RETAINING THE BENEFITS OF MATRICONDITIONING BY CONTROLLED DRYING OF SNAP BEAN-SEEDS

The effects of various drying conditions on seed quality and performance of matriconditioned 'Bush Blue Lake 47' snap bean (Phaseolus vulgaris L.) seeds were studied. An exponential model based on the Page equation provided a good fit (R2 = 0.9) to changes in moisture content during drying. Drying matriconditioned seeds with high initial moisture content (47.2%) for 5 to 6 hours at 35C,30% to 35% relative humidity, and 0.7 to 1.4 m.g-1 air velocity (v) retained, and in some cases augmented, the benefits derived from conditioning. Matriconditioning greatly reduced electrolyte leakage (34.3 vs. 94.7 muS.cm-1.g-4 for nontreated seeds); drying to 15% moisture content at 0.7 or 1.4 m.s-1 v moderately increased the leakage rate (59.1 to 60.9 vs. 34.3 muS.cm-1.g-1), while drying at 0.02 m.s-1 v (ambient) increased the rate to that of nontreated seeds. The leakage rate remained low (43.6 to 50.8 muS.cm-1.g-1) in matriconditioned seeds dried to 22% moisture content at all air velocities. In growth-chamber studies, rapidly drying matriconditioned seeds to 15% moisture content at 1.4 m.s-1 v improved the emergence percentage over that of nontreated seeds, increased the shoot fresh and dry weight over that of nontreated and nondried matriconditioned seeds, and increased the shoot fresh weight over that of seeds dried at 0.02 or 0.7 m.s-1 v. Drying matriconditioned seeds to 15% moisture content at 0.7 m.s-1 v improved plant fresh weight over that produced by nontreated seeds. Rapid drying to 22% moisture content at 1.4 or 0.7 m.s-1 v improved only shoot fresh weight over that of nontreated seeds. In a 1992 field planting, percent emergence of matriconditioned seeds dried at 0.7 or 1.4 m.s-1 v was similar to that of nondried matriconditioned seeds and higher than that of nontreated seeds. No significant differences were noted in plant yield among the treatments.