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Research Article - (2021)Volume 10, Issue 6
Fertilization plays an important role in plant quality and can affect the biology characters of herbivorous insects indirectly. Tobacco planting was usually guided by appointed government organizations in China. A special compound fertilizer (N∶P2O5∶K2O is 1∶1.2∶2.5 in ratio) was recommended to use in many tobacco planting area. An experiment with treatments of five different fertilization levels (75(A), 90(B), 105(C), 120(D) and 135(E) kg/hm2) was carried out to assess the nutritive qualities in tobacco leaves and influencing of development, nutritional indices and fecundity on the Spodoptera litura when reared on them. The results indicated that the S. lituralarvae grew faster, and had longer female longevity and greater fecundity when reared on the tobacco leaves in fertilization level group C than those fed on the leaves in other groups significantly. Then we related this to the nutrient contexts of the leaves in the fertilizer using groups. The plants with higher soluble proteins, carbohydrates and the Relative Water Contents (FMC) in group C might be the important nutrition for development and reproduction. This investigation can provide a suggestion on this fertilizer application affecting the nutritive qualities in tobacco leaves and then the development and feeding behavior of the S. liturawhich feed with these qualities tobacco leaves can be influenced, the adults fecundity were shaped subsequently.
Fertilization level; Tobacco; Nutritional indices; Spodoptera litura.
Tobacco is a very important agricultural commodity due to its significant contribution to the national economy in many countries like China, America, India etc. [1]. But it is usually attacked by several species of insect pests especially the common cutworm (Spodoptera litura) causing heavy losses in the field. Insecticides were applied frequently to control insects in the field. The extensive use of synthetic pesticides has caused the soaring of resistance in insects. The residual pesticides have not only polluted the environment but also became a threat to human life [2]. Agronomic operations might provide potential tactics to manage insect populations. The chemical characteristics in the tobacco leaves are the important parameters to assess the tobacco qualities. This physical process in tobacco plant are affected heavily by textured soils especially the fertilizers management [3,4]. N mineralization in soils is also a most important factor to affect nicotine content in tobacco leaf [5]. Now, a special compound fertilizer (N∶P O ∶K O is 1∶1.2∶2.5 in ratio) was compelled to use in many commercial tobacco plant areas in China. How this agronomic operation affect the chemical contents in tobacco leaves will conduct an instructional fertilizer management. In agro-ecosystems, appropriate use of Nitrogen (N), phosphorus (P) and potassium (K) elements is of great importance to plant growth, development, high yield and significantly affects plant nutrition [6]. And here is growing evidence that dosages of fertilizers have been reported to have various effects on many insect populations in development, body size and weight, reproduction, survival rate and population abundance like Trialeurodes vaporariorum [7], Aphis gossypii [8,9], Bemisia argentifolii [10] Frankliniella occidentalis [11], Trogoderma granarium [12] and Tribolium castaneum [13], though the plant nutrition varies. So if the objective laws how the fertilizer application affect the physiology process of the S. liturawere made certain, we would develop a precision agriculture operation for predicting and reducing this insect risk.
Organisms can allocate limited resources to primary life functions including growth, reproduction and self-maintenance [14]. The nutritive values of host plants can affect the grow rate of insects, survival and thus influence the population dynamics of them [15,16]. The ability to grow and reproduce as fast as possible is crucial importance for many animals [17]. Food nutrition is a biological interpretation of the indices which related to their physiological base in insect. The Relative Consumption Rate (RCR), Relative Growth Rate (RGR), Approximate Digestibility (AD), Efficiency of Conversion of Ingested food (ECI) and Efficiency of Conversion of Digested food (ECD) were the classic parameters which have been widely adopted in ecological, physiological and behavioral studies in insects [18]. The study of food nutritional indices of insects can help us to compare the performance of insects on various host plants [19]. So making clear the nutritional physiology of the S. litura when reared on tobacco leaves under different fertilization levels will be helpful to understand the mechanisms of this pest running rampant. The aim of this study is to determine how the fertilization amount influenced the tobacco leaves qualities. Then examine the influence of the tobacco leaves under different fertilization levels on the development, longevity and reproductive programming of the S. liturawhen reared on them.
Insect rearing
The larvae were reared at 25 °C ± 1 °C and 60%-70% Relative Humidity (RH) with a 14:10 photoperiod on an artificial diet at the College of Agriculture, Yangtze University [20]. The adults were fed with 10% honey. In bio-assay, the larvae were transferred to tobacco leaves gently.
Tobacco plant and fertilizer
The tobacco plant (Yunyan 87) used in this study was provided by the Tobacco Research Institute of Hubei Province. And the research was conducted in the experimental fields of Agriculture at Yangtze University in Jingzhou, Hubei, China. A special compound fertilizer was produced by the Hubei Xiangqing Fertilizer LTD and recommended to use during the tobacco plant growing. Nutrient composition of the fertilizer is N: P2O5: K2O is 1:1.2:2.5 in ratio of weight. In this study, five levels of fertilization, i.e., 75(A), 90(B), 105(C), 120(D), and 135(E) kg/hm2, were employed and the fertilizer was applied to the fields 7 d before transplanting of the tobacco seedlings (Table 1).
Groups | Fertilizer (kg/hm2) | ||
---|---|---|---|
N | P2O5 | K2O | |
A | 75 | 84 | 175 |
B | 90 | 108 | 225 |
C | 105 | 126 | 262.5 |
D | 120 | 144 | 300 |
E | 135 | 162 | 337.5 |
Table 1: The fertilizer levels in different experimental groups.
Tobacco nutritional quality assays
For nutritive qualities detection, after the tobacco plants grown in the fields for 45d post-transplant, middle tobacco leaves were collected from the tobacco plants in different fertilizer applied respectively. Approximate 300 mg samples with 10 ml 0.2M PBS buffer (pH=7.0) was homogenized at 4 °C. The analytical method of soluble carbohydrates [21]. Briefly, the homogenates were incubated in boiling water for 30 minutes and filtered, then diluted to 100 mL with distilled water. 1 mL compound was drawn and centrifuged at 5,000 × g for 10 minutes. Then 0.5 mL anthracene copper, 1 mL water and 5 mL sulfuric acid (98%) were added to 0.5 mL supernatant. After the mixture was incubated in boiling water for another 10 minutes, the absorbance values were analyzed at 620 nm using a spectrophotometer (UV-5100 B, Shanghai China). The glucose was used as a standard. The analysis of soluble proteins concentration was conducted [22]. In summarily, the homogenates were centrifuged at 4,000 × g for 15 minutes at 4 °C. Then 100 µ L supernatant added 900 µ L distilled water and 5 mL Coomassie brilliant blue G-250. The absorbance values were detected at 595 nm using a spectrophotometer (UV-5100 B, Shanghai China). The Bovine Serum Albumin (BSA) was used as standard. Three seasons were repeated. The relative water content detection method [23]. About 1 g tobacco leaves collected from 5 different tobacco plants in each group were dried at 105 °C for 24 h in a dryer. The relative water content (FMC) was counted with the
Formula: FMC=(Fresh leaves weight-Dry leaves weight) ÷ Fresh leaves weight × 100%
Development and resulting female fecundity
Single newly hatched larva was transferred gently to Petri dishes (9.0 cm (diameter) × 1.5 cm (depth)) with tobacco leaves separately (each treatment repeated 50 individuals). And the leaves were changed two times a day until they pupated. The accumulated development time were added until the larvae pupated. Then the pupal duration were observed. After the emergence, 1 female and 2 male were put together for mating. Eggs of 15 individual females in each rearing group were counted and removed every day until the adults died, the total amount of eggs were added for statistical analysis. Three seasons were repeated.
Nutritional indices
After the larvae grow to 3rd on artificial diet, the 4th, 5th, 6th and 7th instars larvae were transferred gently to the tobacco leaves in different groups. Fifteen individuals were analyzed in each group at random. The food utilization indices values the Relative Consumption Rate (RCR), Relative Growth Rate (RGR), Approximate Digestibility (AD), Efficiency of Conversion of Ingested food (ECI) and Efficiency of Conversion of Absorbed food (ECD) were calculated adopted to the classical formulas as follows [24]. Three same seasons were repeated.
Relative Consumption Rate (RCR)=E/AT
Relative Growth Rate (RGR)=P/AT
Approximate Digestibility (AD) (%)=100(E-F)/E
Efficiency of Conversion of Ingested food (ECI) (%)=100 P/E
Efficiency of Conversion of Absorbed food (ECD) (%)=100 P/(E-F)
Where, A: Dry weight of animal during T, E: Dry weight of food eaten, F: Dry weight of feces produced, P: Dry weight gain of insect, T: Duration of experimental period.
Statistical analysis
All data were checked for normality via the Kolmogorov-Smirnov test before the analysis. The data were analyzed by one-way Analysis of Variance (ANOVA) with means separation at 5% level of significance by Tukey’s test using IBM SPSS Statistics 25 (USA) soft-ware.
Effect of fertilizer on tobacco leaves nutritive qualities
In order to assess the biochemical components in the tobacco leaves of five fertilizer levels, the soluble carbohydrates, proteins and Relative Water Contents (FMC) were detected. The results indicated that the soluble carbohydrates (F4, 10=4.53, p<0.005) and proteins contents (F4,10=5.87, p<0.005) varied significantly between the fertilization levels, it had the similar tendency that they were increased with fertilizer amount used first and got down at a special level (group C). And the FMC were greatest in C and least in A (F4, 10=4.83, p<0.005) (Table 2).
Fertilization levels | Soluble proteins (mg/g fresh weight) | Soluble carbohydrates (mg/g fresh weight) | Relative water contents (FMC) (%) |
---|---|---|---|
A | 1.47 ± 0.06bc | 0.98 ± 0.03c | 78.80 ± 0.25d |
B | 1.61 ± 0.06bc | 1.25 ± 0.05ab | 81.93 ± 0.64c |
C | 1.94 ± 0.05a | 1.37 ± 0.07a | 85.27 ± 0.72a |
D | 1.71 ± 0.08b | 1.14 ± 0.05bc | 83.03 ± 0.48b |
E | 1.56 ± 0.08bc | 1.03 ± 0.06c | 81.03 ± 0.96c |
Note: Mean values in a column followed by different lowercase letters are significantly different on the basis of analysis of variance with Tukey’s test (p<0.05). A, B, C, D, E indicated five different fertilization levels respectively. Three same seasons were repeated.
Table 2: Soluble proteins, soluble carbohydrates and relative water contents (FMC) (mean ± SE) of tobacco leaves in five different fertilization level groups.
Larvae life cycle and adult fecundity
To determine whether the tobacco leaves of five fertilizer levels affect the larvae life cycle, duration of pre-pupae and pupae and longevity of adults, 50 individuals were reared on these leaves in each season. The results demonstrated that insects developed fastest when they fed on the tobacco leaves in group C followed by D,B,E and A (F4,625=3.26, p<0.005). A similar result can be found at pre-pupae stage (F4,592=3.13, p<0.005). But there was no significant difference on the pupae duration (F4, 566=2.11, p<0.005). Female live longest in group C and shortest in treatment A but there is no effect on the longevity of male (F4,225=3.17, p<0.005). Individual female laid more eggs when they fed tobacco leaves on treatment C (F4,175=2.97, p<0.005) too. So the plant quality on fertilizer level C was more favorable for the S. lituradevelopment and reproduction (Table 3).
Life cycle of larvae | n | A | n | B | n | C | n | D | n | E |
---|---|---|---|---|---|---|---|---|---|---|
I | 150 | 3.28 ± 0.18a | 150 | 3.1 ± 0.36b | 150 | 2.64 ± 0.30d | 150 | 2.83 ± 0.27c | 150 | 2.74 ± 0.27cd |
II | 141 | 2.38 ± 0.05a | 143 | 2.07 ± 0.05c | 147 | 1.98 ± 0.05c | 145 | 2.21 ± 0.05b | 141 | 2.01 ± 0.04c |
III | 140 | 2.41 ± 0.04b | 141 | 2.66 ± 0.08a | 145 | 2.41 ± 0.13b | 143 | 2.56 ± 0.04ab | 139 | 2.52 ± 0.05ab |
IV | 135 | 2.40 ± 0.03b | 136 | 2.49 ± 0.05b | 143 | 2.32 ± 0.09c | 137 | 2.53 ± 0.04a | 137 | 2.54 ± 0.05a |
V | 132 | 2.65 ± 0.05a | 131 | 2.62 ± 0.06a | 137 | 2.53 ± 0.09ab | 133 | 2.71 ± 0.07a | 131 | 2.63 ± 0.05a |
VI | 128 | 2.61 ± 0.06a | 126 | 2.59 ± 0.10a | 134 | 2.54 ± 0.06a | 129 | 2.49 ± 0.05a | 127 | 2.50 ± 0.05a |
VII | 125 | 3.67 ± 0.07a | 125 | 3.53 ± 0.05ab | 131 | 3.12 ± 0.05c | 128 | 3.38 ± 0.08b | 121 | 3.55 ± 0.06ab |
Total larval duration | - | 19.39 ± 0.17a | - | 19.06 ± 0.26b | - | 17.54 ± 0.15d | - | 18.70 ± 0.13bc | - | 18.49 ± 0.16c |
Pre-pupal duration | 119 | 1.88 ± 0.03ab | 120 | 1.90 ± 0.03a | 125 | 1.53 ± 0.04d | 122 | 1.86 ± 0.04ab | 111 | 1.77 ± 0.03c |
Pupal duration | 113 | 11.24 ± 0.23a | 111 | 11.03 ± 0.14a | 125 | 10.80 ± 0.24a | 115 | 10.72 ± 0.19a | 107 | 11.02 ± 0.21a |
Adult | - | - | - | - | - | - | - | - | - | - |
Female longevity | 46 | 9.79 ± 0.82b | 45 | 10.81 ± 0.72b | 49 | 12.36 ± 0.94a | 47 | 10.73 ± 1.34ab | 43 | 10.22 ± 1.11ab |
Male longevity | 58 | 6.20 ± 2.18a | 56 | 7.78 ± 1.29a | 61 | 8.60 ± 1.19a | 58 | 5.77 ± 2.04a | 49 | 9.68 ± 1.32a |
Fecundity | 36 | 839.38 ± 89.50b | 36 | 899.50 ± 45.79b | 36 | 1344.90 ± 108.26a | 36 | 1230.50 ± 98.81a | 36 | 913.57 ± 56.26b |
Note: Mean values in a row followed by different lowercase letters are significantly different on the basis of analysis of variance with Tukey’s test (p<0.05). The n value shows the sample size for each parameter. A,B,C,D,E indicated five different fertilization levels respectively. Three years same season experiment was combined.
Table 3: Larval duration, pre-pupal duration, pupal duration, female longevity, male longevity and fecundity (mean ± SE) of Spodoptera litura fed on the tobacco leaves in five different fertilization level groups.
Feeding efficiency of larvae
When the larvae grew to 3rd on artificial diet, 15 individuals reared separately on the tobacco leaves in each fertilization level. After they grow to the 4th, 5th, 6th and 7th instars, various leave diets utilization indices were calculated to assess the nutritional indices. The results demonstrated that for the 4th instar, the RCR was greatest in insects fed on tobacco leaves in group E followed by D, C, B, A (F4, 70=3.47, p<0.005). Greatest RGR values were found in E group and poor in group A and B (F4, 70=3.31, p<0.005). On the AD index values, the food quality of tobacco leaves can be arranged with D, E, B, C, A (F4, 70=3.52, p<0.005). ECI values were higher when the insects reared on leaves in groups A, B, C than those of the insects fed on the D and E groups (F4,70=2.91, p<0.005). But ECD value was greatest in group C and lowest in group E (F4, 70=3.19, p<0.005) (Table 4).
Fertilization levels | RCR(mg/day) | RGR(mg/day) | ADï¼?%ï¼? | ECIï¼?%ï¼? | ECDï¼?%ï¼? |
---|---|---|---|---|---|
A | 0.53 ± 0.01d | 0.04 ± 0.01c | 70.75 ± 1.82d | 7.19 ± 0.48a | 6.15 ± 0.10c |
B | 0.56 ± 0.03d | 0.03 ± 0.01c | 84.90 ± 1.09c | 6.00 ± 0.46a | 7.01 ± 0.98b |
C | 3.33 ± 0.36c | 0.31 ± 0.01b | 81.66 ± 1.51c | 5.36 ± 0.66a | 10.18 ± 0.75a |
D | 6.22 ± 0.64b | 0.06 ± 0.01c | 97.65 ± 0.21a | 3.24 ± 0.10c | 7.21 ± 0.59b |
E | 16.35 ± 1.57a | 0.51 ± 0.04a | 91.45 ± 0.73b | 3.62 ± 0.48b | 4.04 ± 0.57d |
Note: Mean values in a column followed by different lowercase letters are significantly different on the basis of analysis of variance with Tukey’s test (p<0.05). RCR=Relative Consumption Rate. RGR=Relative growth rate. AD=Approximate Digestibility. ECI=Efficiency of Conversion of Ingested Food. ECD=Efficiency of Conversion of Absorbed food. A,B,C,D,E indicated five different fertilization levels respectively. Three same seasons were repeated.
Table 4: Mean (± SE) nutritional indices of S.litura fourth instar on tobacco leaves at five different fertilization levels.
During the 5th instar, the RCR values could be arranged with D, C, E, B, A (F4, 67=3.54, p<0.005). Higher RGR values were found for insects fed on tobacco leaves in group E, D, C and lower on group A and B(F4,67=2.74, p<0.005). Highest AD values were recorded fed on tobacco leaves fertilization level group A, then groups C, E, B and lowest on group D (F4,67=2.91, p<0.005). ECI values were higher for insects fed on leaves in groups A, B, C, E than group D (F4,67=3.11, p<0.005). ECD values were evident greatest on group C and least in group D (F4, 67=3.57, p<0.005) (Table 5).
Fertilization level | RCR(mg/day) | RGR(mg/day) | ADï¼?%ï¼? | ECIï¼?%ï¼? | ECDï¼?%ï¼? |
---|---|---|---|---|---|
A | 0.50 ± 0.03d | 0.04 ± 0.01b | 81.06 ± 1.21c | 9.051 ± 0.49a | 11.33 ± 0.78b |
B | 0.70 ± 0.03d | 0.06 ± 0.01b | 86.04 ± 1.50b | 8.15 ± 0.816a | 9.12 ± 1.06b |
C | 5.10 ± 0.27b | 0.39 ± 0.03a | 81.90 ± 0.68bc | 8.00 ± 0.51a | 15.26 ± 3.42a |
D | 8.45 ± 0.47a | 0.36 ± 0.03a | 89.30 ± 1.72a | 4.84 ± 0.65b | 5.27 ± 0.81c |
E | 1.48 ± 0.12c | 0.38 ± 0.04a | 54.38 ± 2.69d | 8.31 ± 1.98a | 10.01 ± 0.72b |
Note: Mean values in a column followed by different lowercase letters are significantly different on the basis of analysis of variance with Tukey’s test (P<0.05). RCR=Relative consumption rate. RGR=Relative growth rate. AD=Approximate digestibility. ECI=Efficiency of conversion of ingested food. ECD=Efficiency of conversion of absorbed food. A,B,C,D,E indicated five different fertilization levels respectively. Three same seasons were repeated.
Table 5: Mean (± SE) nutritional indices of S.litura fifth instar on tobacco leaves at five different fertilization levels.
When the insects grew to 6th instar, higher values of RCR were recorded for rearing on tobacco leaves in group C and lower in group A (F4,61=2.54, p<0.005). For RGR values, greatest number appeared in group D and lowest in group A (F4, 61=3.03, p<0.005). Approximate digestibility value was greatest when insects were fed with tobacco leaves in groups A, B, E (F4, 61=3.12, p<0.005). The value of ECI was greater in insects fed on tobacco leaves in groups A and B whereas the value of this index was reduced in case of groups C, D, E fed insects (F4,61=3.54, p<0.005). ECD values were higher on groups Band C and lower on treatment Dand E (F4, 61=2.84, p<0.005) (Table 6).
Fertilization levels | RCR(mg/day) | RGR(mg/day) | ADï¼?%ï¼? | ECIï¼?%ï¼? | ECDï¼?%ï¼? |
---|---|---|---|---|---|
A | 0.10 ± 0.01c | 0.02 ± 0.01d | 68.48 ± 1.22a | 18.82 ± 0.89a | 27.78 ± 1.40b |
B | 1.77 ± 0.12ab | 0.30 ± 0.02c | 56.97 ± 2.96c | 17.42 ± 1.18a | 33.81 ± 2.16a |
C | 2.58 ± 0.11a | 0.39 ± 0.02b | 66.20 ± 2.28ab | 15.70 ± 1.09b | 36.57 ± 3.98a |
D | 1.56 ± 0.15b | 0.50 ± 0.02a | 55.21 ± 2.15c | 14.57 ± 2.61b | 24.45 ± 2.18c |
E | 2.17 ± 0.57ab | 0.25 ± 0.03c | 61.51 ± 1.66bc | 14.97 ± 1.74b | 24.42 ± 2.40c |
Note: Mean values in a column followed by different lowercase letters are significantly different on the basis of analysis of variance with Tukey’s test (P<0.05). RCR=Relative consumption rate. RGR=Relative growth rate. AD=Approximate Digestibility. ECI=Efficiency of Conversion of Ingested food. ECD=Efficiency of Conversion of Absorbed food. A,B,C,D,E indicated five different fertilization levels respectively. Three same seasons were repeated.
Table 6: Mean (± SE) nutritional indices of S.litura sixth instar on tobacco leaves at five different fertilization levels
After the insects reached 7th instar, greater values of RCR were recorded for feeding on tobacco leaves in groups E, Band A (F4,57=3.33, p<0.005). For RGR values, the larvae reared on group E was found higher than other four groups (F4, 57=2.63, p<0.005). There was no significant difference among all the groups for AD values (F4, 57=3.24, p<0.005). Both the ECI (F4, 57=2.44, p<0.005) and ECD (F4, 57=2.71, p<0.005) values were higher in treatment C (Table 7).
Fertilization levels | RCR(mg/day) | RGR(mg/day) | ADï¼?%ï¼? | ECIï¼?%ï¼? | ECDï¼?%ï¼? |
---|---|---|---|---|---|
A | 1.24 ± 0.08ab | 0.21 ± 0.02b | 45.67 ± 4.22a | 15.98 ± 0.75a | 38.58 ± 4.12bc |
B | 1.51 ± 0.05a | 0.19 ± 0.02b | 51.29 ± 2.00a | 12.35 ± 0.99b | 24.33 ± 1.99c |
C | 1.07 ± 0.22bc | 0.15 ± 0.04b | 46.93 ± 12.48a | 17.81 ± 4.52a | 59.50 ± 13.15a |
D | 0.77 ± 0.12c | 0.15 ± 0.05b | 38.63 ± 10.95a | 17.03 ± 1.27a | 61.75 ± 18.48a |
E | 1.41 ± 0.13ab | 0.26 ± 0.02a | 49.25 ± 2.60a | 15.49 ± 2.91a | 36.98 ± 4.10bc |
Note: Mean values in a column followed by different lowercase letters are significantly different on the basis of analysis of variance with Tukey’s test (p<0.05).RCR=Relative Consumption Rate. RGR=Relative Growth Rate. AD=Approximate Digestibility. ECI=Efficiency of Conversion of Ingested food. ECD=Efficiency of Conversion of Absorbed food. A,B,C,D,E indicated five different fertilization levels respectively. Three same seasons were repeated.
Table 7: Mean (± SE) nutritional indices of S.litura seventh instar on tobacco leaves at five different fertilization levels
Fertilizers are being extensively used to produce high-quality crops, which can increase a plant’s nutritional quality and attractiveness to phytophagous insects [25,26]. Nitrogen supplementation causes vigorous plant growth [27]. It is an important component of many structural, genetic and metabolic compounds in plant cells and also one of the most important performance limiting factors of herbivores insect [28]. Evidence had shown that Phosphorus may be a much more important component for the determinant of fecundity in some phytophagous insects [29, 30]. Potassium nutrition also plays a critical role in plant growth and alters host plant quality for [31]. In this study, the soluble carbohydrates and proteins contents can be raised with the amount of fertilization firstly. But after getting a peak, they would get down again. And the Relative Water Content (FMC) values had a similar tendency (Table 2). These results might have reflected the physiological, biochemical and molecular responses of the plant to the conditions, including the amount of the fertilizer.
In this research, we only concerned how the application of fertilizers affected on the tobacco nutritional quality and biology performance of the S. litura. And do not consider the yield and flavor of tobacco leaves. It is also a defect in our research that we fail to measure nicotine content in the tobacco leaves under the different fertilization level group, nicotine is another important factor to regulate plant defense against herbivory [32].
Fertilizers application can affect insect development and population densities by regulating plant nutritive qualities indirectly [33,34]. Different nutritive values of host plants can influence the development rate and population dynamics of insects also [35]. Insects feeding on protein-rich plants will develop more quickly than those which consume plant material containing less protein [36,37]. Carbohydrate is essential material for insect growth and energy source. Evidence had found that diets with higher carbohydrate will enhance life span [38]. Water content has been shown to be a limiting factor when the caterpillars grow. A lower growth rate was observed when larvae fed with plants containing less water content [39]. In this study, the tobacco leaves in fertilization level group C had the highest contents of the soluble carbohydrates, proteins and water (Table 2). In addition, the larvae eating the tobacco leaves in group C grew faster and longer female adults longevity than those which fed with the leaves in other groups might be related to the higher nutritive chemistry and water in them (Table 3). So higher the soluble carbohydrates, proteins and relative water contents in tobacco leaves might play an important role for the S. litura development and reproduction.
Numbers of eggs of S. lituraproduced by the female adults varied greatly on different food and differ under different environment [40,41]. In this study, numbers of eggs laid by one single female adult ranged from 839 on group A to 1344 on group C (Table 3). This result is very similar to [42]. The S. liturafemale adults oviposited an average of 2540 eggs on the artificial diet in our lab.
Nutritional indices were measured using forth to seventh instars because they were more measurable than the primary instars. For nutritional indices determining, the larger larvae were used in the Helicoverpa armigera [43] and the Cnaphalocrocis medinalis [44].
The utilization of diets by insects is determined by its capacity to ingest, assimilate and convert food into its body tissues [45]. High efficiency of food conversion of digested food means low food consumption to growth, A lower ECD value indicated higher metabolic maintenance costs [46]. Nutritional performance of insects can be influenced by not only the quality and quantity of consumed diet [47], but the physiochemical properties of the food they fed [48]. The relatively high AD might cause by the high water content. And lower water content in plant leaves can induce a lower efficiency of nutrient digestion [49]. The best diets not only can provide the applicable nutritive materials but can also be assimilated and converted into energy and structural substances for the insect developing [50]. In the present study, the high contents of most of the measured nutrients might have been reflected that the high consumption indices when the insect fed on the leaves in group C.
In most insects, the adult reproductive capacity is mainly dependent on nutrients accumulating when they are yang [51]. In this research, a longer longevity and high fecundity rate was observed in the resulting females reared on tobacco leaves in group C compared with the other groups, but no significantly effect on the longevity of males and the female adults lived longer than males (Table 3). Similar results were reported when S. liturareared on cotton. Report also indicated that S.litura male adults lived longer than females and differ on different host plants, and this difference might be affected by temperature.
The total larval developmental time of S. lituralarvae has six-seven instars, in this study, the total larval duration on tobacco leaves ranged from 17.54 to 19.39 d (Table 3). These time were coincided with the obtained by [52]. But they should be, however they shorter than those obtained by. In this study, S. lituraperformed seven instars [53]. But reported that it developed six instars.
It is concluded that the fertilizer application is a vital measure to improve tobacco leaves qualities. However, sometimes it is paradoxical that higher nutritive qualities may cause population outbreaks for polyphagous insects [54]. So we proposed fertilizer application at a scientific knowledge guide.
The present study found out that the soluble proteins, carbohydrates and the relative water contents can be affected by the amount of fertilizer application significantly. The S. lituralarve like to eat the tobacco leaves applied fertilizer with 105 kg/hm much more and grow more quickly. They will give more offspring when grow up.
We gratefully acknowledge Dr. Wenqing Zhang (Sun Yat-Sen University, Guangzhou, China) for kindly supplying the S. liturastrain. This work was supported by the National Natural Science Foundation of China (31772168), Hubei Tobacco Company (027Y2017-004) and Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, College of Agriculture, Yangtze University (KF201408).
We declare that we have no conflict of interest.
Citation: Chen J, Li X, Li Y, Wang D, Wang Y, Li C, et al. (2021) Effect of Fertilization Level on the Tobacco Nutritional Quality and the Development, Nutritional Indices, Fecundity of Spodoptera litura (F.). Entomol Ornithol Herpetol. 10: 245.
Received: 06-Jul-2021 Accepted: 20-Jul-2021 Published: 27-Jul-2021 , DOI: 10.35248/2161-0983.21.10.245
Copyright: © 2021 Chen J, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.