PHYSIOLOGICAL DISORDERS IN MANGO

            Crop physiology refers to that aspect of the plant system which deals with various functions happening  in them. The functions may be respiration, photosynthesis, transpiration, translocation of photosynthates and so on. These functions are very responsive to  environment or any kind of biotic and abiotic stresses.  Sometimes  these response are negative, where normal physiological functions are  affected.  Such negative responses are considered as  physiological disorders. Usually these are disorders other than incidence of diseases or infestation of insect pests.  The physiological  disorders are mainly associated with the factors like  scarcity or abundance   of water and nutrients, hormonal imbalances and  unfavorable climatic conditions.  The mango tree is not an exception in this regard and cultivators undergo serious economic losses if these disorders persists.  Malformations, Spongy tissues,  Jhumka,  Black tip, Soft nose, Girdle necrosis, Jelly seeds, Taper tips, Pitting in fruits, Fruit Drops, Biennial bearing are the common physiological disorders in mango.

Mango Malformation or Mango Malady:

        Mango malformation otherwise known as mango malady which is of  potential threat to cause considerable yield loss. . There are two types of malformation namely, Vegetative and Reproductive. Vegetative malformation may start to occur even during seedling stage and may extend up to flower bearing. Malformation that happens during later state is called reproductive malformation.

        Vegetative malady is characterized by bunching of leaves at the tip of the shoots. Leaves become  reduced in size with  short petioles, some time scaly or rudimentary. Conditions also shows excessive branching or shoot productions with shorter nodes and inter nodes.  Such shoots shows radial extension with stunted growth.   Where as reproductive malady is of symptoms like  production of compacted and crowded panicles with shortened primary, secondary and tertiary rachis.  Panicles bear flowers compactly and the flowers are with shortened, thickened pedicil and other floral parts. Panicle mostly remains greenish and seen attached to trees even during off seasons.

        Exact reasons for mango malady is yet to be known. As per the  some study, reasons found  associated with this condition  is higher level of ethylene production by trees, induced by different biotic and abiotic factors. In contrary,  lower level of nucleic acids like RNA and DNA, plant hormone Auxin also favors the malady.   Increased level of metabolites like carbohydrates also noticed during the disorder, especially in case of  vegetative malformation.

Control: As exact reason is unknown and the  same  is believed to be associated with plenty of factors, exact control measures are not drawn. Thus it is recommended cut and clear  the malformed portions along with few inches of healthy portions attaching to them and then go for  the spray with  carbendazim @0.1%.  It has been  also found useful to spray NAA, a plant hormone@ 100-200 ppm during the month of   October. 

Spongy Tissue In Mango:

         Spongy tissue in mango is yet another physiological disorder, mainly exhibits in Alphonso cultivar. The disorder is manifested off yellow, sour and spongy pulp on ripening or pre- ripening stages of fruits. Fruits taste highly acidic and of depleted  nutrients. Sometimes fruits fail to ripen due to non -hydrolyzing of starch.

         Possible reasons derived for occurrence of spongy tissues are high temperature during fruit bearing stage and convective heat radiated from soil. Shift of the mango stone or seed from development to germination mode is also another reason found  for the disorder.  In  this case, the  stone shows tendency to germinate by drawing nutrients and water from mesocarp surrounding it, leaving the pulp spongy and acidic.  

       Control: Occurrence of spongy tissue can be controlled effectively by mulching,  where  heat convection from soil is reduced. Going for Sod culture where leguminous crops are grown in mango orchards, also considered useful. Not exposing the harvested fruits to sun light and harvesting the fruits in morning hours and  going for early harvesting of fruits, before they reach full maturity are the other measures  recomondeded   in mitigating the problem. 

Black Tip Of Mango:

            Black tip of mango is symptomatic of development of small pale patched area at the tip of the fruits. It may develop at marble stage itself. Patches become prominent and color darkens as fruits grow.   Pulp  of the fruits soften and they  drop off prematurely. It is very common in orchard located in the vicinity of brick kiln, which emit Co, CO2 and SO2 and similar kind of gases. . Dashehari has been  reported the worst affected cultivar.

Control: Better avoid area located in the vicinity of brick kiln to raise the mango orchard.  Increase the height of the chimney to 18 to 20 m from ground level also one of the important   solutions. Spray of Borax 0.6% during flower initiation, flower bloom and early stage of fruit development  has also been found effective in controlling black tip of mango.

Jhumka In Mango:

             The condition Jhumka in mango is also a physiological disorder where in bunch of fruit- lets found hanging from the tip of the panicles. They turn soon into yellow and dry later-on,  but   keep adhering to tree without falling for a longer period. Lack of pollination and fertilization have been considered as the  the main reasons for Jhumka. Excess insecticidal spray which may  kill or deter the pollinating insects visiting the tree during full bloom stage is also a possible cause.  Simultaneous vegetative and fruiting stage which deprives the photosynthates to fruit setting and developments may also contribute to disorder.

Control: Excess or uncontrolled insecticidal sprays are to be avoided during flowering stage. Spray of NAA @200 ppm may also take care of the symptoms.

Soft Nose In Mango:

           The condition of uneven ripening in mango is called soft nose.    Over ripening of fruit at the tip on  ventral side is a common symptom.  The affected portion   later becomes grayish or black and spongy. Actual cause is unknown, but application of higher level of   nitrogenous fertilizer is leading  the greater level of incidences of soft nose. Lack of calcium availability  is also one of the associated  reason reported for  said conditions.

Gelly Seeds In Mango:

         In jelly seed kind of physiological disorder,   pulp surrounding the seed or stone disintegrates to form soft mass. Later the condition spreads to larger area leading to internal cavity in  fruits. Reason associated with the condition is yet to be known.

Girdle Necrosis In Mango:

       In girdle necrosis case,  mango fruit develops certain necrotic lesion on upper half. The affected area shows dotted etiolated area leaving lower half unaffected initially. In advanced condition,  necrosis spread to entire surface. The condition is similar to that of black tips and cause  for the disorder is  location of orchard in the vicinity of brick kiln.

Biennial Bearing In Mango:

            Biennial bearing mango is a condition in which trees  bear fruits once in a two or more  years, rather every year. Usually the tree bears heavily in one year and less or no fruits in succeeding. The reason estimated  is exhaustion of nutrients and vigor due to heavy bearing.  Possibility of  mechanical damage due to heavy bearing and its harvesting can not be ruled out for alternate bearing. Depletion reserved photosynthates and  plant hormones may also contribute to the stress of the trees.    Thus  trees may take lengthier time to recover and produce new flush and flower.

          Thus there are variety of physiological disorders from which mango crop suffers and yield loss is considerable. Reasons for the most of them little known or unknown. The best way to manage such disorders is optimum supply of   nutrients  and water.  Early detection of symptoms,  removal of  affected parts, going for sod-culture and spraying with suitable  growth regulators definitely pay off in managing such distresses.