Influence of Tryptophan on the growth, yield and quality of chilli with and without fertilizer

The influence of Tryptophan on the growth, yield and quality of chilli with and without fertilizer was studied at AMK Research Farm Mardan, during 2019. The experiment was laid out in RCBD with a split plot arrangement having three replications. Factor-A consisted of two treatments i.e., fertilizers applied (100 kg N, 60 kg P2O5 and 25 kg K2O ha ) and without fertilizer was assigned into main plots whereas, Factor-B was Tryptophan levels (0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mg L) which was allotted to sub-plots. It was revealed from the study that those plants which were treated with the application of NPK fertilizer; produced taller plants (80.88 cm), more branches plant (7.44), stem diameter (1.67 cm), leaf area (51.88 cm), early flowering (37.08 days), early fruit harvesting (58.88 days), maximum fruits plant (293.06), least fruit drop (53.61 %), fruit weight (3.58 g), fruit yield (5.86 tons ha), total soluble solids (5.39 °Brix) and ascorbic acid contents (110.78 mg 100g). Tryptophan at 1.5 mg L gave taller plants (85.87 cm), maximum branches plant (8.85), stem diameter (1.70 cm), leaf area (57.71 cm), earlier flowering (39.54 days), early fruit harvesting (57.16 days), more fruits plant (318.17), least fruit drop (38.80 %), maximum fruit weight (4.13 g), fruit yield (7.25 tons ha), total soluble solids (5.60 °Brix) and ascorbic acid contents (115.33 mg 100g) of chilli. It was concluded that Tryptophan along with NPK fertilizer application produced better plant growth, fruit yield and quality of chilli, under the climatic conditions of Mardan.


Introduction
Chilli belongs to the genus Capsicum, specie annuum. It is one of the members of Solanaceae family and it is has been cultivated in tropical and subtropical climates. South and Central America are considered as its origin [1]. After tomato and potato, it is the 3 rd most important crop in the genus Capsicum [2]. Chilli grows well in a different part of Pakistan where the danger of frost is minimum [3]. The optimum required temperature for chilli production is 20-25 0 C [4]. Chilli can be consumed as a salad and dried condiments. In Pakistan there are two species of chilli that grow commercially i.e., Capsicum annum and Capsicum frutescens [5]. Chillies are grown as vegetable and condiments [6]. In developed countries, chilli is used as an insecticide [7]. Chillies have high nutritional value, and source of vitamin A, C, E and B complex along with minerals like P, Mo and Mn. Chilli is one of the most special vegetable that having seven times more vitamin C than orange [8,9]. From an area of about 212 million ha, the total world production of capsicum was about 36.46 million metric tonnes. The major producing country of chilli is china that contributing 36% of the world's cultivated area with a production of 12.53 million tonnes. India contributes an average yearly production of 0.9 million tonnes from 1.85-million-hectare area with a production of 1.8 tones ha -1 [10]. However total production of chillies in Pakistan from an area of 65,275 hectares was 148,114 tonnes, out of which Khyber Pakhtunkhwa contributed 319 ha area with the production of 360 tones [11]. Chilli has the potential to grow on different soils; however, the suitable soil that is considered best for its production is sandy to loam soils. The pH of the soil ranges from 5.0-6.0 but can be cultivated on soil pH ranges from 5.0-6.8 for chillies production [12]. In general, fruit and flower drop are one of the serious problems of chilli due to which their yield is decreasing that is because of physiological and hormonal imbalances in the plant, apart from this, the main cause is an unfavourable condition such as extreme temperature [13]. Tryptophan (TRP) is termed as the precursor of the phytohormone, and is used by the living bacteria for the purpose of indole acetic acid production [14]. Tryptophan had more influence on the growth and yield attributes rather than pure auxins [15]. Tryptophan was compared with pure Auxin, they found a significant effect on the growth of radish at a low concentration at the seedling stage [16]. Auxin is a key plant hormone, helps in root induction, also helps in cell division, cell enlargement, apical dominance, vascular tissue differentiation, flowering, abscission of leaves and fruits, senescence of leaf and also has a key role in fruit setting [17]. Application of Nitrogen (N) to chillies helps in increasing plant growth characters like nutrient content, colour of leaves as well as yield [18]. The yield was also improved with the increased rate of nitrogen application, but the excess application of nitrogen encouraged vegetative growth, as result the yield gets decreases [19]. Phosphorous (P) helps in plant growth and development. Phosphorous involves the plant functions like energy transformation, photosynthesis, starches and sugars transferring and the nutrients translocation within the plant, hence proper phosphorous application is required for better plant growth and yield [20]. Potassium (K) is important for plant metabolism like water relation translocation, photosynthesis and also activation of the enzyme. Although, K is not a component of any plant structures, but it plays a key role in essential regulatory processes of the plant such as plant stomata regulation and water use, regulation of enzyme activities, processes of Osmoregulation, translocation of sugars, carbohydrates formation, plant energy status, synthesis of protein and all other essential processes that help plants for better growth and reproduction [21]. In view of the above importance of Tryptophan and fertilizers (NPK), the objectives of the study were to find the optimum dose of Tryptophan for chilli crop and to study the influence of combined treatment of Tryptophan and fertilizer (NPK) on the performance of chilli crop in District Mardan climate.

Materials and Methods
A trial on " Influence of Tryptophan on the growth, yield and quality of chilli (Capsicum annum L.) with and without fertilizers " was conducted in Research Farm Palatoo at AMK sub-campus Mardan, during April 2019 which lies at 34°20' N Latitude and 72°02' E Longitude. The experimental plots were properly prepared. After levelling of experimental plots, 30 cm raised ridges were prepared and chilli plants were planted at 60 and 30 cm row to row and plant to plant spacing respectively. The experimental field was irrigated just after transplantation of chilli seedlings and further irrigations were practiced when needed. Most of the cultural practices like hoeing and weeding on regular bases were practiced uniformly in all plots. Experimental design Two factors Randomized Complete Block Design was used with split plot arrangement. Each treatment was replicated three times. The field was distributed into three blocks (for three replications) and each replication had two main plots and 12 sub-plots, as a result, the total number of was 36 and each plot size was 1.8 m 2 . There were 2 rows in each plot and each row had 4 plants.

NPK
Fertilizer and Tryptophan Application A recommended dose of fertilizer i.e., N 100 kg ha -1 , P 60 kg ha -1 and K 25 kg ha -1 was used before transplantation [22]. However, nitrogenous fertilizer was applied in split doses, first dose at the time of field preparation, and the second dose after 25 days of seedlings transplanting. Tryptophan was applied as foliar application 20 days before the flowering stage (Table 1).  (Table 2). ANOVA revealed that branches plant -1 was highly affected by Tryptophan with and without NPK fertilizer, whereas their interaction was non-significant. Mean (Table 2) showed that the plants treated with Tryptophan at 1.5 mg L -1 had produced more branches plant -1 (8.85), while minimum branches plant -1 (5.82) was observed in 0 mg L -1 . As concerned with fertilizer, more branches plant -1 (7.44) was found in plots having NPK fertilizer, while minimum branches plant -1 (7.12) was noticed in plots without NPK fertilizer. Branching of plants may play a good role in the growth and yield component of the crops.
[27] found that Tryptophan application significantly improved plant growth i.e., branches of the plant. Tryptophan application can affect the growth and yield [30]. Improvement in the growth phases of the plant may be due to the conversion of Tryptophan into indole acetic acid [28]. The results showed that Tryptophan at 1.5 mg L -1 had significantly influenced over control at the percentage of 52.17 %. Distance between internodes, number of leaves, and branches plant -1 were considerably influenced by the treatment of Tryptophan over control treatment in the okra plant [31]. As concerned with NPK fertilizer, that helps in vegetative, reproductive and quality characters of the plant showed significant influence in terms of plant branching. The same results was cited by [32] that NPK fertilizer with a combination of biocompost had significantly increased primary and secondary branches.

Stem diameter (cm)
Mean data for stem diameter (cm) of chilli as affected by Tryptophan with and without the application of NPK fertilizer are presented in ( Table 2). Analysis of variance indicated that stem diameter was considerably influenced by Tryptophan with and without NPK fertilizer, whereas their interaction was found non-significant. Mean (

Leaf area (cm 2 )
Mean data for leaf area (cm 2 ) of chilli as affected by Tryptophan with and without the application of NPK fertilizer are revealed in (Table 3). Analysis of variance disclosed that leaf area was highly influenced by Tryptophan with and without the use of NPK fertilizer, and also by their interaction. Mean (Table 3) showed that leaf area as affected by foliar application of Tryptophan, the highest leaf area (57.71 cm 2 ) was recorded in Tryptophan foliar application at 1.5 mg L -1 , while the lowest leaf area (40.44 cm 2 ) was recorded in 0 mg L -1 . As concerned with NPK fertilizer, maximum leaf area (52.87 cm 2 ) was noted in NPK fertilizer applied plots, while the lowest leaf area (45.90 cm 2 ) was found without NPK fertilizer plots. Leaf area is one of the important trait that helps in determining the final yield of the crops. [35] reported that leaf area is an essential growth parameter that specifically helps in increasing both the growth and yield of the plants. The results making similarities with the findings of [36] who stated that leaf area development has specifically influenced by foliar application of Tryptophan and rates of synthetic fertilizer i.e., Urea, DAP and TSP. Tryptophan is the functional precursor of the phytohormones that is used by bacteria for the purpose of IAA production [14]. Auxin helps in cell division, cell elongation and induce rooting of plants [17]. Tryptophan has a stimulatory influence on initiating photosynthetic pathway that leads to the formation of chlorophyll, resulted in maximum leaf area [37]. Similar results were found by [38] when Tryptophan was applied to various crops. Furthermore [16] reported that at the seedling stage of radish, Tryptophan was found significantly positive as compared with pure auxin.

Days to first flowering
The data regarding days to the first flowering of chilli as influenced by Tryptophan with and without the application of NPK fertilizer are in (Table 3). ANOVA presented that the days to earlier flowering was considerably influenced by Tryptophan with and without NPK fertilizers, whereas their interaction effect was non-significant. (

Days to harvesting
Days to fruit harvesting of chilli as influenced by Tryptophan with and without the application of NPK fertilizer are presented in (Table 3). ANOVA showed that days to fruit harvesting was considerably influenced by Tryptophan with and without NPK fertilizer, whereas their interaction effect was non-

Fruit drop (%)
Mean data about fruit drop percentage in chilli as influenced by Tryptophan with and without the application of NPK fertilizer are shown in (Table 4). ANOVA exposed that fruit drop was considerably affected by Tryptophan with and without the use of NPK fertilizer, and also by their interaction. (

Length of Fruit (cm)
Fruit length (cm) of chilli as affected by Tryptophan with and without the application of NPK fertilizer are shown in (Table 4). ANOVA presented that fruit length was considerably influenced by Tryptophan with and without the use of NPK fertilizer, and their interaction effect was non-significant. (Table 4) indicated that the treatment of plants with Tryptophan application at 1.5 mg L -1 gave maximum fruit length (10.04 cm), while least fruit length (6.58 cm) was found in 0 mg L -1 . As concerned with NPK fertilizer application maximum fruit length (8.66 cm) was noted in plots having NPK fertilizer, while least fruit length (8.00 cm) was noticed in plots without NPK fertilizer. Size and weight is a key morphological aspects of fruits which are useful for final yield and also for consumer acceptance [56]. Auxin or even their precursor helps in cell separation and cell enlargement resulted in increased rate of cell number that finally leading to greater fruit size [24]. Fruit with maximum length was also found in those plants that are treated with Tryptophan, while least fruit length was noted in plants that are untreated with

Fruit yield (tons ha -1 )
Mean data about fruit yield (tons ha -1 ) of chilli as affected by Tryptophan with and without the use of NPK fertilizer are placed in (Table 5). ANOVA revealed that fruit yield ha -1 was considerably affected by Tryptophan with and without the use of NPK fertilizer, their interaction effect was nonsignificant. ( Ascorbic acid contents of chilli as influenced by Tryptophan with and without the supply of NPK fertilizer are revealed in (Table 5). ANOVA disclosed that Ascorbic acid contents was considerably influenced by Tryptophan with and without the use of NPK fertilizer, whereas their interaction effect was non-significant. (