Abstract
Four maize ( Zea mays L.) synthetic varieties were selfed and approximately 200 S 1 lines of each were grown in separate replicated yield trials with the parental populations to compare inbreeding depressions and yield distributions among the S 1 lines. The four parental populations were (i) ‘iowa Stiff Stalk Synthetic,’ SSS, (ii) an advanced synthetic derived from SSS by seven cycles of recurrent selection based on half‐sib yield, SSS(HT)C7, (iii) ‘Virginia Corn Belt‐Southern Synthetic,’ CBS, and (iv) an advance synthetic derived from CBS by four cycles of recurrent selection for S 1 yield, CBS(S)C4. Inbreeding depression was lower for S 1 lines from each of the advanced synthetics than for those of the corresponding original and was lowest for the S 1 lines from SSS(HT)C7. Inbreeding depressions were 39.1 and 27.8%, respectively, for S 1 lines from SSS and SSS(HT)C7, and 38.3 and 32.5%, respectively, for S 1 lines from CBS and CBS(S)C4. S 1 lines from SSS(HT)C7 averaged 9.3% higher in yield than those from SSS, although the range of yields was less at both extremes for lines from the advanced population. S 1 lines from CBS(S)C4 averaged 27.2% higher than those from CBS with a comparable range of yields. SSS(HT)C7 yielded slightly less than SSS. CBS(S)C4 yielded approximately 19% more than CBS. In all populations the maximum S 1 yield approximated that of the parental source. Two S 1 lines from CBS(S)C4 were comparable in yield to that of a double‐cross hybrid check variety. One effective means of increasing inbred line yields appears to be increasing the yields of parental source populations.
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Claims 14
Claim · model-written summary
Inbreeding depression was lower in advanced synthetics and lowest in SSS(HT)C7.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“Inbreeding depression was lower for S 1 lines from each of the advanced synthetics than for those of the corresponding original and was lowest for the S 1 lines from SSS(HT)C7.”
t0“Maize”
Claim · model-written summary
SSS lines had 39.1% inbreeding depression.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“Inbreeding depressions were 39.1 and 27.8%, respectively, for S 1 lines from SSS and SSS(HT)C7, and 38.3 and 32.5%, respectively, for S 1 lines from CBS and CBS(S)C4.”
t0“Maize”
Claim · model-written summary
SSS(HT)C7 lines had 27.8% inbreeding depression.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“Inbreeding depressions were 39.1 and 27.8%, respectively, for S 1 lines from SSS and SSS(HT)C7, and 38.3 and 32.5%, respectively, for S 1 lines from CBS and CBS(S)C4.”
t0“Maize”
Claim · model-written summary
CBS lines had 38.3% inbreeding depression.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“Inbreeding depressions were 39.1 and 27.8%, respectively, for S 1 lines from SSS and SSS(HT)C7, and 38.3 and 32.5%, respectively, for S 1 lines from CBS and CBS(S)C4.”
t0“Maize”
Claim · model-written summary
CBS(S)C4 lines had 32.5% inbreeding depression.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“Inbreeding depressions were 39.1 and 27.8%, respectively, for S 1 lines from SSS and SSS(HT)C7, and 38.3 and 32.5%, respectively, for S 1 lines from CBS and CBS(S)C4.”
t0“Maize”
Claim · model-written summary
SSS(HT)C7 S1 lines yielded 9.3% more than SSS lines.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“S 1 lines from SSS(HT)C7 averaged 9.3% higher in yield than those from SSS”
t0“Maize”
Claim · model-written summary
SSS(HT)C7 S1 lines had a narrower yield range at both extremes.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“the range of yields was less at both extremes for lines from the advanced population”
t0“Maize”
Claim · model-written summary
CBS(S)C4 S1 lines yielded 27.2% more than CBS lines.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“S 1 lines from CBS(S)C4 averaged 27.2% higher than those from CBS with a comparable range of yields.”
t0“Maize”
Claim · model-written summary
CBS(S)C4 and CBS S1 lines had comparable yield ranges.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“S 1 lines from CBS(S)C4 averaged 27.2% higher than those from CBS with a comparable range of yields.”
t0“Maize”
Claim · model-written summary
SSS(HT)C7 yielded slightly less than SSS.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“SSS(HT)C7 yielded slightly less than SSS.”
t0“Maize”
Claim · model-written summary
CBS(S)C4 yielded approximately 19% more than CBS.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“CBS(S)C4 yielded approximately 19% more than CBS.”
t0“Maize”
Claim · model-written summary
Maximum S1 yield approximated parental-source yield in all populations.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“In all populations the maximum S 1 yield approximated that of the parental source.”
t0“Maize”
Claim · model-written summary
Two CBS(S)C4 S1 lines had yields comparable to a double-cross hybrid check.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“Two S 1 lines from CBS(S)C4 were comparable in yield to that of a double‐cross hybrid check variety.”
t0“Maize”
Claim · model-written summary
Increasing parental-source population yields appears an effective means to increase inbred-line yields.
- Outcome
- increasing the yields of parental source populationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“One effective means of increasing inbred line yields appears to be increasing the yields of parental source populations.”
t0“Maize”