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.     

Relevant factors associated with crown expansion in oil palm (Elaeis guineensis Jacq.)

Summary Trends in crown expansion, the area of the youngest fully expanded leaf (LA) against age were studied in two oil palm progeny trials, and one density x fertilizer experiment, the latter comparing 110, 148, and 186 palms per ha each with four fertilizer levels. LA against age was best fitted by a logistic growth curve with maximum LA (L_m) and the time required to reach 0.95 L_m (t_0.95) as characteristic parameters. Progenies significantly differed in L_m and t_0.95. Increasing planting density significantly decreased L_m and t_0.95, while fertilizers increased L_m and t_0.95 only at the lowest density. Population means of the experiments markedly differed in L_m and t_0.95 values. Based on the, so called, Leaf Expansion Ratio (ER), being the ratio of LA at maximum expansion rate and LA at its final size, individual palms were selected for a rapid increase in LA, but a relatively low final size. The first characteristic means selection for rapid ground coverage, which resulted in palms with a higher Total Dry Matter Production (TDM) prior to canopy closure. The second characteristic appeared to lead to selection for high Bunch Index (the proportion of TDM used for fruit bunch production), indicating that L_m is a measure for the relative sink strength of leaves for assimilates. Selection for high ER values appeared feasible and this would increase yield during the economic life of a planting. The practical aspects of using ER values as a new selection criterion in oil palm breeding were discussed.     

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.     

Factors associated with occurrence of crown disease in oil palm (Elaeis guineensis Jacq.) and its effect on growth and yield

Summary Crown disease was investigated in oil palm families derived from four sources of (Deli) dura female and three sources of pisifera male parents. These families were planted both at Bah Lias (after rubber) and Gunung Melayu (after oil palm) in North Sumatra.We observed the first symptoms on emerging leaves at 8 months after planting; severity reached a peak at 12 months and diminished gradually until virtually no new leaves were affected in palms older than 35 months. At Gunung Melayu crown disease, in terms of severity score on newly emerged leaves and percentage affected palms, was about double that at Bah Lias. At both locations it was highest in material exclusively bred in Indonesia. In this material crown disease significantly retarded vegetative growth, and reduced cumulative yield of oil for the first 6 years of production by about 4.5% with the highest loss in the first year.The relation between crown disease and nutritional status was inconsistent, but a crop rotation effect on crown disease merits further research.The contribution of the dura parents to crown disease was more evident than that of the pisifera. Screening of genotypes appears to be the most effective method of control of crown disease.     

Estimates of within family genetic variability for clonal selection in oil palm

Within family genetic and environmental variabilities in oil palm dura (D) ×pisifera (P) hybrid progenies were estimated from a D × P progeny test trial, a clonal trial and a clonal cum D × P progeny test trial and with the objective of examining the efficiency of selecting source palms (ortets) within family for clonal propagation. The clones were derived from seedling embryos or seedlings that were progeny reproductions of families proven in the first trial. The progenies in the second trial represented the source families of two sets of clones planted in the same trial. Estimates were obtained from: between and within family variance components; between and within clone variance components; and difference between pooled within family variance and pooled within clone variance. Estimates were generally similar with the different methods used. Within family genetic variabilities were generally low in progenies derived from more inbred parents especially in bunch and oil yields. In progenies from more outbred or variable parents, within family genetic variabilities were relatively higher particularly for oil to bunch and palm height; nevertheless environmental variabilities predominated. The low efficiency of within family palm or ortet selection for clone production and the need for repeated clonal tests over time and space to identify outstanding clones are stressed and the implications to commercial clonal propagation of oil palm discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

The physiological basis for genetic improvement of oil palm in Malaysia

Summary Yield of Deli dura oil palms after four generations of selection was 60% greater than that of the unselected base population. Total above-ground dry matter production was increased by selection, apparently through better utilisation of solar radiation. The dry matter requirement for vegetative growth was unchanged, so a greater surplus remained for fruit production in the selected palms. Crossing the dura and pisifera to give the thin-shelled tenera fruit type improved partitioning of dry matter within the fruit, giving a 30% increase in oil yield at the expense of shell, without changing total dry matter production.     

Candidate traits for index selection in choice of oil palm ortets for clonal propagation

Summary The objective of the study was to examine the usefulness of: principal component scores (PC), factor analysis cum stepwise regression identified traits (FASR) and selected traits based on their higher heritabilities and genetic correlations to the objective traits (HGC); as selection traits in a desired gains selection index (Yamada et al., 1975) to improve objective traits (oil yield, kernel oil yield, height increment, bunch index and leaf area ratio) as compared to those based on all the observed traits (AO); in selecting oil palm ortets for cloning.Based on the required selection intensities (i^*) to achieve the desired gains AO indices having smaller i^*'s were most efficient followed by PC, HGC and FASR indices. Expected selection response (1/i^*), however, is expected to increase with additional selection traits. As such HGC (bunch number, kernel to fruit and mesocarp to fruit) and FASR (mesocarp to fruit, fresh fruit bunch yield, fruit to bunch and average bunch weight) indices would be useful as they achieved expected selection responses close to AO indices with a small number of traits and would also minimise the contribution of highly correlated traits to sampling errors. The results also suggested considering selection indices for only two objective traits-oid yield and kernel oil yield-instead of all five objective traits in which case screening of impracticably large populations is needed to obtain desired genetic gains.     

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.     

Optimal set of microsatellite markers required to detect illegitimate progenies in selected oil palm (Elaeis guineensis Jacq.) breeding crosses

Oil palm is continually being improved via controlled crossing of selected palms to ensure sustainable yields and productivity. As such, correct parental assignment is important as the presence of illegitimates will compromise the progress of improvement. In the present study, we determined the optimal number of microsatellite (SSR) markers for detection of illegitimates in selected oil palm crosses with high confidence. Determining the optimal number of markers to assign parentage will ensure that the DNA fingerprinting will be cost effective for routine use as a quality control tool in oil palm improvement programs. Here, we evaluated a wide range of crosses that included a cross derived from wild germplasm palm. The results revealed that markers with high PIC are informative and detect most of the alleles present in a cross, including those exhibited by the illegitimates. A larger number of optimum sets of markers are needed to detect all illegitimates for crosses with higher levels of genetic diversity. The optimal number of polymorphic SSR markers determined in the present study can ensure that appropriate quality control is implemented for oil palm improvement programs.     

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.     

Prediction of precocity in the oil palm (Elaeis guineensis Jacq.)

Summary Precocity in the oil palm (Elaeis guineensis Jacq.) is defined, for the purpose of this study, as the percentage of palms bearing female or hermaphrodite inflorescences 36 months after germination. A method of calculating breeding values for precocity is described and it is shown that the character is predictable. An upper limit for heritability (h²) of 0.68 and a correlation between observed and predicted values of r=+0.77 (significant at P=0.01) have been calculated from the available data. The available information suggests that precocity could easily be adjusted to the desired level by breeding and selection.     

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.     

Epistasis for crown disease in the oil palm (Elaeis guineensis Jacq.)

Summary The presence of crown disease (cc) in the oil palm can be masked by an intermediate gene (I _c). Presence of the gene inI _c i _c-condition results in incomplete genetic penetrance in thecc-genotypes. No penetrance is observed in theccI _c I _c-palms. The existance of theI _c-gene complicates selection work as a testcross with acci _c i _c-genotype is required to identify the genotype of the selections. This procedure requires 3 years.     

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.     

Parent selection for yield and bunch index in the oil palm in West New Britain

Summary Selection criteria of dura female parents and pisifera male parents were investigated by employing a step-wise multiple regression procedure. Independent parental variables entered in the regression equation were (1) yield (Y) and (2) bunch index (BI), i.e. the proportion of total dry matter used for fruit bunches, of the female parents. As secondary characters of both parents were included: (3) leaf-Mg level (LMG), (4) leaf area ratio (LAR), i.e. the ratio of new leaf area produced to new dry matter used for vegetative growth, and (5) sex ratio (SR), i.e. the ratio of female to total inflorescences. The joint contribution of LMG in both parents accounted for 80% of the variance in Y of the offspring. The amount of the total variance in BI of the offspring was substantially explained, in decreasing order, by LMG of the pisifera parents, and Y and LAR of the dura parents. The first two variables explained 70% of the variation in offspring BI. SR and BI appeared to be not significant for explaining Y as well as BI of the offspring. A practical implication is that for pisifera testing programs, pisifera can be efficiently screened on the exclusive basis of LMG. Dura tester parents should be selected for high, and little variable, values of LMG, Y and LAR.     

Prospects of breeding for blast disease resistance in the oil palm (Elaeis guineensis Jacq.)

Summary Breeding for nursery blast resistance in the oil palm can reduce blast from around 50% to 1–6% loss, when a parent is carrier of dominant resistant gene(s). At such low blast levels, most of the costly agronomic methods to reduce blast incidence, need not be used.Plant material originating from the arid regions in Nigeria is more blast susceptible than that from the rain forest areas.     

Tissue culture of the oil palm (Elaeis guineensis Jacq.) as a tool for its vegetative propagation

Summary Coconut and oil palms can be vegetatively propagated by tissue culture (in vitro culture). Experiments with the oil palm had some promising results, viz the formation of a juvenile shoot and the initiation of roots in explants.     

Analysis of growth of the oil palm (Elaeis guineensis Jacq.) I. Estimation of growth parameters and application in breeding

Summary Non-destructive methods for estimation of Crop Growth Rate and Harvest Index of the oil plam (Elaeis guineensisJacq.) are described. These methods were applied in a selection experiment, and the importance of considering Harvest Index, Leaf Area Index and planting density in selecting for increased yields is discussed.     

Disc polyacrylamide gel electrophoresis of pollen proteins in the oil palm (Elaeis)

Summary A preliminary screening of proteins and isozymes in the oil palm was investigated with a view to using the data in discriminating oil palm fruit forms. Protein and enzyme staining was carried out using pollen tissue. Repeatable bands of proteins which showed reproducable variation in banding patterns were obtained. Low percentage similarities between the groups compared for protein banding patterns were obtained. A single enzyme esterase extracted from pollen tissue exhibited repeatable variation between species only. It was intended to obtain information that would supplement morphological markers through electrophoretic data in the identification of different fruit forms of the oil palm.