In 1994, F1 ears were sown for further selfing, in order to search for the restorer cytoplasm in 1995 in selfed progenies (100% fertility in such progeny would be an indicator of the restorer cytoplasm for the appropriate ms gene). But in a few F1s (with 6 varieties), sterile plants unexpectedly occurred in 1994, indicating some other source of sterility besides the ms gene with which it was crossed, i.e., crossing with a ms/+ stock to a plant not carrying the appropriate ms gene would result in a 100% fertile F1.
In Table 1 there is a list of F1s (variety x stock) where sterile plants were noticed.
Table 1. List of F1s where sterile plants occurred in 1994.
|ms1/+||Segr.2 both progenies|
|ms2/+||Segr. both progenies||Segr. 1 progeny||Segr. 1 progeny|
|ms6/+||Segr. 1 progeny||Segr. 1 progeny|
|ms8/+||Segr. 1 progeny|
|ms9/+||1 progeny 100% sterile||1 progeny 100% sterile||Segr. 1 progeny|
|ms11/+||Segr. 1 progeny||1 progeny 100% sterile|
|ms13/+||1 progeny 100% sterile||Segr. 1 progeny||1 progeny 100% sterile||1 progeny 100% sterile||1 progeny 100% sterile|
|ms17/+||Segr. 1 progeny|
|ms22/+||Segr. 1 progeny|
|ms23/+||Segr. 1 progeny|
|ms24/+||Segr. 1 progeny|
In the variety accession No. 366, the occurrence of sterile plants was the most obvious. We supposed that this variety contained some kind of cytoplasmic male sterility, and did additional tests: F1 sterile plants of the ms1/+ stock were pollinated with the line F-7(R), which is a partial restorer for the S cytoplasm, and F1 sterile plants with the ms2/+ stock were pollinated with F-7(R), as well as the line ZPL-217, known as the RfC line.
In 1995, all of the crosses with F-7R and ZPL-217 were sterile, indicating the absence of cms-S, as well as cms-C from population 366. These sterile plants were pollinated with another partial restorer for the cms-S (ZPLB-368/73), as well as with two lines known as restorers for cmsT: R-348 and R455. In 1996, only tests with RfT lines showed full fertility, while others were absolutely sterile. So, variety Zuti zuban from the region of Novi Sad (accession No. 366) carries the T-type of cytoplasmic male sterility.
In this way we checked just the most obvious carrier of cytoplasmic
male sterility in this study. Other varieties that showed sterile plants
in this experiment are included in a broader checking of the male sterility
sources in our gene bank.
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