GENOTYPIC VARIATION IN MUNG BEANS POSSESSING DIFFERENT SEED COAT CHARACTERISTICS FOR RESISTANCE TO INCUBATOR WEATHERING

Under tropical conditions mung bean seed may lose vigor prior to harvest. A field trial was conducted to to
determine mungbean genotypes with higher resistance to incubator weathering and to relate seed coat
characteristics with resistance to incubator weathering. Nine mung bean genotypes of known seed weight,
known lignin content in seed coat and known seed coat permeability were planted in research plots at Agriculture
Faculty, Bengkulu University on April 10, 2003 in a split-plot arrangement, with incubator weathering period as
a main plot and mung bean genotypes as a subplot with three replications.. At physiological maturity pods were
harvested and kept in an incubator at 30
C and 90% relative humidity for 0, 1 and 2 weeks. Their seeds were subjected to accelerated aging and electrical conductivity tests for seed quality evaluation. There were significant genotypic differences and a significant genotype x weathering period interaction for accelerated aging germination and seed leachate conductivity. A marked decline in accelerated aging germination and a significant increase in seed leachate conductivity for all genotypes was observed at 1 week weathering period and at this weathering
period genotypic differences for resistnace to incubator weathering was revealed. Seeds of Bhakti, which had
the highest percentage of hard seed exhibited the most resistant to incubator weathering. Some small-seeded
genotypes were resistant to incubator weathering; others were susceptible. Regression analysis showed that
accelerated aging germination was closely related (R= 0,56*) to lignin content, while a inversely linear relationship
(R2 = 0,85**) was observed between conductivity of seed leachate and lignin content. Overall, there were
genotypic differences in resistance to incubator weathering and this resistance was related to seed coat
permeability, the degree of hardseededness, and lignin content in seed coat.