Genotype-location Interaction Research Articles

Orange-fleshed sweet potato [Ipomoea batatas (L.) Lam] genotype by environment interaction for yield and yield components and SPVD resistance under arid and semi-arid climate of northern Ethiopia

Worldwide, sweet potato (Ipomoea batatas (L.) Lam) ranks the sixth most important crop valued for food security, income, and nutritious diet for poor farming communities. Despite its importance, there is lack of information and knowledge to introduce the crop to Afar region where malnourishment is high. Six orange-fleshed sweet potato genotypes (Amelia, Erica, Gloria, Ininda, Kulfo, and Melinda were evaluated for sweet potato viral disease (SPVD), yield and yield components in three contrasting locations, namely Aba’ala, Mekelle 1, and Mekelle 2 using a Randomized Complete Block Design to produce variance components. Joint regression, and additive main effects and multiplicative interactions were used to test the Genotype × Location Interactions (GEI). Means for significant traits were separated by Least Significant Difference (p<0.05). Results showed ample genetic variability for total tuberous yield (TTY), and SPVD resistance. Genotypes Ininda, Gloria, Amelia, and Kulfo were superior for TTY with high SPVD resistance. Aba’ala was a hotspot for SPVD, Mekelle 2 was with low SPVD and recorded a high mean TTY. Amelia and Kulfo exhibited static stability, Ininda and Gloria displayed dynamic stability, high harvest index, and fresh vine yield, and were recommended for further stability investigations. The information generated in this study may be useful as preliminary data however, the experiment has to be repeated for practical conclusions and recommendation of stable varieties for the studied agro-climatic zones.

Higher Order AMMI (HO-AMMI) analysis: A novel stability model to study genotype-location interactions

Additive main effects and multiplicative interaction (AMMI) model is most widely used to analyze genotype x environment interactions (GEI) wherein interaction effects of location is masked by year effect. Hence, presently available models are not able to estimate interaction effects of genotype x location (GLI) and genotype x year (GYI) separately. Moreover, genotype ranking differs as number of years of evaluation vary making selection of genotype for target location difficult. In the present study, a novel stability model i.e., Higher-order-AMMI (HO-AMMI) analysis which can calculate GLI without the confounding effect of GYI and GLYI has been proposed. GEI of AMMI model and all 2-way interactions of HO-AMMI model follow χ2 distribution, whereas 3-way interaction (GLYI) of HO-AMMI follow noncentral χ2 distribution. With increase in number of years of evaluation contribution of GLI towards total variation increased whereas in AMMI model contribution of GEI towards total variation decreased. Variation explained by multiplicative components is higher in HO-AMMI compared to AMMI model. Genotypes were ranked using GL, GY and GL+GY+GLY interactions of HO-AMMI and GEI of AMMI for stability and yield and compared their ranks with field ranking. Correlation and linear regression analysis have indicated high association of GLI (HO-AMMI) with field ranking with high R2 values. Further, HO-AMMI model was able to remove the confounding effect of GYI and GLYI on GLI for accurate identification of genotype for target location irrespective of number of years of evaluation. Hence, HO-AMMI model can be used under multi-environment trials(MET) for selecting genotypes efficiently.

Environment×Combining Ability Interaction for Quality Traits in Tomato (Solanum lycopersicum L.)

The multilocational studies were conducted to evaluate 21 hybrids of tomato in Pratapgarh(Uttar Pradesh), Varanasi (Uttar Pradesh) and Burdwan (West Bengal), India during August–February of 2015–16 and 2016–17. Data on four quality traits viz., total soluble solids, titrable acidity, carotene content and lycopene content were estimated. Combined analysis of variance (ANOVA) revealed significant effects of locations, genotypes, genotype-location interaction and parents vs hybrids-location interaction for all the traits. The significance of combining ability effects (general combining ability and specific combining ability) and their interaction with location revealed environmental influences on combining ability effects for all the traits. The Present study indicated higher estimates of to , lower estimates of heritability and GCA/SCA ratio for quality traitsandthereby implied preponderance of non-additive gene action in determination of quality traits studied. Desirable parental lines were identified for different traits like EC 620438 and BS 24-2 for TSS, BS 24-2 and Superbug for titrable acidity, Columbia, EC 620438 and Superbug for carotene content, and H 86 and EC 620541 for lycopene content. Similarly, desirable specific combiners for different traits were identified. The hybrid combination EC 620438×BS 24-2 appeared good specific combiner for TSS, carotene and lycopene content. The parental lines/hybrids identified in present study will be useful in identifying hybrids adapted to a range of environments.

Genotype by Environment interactions for egg number and egg weight of five dual-purpose chicken breeds in different zones of Oromia region in Ethiopia

The African Chicken Genetic Gain (ACGG) project (https://africacgg.net/) aims at backyard poultry optimization by commercial dual-purpose breeds introduction into Africa. To measure benefits, genotype by environment interaction (GxE) analysis provides guidance while predicting environmental effects on production traits of breeds. A survey among Ethiopian poultry smallholders showed egg sale being the most important purpose of keeping village chickens in Oromia. Data was available about laying of 894 ACGG chickens in Oromia. Hence current research questions were: 1) Does GxE take place? 2) Which breed performs best regarding laying and in which environment within Oromia? Traits investigated were egg number and egg weight of five breeds (S-RIR, Sasso, Horro, Kuroiler and Koekoek) located in three zones (East Hararge, East and West Shoa) and 5 districts (Adami Tulu, Bako Tibe, Dano, Dugda and Haromaya) in Oromia. Observations were taken as group measure performing weighted analyses. GxE was only present for egg number with magnitude strongest for zone. S-RIR performed best for both traits in both environments, except Kuroiler performing better in East Shoa for egg number and Koekoek for egg weight. This indicates success of crossbreed S-RIR. Sasso and Horro performed worst supported by previous research for Horro but not Sasso. Low precipitation in East Shoa caused bigger distance in egg number predictions, being higher for S-RIR and lower for Horro and Sasso compared to West Shoa. Apart from these final conclusions, social context of breeding and data collection difficulties should not be forgotten. Just like relevance of other performance trait analyses.

Evaluation of Selected Tomato (Solanum lycopersicum L.) Cultivars in Ghana for Superior Fruit Yield

In the present experimental study, we evaluated some tomato cultivars in greenhouse and field conditions in order to determine superior cultivars for yield and yield component traits. The experimental lay out adopted was the Randomized Complete Block Design (RCBD) which was replicated three (3) times. The combined analysis of variance showed significant (p<0.01 and p<0.05) variability among the genotypes, locations and genotype-location interactions (G × L) for almost all the traits. The relative performances of the genotypes differed with location. Among the genotypes evaluated, Mongal F1, Platinum F1, Nkansah HT, Wosowoso, Roma and Sumo F1 displayed superior performance for fruit yield across all locations

Lucerne cultivar adaptation to Italian geographic areas is affected crucially by the selection environment and encourages the breeding for specific adaptation

Plant breeding programmes frequently face the dilemma whether to breed for wide or specific adaptation. This is especially true for forage crop breeding, whose genetic resources may largely include landraces that are adapted to specific growing conditions. This study aimed to (1) investigate the extent and pattern of genotype × location (GL) interaction for biomass yield of recent lucerne cultivars across organically-managed sites of Northern and Central Italy and its relationship with cultivar selection environments, (2) provide an empirical assessment of yield gains derived from specific-adaptation and wide-adaptation breeding strategies, and (3) identify top-performing cultivars for different geographic regions. Cultivar adaptive responses, modelled by additive main effects and multiplicative interaction analysis, displayed wide GL interaction of cross-over type across test sites that reflected remarkably the geographic area and/or the growing conditions (particularly for extent of summer drought) of their selection environment. GL interaction patterns suggested three putative subregions to breed for specific adaptation, namely, Northern Italy north of the Po river, Northern Italy south of the Po river, and Central Italy. Growing specifically-adapted cultivars provided an estimated average advantage of 12.9% across subregions relative to the best-performing widely-adapted cultivar. Yield gains of recent top-performing material over an historical, widely-adapted cultivar indicated that selection for specific adaptation would provide 3.2-fold greater yield gain averaged across subregions, and 3.4-fold greater yield gain over the target region when weighting yield gains on the putative proportion of the target region of each subregion, compared with selection for wide adaptation.

Evaluation of selected tomato (Solanum lycopersicum L.) cultivars in Ghana for superior fruit yield and yield component traits

In the present experimental study, we evaluated some tomato cultivars in greenhouse and field conditions in order to determine superior cultivars for yield and yield component traits. The experimental lay out adopted was the Randomized Complete Block Design (RCBD) which was replicated three (3) times. The combined analysis of variance showed significant (p<0.01 and p<0.05) variability among the genotypes, locations and genotype-location interactions (G × L) for almost all the traits. The relative performances of the genotypes differed with location. Among the genotypes evaluated, Mongal F1, Platinum F1, Nkansah HT, Wosowoso, Roma and Sumo F1 displayed superior performance for fruit yield across all locations.

Corpoica Guayuriba 9: new improved soybean (Glycine max [L] Merril) variety with specific adaptation to the Colombian foothills

Soybean in Colombia is constituted, like corn, as the main raw material for the production of balanced concentrates for animal feeding. The national soybean production satisfies only 7.0% of the demand for poultry-swine chain, with imports in 2014 of 363501 tons of grain and 1018256 tons of soybean meal. Currently, in Colombia, soybean is only produced in the Orinoquia region, mainly in the high plains and foothills and is part of the rice-corn-soy rotation system for the colonization of native savannas. In order to promote cultivation which allows the occupation of 500000 potentially hectares in the foothills with new varieties beyond current and meet domestic demand, Corpoica is responsible for the plant breeding. As a result of a research in plant genetic resources during nine years (2006-2014), the study of a group of elite soybean genotypes on two contrasting regions: high plains and foothills. In addition, main components analysis per genotype-location interaction were determined for L-189 genotype identified with specific adaptation to the foothills and the highest experimental yield of 2660 k.ha-1, superior in more than half a ton to the yield obtained by the control varieties (P-34 and Superior 6); with traits which bring competitive advantages such as a larger number of pods per plant (56) and smaller seeds (15.2g), besides an acquired tolerance to the Cercospora sp. pathogen.

An Experiment In Breeding Cut Roses For The Indonesian Highlands

BIOBREES is a co-operative scientific programme between Indonesia and The Netherlands, of which the rose part aims at breeding cut roses adapted to the tropical highland. Within that scope four direct plant characters of 62 cut rose genotypes in different physiological stages were studied. The genotypes originated from cross-breeding in 1995 and successive selection for cut rose properties in populations at Plant Research International, Wageningen, The Netherlands, in 1996. Plant stages stuAn died were (i) superior adult seedlings in Wageningen in 1996, (ii) clones grafted onto Natal Briar both in Wageningen and Cipanas in 1997. Clonal Plant Research International, Wageningen, Plant Research International, Wageningen, clonal plants in Cipanas had significantly shorter shoots, more thorns, smaller flowers and fewer petals than the adult seedlings in Wageningen. Clonal plants in Wageningen, however, had significantly longer shoots; more thorns, and larger flowers with more petals than the seedlings in Wageningen. Despite differences in level of expression, for each character the absence of genotype-location interaction was ascertained. The expression of characters as influenced by light (both quantitative and qualitative), temperature and cultivation is discussed in relation to selection of cut roses in the temperate zone, which are adapted to the tropical highland.

A comprehensive comparison between ANOVA and BLUP to valuate location-specific genotype effects for rape cultivar trials with random locations

It is of interest to obtain a reliable estimate and statistical test of the simple effects of genotypes at specific locations if a significant genotype–location interaction exists in multilocation trials commonly conducted in plant breeding and variety testing programs. For this task this study compared two different statistical procedures, i.e., the separate analysis of variance (ANOVA), being applied usually in the practical analysis of the multilocation trials with random locations, and the best linear unbiased prediction (BLUP) based on a variance component mixed model, by simultaneous analysis of various cultivar multilocation trails of rape in case of random locations. The phenotypic correlation of genotype effect prediction between trial locations and the average variance of differences between the genotype predictions were used, respectively for assessing the precision and the efficiency of the analysis procedures in evaluating the location-specific genotype effects. The result showed that the use of the separate ANOVA and the BLUP could result in some difference in prediction, ranking and statistical testing of location-specific genotype effects. Compared to the separate ANOVA, the BLUP based a variance component mixed model provided both a high precision and a high efficiency in prediction of the location-specific genotype effects for the rape trials with random locations.

Genotypic Association of Parameters Commonly Used to Predict Canning Quality of Dry Bean

ABSTRACTTo select dry bean (Phaseolus vulgaris L.) varieties suitable for the canning and processing industry, it is essential to understand the genetic and environmental effects on the quality parameters as well as their associations. A dataset of 6 yr of dry bean quality evaluations in the multi‐location provincial registration trials in Ontario, Canada, with data for parameters routinely used by breeding programs to predict the final canning quality of breeding materials was used. Genetic, environmental, and genotype (G) × environmental effects and multi‐variable associations were studied using the estimates of the genotypic least squared means for the balanced yearly data and the best linear unbiased predictors (BLUPs) for the overall unbalanced data. Genetic effects, accounting for 35 to 76% of the variation in navy bean and 38 to 88% of the variation in large‐seeded bean, followed by location (L) effects, accounting for 11 to 66% of the variation in navy bean and 11 to 64% of the variation in large‐seeded bean, were more important than the genotype × location (GL) interaction effects for seed composition parameters. This was not the case for physical and texture parameters, where GL interaction effects were often most important. Positive associations were observed among hydration coefficient, can yield, and protein content in the yearly analyses as well as in the multi‐year analysis. The negative association between percent washed‐drain solids and bean texture after processing was also repeatedly observed over years. The associations reported here may guide further selection efforts in bean breeding programs.

Heterogeneity of error variance and its influence on genotype comparison in multi-location trials

Multi-location trials play an important role when evaluating genotypes at many stages of plant-breeding programs, as well as when recommending varietal plant production. The most common procedure for analyzing these trials is based on the assumption that the residual error variance is homogenous across all considered locations. However, this may often be unrealistic, and therefore limit the accuracy of genotype evaluations or the reliability of varietal recommendations. The objectives of this study were to investigate how frequently and how seriously the problem of heterogeneous variances appears across locations in multi-location trials, and to evaluate the impact of the analytical procedure with different considerations about error variations when comparing genotype effects. A series of 16 multi-location trials from a corn-breeding program in the north of China were simultaneously analyzed from 2005 to 2008 using a randomized complete block design at each location; the analysis used models with homogeneous residual variances, as well as models with heterogeneous residual variances to take into account that different locations may have different levels of precision. The results showed that the residual error variances strongly varied across locations in all of the considered trials. The model with heterogeneous residual error variances was significantly (α<0.001) more appropriate than the one with homogeneous error variances in all of the trials for both fixed and random locations, according to model fitting statistics. Ignoring error variance differences across locations in the analysis procedure of multi-location trials could result in a large Type I error rate for comparisons (F-test) of the main effect of genotypes, especially in case of random location main effects and genotype–location interactions, locations, and genotype–location interactions, as well as an inflation or deflation of statistical Type I error rates for comparisons (t-test) of simple genotype effects depending on specific locations.

Adaptation of contrasting cocksfoot plant types to agricultural environments across the Mediterranean basin

Stress-tolerant forage resources are increasingly needed for the environmental and economic sustainability of extensive Mediterranean livestock systems. Perennial forages such as cocksfoot ( Dactylis glomerata L.) can be a valuable alternative to annuals, if they can survive across successive summer droughts. One Mediterranean cultivar of cocksfoot subsp. hispanica with complete summer dormancy (Kasbah), five non-dormant (Delta 1, Jana, Medly, Ottava) or incompletely dormant (Currie) Mediterranean cultivars of subsp. glomerata, and one Continental cultivar (Porto) of subsp. glomerata, were evaluated for dry matter yield over three years and persistence as final plant survival in six sites of Algeria, France, Italy, Morocco and Portugal, with the objectives of: (i) modeling adaptive responses and targeting cultivars as a function of environmental factors associated with genotype × location (GL) interaction; (ii) defining plant ideotypes, adaptation strategies and opportunities of international co-operation for regional breeding programmes. Adaptive responses were modeled by joint regression, additive main effects and multiplicative interaction (AMMI), and factorial regression. The most predictive models were: (i) factorial regression as a function of site spring–summer drought stress (as long-term potential evapotranspiration minus actual water available), for yield; (ii) AMMI including one GL interaction principal component related to site annual and spring–summer drought stress, for persistence. GL interaction of crossover type for yield and persistence was large and mainly associated with the summer dormancy trait. Completely dormant germplasm was specifically adapted to severe drought. Non-dormant Mediterranean cultivars tended to be specifically adapted to moderate drought stress, although they varied to some extent in adaptive response to drought-stress levels. The Continental cultivar was generally misadapted. The completely summer-dormant germplasm also tended to have greater general persistence across locations. Early flowering tended to correlate with higher yield and persistence of the cultivars across locations. Considerations on experimental conditions along with previous physiological studies from three sites suggested that water use efficiency of the cultivars tended to parallel their site-specific yield response. On the whole, the results suggest different adaptation targets, plant types, genetic resources and cultivar recommendation for northern Africa and southern Europe. Summer-dormant material of subsp. hispanica has prevalent interest for northern Africa. Breeding widely adapted, non-dormant or incompletely dormant Mediterranean cultivars of subsp. glomerata has prevalent interest for southern Europe, especially when targeted to moderate crop duration (3–4 years). However, completely summer-dormant germplasm could gain adaptive potential for Mediterranean-climate European regions in the future, to mitigate the effects of the predicted increasing drought due to climate change.

Response of common wheat varieties to organic and conventional production systems across Italian locations, and implications for selection

Specific breeding for organic systems may help reduce their yield gap relative to conventional systems by exploiting genotype × system (GS) interaction. Likewise, specific breeding for distinct subregions within a region could capitalize on genotype × location (GL) interaction. Grain yield and test weight of common wheat varieties were evaluated under organic and conventional systems in ten locations spanning from northern to southern Italy, with the objectives of: (i) comparing production systems; (ii) investigating the extent of GS and GL interactions and their relationship with genotypic and environmental characteristics; and (iii) preliminarily comparing, in terms of predicted selection gains, different strategies to cope with GS and GL effects. These effects were investigated in the 2-year Data set 1 including seven genotypes. GS effects were also assessed in the annual Data sets 2 and 3 including 13 and 11 genotypes, respectively. The yield reduction of organic systems relative to conventional ones averaged 28% in Data set 1, 29% in Data set 2 and 14% in Data set 3. Organic systems also tended to a modest test weight reduction. Genetic correlations between systems ranged from high to very high (0.88 ≤ r g ≤ 0.98) for yield and test weight, owing to nil or limited GS interaction. Broad-sense heritability tended to be higher in conventional systems than organic ones for yield in two data sets (mainly due to lower experimental error) while being similar in the two systems in the other cases. Predicted selection gains suggested nil (yield) or very modest (test weight) advantage of direct selection in organic systems relative to indirect selection in conventional systems, when targeting organic systems. The scope for selection only in conventional systems was reinforced when comparing predicted gains for selection scenarios which target both systems in relation to their foreseeable marketing importance. GL effects for yield and test weight were significant and were modeled by additive main effects and multiplicative interaction analysis. Site classification based on GL effects for yield revealed a larger subregion A including northern and central Italy and a smaller subregion B comprising southern Italy, accordingly with previous, independent studies. Yield selection only in subregion A (with indirect selection gain for subregion B) implied slightly higher predicted gain for A (+4%) and much lower gain for B (−24%) relative to independent, direct selection in each subregion. Selection for specific geoclimatic subregions may have greater importance than selection for specific production systems.

Developmental stability in oats I. Yield

Gullord. M. and Aastveit. A.H. 1987. Developmental stability in oats. I. Yield. —Hereditas 106: 195–204. Lund, Sweden. ISSN 0018–0661. Received July 14, 1986 This paper deals with stability of Nordic oat lines and cultivars over years and locations. In one series during the years 1981–84 significant interaction between genotypes and locations, and between genotypes and years was found for grain yield. The former interaction component of variation was splitted up into ecovalences, linear regressions and deviations from linearity, and principal components. The main results can be summarized as follows: 1) There seems to be good agreement between the stability parameters calculated by the different methods. 2) The principal component methods both divided the cereal growing area in Norway into the following four sub-regions: Northern inland, Southern inland, South-western areas and Mid-Norway. 3) Temperature and rainfall from tillering until harvest had large influences and opposite effects on the genotype-location interaction. KA1 and PA1 also contributed to the interaction. 4) There was a large genetic variation in developmental stability for grain yield. 5) No close relationship was found between average grain yield and stability over a range of environments.

Developmental stability in oats (A vena sativa L.): II. Quality characters

Gullord, M. and Aastveit, A.H. 1987. Developmental stability in oats (Avena sativa L.). II. Quality characters. —Hereditas 107:65–74. Lund, Sweden. ISSN 0018–0661. Received October 31, 1986 The present paper deals with developmental stability of quality characters of Nordic oat lines and cultivars over years and locations. In one series during the years 1981–84 highly significant interactions between genotypes and locations were found for husk content, test weight and protein content, but not for 1000 grain weight and oil content. The interaction component of variation has been split up into ecovalences. linear regressions and deviations from linearity, and principal components for the characters with significant genotype location interaction. The main results are: 1) The linear regression model did not fit the data sufficiently well for any of the quality characters. However, there seems to be good agreement between the parameter for deviation from regression, Wricke's ecovalence, the principal components and the PLS parameters. 2) The PLS procedure for husk content, test weight and protein content divided the cereal growing area into roughly the same regions as for grain yield. 3) Temperature and rainfall, especially between heading and maturity. had large influence on the genotype x location interactions for husk content, test weight and protein content. 4) There was a large genetic variation in developmental stability for husk content, test weight and protein content. 5). Developmental stability in one character could be associated with stability in other characters but not necessarily so. 6) There was no close genotypic relationship between the quality characters and stability.

Cultivar Adaptation across Italian Locations in Four Turfgrass Species

Crossover genotype × location (GL) interaction may be exploited by site‐specific breeding and cultivar recommendations for distinct subregions. Turf quality and density of 110 elite cultivars belonging to four species [perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), tall fescue (Festuca arundinacea Schreb.), and red fescue (Festuca rubra L. subsp. rubra, litoralis, and commutata)] were assessed at five locations scattered across the Italian peninsula and its main islands. The 110 cultivars were evaluated for (i) assessing the extent of GL interaction and its implications on cultivar selection and recommendation; (ii) comparing additive main effects and multiplicative interaction (AMMI) vs. joint regression modeling of GL effects; (iii) verifying the consistency between species of site similarity for GL effects; and (iv) defining test locations for the Italian national evaluation program and for local breeding programs. The trials were arranged in a Group Block Design with three replicates, grouping cultivars within species. Genotype × location interaction occurred for all traits (P &lt; 0.05) except turf density in tall fescue and Kentucky bluegrass. The selected, one‐dimensional AMMI model always outperformed the joint regression model for predictive accuracy as estimated by the mean square value of the relevant GL interaction parameter. Wide crossover GL interaction was observed for turf quality among top‐ranking cultivars of red fescue and Kentucky bluegrass, justifying site‐specific recommendations. Variation of top‐ranking cultivars across sites also occurred for turf density in red fescue and perennial ryegrass. Site similarity for GL effects was largely inconsistent across species. However, specific adaptation either to cooler, wetter sites or warmer, drier sites emerged for cultivars of red fescue, perennial ryegrass, and tall fescue. Site‐specific breeding may be valuable especially for red fescue, exploiting the trend toward specific adaptation of its subspecies.

Repeatable genotype × location interaction and its exploitation by conventional and GIS-based cultivar recommendation for durum wheat in Algeria

Repeatable genotype × location (GL) interaction revealed by multi-locational trials may be exploited by site-specific cultivar recommendations. There is uncertainty, however, on methods for defining recommendations and extending results to non-test locations. With reference to durum wheat in Algeria, our main objective was the comparison of methods for defining the best pair of cultivars for local recommendation based on: (i) observed data; (ii) joint regression-modeled data; (iii) additive main effects and multiplicative interaction (AMMI)-modeled data; (iv) factorial regression-modeled data; (v) AMMI modeling interfaced with a geographic information system (GIS); (vi) factorial regression modeling interfaced with a GIS. The last two methods extended the recommendations to all sites in a GIS as a function of long-term climatic data. Concurrently, we aimed at assessing: (i) the repeatability over time of joint regression and AMMI parameters of adaptation; (ii) the consistency between predicted and actual yield gains derived from growing recommended cultivars in place of locally most-grown cultivars; (iii) the effect of different numbers of recommended cultivars. Modeling was based on grain yield of 24 genotypes evaluated across 2 years in a total of 31 environments. Cultivar responses at 16 sites in a third year were used for comparing methods according to average yields of recommended materials at individual sites and across sites, and for assessing repeatabilities. The selected AMMI model included one GL interaction principal component (PC 1). Winter mean temperature and rainfall over the cropping season were selected as covariates for factorial regression and as variables in a multiple regression for predicting the PC 1 score of sites in the GIS. Genotypic parameters, especially mean yield and PC 1 score, were highly repeatable ( r > 0.90). Site parameters (PC 1 score, mean yield) showed moderate to fairly low repeatability mainly due to within-site variation in annual rainfall. Recommendations based on modeled data implied less subregions (i.e. sets of locations with same top-yielding material) and provided, on the average, 4–5% higher yields and much better predictions of actual yield gains from recommendation compared with those based on observed data. GIS-based recommendations implied a slight yield decrease relative to those based on conventional modeling. However, they allowed for about 9% higher yields than those of most-grown cultivars, while enlarging the scope for site-specific recommendations and assisting national seed production and distribution systems. Factorial regression showed a slight advantage over the other models. On the average, recommending two top-yielding cultivars (reference criterion) or the top-yielding cultivar provided similar yields, somewhat higher yields than three top-yielding cultivars, and 8–10% higher yields than larger sets of statistically ( P < 0.20) not different cultivars.

DEVELOPMENTS IN BREEDING FOR HORIZONTAL AND VERTICAL FUNGUS RESISTANCE IN ROSES

Garden rose varieties certified as ‘Toproos’ form the best choice for nurserymen and garden lovers in The Netherlands. However, these varieties had not been tested for fungus resistance before 1995. Therefore, 63 ‘Toproos’ varieties planted in 3 different locations during 3 years, unsprayed, were re-selected by Dutch Permanent Judging Committee (VKC) for resistance to black spot, mildew and rose rust, as well as for disease effects on new growth. Re-selection greatly contributed to the status of the certificate, as only 44 varieties (68%) proved to be satisfactory under prevailing conditions. Observations indicated horizontal resistance for each disease; despite annual variation in disease level, genotype-location interaction did not occur. New growth was significantly affected by black spot and rose rust. Varieties infected by black spot and rose rust were the same. The selected varieties form an excellent collection of progenitors in a breeding programme for horizontal resistance. To introduce new black spot and mildew resistant germplasm, interspecific crosses between recurrent flowering, tetraploid (2n=4x=28) Hybrid Tea varieties and non-recurrent, putatively vertically resistant selections from R.moschata (2x), R.bella (4x), R.acicularis (6x), R.nutkana (6x) and R.marginata (8x) were carried out. Most crosses resulted in F1-populations. Sofar, F2-back crosses have yielded seeds. Percentages between 10-40% of recurrent flowering F2-seedlings are expected. Resistance of recurrent F2-plants will be tested.

Breeding Cut Roses for the Tropical Highland

ABSTRACTBreeding and cultivation of cut roses has been confined to the temperate zones since the eighties of the last century. Since then several growers have left their fatherlands and started cut rose production in the tropical highlands of Asia, South America and Africa. Adaptation to the temperate zones of the varieties used, has led to disappointing results in the tropics. In addition to not being adapted to the tropics, the availability of patented varieties in non-UPOV countries has hampered the enlargement of local cultivation. The Dutch-Indonesian co-operative breeding programme BIOBREES aims at varieties of different horticultural crops which are performed better in Indonesia than hitherto. The rose part of BIOBREES aims at breeding cut roses, both by cross-breeding and biotechnology, that are adapted to the Indonesian highland (> 1000m asl). Within that scope the possibilities of breeding and selecting cut roses in the temperate zone, performing the well in the Indonesian highland, has been investigated. In the present experiment 62 cut rose genotypes arisen from cross-breeding in Wageningen (The Netherlands) in 1995, were studied on four direct characters: shoot length, thorniness, flower diameter and petal number, in two physiological stages in two locations. Viz., as adult seedlings in Wageningen in 1996, and as clones onto Natal Briar in Wageningen and Cipanas (Indonesia) in 1997. Taking the adult seedling in Wageningen as a starting point, clonal shoots were significantly longer in Wageningen, but shorter in Cipanas. Thorniness of clonal shoots in Wageningen did not differ significantly, but those in Cipanas were significantly thornier. Flower diameter of clones in Wageningen was significantly larger, but significantly smaller in Cipanas. Number of petals did not differ in Wageningen clones, but those in Cipanas had significantly fewer petals. Despite differences in the level of expression, genotype-location interaction was absent for the characters observed. Various differences in the way of cultivation, in light quantity and in temperature levels are known factors to affect expression of genotypes. It is probable, however, that UV-B exerts most prominent effects in the tropical mountains. If present selection procedure should be maintained, selection in the temperate zone for long shoots, few thorns and large well-filled flowers should be more emphasized. Growing seedlings in a phytotron, simulating the tropical mountainous conditions, seems very conducive to selection. Realizing the complete breeding procedure in the tropics may be a good solution, but involves serious risk.