WEATHERING OF SOYA BEAN [GLYCINE-MAX (L) MERR] IN THE TROPICS, AS AFFECTED BY SEED CHARACTERISTICS AND REPRODUCTIVE DEVELOPMENT

Small seed size, hard seed coat, and reduced interval from the R6 to R 7 reproductive developmental stage are factors associated with resista nce of soya bean [Glycine max (L.) Merr.] seed to field weathering. A study was conducted to evaluate the role of these characteristics on g ermination of 25 genotypes after exposure to field, incubator, and spr inkler-weathering treatments. At physiological and harvest maturity, a nd after both simulated weathering treatments, germination was negativ ely correlated with 100-seed weight and the number of days from R6 to R7. Only under the disease pressure of the incubator treatment was har d seed coat significantly correlated with germination (r = 0.48). Colo ured seed was superior to yellow seed except for large-sized coloured seeds. Small-seeded genotypes had higher germination than large-seeded types, particularly when they matured late or had a short interval fr om R6 to R7. One genotype, OCB, matured early, had relatively large se eds, and few hard seeds, yet had good seed quality, possibly attribute d to a short interval from R6 to R7. The incubator test was the least useful weathering treatment.