A novel integrative approach to study the dynamics of an increase in common spring wheat adaptivity and homeostaticity (on the example of breeding programs in the Northern Trans-Ural)

Though there are a number of evolutionary theories of living nature, no approach is available to quantify changes occurring during long-term breeding programs. By N.I. Vavilov, selection is evolution directed by the man's will. Here, we suggest and used a novel method for studying shifts in statistical genetic parameters which have occurred in sets of varieties of soft spring wheat ( Triticum aestivum L.) over an approximately 80-year period. During 8 years (in 2005-2012), 23 varieties of soft spring wheat zoned in the period from the 1930s were investigated in the conditions of the northern forest-steppe of Western Siberia (experimental field of the Research Institute of Agriculture of the Northern Trans-Urals, Tyumen, 57°09'N, 65°32'E). All of them were successfully cultivated in the Northern Trans-Urals in various years. The effects of genotype by environment interaction changing the crop ranks by year of testing were measured. The average yield of the varieties zoned in the 1940s was 20.2 с/ha (a reference point). These varieties showed a pronounced plasticity and homeostaticity of grain production. The regression lines for yields vs. ecological years (from bad to favorable conditions) were flat with a 31°-39° inclination. Milturum 321, the first zoned variety for the region is stable for grain yields (S2d i = 3.5). During 1950-1970s, Saratov varieties and the late-maturing variety of Siberian selection Milturum 553 have been zoned in the Northern Trans-Urals. The average yield of the group is 23.4 с/ha. The regression lines were above the lines of the first group and had similar inclination. Saratov varieties showed yield homeostaticity similarly to the varieties of the first group but lodging at yields above 20-25 с/ha. In 1970-1990s, the varieties resistant to lodging became widespread. Their yields in testing averaged 29.1 с/ha (+44 % to the reference point), the regression lines inclination reached 39°-47° indicating a decrease in yield homeostaticity. These varieties more strongly responded to a better or adverse environments compared to the varieties of the first and second groups. Strela and Tyumenskaja 80 varieties of local selection are quite stable in terms of yields (S2d i = 4.8-6.1). Currently used medium-ripe intensive varieties capable of producing grain yields of 34.3 с/ha on average (+70.0 % to the reference point) strongly responded to changes in environments, which followed from the inclination of the regression lines (50°-54°, b i = 1.21-1.40). Plasticity and crop homeostaticity are characteristic of the Chernyava 13 variety showing a flat regression line (29°, b i = 0.56). The most stable crop performance was characteristic of the varieties Lutescens 70 and Icar (S2d i = 8.7 and S2d i = 8.6, respectively). Modern zoned early-ripening varieties are less productive than the varieties of the previous group (x = 31.1 с/ha), with flat regression lines (37°-38°). The Tulunskaya 12 and Novosibirskaya 15 varieties are unstable in terms of yields (S2d i = 26.6 and S2d i = 29.0, respectively). The Novosibirskaya 29 variety is more productive (33.3 с/ha) and similar to the medium-ripe varieties from the previous group in terms of plasticity and stability. The assessment of a genotype response to environments affecting crop plasticity and stability (and homeostaticity) evaluates different characteristics of crop adaptability. So this allows us to investigate varieties under changing environments, to assess the effectiveness of their use in the Northern Trans-Urals environment, and to optimize breeding programs. High-yielding varieties with a well-pronounced adaptability should be involved in breeding.