Determination of Genetic Sources and Threshold Environment of Arkansas and Gsor Male Sterile Lines.

Hybrid rice is produced from the crossing of two genetic distinct parents and the resulting F1 hybrid performs greater than its parents. Male sterility is induced in parental lines of hybrid production to replace the need of artificial emasculation to improve the amount of F1 seed. The two-line system is one of the methods in hybrid rice production that requires an environmental sensitive male sterile (EGMS). Male sterility alleles are affected by photoperiod (PGMS), temperature (TGMS), or a combination of the two (PTGMS). In an effort to release hybrid cultivars the University of Arkansas Rice Research and Extension Center (RIRE) has worked on developing EGMS. The objective of this study to find out if those male sterile lines are TGMS, PGMS, or both and determine the threshold environment. A total of four male sterile lines 236s, 801s, 805s, and 811s were developed by the RIRE. Four mutated lines - GSOR 1, GSOR 2, GSOR 3, and GSOR 4 – that developed sterility traits were produced by the Dale Bumpers National Rice Research Center. Ten panicles from 236s, 811s, and the four GSOR lines were pollen stained in growth chambers at the conditions: 01) 21.1C - 23.9C, 02) 23.9C – 26.7C, 03) 26.7C – 29.4C, and 29.4C – 32.2C all with the same day length of 12 hours. Currently 801s and 805s are being evaluated. The GSOR lines were mostly fertile in all conditions with only a few being sterile which suggests that sterility may not be induced by the environment. The results for 811s were that sterility is complete at conditions 03 and 04, whereas it completely fertile at conditions 01 and 02. The results revealed that 236s is completely sterile at condition 04, partial fertile at conditions 02 and 03, and completely fertile at condition 01. The evaluation suggest that 236s and 811s are PGMS. This study continues to evaluate these lines in field condition.