Biochemical changes in seed in relation to corky tissue development of sapota [Manikara achras (Mill.) Fosberg]

Abstract

Corky tissue is a physiological disorder affecting Cricket Ball variety of sapota to the tune of 50% or more especially in the summer season. The affected fruits do not show any external symptoms and becomes apparent only after the fruit is cut open. Corky tissue affected fruits are characterized by a hard lump within the pulp and are less sweet to taste and in extreme cases the fruits give out a unpleasant odour. As such, the corky tissue affected fruits become unit for consumption. Very little work has been reported so far on the biochemistry of the disorder. Studies conducted tin this work showed that CT incidence increased with increasing number of fruits per panicle. GA3 treated fruits showed lower incidence of CT as compared to control and PBZ treatment increased the incidence of CT. CT incidence increased in fruits harvested during summer season (Mar- April) as compared to winter season (Nov-Dec) and similarly incidence was more under rain fed treatment as compared to irrigated treatment. Radio tracer experiment showed there was an increased flow of water away from the fruit to shoot during CT formation. Biochemical studies revealed that in CT affected fruit pulp, reduced sugars, total soluble sugars, proteins, fatty acids, mineral nutrients and enzyme activities like amylase, lipase were reduced and starch content was higher as compared to healthy fruit pulp. And in case of seeds of corky tissue affected fruits, protein, free fatty acids, starch and enzyme activity like total dehydrogenase, lipase and germination percentage showed decreasing trend, but reducing and total soluble sugars content were higher compared to seeds from healthy fruit. These above findings, indicated the dominant role of competition among different sinks and loss of viability of seeds in the induction of CT in sapota