Gibberellic acid (GA3) effects on heading characteristics of ten cytoplasmic male sterile (CMS) lines and on hybrid rice seed production using IR58025a CMS line

Abstract

The effects of gibberellic acid (GA3) as a pre-flowering treatment for cytoplasmic male sterile (CMS) lines in hybrid rice seed production (HRSP) were assessed in a greenhouse study and a field experiment during the 2002 dry season (DS). The greenhouse study determined the differences in panicle exsertion and other heading characteristics among 10 CMS lines using five levels of GA3 at 5-10% heading while the field experiment determined the outcrossing characteristics and seed yield of CMS line IR58025A under various levels and the number of splits of pre-flowering application of GA3. In the greenhouse, foliar application of GA3 significantly increased the panicle exsertion from the flagleaf sheath by a maximum of 80% at 150 g ha-1 concentration. Also, other morphological traits associated with outcrossing such as DPF (distance between panicle tip and flag leaf tip), flagleaf angle, degree of spikelet openings and percentage of spikelets with exserted stigma were also improved by GA3 application, along with significant genotypic differences. The most responsive CMS lines to GA3 application were IR73328A, IR70959A, IR64829A and IR58025A while the least responsive were IR68888A, IR69627A and IR68897A. In the field, foliar application of GA3 significantly increased panicle exsertion, seed set and seed yield of CMS line IR58025Aby a maximum of 80%, 20% and 77%, respectively at 150 g ha-1 concentration. Increase in seed yield was highly influenced by the increase in percentage of seed set presumably as a result of higher panicle exsertion, higher DPF, wider flagleaf angle, higher degree of spikelet openings, and stigma exsertions. During the dry season, the optimum rate of GA3 application in hybrid rice seed production of PSB Rc72H (Mestizo) is 150 g ha-1 applied in at least two splits beginning at 5-10% panicle heading of the CMS population.

Source or Periodical Title

Philippine Agricultural Scientist

ISSN

317454

Page

285-297

Document Type

Article

Subject

Cytoplasmic male sterile (A) line, Gibberellic acid (GA ) 3, Hybrid rice seed production, Panicle exsertion, Restorer (R) line, Seed set, Seed yield

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