Abstract
A study was carried out at the orchard of Jackfruit Research Project, Department of Horticulture, Bangladesh Agricultural University, Mymensingh during the years 2000-2003 to investigate plant characteristics, yield potential, floral biology, pollination behaviour, fruit set and development, fruit deformity and physico-chemical characteristics of fruit of selected jackfruit germplasm. The germplasm bore fruit annually. The harvesting season started from May and ended in August. The harvesting period of individual germplasm lasted for 10 to 45 days. A three years average fruit yield ranged from 44.8 to 324.0 kg per plant with an average of 140 kg. Germplasm J-19/2, J-14/1, J-10 and J-65 were high yielder. Maximum fruits were produced on primary branch. Flowering started from the first week of November and continued up to the last week of May. The inflorescence of jackfruit is spike. Male and female spikes were borne separately on the same tree. Eleven distinct stages of floral bud development were observed in germplasm. Time required for floral bud development varied from 51.4 to 66.8 days with an average of 59.7 days. Spikes were borne on special type of floral branchlets coming out from trunk and branches called "footstalk". Footstalks bore only male spikes or both male and female spikes following 11 different sequences. On an average, a footstalk produced 4.0 to 9.67 spikes. Emergence of anthers on the surface of male spike (anthesis) occurred during day between 10:00 to 18:00h. Maximum anthesis (39.49%) was observed between 14:00 to 16:00h. Dehiscence started at 17:00h and attained the peak (70.29%) from 18:00 to 19:00h and ended at 20:00h on the day of its emergence. The availability of pollen grain on male spike lasted from 4.6 to 6.6 days. The average diameter of pollen grain was 17.34 microns. Germplasm had high pollen viability ranging from 84.22 to 99.21%. Pollen grains retained their viability for 24 hours when stored at room temperature. Maximum pollen germination was obtained in 10% sucrose solution. Protrusion of stigma started 2 days before and continued up to 10.2 days after opening of spathes. The duration of receptivity of stigmas of a female spike was 26.96 days. Jackfruit is an out breeding plant. Cross and open pollination methods together increased maximum fruit weight and percentage of edible portion. Weight and percentage of edible portion of irregular shaped fruit could also be increased by hand pollination. Germplasm could not set any fruit without pollination. Percent fruit set varied from 68.75 to 100 with on an average of 92.56. Maximum fruit set (63.72%) was observed in March. Fruit drop ranged from 5 to 44%. Higher percentage of fruit drop was observed in March and May. The cause of fruit drop was pathological rather than physiological. Jackfruit germplasm followed sigmoid pattern of fruit growth. From growth study it was found that 45 to 75 days old fruit could be used as vegetable. Fruits attained harvesting maturity at an average of 113.14 days after fruit set. Fruit deformity ranged from 0 to 100%. Floral abnormality, improper pollination and infestation of fruit by insect at its early growth stage were probably the causes of fruit deformity. The edible portion of fruit varied from 43.42 to 55.77%. Total sugar and reducing sugar content were 14.13% and 5.92%, respectively. Total soluble solids and titratable acidity were 22.6% and 0.24%. Vitamin C content of fresh jackfruit pulp ranged from 2.79 to 5.08 mg per 100 g while total carotene content varied from 339.20 to 620.90 μg per 100 g. Based on the physico-chemical characteristics, the germplasm J-31/2, J-07, J-31/1 and J-14/1 were found to be superior to the rest of the germplasm studied.