Yield and growth performance of potential sugarcane (Saccharum officinarum L.) hybrid clones

Sugarcane development in Indonesia has been done primarily on dry lands. Therefore developing varieties more suitable to dry-agro-ecological conditions is being attempted as it is easily applicable and economically feasible. This study aimed at assessing the yield of 18 potential sugarcane clones, resulting from crosses with parents which have high productivity. This study used Cenning variety as a control. The research was conducted at Karangploso experimental garden Malang, from October 2019 to September 2020. The research used a randomized block design with four replications. The experimental plot was designed with five rows (5 m length) and rows distance at 110 cm. The evaluation was carried out on the growth and production component. The results showed that genotypes affected the performances of growth and yield characters. All of the clones showed good performances in growth. Clones MLG 18/21/14, MLG 18/42/15 and MLG 18/41/5 had productivity 21.08-34.86 (t/ha) and sucrose content 21.79-38.44 (%) higher than control. The three clones select as promising clones for sugarcane development in dry-agro-ecological land with higher productivity yields.


Introduction
Sugarcane is the primary commodity producing sugar in Indonesia. This plant is developed on dry land with very varied levels of land fertility so that the crystal yield obtained is still low, which is around 5.52 t ha -1 [1]. Efforts to increase sugar yield have been carried out by constructing new superior clones of dry land conventionally and unconventionally. Indonesian Sweetener and Fiber Crops Research Institute (ISFCRI) has been constructing conventionally, namely intra and interspecific crosses, since 2013. This cross included proven parents with high productivity and sugar yield and drought resistance donor parents from other species (Saccharum spontaneum and Erianthus sp.) [2]. The assembly of superior clones has produced new clones with a potential sugar yield of 8.52-10.35 t ha -1 .
Although new superior clones with high potential have been obtained, the sugar yield obtained is still low, so it is necessary to carry out the assembly of superior clones on an ongoing basis until the desired sugar yield results are obtained. Moreover, several elders of potential dry-resistant clones have been obtained from exchanges with institutions/individuals such as HCW 438, HCW 40, HCW 440, and GMP 4 [3]. In 2018 the assembly of superior clones was carried out through crosses between superior sugarcane clones by producing 18 new superior clones. These clones need to know the 2 potential results to be used as material for further testing. Cenning variety is an early ripe variety, so it's used as a control in this study to find early ripe sugarcane. In Indonesia, especially in East Java, late-ripe sugarcane varieties more developed, so to maintain the stability of the variety, we assemble early-ripe varieties. Therefore, a study was conducted to observe the yield of potential droughtresistant sugarcane clones on dry agro-ecological land. It is hoped that from this research can be obtained clones of sugarcane expect to support the development of sugarcane inland with dry agroecological conditions.

Materials and methods
The research was carried out at Karangploso experimental garden Malang, from October 2019-September 2020. The research material consisted of single bud planting from 18 potential clones, Cenning variety for control (Table 1), inorganic fertilizer, organic fertilizer, and other chemicals. The experiment tools include meters, scales, calipers, refractometers, and field equipment.
Crossed clones and control variety arrange in a Randomized Block Design with four replications. The experimental plot design with five rows (five m length) and rows distance at 110 cm. Plant maintenance includes replanting, fertilizing, weeding, repairing channels, irrigation, adherence to leaf sheath, and disease control. Replanting is done two weeks after planting until the plant population becomes normal. Fertilization is done twice at four weeks and three months after planting. Fertilization is carried out in a base area of the plant stem about 10 cm. The dose of fertilizer was 600 kg Phonska and 500 kg ZA. Phonska fertilizer is given at the first fertilization, and ZA fertilizer is provided twice. Pilling was done after fertilization and the plants were 5-6 months old. Irrigation is carried out when the crop appears to have temporarily withered. The control of pests and diseases is carried out according to the level of attack in the field. Adherence to leaf sheath is carried out according to the planting conditions by manually removing the dry leaves. Harvesting is done when the plant is 12 months after planting by cutting the base a stem. Stems were collected according to the plot number and weighed to determine the weight of the stems per plot.
Observations were made before and after harvest. The number of stems counted per row before harvest has a stem length of more than 150 cm and stem diameter more than 2.0 cm in all the branches. The number of stems per meter of the row is calculated by the formula = all stems / the length of the row.
Observations of stem length, diameter, and weight were carried out at harvest. The stems were harvested in 10 stems per plot as sample plants. Each sample plant was observed for its length and diameter. The diameter of the stem was honored at the center of the stem. Stem weight was monitored by weighing all sample plants. The sucrose content is measured from the sample plants that have been squeezed. The sap produced was measured by the weight of juice, brix value, and pol. The squeezed factor (SF) is calculated by the formula: SF = weight of juice / weight of stem The value of juice (VJ) is calculated by the formula: VJ = 0.4 x (brixpol) Sucrose content is calculated by the formula: sucrose content (%) = SF x VJ The cane productivity and the sugar yield is calculated by the formula cane productivity (t ha -1 ) = 8,100 x (stem weight per plot) / (length of row) sugar yield (t ha -1 ) = productivity x sucrose content

Statistical analysis:
The data obtained were analyzed for variance and continued with Duncan Multiple Range Test (DMRT) at α 5% level using MSTAT software version 4.00/EM.

Results and discussion
Sugarcane growth includes stem length and diameter, stem weight, and the number of stems per meter line on the first plant (PC). Performance parameters of growth and yield of sugarcane and production components of 19 sugarcane clones under dry agro-ecological conditions are presented in Table 2 and 3. Observations showed that sugarcane growth and yield varied among the clones. This indicates that the response of sugarcane plants is strongly influenced by genetic factors, in this case, the clones used. [4] also showed the same thing for stem length characters, [5,6] on stem diameter characters [6] on the character of the number, and length of segments [7,8] on the character of stem weight. Sugarcane stem diameter is influenced by plant genetics and the growing environment [9]. Under homogeneous growing environmental conditions, stem diameter is influenced by plant genetics [10].  4 18/52/2 clones had no different stem lengths and the other clones produced shorter stem lengths than the comparison clones. The results of [11] research show that in the same treatment of phosphorus fertilizers the difference in stem length obtained is caused by differences in the sugarcane clones used.
Mathematically, the weight of the rod consists of the volume and density of the rod. The thickness of the rods is assumed to be no different so that the importance of the rods is determined by the volume of the rod. The volume of the rod is composed of the cross-sectional area and the length of the rod, where the cross-sectional area of the rod can be represented by the diameter of the rod so that the weight of the rod can be determined by the diameter and length of the rod. Multiple linear regression analysis of rod weight on diameter and length of rods resulted in an effect value of 79.3%. Clones/varieties with larger stem diameters and longer stem lengths will produce greater stem weights. [14,15] stated that the weight of sugarcane stems is determined by the diameter and length of the stem. If there is no difference in the length of the stem, then the weight of the stem is determined by the diameter of the stem and vice versa [16]. The MLG 18/41/5 clone had the highest stem length and rather large stem diameter, resulting in the largest stem weight (2044.77 g/stem). The clones MLG 18/38/4 and MLG 18/47/6 with short stem length but high stem diameter resulted in moderate stem weight (1463.53-1570.44 g/stem).
The results of [17] showed differences in the number of stems produced due to differences in sugarcane clones/varieties used. One clone (MLG 18/18/8) had more stems harvested, two clones (MLG 18/41/2 and MLG 18/52/2) were not different, and the other 11 clones were more minor than Cenning. The number of sugarcane stalks per unit area of land is influenced by plant genetics and the growing environment [18]. In a homogeneous growing environment, the number of sugarcane stalks is determined by plant genetics [9]. The research results by [19] and [20] showed that genetic differences in sugarcane resulted in differences in the number of sugarcane stalks harvested.
Stem weight and the number of harvested stems are components of sugarcane productivity. Clones/varieties with higher stem weight and more harvested stems resulted in higher sugarcane productivity. [21] and [22] stated that sugarcane productivity is determined by stem weight and the number of stems at harvest. The increase in the number of sugarcane stalks and stem weight led to an increase in sugarcane productivity [23,24]. Considering that stem weight and the number of stems harvested in this study were influenced by plant genetics, sugarcane productivity was also influenced by plant genetics (Table 3). Three clones (MLG 18/42/15, 18/21/14, and 18/41/5) had higher productivity, four clones (MLG 18/24/2, 18/41/2, 18/47/6, and 18/52/2) was not different and the other 11 clones were inferior to Cenning. The study results of [20] and [25] showed differences in sugarcane productivity due to differences in plant genetics used.  Table 4). The productivity of these three clones was higher than the Cenning variety. The average national productivity of sugarcane is below 70 tons/ha [2]. Cane productivity above 70 t ha -1 on dry land is already high [26].
Sucrose content is the second major component in sugarcane cultivation. In this study, the sucrose content was influenced by the clones used (Table 4). Similar results were reported by (26) and (3). Table 4 shows that the sucrose content of the tested clones varied from 7.81% to 10.65%. The highest sucrose content was produced by MLG 18/14/5 (10.65%), followed by MLG 18/21/20 (10.59%), MLG 18/52/2 (10.48%). The sucrose content of the three clones was higher than the comparison variety Cenning (9.70%). Sugarcane clones grown on dry land with sucrose content above 10% have a high potential for sugarcane development in a dry land.
Sugarcane productivity and sucrose content are the main components of sugar yield [27]. In this study, it was found that cane productivity and sucrose content were influenced by the clones used so that the sugar yield was influenced by the sugarcane clones used ( Table 4). The clones produced sugar yield ranging from 3.83-12.39 t/ha, while the comparison clones (Cenning) produced 8.95 t/ha. The clones that produced higher sugar yield than Cenning were MLG 18/21/14 (12.39 t ha -1 ), MLG 18/42/15 (11.00 t ha -1 ) and MLG 18/41/5 (10.90 t ha -1 ). The clones that produced no different sugar yield from Cenning were MLG 18/24/2 (9.91 t ha -1 ) and MLG 18/52/2 (9.96 t ha -1 ), while the other clones produced lower sugar yield. Research [28] and [29] also resulted in the effect of sugarcane clones on the sugar yield obtained. Table 4. Cane productivity, sucrose content, and sugar yield of sugarcane clones at Karangploso experimental garden, Malang