Impact of various horticultural practices on physical and biochemical parameters during flowering and fruiting in mango cv. Alphonso

Introduction

The mango (Mangifera indica L.) is acclaimed as the King of fruits in Indian continent owing to its exquisite taste, flavour, attractive colour, nutritional value and diverse end uses. The Mango is native to South and Southeast Asia from which it was distributed worldwide to become one of the most cultivated and the choicest fruit in the tropical and subtropical world. The Mango is dicotyledonous belongs to family Anacardiaceae and genus Mangifera. In India almost all commercial cultivars belonging to a single mono-embryonic species i.e Mangifera indica L. It is the most important tropical fruit of the world. It can also be grown in the subtropical conditions and up to an elevations of 1400 m above the mean sea level. The optimum temperature range for its growth is 18 to 35 °C and can tolerate temperatures up to 48 °C. It can survive in areas having an average annual rainfall ranging from 250 mm to 2000 mm. Loamy, alluvial, well drained, aerated and deep soils rich in organic matter with a pH range of 5.5 to 7.5 are ideal for mango cultivation. It is originated from Indo-Burma region having 41 recognized species and originating as forest tree with fibrous and resinous fruits (Mukherjee, 1951 and1967) [20, 21] . It is cross-pollinated fruit crop having chromosome number 2n=40. It has been variously called Amra, Chuta, Sahakara, Rasala, Atisourabha in ancient Sanskrit literature, and the tree has been described as wish-granting tree or kalpavriksha. Mango crop particularly in Konkan starts its annual phenological cycle in June with onset of monsoon and ends with a rest period after harvesting of mango in May. Major new vegetative flush is expected to sprout on the tree during June-July which will take a time of International Journal of Advanced Biochemistry Research 2026; SP-10(6): 1547-1554 three month to get mature in low light intensity during rainy season and became mature up to September-October initiating flowering is a normal phenological cycle. These mature flushes remain dormant for next two to three month up November to December. It actively manufactures carbohydrates and then initiates the process of flowering. It takes nearly 100 to 120 days for fruit maturity from fruit set. The annual cycle ends with harvesting of mango fruits in the month of April/May followed by rest up to onset of Monsoon. So, to get early harvest tree must flower early in the season which is ultimately dependant on development of new vegetative flush. Fluctuation in the any phenological stage of the cycle directly affects the yield of crop resulting in gain or loss (Burondkar et al., 2018) [3] . There are many factors which affects the regular flowering in mango i.e external factors due to environment like temperature, rainfall, insect-pest and diseases (bee, fruit fly, mango hopper, malformation, anthracnose, die-back), chemical and pesticides, nutrient supply, disturbed water relations. The internal factors are imperfect flower, genetic incompatibility, physical influences (premature or delayed pollination), nutritive condition of plants. Recently it was also observed that climatic shift affects the flowering in mango (both delay and early), resulting in yield and quality of fruit, variation in temperature, unseasonal rainfall and higher humidity cause altered flowering trends, delays in panicle emergence and fruit set due to disturbance in phenophases. Very low night temperature and unseasonal rains in sub-tropics may result in low fruit set while low day temperature reduces the pollination activities. High temperature during panicle development in mango speed up the growth due to which less number of days are available for effective pollination which may lead to low production and it also causes desiccation of stigma and poor pollination resulting in poor fruit set. Unseasonal rain coupled with variation in temperature may induce the off-season flowering in some cases but the fruit setting will be poor. Rise in carbon dioxide concentration alone increase mango production but when it is combined with high temperature and changes in solar radiation cause decrease in production. Flower buds exposed to cold temperature during night time may change into vegetative ones under warm night conditions. In tropics, cool winter days followed by hot summer days may result in poor flowering. Cool temperature at the time of inflorescence growth reduces the perfect flowers number (Subedi, 2019) [37] .

Material and Methods

The present experiment was conducted at Centre of Excellence for mango, College of Horticulture, Dapoli. The experiment was conducted during the year 2022-23 and 2023-24. During the investigation, the effect of tip pruning, basin exposure, girdling and paclobutrazol on induction of flowering, fruit set, physical parameters and biochemical composition of leaves was studied. Tip pruning was done to make a tree more productive and to bear quality fruits with increased longevity to achieve more manageable shape and to get maximum returns from the orchard. This practice is useful where trees have a vegetative flush just prior to flowering. The young flushes are cutback to mature wood; the resulting flush should be floral one. The new shoots emerged after monsoon was allowed to grow fully till their growth ceased. At this stage the colour of this new shoot was light green. Removal of new shoots was performed on these shoots as per the treatment details. Total 200 shoots were tip pruned in each experimental plant of respective treatment.

Girdling was done as per treatment details on tertiary branches having 3 to 4 cm circumference by giving a deep circular cut penetrating cambium layer with the help of sharp knife as per the treatments. Total 50 per cent branches were girdled per experimental plant. Basin exposure was done by loosening the soil around tree trunk up to radius of 2cm up to 20 to 30 cm depth. This will help in evaporating excess moisture and imparting stress which is prerequisite for flower initiation. Application of paclobutrazol is @ 0.75 ml active ingredient per meter average canopy diameter during 15th July -15th August is advocated and its application methodology has been standardized.

Result and Discussion

The data pertaining of physical parameters and biochemical analysis of leaves are presented in Table 2, 3 and 4. The results revealed significant differences among all the treatments.

Days required for induction of flowering after exposure of treatment

The application of tip pruning, basin exposure, girdling and paclobutrazol were advantageous for induction of early flowering in mango cv. Alphonso. The minimum days required for induction of flowering (38.97 days) was recorded in treatment T6 which was at par with treatment T1 (40.12 days) and T5 (45.57 days), whereas the maximum days required for induction of flowering was recorded in treatment T10 (71.21 days). Pruning reduces the auxin synthesis at the apex of the branches, directing the transport of assimilates and cytokinin's to the axillary buds of branches, creating the favourable condition for flowering (Taiz and Zeiger, 2012). Under such conditions axillary inflorescences are formed (Srivastava, 2002). The annual shoot tip pruning in mango provides reliable synchronized flowering in selected shoots year after year in trees, which also helped to maintain the canopy size of the plants for several years (Davenport, 2006) [39, 36, 7, 29, 5, 33] .

The maximum flowering intensity (68.87%) was recorded in treatment T1 followed T4 (67.01), T6 (64.84), T7 (62.10), T9 (61.17), T5 (59.35), T3 (57.06), T2 (56.83), T8 (53.35), whereas the minimum flowering intensity was recorded in treatment T10 (51.16%). Thus, the application of tip pruning, basin exposure, girdling and paclobutrazol were beneficial for increasing flowering intensity in mango cv. Alphonso. Removal of new shoots would bring an optimum cytokinin/gibberellin balance required for flowering (Rao and Khader, 1980). Higher percentage of flowering due to pruning treatments was attributed mainly due to better availability of photosynthetically active solar radiation to the leaves causing alteration in the IAA activities, which enhanced flowering (Lal and Misra, 2007). The greatest number of inflorescences was observed when tip pruning was used in Palmer mango trees (Oliveira et al., 2015).

Girdling is one of the ways to improve the earliness and intensity of flowering in mango cv. Cogshall ( [25, 18, 22, 12, 42, 30, 16, 44] .

The longest panicle was recorded in T4 (29.64) which was followed by treatment T1 (28.98 cm), T6 (28.10 cm), T7 ( where pinching treatment alone induced the highest increments in total number of panicles per tree in mango cv. Zebda. Rodge and Pujari (2017) found highest length of reproductive shoot in 50 per cent current season pruning method carried out in third week of October in mango cv. Alphonso. Zaeneldeen (2014) studied effect of pinching of early developed panicles from mid-December to mid-February in mango cv. Succary Abiad [38, 12, 34, 27, 26, 43] .

The highest percent of hermaphrodite flower (12.81%) was recorded in treatment T1 which was at par with treatments T4 (12.77%), T9 (12.56%), T5 (12.46%), and T6 (12.35%), whereas the lowest percentage of hermaphrodite flower was recorded in treatment T10 (10.34%). Aghav (2021)

in mango cv. Amrapali [1, 2, 29, 41, 32, 28, 45] .

Fruit set per panicle at pea stage

The highest fruit set per panicle (9.71) was recorded in treatment T4 which was at par with the treatment T1 (9.51).

It was followed by treatment T6 (9.31), T5 (9.30), T9 (9.15), T7 (8.91), T2 (8.80), T3 (8.73), T8 (8.57), whereas the lowest fruit set per panicle was recorded in treatment T10 (7.72). The increase in sink activity and increase in respiration or activation of enzymes or growth promoting substances increased the fruit set (Jadhav, 1996) Baneshan [15, 35, 41, 9, 4, 34, 16, 46, 47] .

The highest fruit retention (0.73%) was recorded in treatment T4 which was at par with treatment T1 (0.72%), T5 (0.71%), T9 (0.71%), T5 (0.71%) and T6 (0.70%), whereas the lowest fruit retention was recorded in treatment T10 (0.55%). Fruit retention is influence by the level of endogenous hormones which directly relates with translocation of assimilates to competing areas of growing shoots and fruits (Jadhav, 1996). All the girdling treatments showed higher fruit set values compared to the control. The fruit retention was maximum on Alphonso mango trees treated by paclobutrazol. Higher fruit retention due to paclobutrazol application was probably due to controlled vegetative growth and higher accumulation of carbohydrates in leaves (Hoda et al., 2001). Similar finding for increase in fruit retention per panicle in response to paclobutrazol application was also recorded in mango by Ram and Tripathi (1993) in cv. Dashehari; Oosthuyes and Jacobs (1997) cv. Sensation and Tommy Atkins [35, 15, 41, 24, 14, 48, 49] .

The total non-structural carbohydrates in terminal shoots were analysed at different stages viz., at one month before flowering (vegetative stage, before exposure of treatment), during flowering stage and after flowering in mango varied significantly among the treatments. One month before flowering, the NSC content was non-significant. During flowering stage, treatment T1 (4.35%) recorded highest NSC content which was at par with T4 (4.33%) T5 (4.30%) and T6 (4.24%) and significantly superior over all other treatments. The lowest NSC content were noted in control T10 (1.84%). Similar trend was also observed after flowering where in treatment T1 (0.68%) had the highest NSC which was at par with T4 (0.66%) and T5 (0.65%). The lowest NSC content was observed in control T10 (0.30%). It was also noticed that, removal of new shoots significantly increased accumulation of non-structural carbohydrates in mango cv. Alphonso. Mango flowering is predominantly influenced by the biochemical constituents present in the twig for the floral stimuli at bud break stage. The state of biochemical constituents primarily determines the synchronizing of flower stimuli which leads early flower induction. Bhuwad et al., (2022) found the highest non-structural carbohydrates content in leaf at two months after treatment exposure followed by one month before treatment exposure while lowest NSC was observed at four months after treatment exposure. The highest total non-structural carbohydrates might be due to increased source sink activity and demand for assimilates (Elkhishen, 2015). Pruning induces hydrolysis and transport of reserves accumulated in the roots (Eyles et al., 2009). Satoh and Ohyama (1977) observed similar results in the mulberry; Rom and Ferree (1985) in peach respectively. Leaf non-structural carbohydrates are mainly composed of soluble sugars in leaves are primarily glucose, sucrose and fructose (Hoch et al., 2003) [2, 10, 11, 50, 51, 52] .

C:N ratio

The C:N ratio was non-significant before flowering. During flowering, treatment T4 (30.35) (2002) reported that the high endogenous ratio of carbon to nitrogen ratio in plants is stimulatory to flowering, whereas a low C:N ratio favours vegetative growth. Fruit set, fruit growth and fruit quality are also closely related with carbohydrates availability [23, 8, 13, 17, 19, 6] .

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