Data on germination, growth and morphological changes of oil palm (Elaeis guineensis Jacq.) zygotic embryos during in vitro culturing

Oil palm (Elaeis guineensis Jacq.) from being almost unknown crop a mere three decades ago is now the most consumed and the most traded edible oil in the world. It is a highest yielding crop producing on an average 4 to 6 tons of oil per ha per year. Due to its innumerable uses in the food, oleochemicals and biofuel industries, cultivation of oil palm has expanded enormously in recent years. Since oil palm is a perennial monocotyledonous species with a single growing apex, the plant cannot be multiplied vegetatively and the conventional propagation through seed is limited by dormancy. Thus in vitro germination has become the key method for multiplication of elite oil palm genotypes. Although there are several reports on in vitro germination of oil palm, still there is a lack of an efficient & repeatable method. Hence an attempt is made to standardize the suitable culture media for direct germination from mature oil palm zygotic embryos. The data presented here represents the effect of genotypes, pretreatments and culture media on Mean Germination Time, Speed of Germination Index, Shoot Formation Index and Root Formation Index during in vitro culturing of oil palm zygotic embryos.

Oil palm Zygotic embryo in vitro Genotype Germination index a b s t r a c t Oil palm (Elaeis guineensis Jacq.) from being almost unknown crop a mere three decades ago is now the most consumed and the most traded edible oil in the world. It is a highest yielding crop producing on an average 4 to 6 tons of oil per ha per year. Due to its innumerable uses in the food, oleochemicals and biofuel industries, cultivation of oil palm has expanded enormously in recent years. Since oil palm is a perennial monocotyledonous species with a single growing apex, the plant cannot be multiplied vegetatively and the conventional propagation through seed is limited by dormancy. Thus in vitro germination has become the key method for multiplication of elite oil palm genotypes. Although there are several reports on in vitro germination of oil palm, still there is a lack of an efficient & repeatable method. Hence an attempt is made to standardize the suitable culture media for direct germination from mature oil palm zygotic embryos. The data presented here represents the effect of genotypes, pretreatments and culture media on Mean Germination Time, Speed of Germination Index, Shoot Formation Index and Root Formation Index during in vitro culturing of oil palm zygotic embryos. © 2019 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).

Data
The present data in Table 1 shows the effect of genotype, pretreatment and culture media and their interactions on mean germination time, the speed of germination index, the speed of shoot formation index and the speed of root formation index taken by oil palm ZEs where between genotype and culture media, no significant difference was noticed for the mean germination time taken by ZEs of oil palm. With respect pretreatment, there was a significant effect. The soaked ZEs recorded more mean germination time (15.63d) than unsoaked ZEs (14.54 d). In three way interactions (between genotype, pretreatment and culture media) the mean time taken for germination of oil palm ZEs showed a Specifications Table   Subject area Agricultural Sciences More specific subject area Plant Tissue Culture Type of data Value of the Data -The present data gives details on the effect of treatment combinations on in vitro germination of the oil palm zygotic embryos. -Data provides the genotypic effect on in vitro germination of oil palm zygotic embryos, which will be useful to evaluate and select the advanced breeding material and hybrid seed production. -Data obtained by the factorial experiment allows understanding the effect of each factor on the response variable as well as the effect of interactions between factors on the responsive variable. -The data presented here will be valuable for evaluating the different growth and morphological stages of zygotic embryos in vitro. -The data can be used as a template for the standardization of in vitro culture media for various genotypic specific. Table 1 Effect of genotypes, pretreatments and culture media on mean germination time (MGT), speed of germination index (SGI), speed of shoot formation index (SSI) and speed of root formation index (SRI). The speed of germination index noticed during culturing of oil palm ZEs did not showed any significant difference between genotype and pretreatments while the culture media showed a significant effect on the speed of germination index. It was faster (6.50) in the ZEs cultured in N6 media followed by Y3 media (6.10) whereas, the speed of germination index was slower (4.86) in ½ MS which was on par with MS þ AC (5.23) and MS (5.09). In three way interactions there was a significant difference observed in speed of germination index. In 20 treatment combinations T 5 recorded faster SGI (7.30) which was on par with T 20 , T 4 , T 19 , T 9 , T 16 , T 10 , T 7 , T 2 , T 15 and T 18 whereas the speed of germination index was lowest (4.01) in T 3 which was on par with T 17 , T 7 , T 11 , T 14 , T 1 , T 12 , T 6 , T 13 , T 18 and T 15 . The present data revealed that the growth of ZEs in 35 days in three different media tested. In the present data, swelling, expansion followed by formation of haustorium leading to the emergence of plumule from the shoot apex was shown.
The speed of shoot formation index showed no significant difference between genotype and pretreatments. The interaction effect of genotype with pretreatments, pretreatments with culture media and genotype with culture media showed non-significant effect for the speed of shoot formation index. Similarly the three way interaction effect between genotype, pretreatments and culture media was also showed non-significant.
The speed of root formation index also followed the same trend as of SSI for the effect of genotype, pretreatments, two way interaction effect (genotype with pretreatments, pretreatments with culture media and genotype with culture media) and three way interaction effect (between genotype, pretreatments and culture media).

Treatment details
The experimental design was three factorial treatment combinations of culture media, plant growth regulators and genotypes arranged in a randomized complete block design. The whole set of experiment was repeated twice with 20 embryos per treatment per replication. The material was from Dura mother palm block in ICAR-IIOPR seed garden where the material belongs to elite dura genotypes. The standardized protocol has been followed for in vitro germination of the zygotic embryos irrespective of genotypes. In which mature oil palm open pollinated fresh fruit bunches of four genotypes were harvested and fruitlets were depericarped using a depericarper in the seed production lab of ICAR-IIOPR, kernels obtained were surface sterilized by adding few drops of Tween-20 and then immersing the kernels in fungicide solution of (1% Carbendazim and 1% Mancozeb) and soaked in distilled water for 5 days, for attaining the required moisture content of the zygotic embryo.
Then the kernels were washed repeatedly with Tween-20 solution (10 drops/100ml v/v) for 15 minutes and washed with running tap water. They were then washed by fungicide solution (1% Carbendazim and 1% Mancozeb). They were then soaked in ethanol for 1 minute and then washed with 20% NaOCl sol for 20 minutes. Then kernels were halved and embryos were sterilized with 20% (v/v) NaOCl for 20 minutes and then washed with sterile double distilled water for three times. Three types of Basal Culture medium [2e4] viz., MS [5] N6 [6] & Y3 [7] were supplemented with 30g/L (W/V) Sucrose, and the pH of the medium was adjusted to 5.8 and added 8.0g/L of Agar (Clerigar™ from HIMEDIA) prior to sterilization at 121 C for 20 min. Half MS medium was prepared by using half strength of chemicals which were used in MS medium, while MSþ0.05% AC medium was prepared by adding 500 mgl À1 activated charcoal to the full strength MS medium. MGT ¼ X Dn . X n Where n is the number of zygotic embryos, germinated on day D, and D is the number of days counted from the beginning of germination.

Speed of germination index of oil palm ZEs
This was calculated as described in the Association of Official Seed Analyst (1983) [9] as follow: SGI ¼ Number of germinated zygotic embryos Days of first count þ ::: þ þ À À À þ

Speed of root formation index of oil palm ZEs
The speed of root formation index (SRI) was obtained from Where Rt was number of roots formed per culture tube on day t [10].

Speed of shoot and root formation index (SSRI)
The speed of shoot and root formation index (SSRI) was obtained from Where Ut was number of shoots and roots formed per culture tube on day t [10].

Data analysis
Data were subjected to analysis of variance (ANOVA) and means were compared by F test, at 5% probability, using ICAR-WASP 2.0 programme developed by ICAR-Central Coastal Agricultural Research Institute, Goa, India (http://www.ccari.res.in/wasp2.0/index.php).
The analysis of variance for each character was carried out as indicated below: Anova  AMSS ¼ Mean sum of squares due to genotypes. BMSS ¼ Mean sum of squares due to pretreatments. CMSS ¼ Mean sum of squares due to culture media. ABMSS ¼ Mean sum of squares due to genotype Â pretreatment interaction. ACMSS ¼ Mean sum of squares due to pretreatment Â culture medium interaction. BCMSS ¼ Mean sum of squares due to genotype Â culture medium interaction. ABCMSS ¼ Mean sum of squares due to genotype Â pretreatment Â culture medium interaction. EMSS ¼ Mean sum of squares due to error.