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.     

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.     

Development of elite families in oil palm (Elaeis guineensis Jacq.)

Summary Data from 29 dura female parents, 14 pisifera male parents and their offspring were assembled to obtain quantitative genetic information on optimizing selection of elite families. Phenotypic values of the offspring were partitioned into general combining ability (GCA) of the parents and their specific combining ability (SCA). Parental GCA-values for leaf-Mg content (LMG), height increment (HT), leaf area ratio (LAR), leaf area (LA), frond production (FPR), vegetative dry matter production (VDM), the rate of increase in leaf area against age (k) and maximum leaf area (L_m) were entered in a multiple regression analysis as predictors of oil-and-kernel yield and Harvest Index (HI), i.e. the proportion of dry matter used for oil and kernel production, of the offspring. The analysis revealed that both selection objectives are positively influenced by indirect selection for high LAR and LMG, and for reduced VDM with FPR as main component. But palms with high values for LA, L_m and HT should not be considered to avoid selecting palms partly for their ability to compete with neighbouring palms for light. The contribution of SCA was relatively small for most of the characters studied, except HT, FPR and HI. From the standard deviations for GCA and SCA of the dura and pisifera parents, i.e. _GCA and _SCA, it was extrapolated that selection can potentially enhance bunch yield (by 24%), oil-to-bunch ratio (19%), kernel-to-bunch ratio (29%), oil-and-kernel yield (31%) and HI (56%) above the mean phenotypic value obtained for the offspring of the present investigation. Heritabilities, calculated as the square of the correlation of the GCA-and phenotypic values of the female parents, were low for bunch yield, oil-and-kernel yield and HI, but moderate for LAR, LMG and VDM; levels were high for oil and kernel extraction rate. These outcomes were confirmed by the correlations between values of the female parent and their offspring. Among the unbalanced incomplete mating designs studied, the rectangular lattice and the alpha design are most suitable to compare GCA-values of pairs of parents. A breeding strategy adapting the recently introduced practical possibility of clonal reproduction is discussed.     

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.     

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.     

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.     

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.     

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.     

Penetrance of creeping-rootedness in clonal progenies of lucerne and observations on underground morphology of plants differing for this character

Elaeis oleifera or ‘caiaué’, a close relative of oil palm (E. guineensis), has some agronomic traits of great interest for the oil palm genetic breeding such as slow growth, oil quality (mostly unsaturated) and disease resistance. An analysis of a Brazilian oil palm germplasm collection was carried out using RAPD (Random Amplified Polymorphic DNA) markers with the objective of understanding the genetic variation of ‘caiaué’ accessions collected in the Amazon Forest in the last two decades. A sample of 175 accessions obtained along the Amazon River Basin was analyzed and compared to 17 accessions of oil palm from Africa. Ninety-six RAPD markers were used in the analysis, of which fourteen were shown to be specific to oil palm, while twelve were specific to ‘caiaué’. Results showed that the Brazilian ‘caiaué’ accessions studied have moderate levels of genetic diversity as compared to oil palm accessions. The data allowed the establishment of similarity groups for ‘caiaué’ accessions, which is useful for selecting parental plants for population breeding. Cluster analysis showed that, in general, genetic similarities are not correlated to geographical distances, but consistent with geographical dispersal along the Amazon River network. AMOVA showed that most of the genetic variation is found within populations, as expected for anallogamous and long-lived perennial species. The study provides important information to define strategies for future collection expeditions, for germplasm conservation and for the use of E. oleifera in breeding programs. This revised version was published online in August 2006 with corrections to the Cover Date.     

低温胁迫对油棕幼苗光合作用及叶绿素荧光特性的影响

在30 μmol/(m2.s)的弱光条件下,以25℃、10℃、7℃、4℃、1℃各处理油棕幼苗3天,测定了油棕幼苗叶片光合参数及叶绿素荧光参数的变化。结果表明：温度由 25℃降至4℃,净光合速率（Pn）显著下降的同时,气孔导度(Gs)、蒸腾速率(Tr)、胞间CO2浓度（Ci）也显著下降,但气孔限制值(Ls)和水分利用效率(WUE)却显著增加,说明光合作用的下降主要由气孔因素引起;之后随温度下降至1 ℃,净光合速率、气孔导度、蒸腾速率、水分利用效率、气孔限制值均出现显著下降,但胞间CO2浓度却显著上升,说明光合作用的下降主要由非气孔因素引起。叶绿素荧光参数显示,随温度下降,初始荧光(Fo)不断上升,PSⅡ最大光化学效率（Fv/Fm）、光化学猝灭系数(qP)、非光化学猝灭系数（qN）不断下降,其中以4 ℃以下的低温胁迫,这些参数的变化最为显著。表明严重低温对油棕幼苗产生了显著的光抑制,过剩的激发能不能通过热耗散途径散失,大量积累于PSⅡ反应中心,使光合机构遭受了较大程度的破坏,最终导致油棕幼苗光合能力的急剧降低。     

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.     

Estimates of genetic variability and heritability for vegetative and reproductive characters of kiwifruit (Actinidia deliciosa)

The results of this study indicated a great deal of genetic variation in a number of characters of horticultural interest in kiwifruit seedling populations, and therefore, a potential to improve kiwifruit by vine selection. High narrow sense heritability was shown for pedicel length(0.62) and flowering duration (0.50) in male vines, and pedicel length (0.67),floral shoot percentage (0.54), leaf length-width ratio (0.64), fruit elongation (0.64) and fruit weight (0.52) in female vines. For these traits, selection of superior seedlings should lead to rapid genetic improvement in these populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phenotypic recurrent selection for oil content in East Indian lemongrass

Summary Phenotypic recurrent selection was carried out for oil content in East Indian lemongrass, Cymbopogon flexuosus (Steud) Wats. In each cycle, the top 5% of plants for oil content were selected. Their ramets were used for the establishment of replicated polycross blocks in isolation. Realized gains from selection were determined by evaluating the populations and the best clones from each population in separate two-year replicated trials. Three cycles of recurrent selection increased oil content by 32% per cycle at the population level. Realized gains from selection were slightly smaller or similar to predicted gains. Mean realized heritability for oil content was 0.56. At the clonal level, the best C₁ and the best C₂ clones had, respectively, a 22% and 73% higher oil content than the best clone from the base population (C₀). Selection for oil content did not adversely affect leaf yield, dry matter content or citral content in oil. Probable reasons for the high response to selection are mentioned.     

Recurrent selection for yield in Glycine max using genetic male-sterility

Summary Recurrent selection, using genetic male sterility to facilitate intermating in Glycine max, was evaluated when selecting among individual space-planted S₀ soybean plants for three yield-related traits: 1) seed yield per se (YLD), 2) apparent harvest index (AHI), and 3) a selection index in which seed yield was regressed on maturity (REG). The original intermating population was a combination of the cultivar Century and two F₂ populations segregating for male sterility. The selection intensity through three cycles of selection was 20%. The YLD population increased in mean yield by 2.8±2.2 g plant^-1 cycle^-1 buf shifted significantly toward late maturity by 3.9±0.6 days cycle^-1. The AHI population decreased in yield by 4.4±2.6 g cycle^-1 while maturity shifted slightly earlier; there was very little change in AHI. The REG population increased in yield by 5.7±2.4 g plant^-1 cycle^-1 while shifting toward later maturity by only 0.8±0.5 day cycle^-1. We concluded that selection among S₀ plants in these populations, using the selection index of yield regressed on maturity, was affective in increasing single plant yields without causing a significant shift in maturity. Selecting for yield per se caused an unacceptable shift toward late maturity and selection for AHI was ineffective for increasing yield or AHI.     

Assessment of genetic variability of olive varieties by microsatellite and AFLP markers

Fourteen developed microsatellite markers were characterized for their use in genotyping and diversity studies of olive varieties. After optimisation of microsatellite assay and allele sizing, ninety-six alleles were found in nineteen varieties, with an average of 6.8 alleles per locus. The characteristics of the microsatellite markers were used to identify markers that can be reliably applied for variety genotyping. Such features were the generation of complex banding patterns supported by underlying allele sequences, `short allele dominance', an unstable repeat structure and a low number of alleles. AFLP analysis was performed on the same set of olive varieties using eight primer pair combinations. The genetic relationships among nineteen olive varieties were compared on the basis of microsatellite and AFLP polymorphisms. Genetic distances between all pairwise combinations of the varieties were calculated using Jaccard's coefficient of similarity and dendrograms were constructed by the UPGMA method. The results of clustering analysis with both molecular systems showed the common genetic background of Tuscan varieties, and genetic divergence within Slovene olive germplasm. Slovenian varieties ‘Buga’, ‘Štorta’ and ‘Samo’ might represent regionally selected olives, while ‘Zelenjak’ and ‘Črnica’ are probably derived from the Central Italian region. The predominant local ‘Istrska belica’ was introduced to Slovenia independently from the other regional varieties and showed the lowest genetic similarity with the other regional varieties. This revised version was published online in August 2006 with corrections to the Cover Date.     

Family selection in plant breeding

Summary Plant breeding programmes rarely take explicit practical account of the two sources of genetic variance, namely between and within full-sib families, even though existence of these two sources of variation has long been recognised. This paper refers to inbred and clonal crops, not to outbred, seed-propagated species. Theory suggests that the two variances should be of similar size, sometimes very similar. Good comparisons have never been made because variance within families is laborious to estimate. It is proposed that sets of families be assayed as to means in formal trials and only the best few, judged against standards as having potential for superior segregates, should be exploited thoroughly. The calculation as to approximate equality of genetic variances between and within families is important. The vast majority of families should probably be discarded without further ado, and at considerable economy. Sensible decision-making requires an economic component in order to exploit the trade-off between the cost of the initial trial and families discarded without further cost. The object of this paper is a critical review of practical principles, not a general review of a large and diffuse literature.     

Effects of plot size and selection intensity on efficiency of selection in the first clonal generation of potato

To improve efficiency of selection in first year clones, investigations were carried out on the use of two-plant plots instead of one-plant ones. Extended plot size did reduce the environmental variance of characters connected with tuber yield, but had only a slightly positive effect on the selection result, as was concluded from a comparison between the first and the second clonal generation. Only lowering selection pressure in the first year clones seems to be a solution for optimizing selection efficiency, as could be concluded by comparing simulated selection percentages of about 5%, 20% and 50%.Owing to genotype × harvest time-interaction for the majority of traits important to either seed or ware potatoes, assessments at both harvest times are necessary for proper evaluation.     

Half-sib family selection for yield of digestible organic matter in kale (Brassica oleraceal L.)

Summary Four generations of half-sib family selection for yield of digestible organic matter have been completed, from an initial population which included marrow-stem kales, thousand-head kales, curled kales, Brussels sprouts and cabbages. Relative to the mean yields of two control cultivars the population means were: 106% (gen₀), 122% (gen₁), 128% (gen₂), 111% (gen₃) and 103% (gen₄). These initially encouraging and then disappointing results are discussed along with suggestions for improvements in the population improvement scheme, particularly with respect to the assessment of genotype-environment interactions.