Effects of soybean seed coat cracks on seed exudation and its influence on pre-emergence damping-off of soybean in soil infested with Macrophominaphaseolina

ABSTRACT: Soybean seed with no visible seed coat cracks (intact seeds), seeds with hypodermal cracks (cracked seeds) and damaged with scarification assayed for seed exudation and seedling quality in soil infested with Macrophominaphaseolina. Seed exudates were collected by soakingandtotal carbohydrates and amino acids were determined using the anthrone and ninhydrin test, respectively. Germinated seeds and seedling quality in soil infested with M. phaseolinasclerotia. The results show that exudation from soaking seeds was influenced by cracks in the hypodermal seed coat layer and scarifying and total carbohydrates leached was significantly higher from cracked and scarified seeds. The concentration of amino acids present in seed leachates was significantly higher only from treated seeds with scarifying. There is significant difference in germination occurred as a result of variation in seed coat conditions. Scarification resulted in a significantly lower (P < 0.01) seedling quality rating than did intact or cracked seeds. The results show the correlation of carbohydrate in seed exudate and seed germination (%) was higher (R2=0.8743) than amino acids (R2=0.499). Apparently adequate sugar is exuded from cracked seeds for optimum development of M. phaseolina and scarification effects on seedling quality are the result of additional stimulation of M. phaseolina by exudates.