Short communication. Decision on germplasm choice to apply breeding within a local population of common vetch is affected by crowding

Abstract

The value of a population as a potential gene pool on which to apply selection may be severely underestimated under competition conditions because of the negative correlation of competitive versus yielding ability. To address this issue, a vetch (Vicia sativa) local population along with a control cultivar was evaluated at densities ranging from 1.15 to 25 plants m -2 . A hyperbolic increasing pattern as density declined was found for both grain and biomass yield. Nevertheless, at the highest density the control cultivar performance exceeded the population, whereas at the lowest density the opposite happened. The results were attributed to the heterogeneity of the population versus the homogeneity of the cultivar combined with the aforementioned negative relationship. It was concluded that severe crowding undervalues the potential of a population because plants representing high yielders cannot exhibit this capacity due to their competitive disadvantage. On the other side, the absence of competition optimizes the yield expression of individual plants. Therefore, absence of competition is recommended as the optimal condition to evaluate populations and make the right decision on the most promising one for breeding.Additional key words: competitive ability; genetic heterogeneity; local population; Vicia sativa; yielding ability. ResumenComunicación corta. La decisión sobre la elección de germoplasma para la mejora de una población local de veza común está afectada por el grado de densidad de siembraEl valor de una población, en el conjunto de sus genes potenciales sobre los que aplicar la selección, podría subestimarse de forma importante en condiciones de competencia, debido a la correlación negativa de la capacidad competitiva frente a la capacidad de producción. Para solucionar este problema, se evaluó una población local de veza (Vicia sativa) junto con un cultivar comercial como control, a densidades que oscilan desde 1,15 hasta 25 plantas m -2 . Se encontró, tanto en producción de grano como de biomasa, un patrón de aumento hiperbólico según iba disminuyendo la densidad. A mayor densidad, el comportamiento del cultivar control fue superior a la población, mientras que a menor densidad ocurrió lo contrario. Los resultados se atribuyeron a la heterogeneidad de la población vs. la homogeneidad del cultivar, combinado con la correlación negativa antes mencionada. Se concluye que las siembras a mayor densidad disminuyen el potencial de una población, porque las plantas muy productivas no llegan a exhibir su capacidad potencial debido a la desventaja competitiva. Por otro lado, la ausencia de competitividad optimiza la expresión de la productividad en plantas individuales. Por tanto, para optimizar la evaluación de las poblaciones para mejora y tomar decisiones correctas, se recomienda la ausencia de competitividad sobre las poblaciones más prometedoras.Palabras clave adicionales: capacidad competitiva; capacidad de producción; heterogeneidad genética; poblaciones locales; Vicia sativa. *Corresponding auth...

Conservation Breeding of Elite Cultivars

“…This relationship renders nil competition indispensable for avoiding selection of strong competitors at the expense of high yielders. To study the issue, Chatzoglou and Tokatlidis (2012) evaluated a genetically heterogeneous vetch ( Vicia sativa L.) variety (landrace) compared with a fairly homogeneous check (pure‐line cultivar) at a range of five densities (Fig. 2).…”

“…The yielding performance of the heterogeneous variety compared with the homogeneous check illustrates the negative association between the competitive and yielding ability of individual plants, implying that at competition, progressive increase of low yielders may cause cultivar degradation, while nil competition is essential to distinguish and select the high yielders. Adapted from Chatzoglou and Tokatlidis (2012).…”

Sustainable Stewardship of the Landrace Diversity

“…This condition implies two major disadvantages. Firstly, the prevailing strong competitors are usually low yielding genotypes due to the inverse connection between yielding and competitive ability [39,40]. Continuous seed reproduction under crowded conditions results in preferential and gradual proliferation of the strong competitors at the expense of the high yielders, leading to a gradual landrace degradation and variety degeneration [32,41,73].…”

“…The hypothesis of a negative connection between yielding and competitive ability was investigated in two studies that considered landraces and their grain yield response to crowding. A genetically heterogeneous vetch (Vicia sativa L.) landrace was compared with a fairly homogeneous check (pure-line variety) across a range of six densities [39]. At intense crowding (25 plants/m 2 ), the landrace lagged significantly behind the check by 29%; however, as density declined their gap was progressively bridged, while at the lowest crowding level (1.15 plants/m 2 ) the landrace was superior by 32% ( Figure 2a).…”

“…The performance of heterogeneous landraces against respective homogeneous checks, (a) across a range of densities; and (b) at typical density (TD) and nil-competition (NC), indicate that high yielding genotypes involved in a landrace are expressed and detectable only at NC. Adapted from (a) Chatzoglou and Tokatlidis[39] and (b) Ninou et al[40].…”