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Cyclic pedigree selection for longer seminal roots was performed in the F₂, F₃ and F₄ generations of hybrid population of spring barley. The total length of roots was measured in seedlings grown in filter-paper rollers. The intensity of selection was 20% (C₁, C₂ cycles) and 26% (C₃). Selection was effective. On an average, the finally selected F₅-pedigrees formed 6% longer seminal root system than the initial F₂'s and much of them exhibited 7-16% improved rooting when compared with the best parent in a sand-vermiculite pot culture. Realized heritabilitiy coefficient of the root length ranged from 0.21 to 0.37 when assessed by the ratio of selection response to selection differential, while those estimated by the parent- offspring regressions attained 0.40-0.53. The obtained results suggest that progeny evaluation and/or selection delayed for later generations should be essential for more effective root selection in barley.
Three steps of multi-stage selection for more vigorous seminal roots were done in two cross combinations of oat. The total length of roots (TRL) was measured in seedlings of the F₂, F₃ and F₄ generations grown in filter-paper rollers. On average, the finally selected F₅ (or F₆) progenies distinguished by 7-11% improved rooting ability than their midparents. Transgressive forms were selected only in one cross combination. Coefficients of realized heritability for TRL were low and ranged from 0.08 to 0.42 indicatinga relatively high proportion of non-additive gene effects in the variance of TRL. Tolerance of the F₆-progenies to water and nutrient limitations was evaluated in pot and field experiments. Correlated selection effects were dependent upon initial cross combination. Only progenies from one cross combination exhibited an improved drought tolerance at the 8-9 Feekes' stage. The both enhanced rooting and decreased S : R ratio of the F₆-progenies correlated with their improved tolerance to reduced P supply at the 4-leaf stage. However, no significant consistence occurred between indices of the tolerance to reduced nutrition at the vegetative growth and those at field maturity. Performed root selection identified more frequently high yielding genotypes with less stable grain yield. No progenies were obtained that outperform their parents under low-input conditions. It was emphasized that root selection should be accompanied by selection for integrated response components.
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