Effectiveness of honeycomb selection for yield superiority at three interplant distances: a field simulation study using chickpea (Cicer arietinum L.) inbred lines

The effect of interplant distance on differentiation and selection a) of the superior lines from a mixture of inbred lines, and b) of individual plants originating from the top lines, was studied in chickpeas (Cicer arietinum L.). For this, 28 chickpea inbred lines were evaluated on a single plant basis in a honeycomb design and in the same field at three interplant distances, for four growing seasons, at Larissa, Greece. The interplant distances were 15 cm (520000plants/ha, strong allo-competition), 30 cm(128630 plants/ha, medium allo-competition) and 100 cm (11500plants/ha, without competition). In addition, the inbred lines were evaluated in replicated plot trials under an agronomically accepted plant stand (520000plants/ha, crop environment) and the ranking of the 28 lines based on the average yield per plot over growing seasons was determined. Selection was applied in each season for each interplant distance and the three and six top lines with the highest average yield per plant were identified. These top lines from each interplant distance were compared with the three and six top lines(say: proven superior lines) identified after their evaluation under crop environment over seasons. In addition, selection was applied at the individual plant level with six selection pressures in each season and each interplant distance. Then we determined for each experiment and selection pressure the number of the selected plants which belonged to the six proven top lines. It was observed that the ranking obtained under crop environment was best correlated with the ranking at the intermediate interplant distance (30 cm), followed by the ranking at the high interplant distance (100 cm). In contrast this correlation was very weak for the ranking at low interplant distance (15 cm).In addition, the interplant distance identifying the highest number of the proven high yielding lines after their evaluation in one season was the intermediate interplant distance followed by the high interplant distance and certainly not the low interplant distance. The relative effectiveness was further increased when selection was based on average performance of the lines across seasons. This, together with the relatively small number of seeds produced per plant, renders selection at low interplant distance less favorable than selection at the intermediate or high interplant distance.The individual plant selection was effective at all three interplant distances. Selection effectiveness generally increased as the selection pressure increased. Again the best results were obtained when selection was applied at intermediate or at high interplant distance. It was concluded that line selection as well as individual plant selection was more effective at intermediate interplant distance and certainly not at low interplant distance. This revised version was published online in July 2006 with corrections to the Cover Date.