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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #61984
Title: GENETIC AND ALLELISM ANALYSES OF HYPERNODULATING SOYBEAN [GLYCINE MAX (L.) MERR.] MUTANTS FROM TWO GENETIC BACKGROUNDS

Author
item VUONG, TRI - UNIV OF ILLINOIS, URBANA
item NICKELL, CECIL - UNIV OF ILLINOIS, URBANA
item Harper, James

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Soybean and other legumes have potential to convert atmospheric nitrogen into a form usable by the plant through a process known as symbiotic nitrogen fixation. Enhanced symbiotic nitrogen fixation is potentially beneficial to soybean productivity and to subsequent crops grown in rotation, such as corn. Soybean lines (termed hypernodulated lines) with increased capacity to form root nodules have been selected and are being evaluated for enhanced symbiotic nitrogen fixation. Establishing genetic control of hypernodulation is essential to introducing that trait into agronomically adapted cultivars. This study identified a new recessive gene controlling hypernodulation. The results extend our understanding of genetic control of hypernodulation, and provide a new gene source from which to attempt increasing symbiotic nitrogen fixation of soybean. Ultimately, it is proposed that enhanced symbiotic nitrogen fixation by soybean can decrease the need for fertilizer nitrogen application to corn being grown in rotation following soybean.

Technical Abstract: Several chemically mutagenized lines of soybean [Glycine max (L.) Merr.] have shown enhanced nodulation and partial tolerance to high NO3- levels. Genetic analyses of hypernodulating or supernodulating soybean mutants indicated that they were genetically controlled by recessive monogenes following simple Mendelian principles. The present study determined the mode of inheritance of hypernodulating mutants selected from different genetic background cultivars, Williams and Enrei, and to investigate the allelic relationship between these mutant genes. Reciprocal crosses between four hypernodulating mutants (NOD1-3, NOD2-4, NOD4, and En6500) and two normally nodulated cultivars (Williams 82 and Harosoy 63), were made. The pattern of nodulation in F1's, F2's, and F2:3 progeny were visually evaluated at 14 d after planting in the greenhouse. Chi squares for each progeny and homogeneity tests for each cross were calculated. The results indicated that hypernodulation in the mutants studied were conditioned by single recessive genes. Of them, three mutants (NOD1-3, NOD4, and En6500) were controlled by a single recessive allele rj7, although they were isolated from distinctly different genetic materials. The allelism study indicated that another non-allelic mutant gene was identified which conditioned hypernodulation in mutant NOD2-4. This new gene has been tentatively designated rj8. With respect to genetic interaction between the mutant genes identified, the segregation ratio in the F2 did not fit a classical pattern and therefore it was speculated that these two genes interact to modify expression in an unknown fashion. Hence, additional genetic analysis is needed to clarify the genetic interaction between rj7 and the proposed rj8 gene.