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 recommended for production of mid-stubble ratooning rice. Ten rice varieties, including Erguangyouzhan 3, Huangguangyouzhan, Huangguanghuazhan 1, Huangguangtaizhan, Yuehesimiao, Nanjingzhan, Yuetaiyouzhan, Wuyouyuehesimiao and Guang8youjinzhan are suitable for production of low-stubble ratooning rice. For mid-stubble ratooning rice, new tillers mainly regenerate from the 4th nodes from the top and other lower nodes below. For low-stubble ratooning rice, new tillers mainly regenerate from the 5th nodes and other lower nodes below

Evaluating Rice Varieties for Suitability in a Rice–Fish Co-Culture System Based on Lodging Resistance and Grain Yield

Rice–fish co-cultures have been practiced for over 2000 years, and they have tremendous potential in terms of increasing food security and economic benefits. However, little research has been conducted into achieving stable yields and high lodging resistance with regard to rice while simultaneously promoting the harmonious and healthy growth of fish in rice–fish co-culture paddy fields. We conducted a field study aimed at selecting suitable rice varieties for rice–fish co-culture systems (encompassing both ratoon and main crop). This selection process was grounded in an evaluation of lodging resistance and grain yield among 33 rice varieties used throughout the studied region. The results revealed a range of lodging indices of the main crop for the second internode, spanning from 62.43 to 138.75, and the annual grain yield (main crop and ratoon crop) ranged from 7.17 to 13.10 t ha−1 within rice–fish co-culture systems. We found that the use of rice–fish co-culture farming could improve the milling quality, nutrient quality, and appearance quality of rice, though the improvement gained through co-culturing varied across rice varieties. Moreover, the lodging index of the three basal internodes of rice plants was significantly and positively correlated with the plant height and the culm fresh weight, but it was negatively correlated with the bending strength of the rice basal internodes. Additionally, the 33 tested rice varieties were clustered in accordance with their lodging resistance (i.e., high resistance with lodging indices 62.43–75.42; medium resistance with lodging indices 80.57–104.62; and low resistance with lodging indices 113.02–138.75) according to the hierarchical cluster analysis. The 33 rice varieties were also clustered in accordance with the annual (main crop and ratoon crop) grain yield (i.e., high yield with 11.17–13.10 t ha−1; medium yield with 10.15–10.83 t ha−1; and low yield with 7.16–9.88 t ha−1). In all, 11 rice varieties were identified by a comprehensive evaluation as suitable varieties for grain production in the rice–fish co-culture system. These varieties displayed favorable traits, including a high annual rice yield, strong lodging resistance, and good grain quality. This is the first study to systematically evaluate rice varieties based on grain yield, lodging resistance, and grain quality in rice–fish co-culture systems