Analysis on Screening of Suitable Varieties for Rice Ratooning and Yield Components under Different Cutting Heights in North Guangdong

【Objective】Based on the evaluation of growth period and grain yield performance of ratooning rice under different cutting heights, suitable varieties were selected for ratooning rice production in North Guangdong.【Method】Thirty-four rice varieties (bred or approved in Guangdong Province) were selected for tests under mid- or low-stubble cutting heights. The growth period, grain yield and yield components under different cutting heights among the tested varieties were investigated.【Result】The main crop yield was 5 210.9-8 566.8 kg/hm2, and grain yield of Huangguanghuazhan 1 was the highest. The ratoon crop yield of low-stubble ratooning rice was 3 335.0-6 357.3 kg/hm2, 16.1% higher than that of mid-stubble ratooning rice (2 084.4-5 940.5 kg/hm2). Qingxiangyou 19 Xiang was the highest in ratoon crop yield under both cutting heights. According to cluster analysis, the ratoon crop yield and total annual grain yield under mid-stubble ratooning rice mode could be categorized to four major groups, namely, high-yield, mid-high-yield, medium-yield, and low-yield levels. Each group contained 4, 7, 18, and 5 varieties for ratoon crop yield and contained 1, 14, 14, and 5 varieties for total annual grain yield under mid-stubble ratooning rice mode. Under low-stubble cutting height, the ratoon crop yield was also categorized to four major groups with 2, 17, 14 and 5 varieties, while the total annual grain yield was divided into three major groups, containing 10, 21, and 3 varieties, respectively. In ratoon season of low-stubble ratooning rice, the growth period was prolonged by an average of 9.1 days, the number of spikelets per panicle was increased, and the effective panicles and seed setting rate were reduced compared with those in ratoon season of mid-stubble ratooning rice. Under mid-stubble cutting height, the ratooning rice regenerated from the 3rd, 4th, and 5th nodes from the top (D3, D4 and D5) contributed 4.7%, 33.3%, and 62.0% of the total grain yield per plant, respectively. Under low-stubble cutting height, the ratooning rice regenerated from D3, D4, and D5 contributed 0%, 11.9%, and 88.1% of the total yield per plant.【Conclusion】If assessed with the criteria of high- or mid-high-level ratoon crop yield and high-level total annual grain yield, 9 rice varieties, including Huangguangyouzhan, Huangguanghuazhan 1, Huangguangtaizhan, Wuyouyuehesimiao, Guang 8 Youjinzhan, Hengfengyou 387, Qingxiangyou 003, Qingxiangyou 132, and Qingxiangyou 19 Xiang are recommend