عنوان مقاله [English]
Background and objectives:
Plant breeders to select their breeding objectives through the physiological and morphological characteristics, require classification of the limitations and capabilities which exists in plants; this issue leads to the concept of the ideotype. Designing plant ideotypes entails appropriate statistical methods. The objective of this study was to introduce a method based on multiple regressions to find ideotype with a case study of sunflower in Gonbad.
Materials and methods:
Sunflower was chosen as an example. Data were produced using 12 sunflower genotypes in a randomized block design in south of Gonbad city. Using multiple regressions in order to determine the important traits and to show the contribution of each trait in formation of yield. The method identified the relation between yield and all variables in a quantify matter. Also according to the positive or negative correlation between the variables affecting the yield, to designing ideotype, various hypotheses put forward and various aspects of them was examined.
Five important traits in determining sunflower yield were recognized in this study. They were total dry mass production, maximum leaf number, grain weight, the percentage of empty achene and the percentage of oil. Then, the optimal values of each trait were determined by the method. These five variables explained 57% of yield. The results indicate that if the correlation between some traits would be changed, it can be used for the benefit of yield. Regarding negative correlation between oil percentage and total dry mass, several hypotheses were evaluated. If the negative correlation between max. dry matter and oil content is not breakable, the yield of ideotype would have an increasing of 812 (from 2080 to 2892) kg ha-1 in comparison with sunflower hybrids. If with increasing max. dry mater, oil content stay at moderate level, it would be an increasing of 873 (from 2080 to 2953) kg ha-1 in ideotype, and if correlation between max. dry matter and oil content is breakable, it would be an increasing of 999 (from 2080 to 3079) kg ha-1 in ideotype.
The designed ideotype would increase grain yield from an average of 2080 kg ha-1 to 2892-3079 kg ha-1 in the ideotype. It was concluded that the method used in this study, because of concerning the genetic differences between varieties, can be used in determining plant ideotypes in conjunction with other methods and it can guide plant breeders to move through ideotype crops.
Keywords: Plant breeding; plant ideotype; multiple regression; correlation.