Estimation of variance components and heritability of bunch yield and yield components in the oil palm (Elaeis guineensis Jacq.)

In an experiment involving 24 single-cross progenies of oil palm conducted at the Nigerian Institute for Oil Palm Research, 9-year data of fresh-fruit yield and its two components, annual bunch number and single-bunch weight, were recorded. Means of progenies of each of the three traits obtained from 1–9-year records were used in analyses of variance according to a repeated-measures design. The results were then used to estimate variance components due to progenies and progeny × year interactions. These estimates were then used to estimate heritability for yield and yield components based on progeny means, which were assumed to be calculated from 1–9 years of harvests. The results revealed that heritability estimates of fresh-fruit yield and its two yield components were not reliable based on the first-year harvest data. The single-bunch weight had a slower rate of improvement than the other two traits when more years were used for the estimation. Heritability can be expected to be over 80% for fresh-fruit yield and bunch number based on 1-, 3-, and 4-year means, respectively. Six-year data are required for single-bunch weight to reach the same heritability measure.     

Assessment of yocoboue wild oil palm (Elaeis guineensis Jacq.) from Côte d'Ivoire

Following a survey involving wild oil palm groves in Côte d’Ivoire as a whole in 1968, 17 parents were chosen at Yocoboué (southernCôte d’Ivoire). Agronomic performance of the 17 parents was assessed through Deli × Yocoboué hybrids in 3 trials grown at La Mé (Côte d’Ivoire), Mondoni and La Dibamba (Cameroon).When compared to the Deli × La Mé progenies used as controls, the Deli × Yocoboué hybrids produced 91% for total bunch weight and86% for oil yields. However, the genetic variability within the Deli × Yocoboué progenies allows to select individual progenies as productive as the Deli × La Mé controls, for breeding purposes. A study of major agronomic traits led to the choice of parent YO 11 T , which combines the largest number of favourable traits. On average, Deli × Yocobouéprogenies have slower vertical growth and are susceptible to Fusarium wilt, except 2 parents (YO 3 T and YO 9 T), which seem to be resistant.     

Experimental modification of reciprocal recurrent selection in oil palm breeding in Cameroon

Reciprocal recurrent selection (RRS) exploits the genetic complementarity of dura populations of palms with a small number of large bunches and tenera/pisifera group of palms with large number of small bunches. An extra phase was introduced to RRS just after the second cycle of selection where outstanding dura derived from (DA3D × DA5D) combinations of the second cycle were self-pollinated for seed production. Best palms based on the phenotype were selected and crossed with pisifera of second cycle offspring of LM2T. [(DA3D × DA5D) self-pollinated × LM2T self-pollinated] progenies were field tested at La Dibamba (Cameroun) from 1987 to 1997. They were precocious with regard to the three-first years’ bunch yields (13.16–15.77 t/ha). Homogeneity for all bunch yield components and homogeneity for vertical growth were illustrated by low values of the variation coefficient (5.75–7.75%). The oil yield was 107% of the control against 115% from [(DA3D × DA5D) × LM2T self-pollinated] progenies of the second cycle of RRS, mostly due to poor mesocarp to fruit and poor oil to mesocarp ratios which led to a low oil extraction rate. The extra selection phase led mainly to homogenisation of progenies but also reduced the fruit quality. However, three progenies whose average oil yield represented 115% of the control (4.87 t/ha) in addition to their precocity can be released to oil palm growers. The extension of RRS did not fully meet expectations and poses the problem of its reliability.     

Breeding of high yielding and dwarf oil palm planting materials using Deli <Emphasis Type="Italic">dura</Emphasis> × Nigerian <Emphasis Type="Italic">pisifera</Emphasis> population

In practice, progeny and individual palm selection are believed to be the most suitable breeding approach for improvement of quantitative traits in oil palm because their phenotypic expressions are strongly influenced by abiotic factors. Therefore progeny selection approach was applied in this study for the selection of high fresh fruit bunch (FFB) and dwarf oil palm planting materials. Cross between Deli dura and Nigerian pisifera resulted into 34 D × P full sib progenies with 1036 seedlings. For six consecutive years, data were collected on yield and yield component traits, while vegetative traits were recorded once. Bi-parental analysis was carried out using analysis of variance, followed by progenies mean comparison, variance components, heritabilities and cluster analysis. Highly significant (P ≤ 0.01) progeny effect was recorded in this study and this had a pronounced effect on the expression of all the quantitative traits. Progenies performance of FFB varied significantly and it ranged from 166.49 to 220.06 kg/palm/year (kg/p/yr) with trial mean of 192.93 kg/p/yr. Palm height after 8 years of field planting ranged from 1.67 to 2.78 m (control cross) with trial mean of 2.12 m. Broad sense heritability (\({\text{h}}_{\text{B}}^{2}\)) was found to be very low (<17.60%) for all the yield traits, however this parameter was high for vegetative traits with palm height having \({\text{h}}_{\text{B}}^{2}\) of 90%. Cluster analysis based on all the quantitative traits grouped all the 34 DP progenies into nine distinct clusters. From this study, five progenies (DP3, DP4, DP5, DP8 and DP24) were identified to be high yielding and dwarf palms compare to trial mean. At density of 140 palm/ha, they will produce FFB of 28.63–30.81 t/ha and average of 29.69 t/ha which is about 27.15% higher in FFB when compared to the current planting material with FFB of 23.35 t/ha. In addition, the selected progenies possessed average annual palm increment of 29.82 cm/yr with range of 26 and 32.5 cm/yr which was 57.33% shorter than the current planting material with palm height increment of 45–75 cm/yr.     

Breeding for oil yield and short oil palms in the second cycle of selection at La Dibamba (Cameroon)

Breeding in oil palm aims mainly at improving palm oil yield. Short palms are also desired because they are easy to harvest and increase the economic life of the plantation. A total of 23 progenies from Deli × La Mé and Deli × PO 1097 P (Yangambi) crosses were field tested at La Dibamba Oil Palm Research Centre in Cameroon from 1988 to 1998. Oil yield components were measured on per palm basis from 3 to 9 years after planting, and the vertical growth at 6 years after planting. The mean oil yield of the trial was average, representing 102% of the control (3.515 t/ha), and the mean height 6 years after planting was 101% that of the control (88.0 cm). The analysis of variance detected differences among progenies for various yield parameters and vertical growth. The comparison of means showed clear separation of groups of progenies for oil yield at the juvenile period (3–5 years after planting). At maturity (6–9 years after planting), the groups of progenies were overlapping indicating that progenies were comparable each other. However, four precocious progenies and high oil yielding at maturity (119–122% of the control) in absolute values can be released to planters. Though their vertical growth represented 116–127% of that of the control, short pisifera palm are expected from parental selfs or crosses given the intrinsic heterozygosity of oil palm.     

Ranking parents by best linear unbiased prediction (BLUP) breeding values in oil palm

Summary Breeding values obtained from best linear unbiased prediction (BLUP) were used to rank nine pisifera (P) male parents belonging to two different but related genetic groups, utilising highly unbalanced data from three D (Dura) × P progeny-test trials of oil palm. The traits studied were fresh fruit bunch yield (FFB), total number of bunches (BNo), average bunch weight (BW), oil to bunch percentage (OB) and average annual height increment (HINC). Four P's from the AVROS genetic group had higher breeding values for FFB, BNo and OB while five P's from the Dumpy-AVROS group were superior in breeding values for BW and HINC. Selection of parents based on the average of the rankings in breeding value for BNo, OB and HINC for each parent tended to favour AVROS P's. However, selection of parents based on the aggregate genetic worth function involving relative economic values, tended to favour Dumpy-AVROS P's. The latter method is preferred to the average ranking method because of its emphasis on relative economic values and the selection index approach.It is suggested that the BLUP technique may prove to be a very useful tool in oil palm breeding.     

Selection for early flowering in progenies of interspecific crosses of ten species in the genus Dianthus

Summary Twenty-seven progenies of interspecific crosses, involving ten Dianthus spieces (D. caryophyllus, D. chinensis, D. superbus, D. barbatus, D. japonicus, D. brachyzonus, D. versicolor, D. trifasciculatus, D. serotinus and D. knappii) and some complex interspecific hybrids (Diantini genotypes and D. Allwoodii selections) were grown from seed under 8 hr days at two light intensities: 12 W/m² and 22 W/m². Observations on individual plants were made on vegetative development and date of flowering. After six months, 178 plants were selected from 23 seedling progenies and the resulting clones were compared under 22 W/m² and two photoperiods: 8 hrs and 24 hrs per day for a period of nearly six months. In the seedling stage, large differences were observed between progenies, e.g. in percentage generative plants (0–100%), plant length (3–78 cm) and plant fresh weight (0.5–68 g). Effects of light intensity were most pronounced in plant fresh weight (0.2–18 g in 12 W/m² and 0.5–68 g in 22 W/m²). Progenies of D. chinensis were the earliest to flower. Most progenies of crosses between D. superbus and D. barbatus segregated into flowering and non-flowering (rosetting) plants. In the clonal stage, most clones originating from non-flowering seedlings remained vegetative (rosetting), while all clones from flowering seedlings were either in flower or in bud within six months. Average dates of flowering of seedling progenies and of their clones were highly correlated, suggesting that selection on flowering date at the seedling stage is effective. High correlations were also found between the average flowering date of seedling progenies and the number and total weight of flowers harvested per plant in their clones within six months from planting. Overall effects of LD in the clonal stage were much less spectacular than the effects of light intensity in the seedling stage.     

Genetic control of fertility in the oil palm (Elaeis guineensis Jacq.)

Summary A study was conducted on the segregating populations from tenera × tenera, tenera x fertile Pisifera crosses and tenera selfings. Pisifera palms were categorised as (1) fertile Pisifera palms if producing mature ripe bunches regularly under natural conditions, and (2) partially female sterile pisifera palms if producing a few or no bunches in several years.Based on observations on the segregation patterns of the fruit forms (dura, tenera and pisifera) and bunch production patterns, a genetic model was formulated to explain the genetic basis of fertility in the oil palm. Fertility in the oil palm is shown to be controlled by a single gene which is linked to the gene controlling fruit form. Chi-square tests confirmed that the model agreed with the segregating ratios of fruit form and fertility observed.The implications of this finding with regard to oil palm breeding and improvement, and the potential of the fertile pisifera palm for increasing palm oil yields in plantations are discussed.     

Interrelations among vegetative,yield and bunch quality traits in short-tem oil palm progenies

Summary Breeders usually obtain information on a large number of traits in their breeding and selection programmes. However, since some or many of these traits could be related, it is desirable to reduce the number being handled to the barest minimum without sacrificing efficiency. Breeders often use correlations, stepwise multiple regressions and path coefficient analyses to determine the nature of relationships among such characteristics. The objective of this study was to use these statistical methods to determine traits that could be useful in predicting number of bunches (NB), fresh fruit bunch yield (FFB) and mean bunch weight (MBW) for 13 backcross progenies of oil palm (Elaeis sp.) grown in four replications with 12 palms per replication. Data were collected over a period of 3 or 11 years, depending on the trait. Progeny means and individual palm data, averaged across replications and years, were used for each of these analyses.Results showed that correlations involving individual palm data were similar to the progeny mean correlations. Five to seven traits accounted for about 70–90% of the variations in the dependent variables. Traits that showed the highest correlations with the dependent variables always accounted for the largest proportion of the variation (r²) in multiple regression models, but did not always have the highest direct effect (i.e. path coefficients) in path analysis of the dependent trait. Number of leaves per palm had the highest correlation (r=0.729) with, and accounted for 53.2% of the variation in NB. Path analysis however showed that percentage fruit per bunch (% F/B) was the most important determinant of NB. It exerted the highest direct effect of 0.537. The highest correlation with FFB involved number of leaves (r=0.660), which, in multiple regression models also accounted for the largest proportion (44.0%) of the variation in FFB. Path analysis showed that percentage mesocarp per fruit gave the highest direct effect (p=–0.974) for this trait. It was concluded that various combinations of number of leaves per palm, sex-ratio, percentage fruit per bunch and percentage mesocarp per fruit would be effective as indirect selection criteria for NB, FFB and MBW in this set of material.     

Genetic variation for seed dormancy in Cuphea laminuligera and Cuphea lanceolata

Summary Various Cuphea species are adapted to temperate climates and characterized by caprylic, capric, and lauric acid-rich seed oils. These fatty acids are solely commercially available from palm kernel and coconut oils; thus, there is considerable interest in Cuphea as an alternative source of these fatty acids. Cuphea is a genus of undomesticated species characterized by seed dormancy and seed shedding. Our goal is to eliminate these domestication barriers in a few species with agronomic potential. Our objective was to survey existing Cuphea laminuligera and C. lanceolata germplasm for genetic variation for seed dormancy (germination percentage after a certain seed storage period). Recurrent half-sib family selection was practiced in various open-pollinated and synthetic populations. Half-sib family seed were evaluated for germination percentages at 26° C after various seed storage periods. There was significant genetic variation among families in every population. Additive genetic variance, half-sib family-mean heritability, and expected selection response magnitudes depended on the length of the seed storage period within a given population. Estimates of these parameters were significantly greater for longer seed storage periods within a population. Heritability estimates ranged from 0.00 to 0.79. Expected half-sib family selection responses ranged from 0.0 to 23.9%. Our study demonstrated there is substantial genetic variation for seed dormancy in C. laminuligera and C. lanceolata.     

Heritility of field resistance to potato leafroU virus in cultivated potato

Potato progenies in a line x tester mating design and the clonal parents were screened for field resistance to potato leafroll virus (PLRV) to determine the heritability of this trait. Twelve advanced potato clones or varieties were crossed as pistillate parents to two pollen testers. The seedling progenies and clonal parents were exposed to aphid-transmitted potato leafroll virus for two growing seasons. Cumulative infection by potato leafroll virus was determined by post-season sero-logical indexing of foliage grown from sprouted tubers after 2 years of exposure. Narrow-sense heritability was estimated from regression of mid-parent on progeny as h = 0.72. This estimate indicates a high level of useabie genetic variance for PLRV resistance in advanced breeding materials. Although variation in resistance to PLRV appears to be a quantitative trait in susceptible and moderately resistant clones, per-formance of the most resistant parents suggests that genes with major effects may be present. These results are similar to the conclusions of other researchers who found one or two genes controlling the pheno-types of extreme resistance, resistance to infection, or suppression of virus titre.     

Suitability of RAPD analysis for the detection of somaclonal variants in oil palm (Elaeis guineensis Jacq)

Random amplified polymorphic DNA (RAPD) analysis using arbitrary 10-mer oligonucleotide primers was employed in order to investigate the genetic fidelity of somatic embryogenesis-derived regenerants of oil palm (Elaeis guineensis Jacq). Clonal palms bearing the ‘mantled’ phenotype were identified in the field and the ability of RAPD markers to distinguish these variants from palms of the normal type was assessed. Of the 387 arbitrary primers used, 259 (67%) were successfully used to amplify oil palm DNA genomic fragments with consistently reproducible banding. Of these 387 primers, 73 (19%) primers enabled the identification of polymorphism between clones. No intraclonal variability and no differences between mother palms and regenerants could be identified using the total number of markers scored (8900). Twenty-four of these 73 primers were chosen for use in a larger experiment aimed at comparing, first, the mother palm genome with that of its clonal offspring and, second, true-to-type and variant regenerants. Thus, the regeneration protocol based on somatic embryogenesis set up for oil palm clonal propagation does not induce any gross genetic changes. The results obtained revealed however, that the RAPD approach is not suitable for the detection of the ‘mantled’ variant phenotype. The use of RAPD markers for the detection of somaclonal variation in oil palm is discussed.     

Late blight resistance in a diploid full-sib potato family

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

Effects of inbreeding on growth and yield of oil palm

The effects of inbreeding were studied in three oil palm (Elaeis guineensis Jacq.) trials in the Democratic Republic of Congo (Congo). In selfings, marked inbreeding depression was observed for yield of fruit bunches, mean bunch weight and bunch number, but there was little effect on bunch composition. Most vegetative measurements were significantly affected by selfing, but leaf production rate and leaf area ratio were unaffected. Sib-crossing had less depressive effect than selfing, and in some families sib-crosses were superior to outcrosses. Where selection needs to be done within inbred families, our study suggests that leaf area ratio and bunch composition would be useful criteria.     

Random amplified polymorphic DNA variation within and among meadow bromegrass progeny types

Ten meadow bromegrass genotypes tested as half‐sib (polycross, PX; open‐pollinated, OP) and selfed (S₁) progenies were surveyed using random amplified polymorphic DNA. Fourteen primers, which produced 32 markers, were selected to determine the genotypes of 360 individuals from the three progeny tests. Analysis of molecular variance was performed in each progeny test, and genetic distances between genotypes and progeny types were determined. Among genotype genetic variation in half‐sib (PX and OP) progenies was similar. Genetic variation among genotypes for S₁ progenies (30.5%) was about twice that found in the half‐sib progenies. Variation between individual S₁ progenies ranged from 15.7% to 50.1%, while in the half‐sib progenies, the range was 6.9‐24.1%. Based on average distances between progeny types for a given genotype, OP and PX were closer to each other than to the S₁. An analysis of variance of the molecular marker frequency occurrence was performed for 12 plants within each progeny type of each genotype. Marker frequencies, expressed in percentages, ranged from 10.7% to 84.3%. No significant differences were found for genotype and progeny type‐genotype interaction suggesting that all genotypes behave in a similar manner across the different progeny types.     

Increasing biodiversity of irrigated rice in Africa by interspecific crossing of Oryza glaberrima (Steud.) × O. sativa indica (L.)

The African rice Oryza glaberrima, traditionally cultivated since more than 3.500 years, is of poor agronomic performance but resistant/tolerant to various stresses and diseases. The introduction of these characters into O. sativa cultivars is difficult since crossing barriers cause spikelet sterility in F1. Backcrossing can restore fertility and recently facilitated the development of fertile O. glaberrima × O. sativa ssp. japonica hybrid progenies for rain fed systems. With the objective to gain access to African rice germplasm for improvement of irrigated rice, crosses were performed with eighteen O. glaberrima and twenty O. sativa ssp. indica accessions. In total about one hundred F1-hybrid grains were obtained. The F1 plants were all completely sterile and backcrossing (BC) to O. sativa was performed in order to restore spikelet fertility. Monitoring of Tog5681 × IR64 hybrid progenies under field conditions revealed a broad genetic diversity within the BC₁ and BC₂ populations. Some BC₁ and BC₂ progeny plants outperformed the O. sativa parent, indicating that the heterozygocity level and complementary gene action after two backcrosses are still sufficient to positively influence plant vigor. Spikelet fertility of progenies was highly variable, but almost complete fertility was already observed within the BC₁F₂ population. High spikelet fertility was preserved in one out of two analyzed BC₁F₃ families and inmost of the BC₂F₃ families. The ability to restore spikelet fertility within few generations and the potential of the genetic diversity present in interspecific progenies facilitates the development of plant types specifically designed for the African irrigated and lowland environment. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of QTLs mapped in RILs and their test-cross progenies of tropical maize for insect resistance and agronomic traits

Quantitative trait loci (QTL) affecting resistance to south-western corn borer Diatraea grandiosella (SWCB) and sugarcane borer Diatraea saccharalis (SCB) have been identified previously in F_2:3 lines and recombinant inbred lines (RILs) of tropical maize using restriction fragment length polymorphism (RFLP) analyses. Our objective was to determine whether QTLs identified in these generations are also expressed in test crosses (TC) of RILs. A population of 166 TC progenies was developed by crossing RILs from the cross CML131 (susceptible) × CML67 (resistant) with the unrelated, susceptible tester line CML216. Resistance to first-generation SWCB, measured as leaf-feeding damage (LFD) under artificial infestation, and other agronomic traits were evaluated in two environments for the TC progenies and three environments for 183 RILs. The correlation between line per se and TC performance was low for LFD and intermediate for most agronomic traits. Estimates of the genotypic variance and heritabilities were smaller in the TC progenies than in the RILs for all traits. Quantitative trait loci were identified using an RFLP linkage map with 136 loci. For LFD, four QTLs were detected in the TC progenies, of which two were in common with nine QTLs previously mapped in the RILs. Few QTLs for agronomic traits were common to the two types of progeny, because of the low consistency of QTL positions for all traits in RIL and TC progenies, the use of TC progenies should be considered in QTL mapping studies as the first step for marker-assisted selection in hybrid breeding.     

Spectrum and inheritance of resistance to the root-knot nematode Meloidogyne hapla in Rosa multiflora and R. indica

The spectrum and inheritance of resistance to the root‐knot nematode Meloidogyne hapla was studied in the diploid species Rosa multiflora and R. indica. The host suitability of seven rose rootstocks, namely five R. multiflora (K2, K1, Floradale, CE63 and CE65) and two R. indica (CE35 and Maroc) clonal accessions, was evaluated using four geographic isolates of M. hapla. Plants grown under greenhouse conditions were tested at high and durable inoculum pressure of nematodes and rated for nematode infestation five months after inoculation on a 0–5 gall index. Different host suitabilities to M. hapla were demonstrated depending on the nematode isolates: in R. multiflora, the clone K2 had a resistant (R) response to all isolates; the clone K1 ranged from intermediate (I) (isolate ‘Canada’) to resistant (other isolates), Floradale was shown to be intermediate, whereas CE63 and CE65 were moderate to good hosts (H). In R. indica, both rootstocks were good to excellent hosts for the isolate Canada but resistant to all three other isolates, thus expressing an isolate‐specific resistance. A study on the genetics of resistance in R. multiflora to the M. hapla isolate Canada was then conducted using an incomplete diallel cross involving all previous clones except Floradale. A total of 120 hybrid individuals belonging to several progenies representing the cross combinations R × I, R × H, I × H and H × H were evaluated. Individuals of each progeny generally ranged into a monomodal distribution that suggests polygenic inheritance of resistance. In the family Rosaceae, the differences in the resistance genetics to the meiotic species M. hapla and to the mitotic species, M. arenaria, M. incognita and M. javanica are discussed in relation to the reproductive status of the nematodes.     

Resistance to Pseudomonas solanacearum in the potato: I. Effects of sources of resistance and adaptation

Summary F1 hybrid true potato seed progenies with multiple sources of specific resistance to Pseudomonas solanacearum and adaptation were evaluated under tropical greenhouse conditions for resistance to a race 1 isolate of P. solanacearum. Results indicated that genes for adaptation are involved in conferring resistance to bacterial wilt. The effect of a particular resistant parent clone on the resistance level of its progeny depended on the resistance, adaptation or the combination of both characteristics of its mate. A heat tolerant parent gave a higher frequency of resistant offspring in combination with an ascertained source of resistance. Combining ability was an apparent feature of resistance to bacterial wilt and resistance was highest in the majority of the crosses that had a wide genetic background for both resistance and adaptation. The possible genetic nature of the resistance to bacterial wilt is discussed.     

Resistance of Coffea arabica cv. Ruiru 11 tested with different isolates of Colletotrichum kahawae, the causal agent of coffee berry disease

Seven single conidia isolates of Colletotrichum kahawae varying in pathogenicity were used to inoculate hybrid progenies from 66 crosses ofCoffea arabica cv. Ruiru 11. The objective of this study was to investigate the effect of pathogen variation on resistance of the Ruiru 11 cultivar. The main effects of crosses and isolates were significant (p ≤0.05) while their interaction effects were non-significant. Partitioning variance components indicated that the proportion of phenotypic variance for resistance that is due to genetic effects was low. It was concluded that variation for resistance among hybrid progenies of the Ruiru 11 cultivar was probably due to differences in aggressiveness of the pathogen as reflected by the significant main effects of crosses and isolates in combination with other environmental factors which influence disease epidemics. The coffee berry disease pathogen is unlikely to have adapted to the cultivar because of the non-significant crosses × isolates interaction effects. This revised version was published online in August 2006 with corrections to the Cover Date.