Abstract
Phomopsis vexans isolates from eggplant (Solanum melongena L.) were examined using traditional mycological characteristics and molecular methods. Variation exists among the isolates of Phomopsis vexans collected from core eggplant growing areas of Bangladesh covering two types of farm having two ecosystems and the isolates were grouped into five distinct groups based on their cultural properties. The pathogen grew best at 25°C, under 12/12h cycle light and pH 5.5 levels of culture media. Number of spores per ml was also maximum at 25°C temperature, 12/12h cycle light and pH 5.5. Brinjal Fruit Extract Agar media supported the maximum growth and sporulation. Two types of spores a and ẞ were detected in Phomopsis vexans. Five isolates had variation in growth and sporulation under different levels of temperature, light, culture media and pH. a and ẞ conidia varied in size among five isolates groups. DNA concentration of 44 isolates varied from 12.5 - 50 ng/ul. DNA fingerprinting by VNTR and AFLP supported the grouping of the 44 isolates into five distinct groups. Fifty three eggplant cultivars/entries from home and abroad showed differential reactions against Phomopsis vexans. Percent disease index of fruit ranged from 0.0- 61.35% among the 53 accessions where 13 cultivars were found highly susceptible, 21 susceptible, 8 moderately susceptible and 9 showed moderately resistant while cultivar Katabegun and wild. accession were resistant. Under induced in vitro conditions, four cultivars (Khatabegun- white spine, Jessore-local, Ishurdi-local and ISD-006) were resistant, four tolerant, 13 moderately susceptible, seven susceptible and one was highly susceptible. Existence of variation in eggplant cultivars and variability to isolates of Phomopsis vexans were envisaged. Hybridization between eggplants cultivars indicated that cross between Katabegun WS x Dohazari was the best with respect to fruit setting. Crosses between. wild and cultivars did not form any fruit. The cross inoculation results of F2 generation indicated that isolates group-1 and 5 were more aggressive in causing fruit rot in all the varieties inoculated. Dohajari was proved most susceptible cultivar against Phomopsis vexans. Cultivar Katabegun WS and all F2 fruits were resistant. F1 and F2 plants derived from Katabegun WS X Dohazari and Katabegun WS X Laffa S inoculated under confined field condition remained free of infection from Phomopsis vexans. DNA and RNA fingerprinting by VNTR and AFLP PCR prompted the grouping of 6 resistant and susceptible cultivars into two groups. Genomic DNA concentration of cultivars and F1 plants varied from 30 - 50 ng/ul. F, generation of eggplants were categorised into 5 groups by VNTR-PCR. DNA concentration of F2 generation of eggplants varied from 12.5 50 ng/μl and F2 eggplants were grouped into three by VNTR-PCR and two by RAPD-PCR.For the development of regeneration protocol of eggplant, 16 hormonal supplements and three explants from six eggplant cultivars were used. Among the different combinations of MS media containing 2.0 mg/l BAP + 0.5 mg/l NAA showed better callus induction and regeneration required minimum days from stem followed by leaf irrespective of cultivars. Root showed lower response for callus induction and regeneration. There was no regeneration ability without hormone.