春小麦竞争能力与产量的关系

采用deWit替代系列实验确定了4个春小麦品种混播时的竞争能力与单播产量之间的关系。4个春小麦品种竞争能力由强到弱的排序依次为定西-24、和尚头、陇春-8139和高原-602。各品种单播时产量由高到低的排序依次为现代品种定西-24、陇春-8139、高原-602与地方品种和尚头。该结果表明,以优化个体适合度为目标的自然选择,导致个体竞争能力提高、繁殖分配下降,因而产生‘生长冗余’及群体表现下降。现代小麦育种通过降低竞争能力,剔除生长冗余,可以提高小麦单位面积产量(如地方品种和尚头与现代品种高原-602和陇春-8139的比较)。然而,如果现代小麦育种可以同时提高收获指数和地上生物量(如现代品种定西-24与陇春-8139和高原-602的比较),那么具有相对较高竞争能力的品种仍然可望获得较高产量,其前提是具有较高竞争能力的育成品种有着较高的收获指数。因此,春小麦品种的个体竞争能力并不必然地与产量相关,当选育的品种可以使竞争能力与收获指数同步提高,或者伴随着竞争能力的提高,收获指数具有更大幅度的提高,仍然可以获得高产。半干旱地区作物育种应集中于收获指数和地上生物量的同时提高。

The relationship between competitive ability and productive performance of spring wheat cultivars

de Wit series experiments were conducted to determine the relative competitive ability and grain yields of four spring wheat varieties which include landrace Heshangtou and the modern varieties Longchun-8139, Dingxi-24 and Gaoyuan-602. Various pairs of varieties were grown in a mixed fashion and were compared with monoculture. The experiments were conducted in 2005 on the semiarid area of Loess Plateau, Gansu Province, China. Dingxi-24 had highest competitive ability, followed by Heshangtou, Longchun-8139 and Gaoyuan-602 in decreasing order, while yield ranged from the higher varieties of Dingxi-24, Longchun-8139, Gaoyuan-602 to lower landrace Heshangtou. The results showed that the varieties with higher competitive ability produced lower yield when the landrace Heshangtou were compared with the modern varieties Lonchun-8139 and Gaoyuan-602, but when a comparison was made among the modern varieties Dingxi-24, Longchun-8139 and Gaoyuan-602, the varieties with higher competitive ability had higher seed yield. The results showed that natural selection aiming at maximization of individual fitness by increase in competitive ability resulted in growth redundancy, with the more resources being invested into the competitive organs at the expense of the reproductive organs. The implications are that shifting resources into reproductive organs by reducing competitive ability through crop breeding can increase wheat production under certain environments, which is consistent with Donald's ideotype. The reverse results revealed that if more resources were simultaneously invested into reproductive and competitive organs, the bred varieties can also perform better than varieties with lower competitive ability. Our results indicate that competitive ability is not necessarily correlated with seed yield and the key to increase yield is to develop varieties with higher harvest indices and total biomass. Natural selection aiming at maximization of individual fitness would inevitably result in occurrence of redundancy particularly in the case where more resources were partitioned into the competitive organs. Therefore, competitive ability is not the single criterion of crop breeding as Donald has proposed. Wheat breeding in semiarid areas should focus on the improvement of harvest index and increase of aboveground biomass.