The susceptibility of soybean cultivars (cvs) to boron (B) deficiency was examined in three experiments on a Typic Tropaqualf in Northern Thailand: one experiment also included peanut cv Tainan 9 and black gram cv Regur.

Without added B (B0), B deficiency depressed seed yield by 60% in soybean cv NW1 compared with 30% in cv SJ5, 40% in cv 7016, 45% in peanut, and 93% in black gram. B deficiency also induced a localised depression on the internal surface of one or both cotyledons of some soybean seeds resembling the symptom of ‘hollow heart’ in peanut seeds. It induced 50% hollow heart in peanut, 17% in soybean cv NW1, 5% in SJ5, and 1% in 7016: black gram seeds had no symptoms. Addition of B decreased or eliminated the symptoms.

In a comparison of 19 soybean cvs, the incidence of hollow heart symptoms in seeds at B0 varied widely from none in two cvs to 75% in cv Buchanan: cv NW1 showed intermediate susceptibility to B deficiency with 36% hollow heart in its seed while SJ5 was insensitive with 1%. Application of B eliminated hollow heart except from one seed in one cultivar. The results suggest that susceptibility to B deficiency is sufficiently important and variable among soybean genotypes to warrant its inclusion as a selection criterion when breeding cultivars for areas with low soil B.