Prospects for breeding of high-protein soybean cultivars: selection of soybean lines with different mechanisms of protein increase in the seeds (report 2)

The breeding effectiveness of high-protein soybean cultivars currently is random and does not guarantee a successful combination in one genotype traits of high yield and high protein content. This fact proves an actuality of studying the possible additional mechanisms of protein accumulation and allocation among them the most useful for breeding to ensure a successful breeding of high-protein and high-yielding soybean cultivars. Researches carried out in 2010-2015 at VNIIMK (Krasnodar region) and "Don Experimental Station by L.A. Zhdanov" (Rostov region). Soybean cultivars and lines with increased protein content were studied. Mid-protein (38-40%) cultivars were used as standards. The calculated coefficients K1 (amount of protein and oil) and K2 (the ratio of protein/oil) were used to detect the different types of balance of oil and protein contents in the seeds. Four dynamic models of additional proteins accumulation in the soybean seeds have been formulated: ecological (EM), cumulatively-protein (CPM), lipid-degradation (LDM) and carbohydrate-degradation (CDM). Analysis of the dynamics of proteins and oils balance in mid-protein and high-protein soybean cultivars and lines showed the presence of genotypes among the experimental samples, corresponding to all four theoretical models of additional protein accumulation in the seeds. The accumulation of the protein in the new high-protein soybean lines by VNIIMK breeding corresponds to the implementation of cumulative-protein model. Their yield, comparable with this trait in midprotein cultivars, certifies overcoming the negative correlation between yield and protein content in the seeds, as well as their suitability to the direct commercial cultivation in the conditions of the south of Russia.