STUDIES ON THE EFFECT OF MALFORMATION ON GROWTH, SEX RATIO, FRUIT SET AND YIELD OF MANGO

Mango malformation is widespread in the country. The incidence of this disease is variable in different climatic conditions of India. It is most severe in North India and is less in other regions. In the present paper attempts were made to find out the effects of malformation on growth, sex-ratio, fruit set and yield, so as to understand further on the causative agents of this maladay.

Malformation modifies plant growth in various ways. The modification of vegetative parts gives the disease appearance as is usually called 'vegetative' malformation, in which case all the axillary buds start growing simultaneously. These sprouts possessed very short internodes and the lamina is converted to needle like outgrowths (figure 1). Similar modification was also observed in case of floral buds, where sprouts simultaneously appear throughout the length of the shoot (figure 2). The above two cases clearly demonstrate the complete destruction of apical dominance in malformed parts. The other type of modifications of vegetative part were usually found in grown up trees. Instead of typical vegetative malformation symptoms as described above, the axillary buds at the internode and sometimes on the whole shoot, become swollen. These outgrowths have been termed as 'scars'. A positive correlation was found to exist between the scar on the shoot and the floral malformation.

The malformed panicles were classified according to degree of compactness as 'Heavy'. 'Medium Heavy' and 'Light' (figure 3). Of the three types of malformed panicles, 'Heavy' and 'Medium Heavy' types are persisting in nature and hang on a tree even after the flowering season is over. The distribution of different types of malformed panicles in the commercial varieties of North India is shown in table 1.

The frequency of 'Heavy' type of malformed panicles was lowest in Bombay Green which on the other hand showed the highest incidence of 'Light' type of panicles. Dashehari, Chausa and Langra bore both 'Heavy' type of panicles in quite high frequency.

Malformed panicles continue flowering far ahead of the normal flowering season. As a result of which the number of flowers per panicle are increased tremendously. The number of flowers in case of 'Heavy' type of panicles was about 5 times in case of the variety Langra and about twice greater than the normal panicles of the varieties Dashehari and Chausa (table 2).

In the 'Medium Heavy' type of panicles, the number of flowers were three times in the variety Langra and one and half times greater in the