Each oil palm tree was measured in terms of agronomic and yield traits. For the agronomic traits, the plant height (PH), stem diameter (SD), leaf length (LL), leaf width (LW), leaf number (LN), rachis length (RL), petiole diameter (PD), and petiole width (PW) were measured in the field, while the leaf area (LA) and leaf dry weight (LDW) were estimated by the calculation methods reported by Corley et al. (1971). For the yield traits, the bunch number (BN) was counted in the field. The selected bunches were harvested and transferred to the laboratory for analysis. The fresh fruit bunches (FFB) were weighed, and their fruits separated to analyze the oil yield (OY), average fruit weight (AFW), average kernel weight (AKW), fruits per bunch (F/B), kernels per bunch (K/B), shell per fruit (S/F), kernels per fruit (K/F), oil per fruit (O/F), and oil per bunch (O/B), by the method described by Mandal (2008) and Corley (2018). The experiment was conducted between January 2019 and June 2020.

The variables of agronomic and yield traits were analyzed, with the significant variables calculated as the principal component analysis. The variables were analysed by the R software for data analysis (version 3.6.1) with the agricolae, devtool, and factoextra packages (de Mendiburu, 2019; Wickham et al., 2020; Kassambara and Mundt, 2020).

The results of the analysis of variance (ANOVA) of the agronomic traits of hybrid tenera oil palms are illustrated in Table 1 and the boxplot on the agronomic traits of six tenera oil palm progenies is presented in Figure 1. Most agronomic traits (LL, LW, LN, LA, RL, LDW, PD, and PW) were significantly different among the various oil palm progenies at p < 0.05 or 0.01. Only PH and PD were not significantly different among the various oil palm cultivars. The highest coefficient of variation (CV) was obtained from LW (35.84 %) and LA (35.84 %), and the lowest CV was obtained from RL (2.46 %).

Table 1

Note: ns: non-significant difference, ^{*, **}: significant difference at p < 0.05 and 0.01, respectively. MSTr: mean square treatment, MSE: mean square error, CV: coefficient of variation, PH: plant height, SD: stem diameter, LL: leaf length, LW: leaf width, LN: leaf number, LA: leaf area, RL: rachis length, LDW: leaf dry weight, PD: petiole diameter, PW: petiole width.

Figure 1

The results of the analysis of variance of the yield traits of hybrid tenera oil palms are illustrated in Table 2 and the boxplot on the yield traits of six tenera oil palm progenies is presented in Figure 2. BN, OY, AFW, AKW, K/F, O/F, O/B, and K/B were significantly different among the oil palm progenies at p < 0.05 or 0.01, while FFB, F/B, and S/F were not significantly different among the oil palm cultivars. The highest CV was obtained from AFW (43.40 %), and the lowest CV was obtained from F/B (3.90 %). The significantly different agronomic and yield traits were calculated as principal component analysis to classify their groups and to find relationships between certain oil palm cultivars and their agronomic, and yield traits.

Table 2

Note: ns: non-significant difference, ^{*, **}: significant difference at p < 0.05 and 0.01, respectively. MSTr: mean square treatment, MSE: mean square error, CV: coefficient of variation, FFB: fresh fruit bunch, BN: bunch number, OY: oil yield, AFW: average fruit weight, AKW: average kernel weight, F/B: fruits per bunch, K/B: kernels per bunch, S/F: shell per fruit, K/F: kernels per fruit, O/F: oil per fruit, and O/B: oil per bunch.

Figure 2

The details of eight components of agronomic traits are presented in Table 3. The eigenvalues of PC1 to PC3 are 4.70, 1.33, and 1.12, respectively, and their variances are 58.78 %, 16.61 %, and 13.99 %, respectively, representing 89.38 % of the components.

Table 3

The biplot between PC1 and PC2 of six tenera oil palm progenies and their agronomic traits is shown in Figure 3. This biplot illustrates two groups of oil palm samples according to their respective dominant agronomic traits. The first group (UN-1, UN-2, UN-3, PSU-1, PSU-2, and PSU-3) dominated in PD, LDW, LL, RL, PW, and LA, while the second group (GT-1 and ST-2) dominated in LN and LW.

Figure 3

The details of eight components of yield traits are presented in Table 4. The eigenvalues of PC1 to PC3 were 3.34, 1.87, and 1.38, respectively, and their variances were 41.75 %, 23.21 %, and 17.30 %, respectively, representing 82.37 % of the components. The biplot between PC1 and PC2 of six tenera oil palm progenies and their yield traits is shown in Figure 4. This biplot illustrates two groups of oil palm samples according to their respective dominant yield traits. The first group (PSU-1, PSU-2, YG-2, YG-3, NP-2, and ST-1) dominated in BN, K/F, K/B, and AKW, while the second group (PSU-3, UP-1, UP-3, and UN-1) dominated in O/F, O/B, AFW, and OY.

Table 4

Figure 4