Int.J.Curr.Microbiol.App.Sci (2021) 10(01): 1218-1235 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 10 Number 01 (2021) Journal homepage: http://www.ijcmas.com Review Article https://doi.org/10.20546/ijcmas.2021.1001.146 Alternate Bearing in Fruits Trees: A Review Ashok Kumar1*, B. D. Bhuj2 and C. P. Singh2 1Department of Horticulture, SGT University, Gurgram, Haryana, [NCR Delhi], India 2College of Agriculture, G.B.P.U.A &T- Pant Nagar, U.P., India *Corresponding author ABSTRACT Alternate Bearing is an alternating pattern of large and small crops occurring in many fruit species that is internally regulated by the plant. Alternate bearing in mango appeared to be related to complex relationships between vegetative and reproductive growths and it is varied according to the cultivar. Flowering is the main event that set the stage for mango K eyw or ds production each year. For the attaining the fruit flower initiation is very important and it is very complex phenomena in mango. Flowering is the main event that set the stage for Mango (Mangifera indica L., Fruit mango production each year. For the attaining the fruit flower initiation is very important production, Cultivar and it is very complex phenomena in mango. In mango trees flowering is make them evaluation, especially challenging for physiologists, breeders, and growers. North, east and central Breeding , Irrigation Indian commercial cultivars showed the biennial bearing is very serious problem, while most of the south Indian varieties bear regularly. Therefore, different control measures for Article Info the biennial bearing are application of different chemicals, smudging, pruning etc. most widely used in view of its high potential mango production. This review classifies the Accepted: multiple hypotheses as internal, genetic, carbohydrate resources and hormones or 12 December 2020 environmental, abiotic and biotic stresses. The biennial bearing or alternate bearing habit Available Online: of mango (Mangifera indica L.) is a major problem for its commercial cultivation for 10 January 2021 getting expected productivity, alternate bearing, alternate year cropping, irregular bearing or cropping, periodicity in mango cropping, biennial bearing, are all synonymous terms which are different from the unfruitfulness and shy cropping. Introduction is internally. Regulated by the plant. This alternate bearing pattern is common in many Mango (Mangifera indica L.) is an evergreen of the perennial trees and shrubs but is not tree in the family Anacardiaceae grown for its universal. Apple is one of the heavily-studied edible fruit. The mango tree is erect and fruit crops with regard to alternate bearing branching with a thick trunk and broad, because of its high economic importance. rounded canopy. The tree produces dense Alternate bearing is an important economic clusters of flowers with cream-pink petals on problem for a number of fruit and nut growers branched panicles. Alternate Bearing means worldwide. Under normal conditions, olive an alternating cropping pattern of the tree that trees produce heavy crops one year (the “on” 1218 Int.J.Curr.Microbiol.App.Sci (2021) 10(01): 1218-1235 year) and light ones the next (the “off” year). few QTLs associated with AB, and suggested Experience has shown that large olive yields that hormone-related genes are likely to play a tend to lead to smaller crops the following role in the phenomenon. Once a woody year. The potential light crop is predictable perennial plant has passed the juvenile period from the limited amount of new growth when it cannot be induced to flower and has present in the trees. The previous heavy crop reached its adult phase of reproductive limits shoot growth and, because flowers are competence, a proportion of its meristems produced only on the new shoots of the will initiate floral organs annually. previous season, the tree's potential for olive production is reduced. This alternate bearing Flowering in temperate tree species can be is one of the most important limitations of divided into several stages that include flower natural extensive olive cultivation. induction, flower initiation, flower differentiation, and blooming. Flower The mechanism(s) by which the developing initiation is the key developmental stage for crop influences return bloom and yield the fruit trees, particularly for horticultural crops following year is not fully understood. Two such as the apple (Malus×domestica Borkh.), hypotheses have been suggested. The because it determines the success of “nutritional” hypothesis holds that return commercial orchards (Buban and Faust, bloom and yield are proportional to tree 1982)(4) by its influence on fruit quantity and carbohydrate status. Lack of carbohydrate in quality (Link, 2000)(21), as well as stability the ON year directly or indirectly reduces of production from year to year (Schmidt et flowering the following year. Support for this al., 1989)(32). Flower initiation can be hypothesis has been provided by showing strongly limited by an excessive crop, leading positive correlations between carbohydrate to the phenomenon known as biennial bearing levels and AB status, whereas others have (Jonkers, 1979; Monselise and Goldschmidt, shown no consistent relationship between tree 1982) (20, 26, 14). Commonly used terms carbohydrate status and floral intensity at related to alternate bearing include biennial return bloom. The “hormonal” hypothesis bearing and irregular bearing. Biennial proposes that developing fruit produce an bearing is characterized by large yields of inhibitor that directly or indirectly reduces small sized fruit in „on‟ years, and low yields, flowering in the spring following the ON sometimes even no fruit, in „off‟ years. This crop. alternation is a widely spread phenomenon, occurring in both deciduous and evergreen Although a number of studies have shown trees, and in different tree families and correlations between abscisic acid or indole- species such as nuts (hazelnuts, pecans, 3-acetic acid and AB status, no direct pistachios, and walnuts), temperate fruits evidence has been provided for their (apple, apricot, pears, and prunes), subtropical involvement in the return bloom. Gibberellins fruits (avocados, citrus, and olives), tropical (GA) is well-known inhibitor of flowering in fruits (litchis and mangos), and forest trees citrus; thus, fruit-produced GA has been (beeches, oaks, pines, and spruces) presumed to be involved in AB. Despite these (Monselise and Goldschmidt, 1982)(14). findings, the roles of carbohydrates and hormones in AB remain unclear and more Although generations of scientists have tried research is needed to identify factors affecting to understand this phenomenon, the cause of floral intensity following ON and OFF years. alternate bearing is still largely unknown Genetic analysis of AB in apple identified a (Hoad, 1978; Jonkers, 1979; Monselise and 1219 Int.J.Curr.Microbiol.App.Sci (2021) 10(01): 1218-1235 Goldschmidt, 1982; Bangerth, 2006, 2009) through the pedicel than annual bearing (19,20,26,14,3). External factors cultivars do (Hoad, 1978)(19), and the peak (photoperiod, temperature, and water stress), activity of GA in apple seed coincides with FI internal factors such as the carbon-to-nitrogen (Luckwill, 1970)(23), it has been difficult to ratio and hormones (auxins, cytokinins (CKs), obtain convincing evidence for the transport abscisic acid, ethylene, and gibberellins of GA from seed in sufficient quantities to (GAs)), as well as interaction with other inhibit FI. Bangerth (2006)(3) proposed that organs (leaves, terminal shoot growth, and auxin could be the mobile signal and might fruit) affect flower formation in apple (for stimulate GA synthesis in the meristem. In reviews, see Hanke et al., 2007; Bangerth, this model, GA and auxin could potentially 2009) (17,2). The negative relationship act as FI-inhibiting signals working in between fruit development and flower bud concert, GA as the primary messenger that differentiation is one of the most investigated stimulates the synthesis/transport of the causes of flower set variability in apple, as the second messenger auxin. However, differentiation of flower buds in apple characterization and quantification of both overlaps with embryo development in the GA and auxin in the meristem still need to be previous season's fruit (Harley, 1942; Foster performed and, moreover, an inhibitory effect et al., 2003)(18,13), leading to competition of GA/auxin and stimulation by CK on the between flower initiation and fruit formation. expression of genes related to FI remain to be demonstrated (Bangerth, 2006)(3). Experiments using „Spencer Seedless‟, which can bear both parthenocarpic and seeded fruit, Technologies to induce regular bearing in suggested that seed development rather than mango nutritional competition may be a factor in alternate bearing (Chan and Cain, 1967; The flowering phenomenon in mango is a Neilsen and Dennis, 2000)(7,27). The number complex one. Normally, it crops heavily in of seed per fruit or per bourse (flowering one year (on year) and bears less or no crop growth unit) has an effect on biennial bearing, the following year (off year). Again, it yields which can be overcome by a high vegetative heavily the next year. Thus the rhythm of growth rate of the bourse shoot itself (Chan bearing in mango is not strictly „alternate' but and Cain, 1967; Grochowska and „irregular' or „erratic'. Research findings have Karaszewska, 1976; Hoad, 1978; Neilsen