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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #88475
Title: INSTABILITY AT THE K2 MDHL-N Y20 CHROMOSOMAL REGION IN SOYBEAN

Author
item CHEN, XIANFENG - IOWA STATE UNIVERSITY
item Palmer, Reid

Submitted to: Molecular and General Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Mutation is a major source of diversity in crops. A greater understanding of any of the many possible mechanisms by which mutations occur can and has been used by breeders in targeted generation of novelty. An unusual number of independent spontaneous mutations have occurred in a specific region of the genetic material of soybean and have resulted in several mutants with yellow-green foliage color, patterned seed color, and lack of production o an important enzyme. To investigate the cause of this high mutation rate, crosses were made between the mutants, and their progeny were evaluated. The analyses indicate that the cause of mutations is a loss of a DNA segment. Possible mechanisms for the DNA loss are discussed. Understanding such mechanisms is increasingly important to breeders as more advanced breeding technologies gain wider usage.

Technical Abstract: Ten mutants have been reported at the k2 (tan saddle seed coat) Mdhl-n (mitochondrial malate dehydrogenase 1 null) y20 (yellow foliage) chromosomal region in soybean. The precise mechanism(s) generating these mutants is (are) not known. The objective of this study was to determine whether chromosomal instability exists at this region. We introduced the w4-m and Y18-m mutable systems into the three independent sources of tan saddle seed coat mutants, T239 (k2), T261 (k2 Mdhl-n), and L67-3483 (k2). A total of 12 bright yellow mutants were isolated with tan saddle seed coat, malate dehydrogenase null phenotypes. Among them, 11 were found in 11 F2 mutant families out of 977 total F2 families derived from crossing T239 (k2), T261 (k2 Mdhl-n), and L67-3483 (k2) with six lines that were susceptible to contain active transposable elements. One was found in the F3 generation derived from the cross A1937 X T239 (k2). Among the 11 F2 mutant families, 10 out of 381 were associated with T239 (k2) genetic background, and one out of 323 was associated with T261 (k2 Mdhl-n) genetic background. Allelism and inheritance studies indicated that these 12 bright yellow mutants were new mutants at the k2 Mdhl-n y20 chromosomal region. Thus, chromosomal instability was established at this region when introducing the w4-m and Y18-m mutable systems into T239 (k2) and T261 (k2 Mdhl-n) genetic backgrounds. However, no yellow mutants were identified in a total of 883 F2 families in the control crosses with Harosoy, a T239 near-isogenic line, as one parent. The genetic mechanism responsible for this high frequency of instability at the k2 Mdhl-n y20 chromosomal region was suggested to be due to receptor element activities at this chromosomal region.