Spraying Marine Algae Extracts and Some Growth Regulators to Enhance Fruit Set, Yield and Fruit quality of Winter Guava

Introduction

Guava (Psidium guajava L.) which belongs to family Myrtaceae is a native of tropical America. The fruit is rich in Vitamin-C and pectin besides being a good source of thiamine and riboflavin. It is known as ‘apple of tropics’ and can be grown in wide range of soil and climatic conditions. Guava is important fruit crop which is grown commercially in tropical and subtropical regions of the world (Gollagi et al., 2019).

Seaweeds or algae extracts include green, brown and red marine macro-algae, and brown seaweed extracts are widely used in horticulture crops. The raw material, geographical location of harvested algae and algal species, as well as the extraction method, all influence the composition of seaweed extracts, Polysaccharides, proteins, polyunsaturated fatty acids, pigments, polyphenols, minerals, plant growth hormones, and other physiologically active chemicals are transported from algal biomass to the liquid phase. They benefit humans, animals, and plants by primarily protecting an organism from biotic and abiotic stress and have various commercially valuable products such as pharmaceutical and cosmeceutical compounds ( Al- Musawi, 2019)

Plant growth regulator like GA₃ and NAA affects flower and fruit setting, cell growth, apical dominance, geotropism and photoperiod. GA₃ had the highest fruit retention and yield followed by amcotone, activated dry yeast and NAA in both winter and rainy seasons. The growth regulators spray in addition increases fruit weight, total soluble solids (TSS), fruit weight, carotene, reducing sugars, total sugars and vitamin-C and decreased tannin and fruit acidity. The Triacontanol is present as a natural component of plant wax and bee wax (Abubakar et al., 2013).

GA₃ is responsible for cell elongation, rather than cell division (Francis and Sorrell 2001). Gibberellins are natural growth hormones playing a primary role in stimulating the auxin reaction, which helps controlling the growth, as well as its direct effect on in­ternode elongation, flowering, fruiting, quality and yield. The most typical property of gibberellins is the promotion of stem growth (Graebe, 1987). GA₃ encourages the cell division and elongation; increases the stalk length, enhances flower and fruit volume. Auxins promote shoot elongation, thin tree fruit and flower formation (Fishel, 2006).

 Naphthaleneacetic acid ( NAA) is an organic compound, which is a plant hormone in the auxin family and is an ingredient in many commercial horticultural products; it is also a rooting agent and used for the vegetative propagation of plants from stem and leaf cutting (Dimitrios et al., 2008).  It has important role in fruit formation, abscission cell elongation, apical dominance, photoperiod and geotropism (Haidry et al., 1997).

The purpose of this study was to investigate the effect of foliar application of seaweeds, GA3 and NAA on vegetative growth, fruit set, yield, fruit quality and leaf mineral of 'Maamoura' guava trees.

MATERIALS AND METHODS

This study was conducted during 2018 and 2019 seasons to investigate the effect of foliar application of marine algae extracts (Ascophyllum nodosum), GA3 and NAA to reduce fruit drop and improve fruit yield, fruit quality and leaf mineral content of winter guava cv. ‘Maamoura’ trees grown in Rasheed area, El Beheira, governorate, Egypt and cultivated at a distance of 4 x 4 m. the irrigation method was flood irrigation from the Nile River. During the entire season, all trees under study received the same applied fertilization program in orchard i.e. 2-3 miqtaf decomposed livestock manure +1 kg super phosphate and  incorporated well in the soil in winter. In March and July, 200 - 250 g nitrogen was added to each tree in two batches. Potassium fertilizer was also added in two batches, exchange with nitrogen, at the rate of 150 - 250 kg per acre. Microelements was added both as foliar application to the shoot system and as soil application when deficiency symptoms appear. The physio-chemical analysis of experimental soil is indicated in Table (1).

Table (1): The physical and chemical analysis of the experimental soil

The following treatments were sprayed on the trees:

1. Control (Tap water)
2. Seaweed extract at 5 mg/l. (Sea- Hammer)
3. Seaweed extract at 10 mg/l.
4. Seaweed extract at 15 mg/l.
5. GA₃ at 1 mg/l.
6. GA₃ at 2 mg/l.
7. GA₃ at 3 mg/l.
8. NAA at 1 mg/l.
9.  NAA at 2 mg/l.
10. NAA at 3 mg/l.

The Sea Hammer compound was used as the source of the algae escophyllum nodosum sp. ( 85% alge extract ,10% humic acid  and 5% potassium).

Gibberellic acid ( From Green Geb 10% GA3 tablets) and naphthalene acetic acid ( from Green hand tonic) (contains: 1.2% Sodium A Naphthyl acetic acid, 0.6% Sodium O- Nitrophenollate, 0.9% Sodium P- Nitrophenolate and 0.15% Sodium 2,4- Dinitrophenolate).

They were sprayed three times:

1. one month before full flowering (25 May)
2. one month after fruit setting (10 July)
3. one month before harvest (20 August)

The previous treatments were arranged in Randomized Complete Block Design (RCBD), each treatment was replicated on 3 trees. The effect of the previous treatments was studied by evaluating their influence on the following parameters.

1.Vegetative Parameters

Samples of three trees of each experimental unite were taken to determine growth parameters at the middle of each season as follows.

1.1    Shoot length (cm)

1.2    Shoot diameter (mm)

1.3    Total chlorophyll in the fresh leaves was determined as SPAD units by using Minolta chlorophyll meter (SPAD, 501).

2.Fruit set (%), yield (kg/tree) and yield components

2.1 Fruit set (%)

Twenty branches from each of the eight treatments were chosen at random to evaluate the percentage of fruit set; they were then tagged, and their blooms were counted when they were in full bloom. Fruitlets were also counted and recorded in mid-June, as fruit set was ideal. As a percentage of the total number of blooms, fruit set was estimated as follows:

Fruit set (%) =

2.2 Yield (kg/tree)

At harvest time, in 10th, October in the two seasons, the yield of each treatment was measured in kilogrammes per tree. (mature fruits were picked, counted and weighed in Kg per tree).

Sample of 10 fruits per tree from each replicate was collected randomly, i. e. 50 fruits from each applied Samples were taken at random at harvest in both seasons and brought to the laboratory quickly to determine physical and chemical fruit characteristics.

2.3 Yield components

2.3.1 Physical fruit characteristics

The following parameters were determined:

2.3.1.1 Fruit weight (g/ fruit)

Fruit samples were weighted and the average fruit weight for each replicate was calculated in gram.

2.3.1.2 Fruit length (cm) and diameter (cm):  were measured by using Hand caliper.

2.3.1.3 Fruit firmness (pound/ Inch²): Flesh firmness was measured in two opposite sides of the fruit using magness taylor pressure tester and expressed as (pound/ Inch²) according to (Magness and Taylor, 1982).

2.3.2 Chemical fruit characteristics

2.3.2.1 Total soluble solids ( TSS %)

The percentage of TSS was determined in guava fruit juice using a hand refractometer according to (A.O.A.C, 1995).

2.3.2.2 Total acidity (%)

The percentage of total acidity in fruit juice was calculated using Chen and Mellenthin (1981) method. Five milliliters from the obtained juice were used to determine the titratable acidity. The titratable acidity was expressed as grams citric acid/ 100 milliliters fruit juice.

2.3.2.3 Vitamin C (Ascorbic acid) ( mg/ 100g pulp)

The ascorbic acid content of the juice was determined by titration with 2, 6 dichloro phenol-indo-phenol (A.O.A.C., 1995) and calculated as milli-grams per 100 ml of juice.

2.3.2.4 Total sugars (%)

Total sugar (%) was determined calorimetrically using phenol and sulphuric acid, according to Malik and Singh (1980) extracted from 5-gram fresh pulp.

3.Leaf mineral compositions (N,P and K)

Samples of the third pairs of leaves from the base of none fruiting shoots were collected in mid -August in both seasons of the study. At random from the previously tagged shoots, samples of 40 leaves /tree were taken, The leaf samples were washed in tap and distilled water before being oven dried at 70°C to a consistent weight and crushed. To assess the leaf mineral content, each sample's ground material was digested with H₂SO₄ and H₂O₂ according to the manufacturer's instructions Wolf (1982). Total nitrogen and phosphorus in the digested material were measured colorimetrically according to Evenhuis and De waard (1980) and Murphy and Riley (1962), respectively and potassium was determined using a flame photometer, as stated by Chapman and Pratt (1978). The concentrations of N, P and K were expressed as percent.

4.Statistical analysis

The results of the measured parameters were subjected to a computerised statistical analysis of variance (ANOVA) using the MSTAT programme, and the means of treatments were compared using LSD at 0.05 according to  Snedecor and Cochran (1990).

The purpose of this research was to see how foliar spraying of seaweed extract, GA3, and NAA on guava cv. "Maamoura" trees improved fruit set %, vegetative development, yield, fruit quality, and leaf mineral content.

RESULTS AND DISCUSSION

1. Effect of seaweed extract, GA3 and NAA growth regulators on vegetative growth properties

The results regarding the shoot length (cm) and diameter (mm) and total chlorophyll (SPAD) of guava cv. "Maamoura" as influenced by seaweed extract, GA₃ and NAA levels, during 2018 and 2019 are presented in Table (2).

As for seaweed, in the two seasons, the three concentrations of seaweed significantly increased the shoot length (cm), shoot diameter (mm) and the leaf total chlorophyll (SPAD) of guava cv. Maamoura compared to the control. In the meantime, increasing seaweed extract concentration significantly increased the shoot length, shoot diameter and the leaf total chlorophyll of guava cv. "Maamoura".

As for GA3, in the two seasons, the three concentrations of GA3 significantly increased the shoot length (cm), shoot diameter (mm) compared to the control. In the meantime, there were significant differences among the three GA3 concentrations so that the shoot length and shoot diameter increased by increasing the concentrations of the GA3. in the two seasons, the two higher (2mg/l and 3mg/l) concentrations of GA3 significantly increased the leaf total chlorophyll of guava cultivar Maamoura compared to the control and the lowest concentration of GA3(1mg/l) treatment. While, the lowest concentration of GA3 (1mg/l) caused a significant decrease in the leaf total chlorophyll of guava cultivar Maamoura compared to the control in the two seasons. 

As for NAA, in the two seasons, the two higher concentrations of NAA (2mg/l and 3mg/l) significantly increased the shoot length (cm) and shoot diameter (mm) compared to the control treatment. The highest concentration of NAA(3mg/l) caused a significant increase in leaf total chlorophyll (SPAD) of guava cultivar Maamoura compared to the control and the two lower concentrations (1mg/l and 2mg/l). In the meantime, the lowest concentration caused a significant decrease in the leaf total chlorophyll of guava cultivar Maamoura compared to the control and the other treatments, in the two seasons of the experiment.

It was clear that seasweed had a good influence on vegetative growth because of its high content of growth promoting hormones like IBA, cytokinins, IAA, gibberellins, and amino acids,vitamins, antibiotics and micronutrients (Zodape et al., 2008). Chlorophyll content was enhanced by seaweeds and seaweed products (Blunden et al., 1997), due to the reduction in chlorophyll degradation, which caused in part by betaines in the seaweed extract (Whapham et al., 1993).  Because of increased photosynthetic rates or the most efficient use of photosynthetic yields, gibberellic acid GA3 has the ability to boost plant growth and improvement in a number of experimental settings(Hifny et al., 2017). There have been various investigations on the role of GAs in photosynthetic processes in this scenario. Davies (1987) NAA is the artificial version of auxins, as indicated. Which play an important part in vascular tissue, cell division, differentiation, apical dominance, leaf withering, and fruit abscission.

Table (2):Effect of seaweed extract, GA3 and NAA growth regulators on vegetative growth and total chlorophyll

Means with the same letters within each column are not significantly different at 0.05 level of significance

2. Effect of seaweed extract, GA3 and NAA growth regulators on fruit set and yield components

Results regarding fruit set (%), fruit weight (g), number of fruits/ tree and yield (kg/ tree) of guava cv. "Maamoura" as influenced by seaweed extract, GA₃ and NAA levels are presented in Table (3).

Results presented in Table (3) indicated that, in the two seasons, the three concentrations of seaweed significantly increased fruit set (%), fruit weight (g), number of fruits/ tree and yield (kg/ tree) of winter guava cultivar Maamoura compared to the control treatment. In the meantime, there were significant differences among the three treatments so that fruit set (%) and fruit weight(g), number of fruits/ tree and yield (kg/ tree) increased by increasing the concentrations of seaweed extract.

As for GA₃, in the two seasons, the three concentrations of GA3 significantly increased fruit set (%) and fruit weight(g), number of fruits/ tree

and yield (kg/ tree) of winter guava cultivar Maamoura compared to the control treatment, except for the lowest concentration (1 mg/l) for the number of fruits/ tree in the two season. In the meantime, there were significant differences among the three treatments, in the two seasons for the four measured traits.

As for NAA, in the two seasons, the three concentrations of NAA significantly increased fruit set (%) and fruit weight(g), number of fruits/ tree and yield (kg/ tree) of winter guava cv. Maamoura compared to the control treatment, except for the lowest concentration (1 mg/l) for the number of fruits/ tree in the two seasons and the lowest concentration for yield (kg/ tree) in the second season. In the meantime, there were significant differences among the three treatments for all traits, except between the two higher concentrations (2 and 3 mg/l) in the first season for the number of fruits/ tree.

The above results clear that, seaweed has a good influence on yield and fruit quality and this could be because of its high content of growth promoting hormones like IBA, IAA, cytokinins, gibberellins,vitamins, micronutrients, amino acids, and antibiotics (Zodape et al., 2008). Baghdady et al. (2014) sprayed In comparison to control plants, Valencia orange trees treated with GA3 at concentrations of 15 or 25 at full bloom stage had higher initial and ultimate fruit set percentages. Fruit weight increased by increasing the beneficial effect of GA3 from the mobilization of food reserves and accumulation of more pulp. This result is in conformity with that of  Lal et al. (2013) on guava.

The exogenous supply of NAA treatment aided in the strengthening of the middle lamella and, as a result, the cell wall, and may have increased the mobilisation of food materials and minerals from other parts of the plant towards the development of highly active metabolic sink fruits, resulting in increased fruit weight. (Katiyar et al., 2009). These observations are also in line with what has been described by Anawal et al. (2015) in the pomegranate and Pandey et al. (2001) in guava. Vani et al. (2020), also found that, The use of GA3 and NAA enhanced cell proliferation and cell elongation, which resulted in larger fruits.

The rise in yield, which was accompanied by an increase in the quantity of fruits, a low percentage of fruit drop, higher fruit retention, and increased fruit size and weight under the growth regulators treatment, was verified by those previously reported by Jawed (2017).

Table (3): Effect of seaweed extract, GA3 and NAA growth regulators on fruit set and yield components

Means with the same letters within each column are not significantly different at 0.05 level of significance

3. Effect of seaweed extract, GA3 and NAA growth regulators on some fruit physical properties

The results regarding  fruit length (cm), diameter (cm) and firmness (Ib/ inch²) of guava cv. "Maamoura" as influenced by seaweed extract, GA₃ and NAA levels are presented in Table (4).

As for seaweed extract, results in Table (4) showed that, in the two seasons, the three concentrations of seaweed extract significantly increased fruit length (cm), fruit diameter (cm) and fruit firmness (Ib/ inch²) compared to the control treatment, except for the lowest concentration (5 mg/l) for fruit diameter (cm), in the two seasons. In the meantime, there were significant differences among the three concentration (5, 10 and 15 mg/l) for fruit length, diameter and firmness which increased by increasing the concentrations of the seaweed extract.

As for GA3, in the two seasons, the three concentrations of GA3 significantly increased fruit length (cm), fruit diameter (cm) and fruit firmness

(Ib/ inch²) compared to the control treatment. In the meantime, there were significant differences among the three GA3 concentrations for fruit length, diameter and firmness which increased by increasing the concentrations of GA3 during the two seasons.

As for NAA, in the two seasons, the two higher concentrations of NAA significantly increased fruit length (cm) and fruit firmness (Ib/ inch2) compared to the control and the lowest concentration of NAA.  In the meantime, there were significant differences between the highest concentration (3 mg/l) compared to the middle one (2mg/l), during both seasons. While, the highest concentration of NAA (3 mg/l) caused a significant increase in fruit diameter compared to the control and the two lower concentrations (1 and 2 mg/l) in the first season and compared to the control and the lowest concentration (1 mg/l) in the second season.

Form the above  results, seaweed has a good influence on yield and fruit quality and this  could be because of its high content of growth promoting hormones like IAA, IBA, cytokinins, gibberellins, and amino acids, vitamins, antibiotics and micronutrients (Zodape et al., 2008). It is well known that, NAA and GA3 had many functions in plant nutrition and growth that influence physical properties of fruits. These included enhancing metabolic processes such as protein synthesis; cell division and fruit growth. The aforementioned roles of the two growth regulators could explain its effect on improving fruit physical properties and photosynthesis; activation of carbohydrate metabolized for synthesis of amino acids (Arunadevi et al., 2019 and Abd El-Sabor, 2020) on lime trees.

Table (4):Effect of seaweed extract, GA3 and NAA growth regulators on some fruit physical properties

Means with the same letters within each column are not significantly different at 0.05 level of significance

4.Effect of seaweed extract, GA3 and NAA growth regulators on some fruit chemical characters

Results regarding the percentage of total soluble solids (TSS%), acidity (%), vitamin C (mg/ 100 ml) and total sugars (%) of guava cv. "Maamoura" as influenced by seaweed extract, GA₃ and NAA levels are presented in Table (5).

As for seaweed, in the two seasons, the three concentrations of seaweed extract significantly increased the fruit total soluble solids (TSS), vitamin C (mg/ 100 ml juice) and total sugars (%) compared to the control treatment. In the meantime, there were significant differences among the three seaweed extract concentrations for fruit total soluble solids percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) which increased by increasing the concentrations of the seaweed extract. In contrast, the three concentrations of seaweed extract significantly decreased fruit acidity percentage compared to the control  treatment in the two seasons. In the meantime, there were significant differences among the three seaweed extract concentrations for fruit acidity which decreased by increasing the concentrations of the seaweed extract.  

As for GA3, in the two seasons, the three concentrations of GA3 significantly increased fruit total soluble solids (TSS) percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) compared to the control treatment. In the meantime, there were significant differences among the three GA3 concentrations for fruit total soluble solids percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) which increased by increasing the concentrations of GA3 during both seasons. In contrast, the three concentrations of GA3 significantly decreased the fruit acidity percentage compared to the control treatment in the two seasons. In the meantime, there were significant differences among the three GA3 concentrations for fruit acidity which decreased by increasing the concentrations of GA3.

As for NAA, in the two seasons, the three concentrations of NAA significantly increased fruit total soluble solids (TSS) percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) compared to the control treatment. In the meantime, there were significant differences among the three NAA concentrations for fruit total soluble solids percentage, vitamin C (mg/ 100 ml juice) and total sugars (%) which increased by increasing the concentrations of NAA during both seasons. In contrast, the three concentrations of NAA significantly decreased the fruit acidity percentage compared to the control treatment in the two seasons. In the meantime, there were significant differences among the three NAA concentrations for fruit acidity which decreased by increasing the concentrations of the NAA.

This considerable rise in TSS content of fruit could be explained by GA3 stimulating the operation of a number of enzymes in the physiological process, which likely caused the reported increase in TSS content of fruit by Garmendia et al. (2019). According to, the drop in acidity in growth regulators treated fruits could be related to the quick consumption of organic acid during respiration at maturity by Agnihotri et al (2013) and Rajput et al (2016).

         The GA3 treatment raised the sugar content in the fruit by stimulating the production of the hydrolytic enzyme, which dissolved complex polysaccharides into simple sugar. Growth regulators promoted the transfer of photosynthetic metabolites from other areas of the plant to growing fruits. This discovery is consistent with the findings of Kumar  and Rattanpal  (2010) in guava. The proportion of total sugars could be ascribed to growth regulators' assist in photosynthesis, which resulted in further oligosaccharides and polysaccharides getting formed. They also control enzymatic activity, ensuring that enzymes swiftly convert starch to soluble sugars, resulting in early ripening in response to growth stimuli. Observations similar to these were made by Agnihotri et al (2013) in guava.

Table (5): Effect of seaweed extract, GA3 and NAA growth regulators on some fruit chemical characters

Means with the same letters within each column are not significantly different at 0.05 level of significance

5. Effect of seaweed extract, GA3 and NAA growth regulators on some leaf macro nutrients

The results regarding the percentages of nitrogen, phosphorus and potassium contents of guava cv. "Maamoura" as influenced by seaweed extract, GA₃ and NAA levels are presented in Table (6).

The data in Table (6) showed that, in the two seasons, the three concentrations of seaweed extract (5, 10 and 15 mg/l) significantly increased the leaf nitrogen, phosphorus and potassium percentages compared to the control treatment. In the meantime, there were significant differences among the three seaweed extract conentrations for nitrogen, phosphorus and potassium percentages content which increased by increasing the concentration of the seaweed extract.

As for GA3 in the two seasons, the three concentrations of GA3 (1, 2 and 3 mg/l) significantly increased the leaf nitrogen, phosphorus and potassium percentages compared to the control. In the meantime, there were significant differences among the three GA3 concentrations for nitrogen, phosphorus and potassium percentages content which increased by increasing the concentration of the GA3.

As for NAA, in the two seasons, the three concentrations of NAA (1, 2 and 3 mg/l) significantly increased the nitrogen, phosphorus and potassium percentages compared to the control treatment. In the meantime, there were significant differences among the three NAA concentrations for leaf nitrogen, phosphorus and potassium percentages which increased by increasing the concentrations of the NAA.

                It was clear that, seaweed contains a high amount of potassium, nitrogen and phosphorous (Elumalai and Rengasamy, 2012). The content of macronutrients in the leaves of seaweed extract has been found to improve (Mancuso et al., 2006). In addition, the quantities of K, Fe, and Cu in the leaves of olive trees sprayed with marine extract increased (Chouliaras et al., 2009). A promoting of biomass has been shown to exert production of Gibberellic acid induces DNA, RNA, and protein synthesis along with ribose and polyribosome proliferation in vegetative organs. GA3 treated trees accumulate biomass Improvements in enzyme activity and membrane permeability may make mineral nutrient absorption and utilisation easier and transport of photosynthates (Miceli et al., 2019).

Table (6):Effect of seaweed extract, GA3 and NAA growth regulators on some leaf macro nutrients

Means with the same letters within each column are not significantly different at 0.05 level of significance