Nutrient solution systems have been considered an alternative method to field evaluations for studies of iron deficiency chlorosis (IDC) and for breeding soybeans [Glycine max (L.) Merr.] with improved iron efficiency. Although rates of gain are similar for both methods, it has not been previously demonstrated that field tests and nutrient solution tests for IDC measure similar genetic mechanisms. To test this, quantitative trait loci (QTL) identified in nutrient solutions were compared with those previously identified in field studies. F~.4 lines from two populations, Pride B216 × A15 and Anoka × A7, were grown in nutrient solution and evaluated for IDC by visual scores and determinations of chlorophyll concentrations. In the Anoka × A7 population, one major gene on linkage group N, and modifying QTL on linkage groups A1 and I, that were previously mapped during field tests, also were identified in the nutrient solution test. In the Pride B216 × A15 population, one QTL previously mapped on Linkage Group ! during field tests was not identified in the nutrient solution test, and a newly identified QTL was mapped on Linkage Group BI. QTL on Linkage Groups B2, G, and N were identified in both field and nutrient solution tests. We concluded that similar QTL are identified in nutrient solution and field tests and, therefore, both systems identify similar genetic mechanisms of iron uptake and/or utilization.

Nutrient solution systems have been considered an alternative method to field evaluations for studies of iron deficiency chlorosis (IDC) and for breeding soybeans with improved iron efficiency. To map genes controlling IDC in nutrient solution, 120 F 24 lines in a Pride B216 × A15 population, and 92 F 24 lines in an Anoka × A7 population were grown in nutrient solution in greenhouse plantings and evaluated for IDC by visual scores and determinations of chlorophyll concentrations. Eighty-nine restriction fragment length polymorphism (RFLP) and 10 simple 1916 LINETAL.sequence repeat (SSR) markers in the Pride B216 x A15 population, and 82 RFLP, 14 SSR and one morphological (hilum color) markers in the Anoka x A7 population were used to construct linkage maps and to locate quantitative trait loci (QTL) controlling IDC. In the Anoka × A7 population, one major gene on linkage group N, and modifying QTL on linkage groups A1 and I previously mapped during field tests also were identified in the nutrient solution test. Different genetic linkage groups in soybean have been identified by letters, and as such will be used throughout the paper. One newly identified QTL was mapped on linkage group B2. In the Pride B216 × A15 population, one QTL previously mapped on linkage group I during field tests was not identified in the nutrient solution test, and two newly identified QTL were mapped on linkage groups A2 and B1. QTL on linkage groups B2, G, H, L, and N were identified in both field and nutrient solution tests. Due to significant interaction between genotype and environment in both field and nutrient solution tests, QTL identifications from multiple environments were used to compare the similarity between field and nutrient solution tests. We concluded that similar QTL are identified in nutrient solution and field tests and therefore, both systems identify similar genetic mechanisms of iron uptake and/or utilization.

To facilitate anther culture in soybeans [Giycine max (L.) Merr.], five bud stages from the cultivar ‘Hark’ are described. Combinations of bud length, corolla development, and anther development were indicators used to classify buds as stages 1 through 5, Stage 3 contained microspores that were predominantly individualized, uninucleate, and devoid of starch. Culture contamination, which ranged from 3.3% with buds from the winter greenhouse, to 100% with material from the field, was best controlled by treatment with 95% ethanol for 2 min, 5.25%N aOCfIo r 5 min followed by a sterile water rinse. Miller's and Nitsch's basic media are evaluated for callus growth and plantlet development, with addition of various levels of coconut milk, kinetin, iron, and auxins. No embryoids or plantlets were observed and. the callus formed was diploid.