不同株型木薯品种干物质生产和氮素累积及利用特征比较

  【目的】  理想株型和氮素高效利用是作物育种和引种的重要指标。作物生长发育和形态建成特征与产量形成和氮素积累密切相关。研究不同株型木薯品种的干物质生产与分配、氮素积累与利用、产量形成等方面的差异,以期筛选出高产、氮素高效利用的株型和品种,为木薯高产栽培和氮素高效利用提供理论依据。  【方法】  试验以紧凑型品种华南205 (SC205)、华南8号 (SC8)、桂热4号 (GR4)、新选048 (XX048) 和伞型品种华南9号 (SC9)、华南12号 (SC12) 为材料,于块根形成初期 (种植后70天)、膨大初期 (种植后110天)、膨大中期 (种植后175天) 和成熟期 (种植后240天) 取样,分析干物质和氮素吸收积累量。  【结果】  紧凑型品种的生物产量、鲜薯产量、单株薯重和收获指数较伞型品种分别提高16.42%、36.85%、43.93%和40.00%。随着生育时期的推进,叶片的干物质和氮素分配比例随之下降,块根的干物质和氮素分配比例以及茎秆的氮素分配比例随之提高,而茎秆的干物质分配比例相对稳定。紧凑型品种地上部的干物质和氮素分配比例在块根形成初期高于伞型品种,而在块根膨大期低于伞型品种。紧凑型品种的氮素利用效率、氮肥偏生产力和氮素收获指数较伞型品种分别提高了28.91%、35.67%和36.00%,而100 kg鲜薯需氮量较伞型品种降低了27.27%。通径分析表明,块根生长后期的干物质生产量和氮素积累量对总量的贡献最大,块根生长中期其次,块根生长前期第三,苗期最小。在块根成熟期,紧凑型品种地下部的干物质和氮素分配比例较伞型品种分别提高了10.85和9.13个百分点。相关分析表明,块根生长后期的干物质和氮素积累量、生物产量、单株薯重和收获指数与鲜薯产量呈极显著正相关。  【结论】  紧凑型品种地上部的干物质和氮素分配比例在块根形成初期高于伞型品种,而在块根膨大期低于伞型品种。紧凑型品种的产量和氮素利用效率较高,而伞型品种的产量和氮素利用效率较低。在生产中,宜选择株型紧凑的木薯品种,以利于木薯高产和氮素高效利用。

Comparison of dry matter production,nitrogen accumulation and utilization of cassava cultivars with different plant types

  【Objectives】  Ideotype and N high efficiency are important indicators for crop breeding and introduction. Crop growth, development and morphogenesis are closely related to yield formation and N accumulation. The differences of dry matter production and distribution, N accumulation and utilization and yield formation among cassava cultivars with different plant types were studied for the screening of the ideotype and cultivars.  【Methods】  The tested cassava cultivars included compact-type of SC205, SC8, GR4, XX048 and umbrella-type of SC9, SC12 in a field experiment, which was conducted in Fuzhou, Jiangxi Province. At the initial forming, initial and middle expanding and maturing stages of tuber (70, 110, 175, 240 days after planting), plant samples were collected for the measurement of dry matter production and N accumulation, and tuber yield were weighed at harvest.  【Results】  The biomass, fresh tuber yield, tuber weight per plant and harvest index of compact-type cultivars were 16.42%, 36.85%, 43.93% and 40.00% higher than those of umbrella-type ones. With the development of cassava, the proportion of leaf dry matter and N distribution were decreased, those of tuber dry matter, tuber N distribution and stem N distribution increased, while the stem dry matter distribution ratio was relatively stable. The above-ground distribution ratios of dry matter and N in compact-type cultivars at the initial forming stage of tuber were higher than those of umbrella type ones, but lower than umbrella-type ones at the tuber expansion stage. N utilization efficiency, N partial factor productivity and N harvest index of compact-type cultivars were 28.91%, 35.67% and 36.00% higher than those of umbrella-type ones, respectively, while the N requirement of 100 kg-fresh tuber was 27.27% lower. According to the path analysis, dry matter production and N accumulation in late tuber growth stage contributed the most to the total, followed by those at the middle tuber growth stage, and then at the early tuber growth stage and the least in the seedling stage. At tuber maturity stage, the under-ground allocation ratio of dry matter and nitrogen in the compact-type cultivars were increased by 10.85 and 9.13 percentage points, respectively. Dry matter and N accumulation in the late tuber growth stage, biomass, tuber weight per plant and harvest index were significantly and positively correlated with fresh tuber yields.  【Conclusions】  The above-ground allocation ratios of dry matter and N of compact-type cultivars are higher than those of umbrella-type ones at the tuber initiation stage, but lower at the tuber expansion stage. The compact-type cultivars have higher yield and N utilization efficiency, so enjoy more priorities for the breeding of new cultivars.