(23(1):1-8)STUDIES ON THE HYBRID VIGOR OF RICE (III) THE RESPONSES IN GRAIN YIELD AND YIELD COMPONENTS OF F2 POPULATIONS AND VARIETIES UNDER FOUR DIFFERENT GROWING CONDITIONS

Abstract

本試驗主要目的，在探討F2羣體在不同栽培條件下對稻谷產量及產量構成要素的影響。供試材料有臺中65號，F2（臺中65號×臺南3號），臺南3號；光復401號，F2（光復401×臺農38號），臺農38號及臺農61號，臺北309號等8組合。行株距兩處理，即25cm×20cm及25cm×10cm；肥料兩處理，即N-P2O5-K2O分別為80-60-60及120-60-60(kg/ha)。試驗結果以對照品種臺農61號的產量最高，臺北309號居次，臺中65號的產量最差。兩F2羣體的平均產量比其四親本的平均數為高。F2羣體在四種不同栽培環境下的反應，一般而言，均與其親本或對照品種相一致。在第一期作密植對產量無顯著的效果，雖然單位面積穗數因密植而增加，但一穗粒數則相對的減少。增肥在普植區可以增加一穗粒數，卻使千粒重及結實率下降，結果產量低減。增肥密植的結果，一穗粒數並無顯著的增加，千粒重及結實率卻顯著的下降，而使產量低落。第二期作除密植顯著的增加單位面積穗數之外，不同栽培環境對水稻的產量及產量構成要素無明顯的效果，但F2羣體在不同栽培環境下的變異範圍似較其他品種為小。水稻本身似具有相當的調節力量，以適應不同的栽培環境。 The objective of this experiment is to compare the responses in grain yield and yield compoents of F2 populations to that of their parents as well as commercial rice varieties under four different growing conditions. Two F2 populations, Taichung 65 x Tainan 3 and Kwanfu 401 × Tainung 38 ; four parents, Taichung 65, Tainan 3, Kwanfu 401, and Tainung 38 ; and two commercial varieties, Tainung 61 and Taipei 309 were used as experimental materials. Two spacings, 25cm × 20cm and 25cm × 10cm, and two nitrogen levels, 80 and 120 kg/ha of pure nitrogen were combined into four different growing conditions, and all F2 populations and varieties were planted under the four treatments. The field layout was a split-split plot design with four replications. In general, the respones in grain yield and yield components of the two F2 populations under four different growing conditions revealed the same tendency as their parents and the two commerial varieties. In first crop of 1971, close spacing increased the panicles per unit area, but decreased the grain number per panicle, showed little response in grain yield. The high rate of nitrogen application positively responsed in grain number per panicle, but negatively responsed in 1,000 kernel weight, percentage of fertility, and grain yield. The close spacing with high rate of nitrogen application could only decline the 1,000 kernel weight, percentage of fertility and grain yield. In second crop of 1971, all the materials planted under different spacings and nitrogen applications did not show any clear trend in grain yield and yield components except the close spacing did increase panicles per unit area. The responses in grain yield and yield components of F2 populations, however, showed a little bit narrower range of variation than the rice varieties under the four growing conditions. The data of this experiment also indicated that rice plant has the ability of compensation through its yield components under different growing conditions