MSc

Avocado (Persea americana Mill.) popularly known as butter fruit, is a subtropical fruit belonging to family Lauraceae. The present work undertaken in the Department of Fruit Science during the period 2018-19 to study the morphology, flowering pattern and fruit set in avocado (Persea americana Mill.) grown in high ranges of Kerala is the pioneer study done in avocado. Basic characterization of 25 accessions of avocado maintained at Regional Agricultural Research Station, Ambalavayal in Wayanad district was carried out. Morphological and phenological characters of tree, leaf, inflorescence, fruit and seed were evaluated as per the IPGRI descriptor for avocado (Persea spp.).
The age of accessions ranged from 6-51 years and hence wide variability with respect to tree characters such as tree height (5.87 to 14.50 cm), trunk girth (33.10 to 274 cm), crown shape (circular, columnar, obovate and irregular), branching pattern (axial, ascendant, horizontal and verticillate), leaf blade length (15.46 to 23.47 cm), leaf width (5.54 to 13.15 cm), leaf blade colour (dark green and green), leaf shape (lanceolate and narrowly obovate), shoot length (89.60 to 42.02 cm) and internodal length ((1.82 to 5.78 cm) were observed among the accessions.
Out of the 25 accessions studied, 23 accessions flowered during the period of study. Avocado is known to exhibit a distinct flowering pattern and both A type (in 8 accessions) and B type (in 15 accessions) flowering pattern were noticed. Greenish yellow inflorescence were found to be borne terminally on shoots. Average number of flowers per inflorescence was 137.20 with average inflorescence length of 8.16 cm and width of 10.25 cm. Flushing in avocado occurred during the months of February (3 accessions), March (2 accessions) and September (2 accessions) and flushing was noticed twice in a year during August and February (6 accessions), September and February (6 accessions) and September and March (6 accessions). All the 23 accessions flowered during September to October and 18 out of 23 accessions
flowered again in February to March. Flowering continued from 25 to 45 days and flowers were found to set fruits in 12 to 35 days and fruits reached harvest maturity in 109 to 164 days. Both single fruiting season (47.7 %) and double fruiting season (51.8 %) were observed.
On an average, yield per tree was 89.29 kg and number of fruits per tree was 904. Variability was observed in fruit characters such as fruit weight (152.40 to 434.20g), fruit shape (narrowly obovate, clavate, obovate, ellipsoid, spheroid and pyriform), fruit length (7.68 to 14.66 cm), diameter (5.30 to 8.42 cm), base shape (depressed and inflated), apex shape (flattened or rounded), apex position (asymmetric or central) and pedicel position (central or asymmetrical). Fruit skin characters observed were thickness (1 mm and 2 mm), ridges (absent or entire), glossiness (weak or intermediate), surface (smooth, intermediate and rough) and colour (purple or light green). Fruit pulp was buttery in texture with light green colour near to skin and yellow or light yellow near to seed in all the 23 accessions. The fruits ripened in 3 to 15 days and had short shelf life of 1 to 2 days.
Avocado seeds showed variability in terms of weight (26.20 to 100.10g), length (3.40 to 5.57 cm), diameter (2.37 to 5.82 cm) and total phenolic content (2.4 to 37.37mg g–1). Variability was also observed for qualitative characters of seeds such as seed shape, cotyledon surface, cotyledon colour, seed position and free space of cavity.
Quality attributes such as TSS (6.3 0Brix to 10.4 0Brix), titrable acidity (0.64 to 1.28 %), TSS/acidity ratio (5.92 to 15.78) and fats (2.63 to 6.78 %) were estimated. When organoleptic evaluation of the fruits were conducted, the accessions AV-24 and AV-10 were found to be more acceptable.
Principal Component Analysis (PCA) was done for different characters and the first three components accounted for variability in tree, inflorescence and fruit
characters, whereas first two components accounted for variability in seed and quality characters. Clustering based on first two components for tree, inflorescence, fruit, seed and quality characters led to the grouping of accessions into six, eight, six, six ad five clusters respectively.
From the present study, accessions AV-3, AV-11, AV-25, AV-2, AV-10 and AV-24 were identified to be the most promising accessions in terms of yield, quality and sensory attributes.