Yields of soybean cultivars with different crop rotation models
The results of
Taryono et al., (2022) showed an interaction between soybean cultivars and crop rotation models in the agroforestry system. The best linear unbiased prediction (EBLUP) revealed that the Dering I cultivar had the highest yields in F-S and R-S by 1.267 and 1.375 tons ha
-1, respectively, whereas the Grobogan cultivar in M-S and S-S obtained 1.200 and 1.349 tons ha
-1, respectively (Fig 1). This result is due to the interaction phenomenon between genotype and environment and each cultivar is adaptable and stable in different environments
(Kasno and Trustinah, 2015).
Morpho-physiological and biochemical fingerprints of soybean cultivars and crop rotation models
Heatmap clusters are generally used to assess proximity and classify soybean cultivars based on morpho-physiological and biochemical variables. The heatmap cluster contains two main clusters based on the soybean cultivars. The first cluster consisted of G3, G15, G4, G14, G5 and G8, whereas the second cluster consisted of G9, G13, G10, G1, G2, G6, G11, G7 and G12 (Fig 2). Most of the genotypes belonging to the same cluster are also grouped in the cluster heatmap.
Cantelli et al., (2016) reported similar results for soybean (
Glycine max). Soybean cultivar grouping with each fingerprint identification can be continuously visualized using PCA-biplot.
The PCA-biplot showed morpho-physiological and biochemical differences that serve as fingerprints for each soybean cultivar and crop rotation model. The PCA-biplot classified soybean cultivars into four major groups based on morpho-physiological and biochemical fingerprints. The first group (quadrant I) was composed of G2, G4, G14 and G15, with H
2O
2 and O
2- fingerprints. The second group (quadrant II) was composed of G6, G10, G11 and G12, with LTR, SC, CO
2, TC, PC, KC and NP fingerprints. The third group (quadrant III) included G1, G5 and G8, with RL fingerprint, whereas the fourth group (quadrant IV) was G7, G9 and G13, with WS, RDW, STW, RSA, POD, SY, NC, SOD, LA and LDW fingerprints (Fig 3a).
Based on the PCA-biplot of crop rotation models, three groups were identified. The first group (quadrant I) included S-S, with O
2- fingerprint. The second group (quadrant III) was composed of F-S and M-S, with RL fingerprint, whereas the third group (quadrant IV) comprised R-S, with NRA and TC fingerprints (Fig 3b).
PCA was used to simplify the relationship among the correlated variables. This analysis generates new variables, also known as principal components, which include important information from the original data set
(Lever et al., 2017). Each of the main components can be interpreted in more detail to identify the variables that have the most significant contribution to being fingerprints for each soybean cultivar and crop rotation model.
Screening of morpho-physiological and biochemical fingerprints that affect soybean yield
The ANOVA results showed that all morpho-physiological and biochemical variables showed significant differences (
P< 0.001), with a coefficient of variance of <40%. Therefore, all variables could be continuously analyzed using factor analysis
(Alam et al., 2019 andrews et al., 2002, Suryanto et al., 2020, Suryanto et al., 2020). Factor analysis indicated two sets of factors (Table 1). Factor 1 consisted of RSA, RL, RDW, STW, LDW, LA, NP, CO
2, LPR, NC, PC, KC, NRA, SOD and H
2O
2. Factor 2 consisted of LA, WS, CO
2, SC, LTR, LPR, TC, POD, O2- and H
2O
2. Variables with a value and communality of >0.500 can be continued with SEM-PLS and standardized stepwise regression. Factor analysis is a multivariate technique used for high data. Varimax rotation improves the ability to interpret uncorrelated components
(Govaerts et al., 2006, Yao et al., 2013).
In general, the results of SEM-PLS showed that the variables that directly affect soybean yield were physiological (-0.487**) and morphological (1.211**, Fig 4). Based on standardized stepwise regression, the variables that affected soybean yield included RSA, SOD and NC. The standard stepwise regression equation was calculated as follows:
Y= 0.060** + 0.005 RSA** + 0.051 SOD** + 0.050 NC** (R2= 0.999**).