Identification of the most stable genotypes in multi-environment trials by using nonparametric methods | Določanje najbolj stabilnih genotipov v različnih okoljih z neparametričnimi metodami

إنجليزي. Genotype performances in multi-environment trials are usually analyzed by different univariate and multivariate parametric models for assessing yield stability and genotype × environment (GE) interaction investigation. One of the alternative strategies can be nonparametric statistics approach which is particularly useful in situations where parametric statistics fail. For an estimation of yield stability of genotypes in various environments two new nonparametric stability statistics (NSi(1)and NSi(2)) have been used which are based upon the ranks of the genotypes in each environment. These statistics use median as a nonparametric central tendency, and two nonparametric index of statistical dispersion as interquartile range and inter-decile range. The NSi(1) and NSi(2) nonparametric stability statistics which presented here is similar to the nature and concept of environmental coefficient of variation. Results indicated that the most stable genotype based on the lowest values of these two nonparametric statistics, had the highest mean yield among studied genotypes. Plotting of mean yield versus NSi(1) and NSi(2) verified the above results and indicated that the highest mean yielding genotype is identified as the most stable genotype. These nonparametric statistics would be useful for simultaneous selection for mean yield and stability. They can be very helpful in selection for yield stability and determination of favorable genotypes in plant breeding programs.

السلوفينية. Za analizo in ocenjevanje stabilnosti pridelka in interakcije genotipov z različnim okoljem se navadno uporabljajo univariatni in multivariatni parametrični modeli. Eden izmed alternativnih pristopov bi lahko bila uporaba neparametričnih modelov, še posebej v primerih kjer je parametrični pristop težko izvedljiv. Za ocenitev stabilnosti pridelka genotipov v različnih okoljih sta bili uporabljeni dve novi neparametrični metodi (NSi(1) in NSi(2)), ki temeljita na rangih genotipov v danem okolju. Ti metodi uporabljata mediano kot neparametrično osrednjo tendenco in dva neparametrična indeksa porazdelitve kot inter-kvartilno in inter-decilno območje. Predstavljeni neparametrični metodi, NSi(1) in NSi(2), sta podobni konceptu koeficienta okoljske spremenljivosti. Rezultati so pokazali, da so imeli najbolj stabilni genotipi, opredeljeni z najmanjšimi vrednostimi NSi(1) in NSi(2) največji pridelek med vsemi analiziranimi genotipi. Primerjanje povprečnega pridelka z NSi(1) in NSi(2) je potrdila zgoraj navedene rezultate, kar kaže, da so genotipi, ki dajejo največji pridelek tudi najbolj stabilni. Te neparametrične metode bi lahko bile uporabne za hkratno selekcijo povprečnega pridelka in njegove stabilnosti. Lahko bi bile v pomoč pri selekciji primernih genotipov za stabilnost pridelka v žlahtniteljskih programih.