Study of morphological characteristcs, physiological indices, grain yield and its components in rice (Oryza sativa L.) landraces and improved cultivars

In order to study growth indices, morphological and physiological traits, grain yield and its components in rice landraces and Improved cultivars, a field experiment was carried out in the Rice Research Institute of Iran (Amol) located in the north of Iran in 2003 cropping season. This experiment was laid out in randomized complete block design with three replications, Eight improved cultivars; Neda, Dasht, Fajr, Pouya, Khazar, Shafagh (Indica), Onda, Fuji Minori Japonica and two landraces; Tarom and Ramazan Ali Tarom were studied. Because of the differences in developmental pattern among the cultivars growing degree days (GDD) was used instead calendar days in calculating growth indices. Growth indices (Crop Growth Rate = CGR, Relative Growth Rate = RGR, Net Assimilation Rate = NAR, Leaf Area Duration = LAD, Leaf Area Ratio = LAR, Leaf Area Index = LAI) and traits such as number of vascular bundles, flag leaf angle, SPAD value, peduncle length, internode length, tillering capacity and plant height were measured. Results showed that growth indices (TDM, CGR, SLW and LAI) of improved cultivars were greater than landraces. But RGR and NAR of landraces were higher than improved cultivars. Neda had the greatest LAI (5.7) and highest grain yield. Cultivars which had the greatest and the lowest TDM, had the highest and the lowest grain yield, respectively (Onda and Ramezan Ali Tarom). In this study, landraces had taller plant height, less tillering capacity and lower grain yield than improved cultivars. The modern cultivars had greater number of vascular bundles and flag leaf vein than landraces. Onda had the greatest SPAD value (48.35). Neda had the highest panicle/m2 because of greater fertile tillering number. Indica improved cultivars, due to high tillering capacity, Total Dry Matter, Crop Growth Rate, Leaf Area Index and Harvest Index had higher grain yield. However landraces had lower tillering capacity, Total Dry Matter, Crop Growth Rate, Leaf Area Index and Harvest Index therefore lower grain yield. It is concluded that increasing grain yield in rice can be achieved ruough increasing total dry matter and improveing physiological indices.