt helaas verduisterd door de resultaten van de individuele proefkruisingen welke wijzen op een verschuiving van de frequentieverdeling in negatieve zin ten opzichte van de oorspronkelijke populatie. Als mogelijke oorzaken van deze tegenstelling kunnen worden aangewezen jaarinvloeden en tevens het feit dat onder de klonen uit de oorspronkelijke populatie een scherpe selectie op het oog werd toegepast terwijl die uit het na één cyclus verkregen syntheticum werden afgeleid van volkomen willekeurig genomen individuen.

     

Genetic evaluation and selection index in tetraploid Brachiaria ruziziensis

Half‐sib progenies of congo signal grass (Brachiaria ruziziensis Germain & Evrard, syn.: B. eminii, Urochloa ruziziensis) were analysed using a mixed model methodology. The objective was to estimate genetic and phenotypic parameters, predict individual genetic values, estimate correlations between characters associated with biomass production and forage nutritive value and use this information to determine the economic weights to compare three multiplicative selection indices. Individual narrow‐sense heritabilities corrected for inbreeding varied from 0.14 to 0.91 for characters associated with biomass production and from 0.04 a 0.24 for nutritional value characters. The correlations among characters associated with annual biomass production were of high magnitude. In contrast, biomass production characters were negatively correlated with crude protein, acid detergent fibre and lignin. Total dry matter yield, crude protein and regrowth ability were weighted separately in evaluations during wet and dry season or annually in selection indices. Index that considered characters annually resulted in better distribution of forage production along the year than indices that separated wet and dry season production.     

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.     

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.     

Some remarks on honeycomb selection

Summary Up to now the only experiences in favour of the method of honeycomb selection were reported by the spiritual father of the method, i.e., Fasoulas. Three other reports presented very moderate results. Possible causes for these contrasting results are discussed. Fasoulas' preference for growing the plants in the selection field in absence of competition is in conflict with the conditions in commercial crops where intragenotypic competition occurs. This preference is considered in comparison with the more popular preference for growing the plants in the selection field in presence of intergenotypic competition, which in turn also deviates from the conditions in a commercial field. It is suggested that at some degree of interplant competition the highest response to honeycomb selection will be obtained. Further, it is explained why the average of the phenotypic values of the six neighbours of a central plant may be an unreliable measure for the growing conditions for the central plant.     

Effect of selection for coleoptile length in rye,Secale cereale L.

Summary Two hundred and forty seedlings from each of three diverse populations were measured for coleoptile length. Significant differences between populations were found for mean coleoptile length. Considerable variability was obtained within each population with coefficient of variation values ranging from 32 to 42%. Forty seedlings from each population were placed into one of three selection groups: random (0); shortest 20% (S20); and longest 20% (L20). The plants within each group in each population were allowed to interpollinate. The coleoptile length of 100 seedlings from each group obtained from the interpollination was then measured. This experiment was repeated in each of two successive years. Positive response to selection was found in all populations in both years. The means of the L20 selection group were significantly higher than the means of the 0 group in 6 out of 6 comparisons. The means of the S20 group were significantly lower than the means of the 0 group in only 2 out of 6 comparisons. Selection response values also reflected these results. Therefore, selection for long coleoptile length was considerably more effective and consistent than selection for short coleoptile length. These results suggest that short coleoptile length may be partially dominant to long coleoptile length. No significant correlation between seed weight and coleoptile length was found indicating that selection for coleoptile length on the basis of seed weight would probably be ineffective.Journal Series No. 5325, Florida Agricultural Experiment Station.     

Recurrent selection as a breeding procedure for rye and other cross-fertilized plants

Summary The inadequacy of the established breeding methods (mass selection, family selection) and the fact that a breeding procedure based on heterosis is not feasible for all crops, have given the incentive to search for more effective breeding methods, in particular for cross-fertilized plants.On the basis of experiments with rye, the writer comes to the conclusion that a breeding system founded on the polycross test is somewhat unsatisfactory, because it leads too soon to a narrowing of the material, so that the degeneration caused by inbreeding cannot be avoided.Better possibilities are offered by the methods of recurrent selection developed for maize, particularly by those schemes initiating from two entirely unrelated populations (reciprocal recurrent selection). The two populations are subjected to a test cross system whereby individuals from one population are outcrossed on representative groups of individuals from the other one, and conversely. Tests of the progenies obtained in this way reveal which individuals from the population K combine well with population L, and vice versa. By following the line described in the article, a narrowed population K (indicated as K₁) and a narrowed population L (indicated as L₁) are obtained which more or less complement each other. This complementary character is enhanced by repeating the selection process. Crossing in mass of these two narrowed populations may result in a valuable hybrid which is best referred to as a varietal hybrid. It seems that here the danger of inbreeding is reduced to a minimum.This method has already yielded favourable results at the Plant Breeding Station of the Central Bureau at Hoofddorp c.f. Koopman (7). From the current experiments at the Institute of Agricultural Plant Breeding at Wageningen it also appears that by the breeding system described in this paper many fallacies of the old procedures are eliminated.     

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     

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.     

Direct and indirect selection for drought tolerance in alien tetraploid wheat x durum wheat crosses

After the evaluation of numerous accessions of primitive wheats for yield components and morphophysiological traits related to drought tolerance (e.g., maintenance of high relative water content, RWC; photochemical quenching of chlorophyll fluorescence, qQ; and chlorophyll loss, chl, under moisture stress conditions), several accessions belonging to three species (Triticum dicoccum, T. polonicum, and T. carthlicum) were crossed with the improved durum wheat varieties Cham 1 and Om Rabi 5. A direct selection (F₂ progeny) for yield and an indirect physiological trait were applied on interspecific T. durum x T. dicoccum, T. durum x T. polonicum, and T. durum x T. carthlicum populations. Divergent selection was applied to validate the possible use of morphophysiological traits (root parameters, RWC, photochemical quenching, proline content, and carbon isotope discrimination) in selection, and to evaluate the resulting effects on yield. Heritability and selection response of these traits has been evaluated, and the impact of divergent selection for morphological and agronomic characters was studied under field conditions. The divergent populations were evaluated under different environmental conditions in France, Syria, and Yemen. Selection for morphophysiological traits related to moisture stress, such as root parameters, RWC and carbon isotope discrimination was possible due to high h² values and effective, resulting in high genetic gains. However, the effect of selection for these traits on yield stability needs to be further studied. Furthermore, a modified bulk method (F₂ 'progeny method') was developed. Direct selection for grain yield per plant in F₂ was carried out and yield per line in F₃ was evaluated under contrasting environmental conditions in France, Syria, and Tunisia. Results revealed that some F₃ lines were higher yielding than the improved durum wheat varieties Cham 1 and Om Rabi 5 under both stressed (Aleppo) and favourable (Montpellier) environmental conditions. Lines were evaluated in preliminary yield trials at Montpellier (France), Aleppo (Syria), and Constantine (Algeria). Results indicated that the use of related species combined with the use of the modified bulk breeding method is promising not only for increasing durum wheat yield in drought prone environments, but also for improving durum wheat yield stability across contrasting environments. Results of both breeding strategies are presented, and the potential advantages of using related tetraploid species in durum wheat breeding for drought tolerance are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Germinal pore number in pollen grains as a selection basis in the production of tetraploid clover

Experiments with the variety Fahl of Berseem clover and with different material of red clover have shown that the occurrence of tetraploid and diploid tissues can be detected in a rapid and reliable way by determining the number and arrangement of germinal pores of the pollen. The advantages over the conventional methods are mentioned and described.The determination of the germinal pore pattern, which is combined with pair crossing of the tetraploid heads, makes it possible to obtain in an efficient way completely tetraploid material with a great genetic variability.Samenvatting Proeven met het ras Fahl van Alexandrijnse klaver en met verschillend materiaal van rode klaver hebben uitgewezen dat het voorkomen van tetraploide en diploide weefsels op een snelle en betrouwbare wijze aangetoond kan worden door middel van bepaling van het kiemporiënbeeld van het stuifmeel.De bepaling van het kiemporiënbeeld gevolgd door paarsgewijze kruising van de tetraploide hoofdjes maakt het mogelijk op een efficiënte wijze te komen tot zuiver tetraploid materiaal met een grote genetische variabiliteit.     

Some data and figures on potato breeding in the Netherlands

Summary The rapid growth of the number of potato breeders in the Netherlands was favourably influenced by a wide spread interest for all problems concerned with potatoes, by financial support and advice.In 1954, the number of potato breeders was 193; 46 of them can be considered professional breeders, while of 20 breeders one or more varieties figure in the Dutch List of Varieties 1954.The creation of the Foundation for Agricultural Plant Breeding resulted in the enhancement of the level of potato breeding and the increase of the number of potato seedlings raised every year.     

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.     

Chloroplast microsatellite variations in tetraploid alfalfa

Four chloroplast simple sequence repeat (cpSSR) loci were identified in alfalfa (lucerne), Medicago sativa L. The occurrence of allelic variation at these loci was evaluated in 100 plants from 10 populations of tetra‐ploid alfalfa, belonging to four Italian ecotypes and to an Italian (‘Lodi’) and an Egyptian (‘Iside’) variety. Twenty‐four different alleles were identified, four of which were exclusive to the ‘Iside’ variety. The genetic relationship among plants and among populations was analysed by computing an analysis of molecular variance and an unweighted pair group means analysis clustering. This analysis allowed clear separation of the ‘Iside’ variety from Italian germplasm and the recognition of close relationships within the Italian populations. The data presented suggest that cpSSR analysis of tetraploid alfalfa could be used for germplasm polymorphism analysis.