Maternal effects and generation mean analysis of seed-oil content in cotton (Gossypium hirsutum L.)

Summary The nature of gene action and of maternal influence governing cottonseed oil attributes were determined with four lines, two each with high and low seed-oil percentage. For this purpose, P1, P2, F0, F1, F2 and alternative sets of BC1 and BC2 generations were analysed in six cross-combinations and their reciprocals. Marginal extents of heterosis for seed-oil percentage were noticeable in F1, with inbreeding depression in F2. Data from reciprocal backcrosses provided evidence in favour of maternal rather than cytoplasmic effects of seed-oil development. Relatively higher extents of heterosis, sizeable inbreeding depression and reciprocally unequal F2 averages were characteristic of the seed index trait, which often showed a reversal of effects from F1 to F2. Reverse reciprocal backcrosses exhibited some differences, including greater resemblance between the types, (A/B)A and (B/A)A, in addition to variable dose effects in seed index. Thus, the differences between F1 seed index values were not due to cytoplasmic influence. Positive heterotic effects for seed-oil index, especially among the backcrosses, ranged between 16.08% and 47.29% over midparent averages. Genetic component estimates from analysis of similar sets of crosses differing only in reciprocal backcrosses, and also from sets of reciprocal crosses between any two parental combinations, were inconsistent. Scaling tests detected presence of epistasis within and between a majority of cross-combinations. Despite reciprocal differences, additive gene effects for seed-oil percentage were significant in 7 out of 24 crosses, representing high x low, low x high and low x low seed-oil parents. Those were, however, accompanied by significant dominance effects of higher order. In crosses involving low seed-oil percentage parents SA1060 and SA229, all six components were detected significant, with opposite effects of dominance and dominance x dominance epistatic components. Significant additive components were also detected for seed index and seed-oil index in 7 and 5 out of 24 crosses, respectively. In the inheritance of seed index and seed-oil index, dominance effects were more important. Epistatic components of additive x additive, and to a lesser extent, those of dominant x dominant were found significant.     

Ordination of vegetation change in Guadalupe Mountains,New Mexico,USA

Vegetation change over a nine-year period was studied in Guadalupe Mountains, New Mexico. Permanent transects in desert shrub vegetation were sampled in 1972 and 1980. Emphasis was given to shrubs because of their importance to big game diets. Univariate paired t-tests and reciprocal averaging ordination were used to detect and display coordinated changes in species composition over time. Despite apparently less browsing pressure in desert shrub vegetation in 1980 there were few significant changes in species composition. In addition, preferred forage species showed reduced reproduction while species of intermediate and poor forage value dis-played increased reproduction during this time. These data do not support traditional rangeland succession theory which states that enhanced reproduction of preferred species should follow grazing or browsing pressure reduction.     

Effects of detrending and rescaling on correspondence analysis: solution stability and accuracy

Detrending and non-linear axis rescaling potentially improve the accuracy of gradient recovery in correspondence analyses but also reduce the stability or consistency of solutions. Variation among bootstrapped ordination solutions was compared across methods in analyses of both field and simulated data. Solution accuracy, measured with mean squared errors from Procrustes analysis, was compared using simulated data with known structure.Standard detrending-by-segments combined with non-linear rescaling entailed some cost in solution stability, but could improve the accuracy of solutions for long gradients. Without non-linear rescaling these solutions were usually less stable and less accurate. Although detrending-by-polynomials might be preferable on other grounds, it did not produce more accurate or stable solutions than detrending-by-segments.Abbreviations CA = correspondence analysis - DCA = detrended correspondence analysis - MSE = Procrustes mean squared error statistic - SD = standard deviation units of species turnover - SRV = scaled variance in species ranks     

Additive inheritance of resistance to pod rot caused by Phytophthora palmivora in cocoa

Summary Quantitative inheritance of resistance to Phytophthora pod rot (Ppr) was studied in cocoa hybrid progeny from 12 Trinitario x Amazonian crosses and their reciprocal crosses. The crossing scheme was similar to a factorial design. Disease was assessed by the number and percentage of infected pods on each tree. Highly significant differences due to general combining abilities (GCA) were obtained for all characters, except for the GCA of Trinitario on total pod production. Differences for specific combining ability (SCA) were not significant for all characters. There were no significant differences between reciprocal crosses. The Trinitario clone K82 provided the only source for the hybrid progenies of strong Ppr resistance to the hybrid progenies, while K20 provided moderate resistance. Other parental clones — KA2-101, KA5-201, KEE 2, KEE 5, and KEE 52 — produced progenies which were susceptible to Ppr. It is evident that resistance to Ppr in cocoa is inherited additively. Maternal and cytoplasmic effects were assumed to have no influence on inheritance of resistance. It is also concluded that resistance to Ppr of the kind shown by K82 is likely to be horizontal resistance. Breeding for high-yielding cultivars combined with Ppr resistance is the most effective way of controlling Ppr of cocoa on the crops of growers with small holdings in Papua New Guinea.     

鱼类远缘杂交正反交杂种胚胎发育差异的细胞遗传学分析

本文报道了鲤(Cyprinus carpio)×鲢(Hypophthalmichthys molitrix)、鲫(Carassiusauratus)×鲢、白鲫(Carassius auratus cuvieri)×鲢和鲢×鲤、鲢×鲫、鲢×白鲫的正反交试验。在鲤×鲢、鲫×鲢和白鲫×鲢3个正交组中,胚胎发育基本正常,尽管孵出的鱼苗绝大多数生命力弱,但孵化率都在50％左右;而在鲢×鲤、鲢×鲫和鲢×白鲫3个反交组中,胚胎发育均为畸形,不能孵化出苗。 胚胎发育细胞遗传学分析表明,鲤×鲢、鲫×鲢和白鲫×鲢的杂种胚胎几乎都是整倍体,而鲢×鲤、鲢×鲫×鲢×白鲫的杂种胚胎基本上是非整倍体,染色体数变化较大。这些正反交杂种胚胎发育的显著差异可能与其亲本物种间的基因组大小有关。文中还分析讨论了这些正反交差异与天然多倍体物种以及胚胎发育速度的相关性,认为天然多倍体物种可能具有一些不同于普通二倍体物种协调外源基因组的能力。     

Adaptation to salinity inHordeum jubatum L. populations studied using reciprocal transplants

Tillers and seedlings ofHordeum jubatum L. from three sites with contrasting salinity regimes in central Saskatchewan, Canada were reciprocally transplanted in order to examine the tolerance of populations of this species to salinity and related habitat factors. Survival, growth and fecundity of the three populations were controlled more by transplant site characteristics than by genetic differences, i.e. differences among populations at a site tended to be smaller than differences among sites. Survival, growth and reproduction of all three populations were best at the non-saline site. The population originating at the non-saline site showed the poorest growth in the two saline habitats, but still had substantial salt tolerance. Fecundity was greatest when the populations were grow at their site of origin.     

Analysis of the genetic effects for several traits in oil palm (Elaeis guineensis Jacq.) populations. I. Population means

An oil palm experiment was set up in the Ivory Coast to compare the effects of crossing and selfing within two origins, Deli and La Mé, on the mean and the variability of Deli x Mé between-origin hybrids. The originality of the experiment lay in the crossing plan, which provided access to genetic parameters related to additivity, dominance and different components of epistasis. This first part covers the analysis of the components of the mean. The parents used were obtained from four palms, two from each origin. Those of La Mé origin were half-sibs. The common parent came from a wild stand in the Ivory Coast. Those of Deli origin were from two different populations bred in Southeast Asia for several generations from a narrow genetic base. These four parents gave rise to nine Deli x La Mé hybrid populations with double-cousintype links. The additive component is more important within the Deli origin than within the La Mé origin. This may be explained by the large genetic divergence between the two Deli parent palms. On the other hand, the additive^* additive epistasis is more substantial within the La Mé origin, probably because of inbreeding. The discussion concentrates on how this information should be used when choosing parents to be crossed and tested and to produce improved populations. The crossing plan proposed can be of general use and is suitable for other species in a reciprocal recurrent selection programme.     

Parental effects on growth in Solanum conditioned at multiple levels

Summary Reciprocal crosses were made between plants that had nuclear genes of S.tuberosum L. ssp tuberosum combinated, by recurrent backrossing, with cytoplasmic factors of S. phureja Juz. & Buk. and, separately, of S. tuberosum ssp. andigena (Juz. & Buk.) Hawkes. Significant differences in growth between 19 of 23 intra-cytoplasmic reciprocal progenies occurred in vigor at one or more growth stages during the season and/or in yield as measured by tuber number and weight. If no transmission of cytoplasmic factors occurred through the pollen, the cytoplasmic factors of the parents were the same, and these reciprocal differences were caused by parental chromosomal gene mechanisms such as maternal effect, pollen-tube selection, and/or imprinting. Early seedling vigor was, in some cases, associated with greater seed weight, but this did not account for all of the reciprocal contrasts. The data do not show whether these parental effects are a result of maternal and/or paternal effects. Analysis to determine whether parental effect was a single gene character or alleles expressed at two levels, or multi-genic and so expressed at multiple levels, was based on a study of progeny of ten parents that were used in more than one reciprocal pair combination. The data showed that the parents could be classified at eight successive levels of relative effectiveness as staminate or pistillate parents. Of 23 crosses, 19 showed significant differences between reciprocal progenies that were consistent with this eight-level array. The data support the interpretation that parental effect is a multi-genic character.Authorized for publication as paper No. 163 of the Department of Horticulture     

Pattern analysis in Belgian limestone grasslands

Pattern analyses were made in several limestone grasslands of Belgium. Vegetation has been sampled in continuous transects. Monospecific patterns are defined by means of two non-parametric indices; multivariate analysis (reciprocal averaging) completed the analysis. The following kinds of pattern are described and explained: random, aggregate, clump, gap, stationary density variation, non-stationary density variation, gradient and many complex patterns. The multivariate analysis leads to a careful phytosociological study of the transects and to the definition of floristically homogeneous regions. Some particular points of pattern analysis, the problem of vegetation sampling and some perspectives are discussed.     

Book reviews

Editing of community data matrices is complementary to analyzing data by multivariate techniques of classification and ordination in the overall task of data analysis. A computer program, DATAEDIT, is described that can perform numerous editing functions, including data transformation, deletion of certain species or samples, deletion of rare species, deletion of outliers, separation of disjunet sample groups, reordering of the species or samples of a data matrix, and the formation of composite samples or of sample subsets. DATAEDIT can use the information in a nonhierarchical or hierarchical classification, and includes its own internal routine for reciprocal averaging ordination.We appreciate valuable suggestions from the late Robert H. Whittaker, and from Philip Dixon, David Hieks, Laura Huenneke, Linda Olsvig-whittaker, and Mark Wilson. Mark O. Hill kindly supplied a fast subroutine for reciprocal averaging.