In this study, the cultivars chosen for testing came from breeding units throughout China with unrelated parents. The average GY of the 53 cultivars grown

in 2007 was 13.7 t ha− 1 find more and the average GY of the 48 cultivars grown in 2008 was 15.1 t ha− 1. These values were close to the highest rice yield recorded [18], [19], [20] and [21]. In 2007, Xieyou 107, II You 2186, and II You 318 were the top three cultivars, with GY above 16.5 t ha− 1. In 2008, the two highest-yielding cultivars were Xieyou 107 and II You 107, with GY of 18.5 and 18.4 t ha− 1, respectively. Final yield is a function of the length of growing season [29]. If the potential size of a crop is predetermined, the length of PHP is also important. In this study, PHP was significantly and positively correlated with PH and PW for both years and was positively correlated with GY in 2008, suggesting that a longer PHP can benefit the growth of vigorous rice plants and improve GY. Because GY is determined during grain filling between heading and maturity stages, crop physiologists have indicated the importance of increased biomass production after heading in rice for high GY [30] and [31]. Yang et al. [32] reported that HM was a crucial determinant of genotypic variation of GY in field-grown

tropical irrigated rice. Days from heading to maturity was not significantly correlated with GY, given that the values of HM in the 101 tested cultivars were all around 40 days. Although no comparison of dry Trichostatin A chemical structure matter accumulation after heading was calculated, the results clearly revealed that Ribose-5-phosphate isomerase the improvement of GY was mainly the result of an increase in the crop growth rate after

heading. Similar findings were reported by Takai et al. [33] and Li et al. [31]. Pre-heading period varied significantly across sites but not across years, whereas HM did not vary significantly across sites or years [21]. Plant height is an important morphological index and criterion for rice breeders. In this study, PH varied minimally across sites and years. The first significant advance in rice yield potential was a result of dwarf breeding. The new plant type proposed by the International Rice Research Institute (IRRI) is a PH of 90–100 cm. Yuan [34] proposed a PH of at least 100 cm from the soil surface to the unbent plant tip at maturity. Peng et al. [35] reviewed the PH of popular Chinese rice cultivars, which included Xieyou 9308 (PH of 120–135 cm) and Liangyoupeijiu (115–125 cm). Although PH was positively correlated with GW, increases in PH could enhance the risk of lodging. Therefore, the suitable PH for high-yielding rice is hypothesized to be 110–125 cm. LAI is one of the major determinants of crop photosynthesis [36]. LAI was significantly correlated with SM and GY, verifying that LAI could be a basic index for rice yield [37].