Possibilities to increase accuracy of soybean breeding seeds yield estimations in early nurseries
Connection between yield in a control nursery (CN) and competitive variety trial (CVT) with indicators of seeds weight and harvesting index were analyzed in three types of breeding nursery (without protective rows and repetitions): one-row plot with a length 2.5 m (1<sup>st</sup> variant), two-row plot with a length 2.5 m (2<sup>nd</sup> variant) and one-row plot with a length 5 m (3<sup>rd</sup> variant). Correlation between seed yield in CN and CVT and harvesting index in breeding nurseries of all types is estimated to be more significant than with seeds weight in years with insufficient precipitations during period of seeds formation. Connection between seed yield in CVT and 1000 seed weight only in 1<sup>st</sup> and 2<sup>nd</sup> variants which is reliable on 0.1% significance level, is recorded in years with favourable water supply. A high range of yield variation in all types of breeding nurseries is shown herein variation ratio on harvesting index was less in 1.6 times. Comparison of identic traits in the breeding nurseries of the different types indicated closer and more significant connection between all types of breeding nurseries on a harvesting index (r = 0.405-0.821), at the same time connection with 1000 seeds weight is r = 0.230-0.548. Research showed that cultivation in breeding nursery with one-row plot with a length 2.5 m is more efficient as sufficient good correlated estimations of the harvesting index and seed yield are reached on larger plots at less labor efforts and sowing area. Selection on 1000 seed weight per a plot in breeding nursery is reasonable only in years with favorable conditions for soybean plants development during the whole vegetative period.