Pomology
Fatemeh Nekounam; A. Salehi
Abstract
Introduction Apple (Malus damestica L.) is one of the most popular temperate fruits in the world as well as Iran. One of the challenges in managing apple orchards is excessive fruit formation or excessive fruit drop especially in the pre-harvest stage, which affects the performance and marketable product. ...
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Introduction Apple (Malus damestica L.) is one of the most popular temperate fruits in the world as well as Iran. One of the challenges in managing apple orchards is excessive fruit formation or excessive fruit drop especially in the pre-harvest stage, which affects the performance and marketable product. Therefore, the control fruit set is required to help regular fruit production. Currently, the application of synthetic auxins as plant growth regulators are successfully practiced and mainly used in various countries, including all aspects of modern apple production to control and manipulate vegetative growth and regulation of flowering, reduce immature fruit drop, fruit maturity, firmness, and manage apple harvest. Among the auxin-type growth regulators, NAA is a synthetic auxin analogue that may down-regulate abscission-related genes and reduce the sensitivity of the abscission zone to ethylene. It has long been used to reduce or totally prevent pre-harvest fruit drops, to preserve fruit flesh firmness, and to prevent starch degradation in apples. Therefore, this experiment was conducted to evaluate the effects of NAA foliar application at different days after full bloom on controlling fruit drop and improving physical and biochemical attributes of ‘Red Delicious’ apple fruits. Findings described here may help to understand the effects this PGR on apple quality and also help on the development of strategies to reduce post-harvest losses of apple fruits.
Materials and Methods In order to study the effect of NAA on controlling fruit drop, fruit yield and quality, a factorial experiment based on randomized complete blocks design with three replications was conducted under Zanjan climatic conditions during 2023. Ten year-old ‘Red Delicious’ Standard apple trees grafted on M.9 rootstock were used as plant material. Treatments consisted of different concentration of NAA (15, 30, 50 and 75 mg L-1) sprayed at different days after full bloom (10, 25 and 40 DAFB). The date of full bloom was 04/22/2023. The fruit growth pattern was based on fruit weight and diameter during DAFB. According to fruit growth pattern, fruit were harvested at physiological maturity stage. Fruit number per replicate, fruit weight, diameter and shape index, fruit firmness, total soluble solids content and taste index were measured. Also, fruit drop percentage, fruit yield as well as fruit efficiency was estimated.
Results and discussion Advanced knowledge of apple fruit development from fruitlet to maturity is crucial for optimal prediction of year-to-year yields and fruit quality. Apple fruit growth has been defined as sigmoidal increase in fruit diameter or fresh weight. Studying two fruit growth patterns based on fruit weight and diameter data showed that fruit weight is a more appropriate indicator for drawing fruit growth patterns, and according to that, the fruits were harvested at the physiological maturity stage. Foliar spray of NAA during different DAFB showed different significant effects on fruit drop and yield efficiency. The highest rate of fruit drop (95.7 % and 85.9 %) was observed with foliar application of NAA at 10 and 25 DAFB, respectively, but its application at 40 DAFB reduced fruit drop by 46.9% compared to the control, and correspondingly the fruit yield increased by 22% compared to the control treatment. The lowest number and weight of fruits per unit shoot cross sectional area was observed in trees treated with different concentrations of NAA at 10 DAFB. The maximum fruit length (72.3 mm), diameter (75.8 mm), weight (180 g) and fruit volume (240 cm3) were obtained with application of 75 mg L-1 NAA at 10 DAFB. The foliar spray of NAA at 10 DAFB significantly increased the fruit density, flash firmness and TSS. But their use in 25 and 40 DAFB had no significant effect on fruit density and flash firmness, and significantly decreased fruit TSS by 23.9% compared to the control trees. Unlike the TSS, the value of fruit titratable acidity showed a significant increase in all three times of naphthalene acetic acid treatment compared to the control, and as a result, the fruit taste index decreased.
Conclusions The present study concluded that the positive effects of NAA in controlling fruit drop and improving the yield and fruit quality will be different depending on the time of application and the weather conditions of the region under study. According to the results, the application of NAA at 40 DAFB reduced fruit drop and increased fruit yield efficiency.
Pomology
afsaneh Salehi; Fatemeh Nekounam; Farhang Razavi
Abstract
Introduction
Apple (Malus domestica) belongs to the Rosacea family and is one of the most important fruit trees in temperate regions. Apple fruit is a rich source of vitamins, sugars, organic acids, minerals, fibers, and bioactive compounds and is widely cultivated due to its pleasant taste, aroma, and ...
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Introduction
Apple (Malus domestica) belongs to the Rosacea family and is one of the most important fruit trees in temperate regions. Apple fruit is a rich source of vitamins, sugars, organic acids, minerals, fibers, and bioactive compounds and is widely cultivated due to its pleasant taste, aroma, and texture. Due to the rising need for food and fiber per unit of land area, chemical fertilizers are becoming increasingly popular to increase yields from small plots of land. Chemical fertilizers pose major health risks and harm the environment when they are used in excess. Because of this, research in this area is heavily focused on finding and evaluating the efficiency of new products. One such approach is using biostimulants that can enhance the effectiveness of conventional mineral fertilizers. Plant biostimulants contain some nutrients (marine plant extracts, humic acids, amino acids and other natural products such as saponins and compost teas) that stimulate plant growth, even when administered in small amounts. Foliar application of seaweed extracts at 0.2% recorded maximum no. of fruits/tree, fruit weight, and yield/tree in valencia orange.
Materials and methods
In order to investigate the effect of biofertilizers on growth, yield and leaf nutrient contents of apple under climatic conditions of Zanjan, the experiment was carried out in a completely randomized block design with three replicates in 2023. Different concentration of seaweed (Alg; 0.075 and 0.15%), amino acid (GF Amino; 0.1 and 0.2%), humic acid (HA; 0.3%), commercial fertilizer Homarang, (Homa fert; 0.5%), combined chemical fertilizer (nitrogen, zinc and boron (Combinate fert; 1% urea, 0.3% zinc chelate and 0.1% boric acid)) and distilled water as a control were sprayed on the trees at 40 days after full bloom stage until runoff using a mechanical mist sprayer, and repeated three times with an 30 days interval until the physiological ripening of fruits. The experiment was carried out on 10-year-old Red Delicious apple trees grafted on M9 rootstocks. Shoot length, chlorophyll index, fruit drop percentage, yield efficiency, leaf area, leaf dry matter, leaf macro and micro nutrient were measured. The analysis of variance (ANOVA) and least significant difference test (P≤ 0.05) used to compare means within each sampling date. The Statistical analysis and standard error calculation were carried out using SAS software (V. 9.3).
Results and Discussion
The results showed that the foliar application of bio and chemical fertilizers significantly increased growth and fruit yield. So that, the highest increase in shoot length (39%) and leaf area (74.30%) compared to the control was obtained with application of seaweed 0.075%. Also, seaweed 0.15%, amino acid 0.2%, humic acid and amino acid 0.1% caused a significant increase in leaf area (42.02, 35.57, 22.27 and 16.20%, respectively) compared to the control. Foliar spray of seaweed, amino acid and chemical fertilizer increased chlorophyll index. The highest increase in chlorophyll index (50%) compared to the control was obtained with application of combined chemical fertilizer at 130 days after full bloom. These results are in agreement with the outcomes of other experiments conducted with seaweed on apple and on other crops such as grapevine. Therefore, this represents a further evidence of a possible role of seaweed extracts in the reduction of chlorophyll degradation and in delaying leaf senescence. The highest amount of nitrogen (1.66%), potassium (1.03%) zinc (150 mg g-1DW) and boron (82.5 mg g-1DW) and the lowest amount of phosphorus (0.44%) were obtained with application of combined chemical fertilizer. The highest value of iron was observed in leaf of trees treated with seaweed 0.15%, humic acid and commercial biofertilizer. Based on the results, it was observed that the amino acid, seaweed and combined chemical fertilizer have the greatest effect in reducing fruit drop (36.97, 33.37, 29.07%, respectively) compared to control) and increasing yield efficiency (respectively 2.75, 2.73 and 2.8 compared to control with 0.22 fruits No. cm-2 SCSA). These results partially are in agreement with another research performed on apple, where the use of a similar seaweed extract (Ascophyllum nodosum) was found able to induce a higher final yield. The hormonal components found in the extracts, particularly cytokinins, are assumed to be responsible for the increased yield in plants treated with seaweed. Previous studies mentioned that the application of biological fertilizers alone or in combination with the mineral fertilizers had positive influences on the leaf plate area, mean fruit weight and fruit chemical composition.
Conclusions
According to the results of this research, the use of biofertilizers, especially seaweed (0.15%) and amino acid (0.1%), are suitable and nature-friendly substitutes for chemical fertilizers and can play a significant role in increasing growth indices and yield of apples.
