Sterility Induced in Barley by a Synthetic Pyridone1

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Abstract
A chemical gametocide capable of inhibiting pollen production but not affecting female fertility, would be very useful in the production of hybrid barley (Hordeum vulgate L.). In this study, ‘Betzes’ and two ‘Unitan’ two and six row isogenics were sprayed with 0, 1, 2, and 4 kg/ha of sodium 1‐(p‐chlorophenyl)‐l,2‐dihydro‐4,6 dimethyl‐ 2 oxonicotinate (RH‐531) at the five and six‐leaf stages in an attempt to induce male sterility. Seed set was lowest on plants treated at the 4 kg rate and was as follows: Betzes, 18% at five‐leaf stage; Unitan two‐row 33% at six‐leaf stage; and Unitan six‐row 29% at six‐leaf stage. Four kilograms of RH‐531 caused 40% female sterility. Female sterility was greatest when plants were treated at the six‐leaf stage and Unitan six‐row had the most female sterility at that stage.As rates of RH‐531 were increased, yield, plant height, flowers per spike, lodging, kernel size, and spike length of treated plots decreased. Yield and grain protein were negatively correlated (r = —0.90**), but grain protein/ ha was less in the 4 kg/ha plots because of lower yield. Spraying at the six‐leaf stage reduced yield and plant height more than spraying at the five‐leaf stage. Treatment affected the growth characteristics of Unitan six‐row less than it did the other two cultivars. The number of flowers per spike was reduced less at the six than at the five‐leaf treatment stage in the Unitan isollnes.RH‐531 did not produce sufficient male sterility to be useful in hybrid barley production, and adverse side effects such as reduced female fertility and stunted plants were drastic.