Investigating the possibility of cultivating late rice cultivars through nursery under plastic cover in Lordegan region

Introduction:
Rice (Oryza sativa L.) is the most important cereal after wheat (Kazemi-Arbat, 1995). Suitable cropping dates will cause plants to better utilize the factors that are effective in their growth and development, thereby leading to the formation of desired yields. Thereofore, the selection of proper cropping date can play a crucial role in crop production (Rashedmohasel, 1997). Rice plant has a special place in Chaharmahal and Bakhtiari province where an area of about 3,000 hectares is dedicated to its cultivation. It seems that the introduction of high-quality cultivars will expand the rice cultivation area in the province. Therefore, six rice cultivars from the northern provinces of the country, named Domsiah, Hashemi, Tarom, Sahel, Shafagh and Kadous, along with traditional cultivar of Kouhrang as a check were evaluated (Lotfi Chamgawi, 2007).
Materials and Methods:
In order to investigate the possibility of early cultivation of late-maturing cultivars from northern peovinces through the nursery with plastic cover in the Lordegan region during 2010 and 2011, a study was conducted in a randomized complete block design with three replications. Cultivars were Tarom, Domsiah, Hashemi, Kadous, Shafagh and Sahel with Koohrang cultivars as check. The seeds of each cultivar were transplanted into separate trays and after the emergence under the dark conditions, they were covered with the plastic in the nursery. The yield and yield components were measured and the results were analyzed by SAS software. The mean comparison was performed by LSD at P=0.05 probability level.
Results and Discussion:
The results of the combined analysis of variance showed that the studied cultivars exhibited significant differences in the all meausured agronomic traits. The difference between cultivars was significant in terms of number of days to flowering and maturity stages. Among the cultivars, Shafagh and Hashemi cultivars were the latest matuity cultivars with 127.7 and 115.2 days from planting to maturity, rspectively. Shafagh cultivar with a height of 68.5 cm was recognized as the shortest cultivar. On the other hand, Tarom, Domsiah, Koohrang and Hashemi cultivars were not significantly different from each other where their heights averaged about 120 cm. Domsiah cultivar had the highest total number of seeds and the highest number of filled grains per panicle amongst the cultivars. The 1000-seed weight of the cultivars studied varied from 21.77 g for Kadous cultivar to 19.02 g for Tarom cultivar. In this study, paddy yield was affected by the main effect of year and cultivar and also their interactions. Demsiah cultivar with the average yield of 6436 kg ha-1 was recognized as the most productive cultivar and superior to the control. The Koohrang cultivar had an average yield of 5736 kg ha-1. The lowest yields of 1117 kg ha-1 and 1171 kg ha-1 were obtained from Shafagh and Kadous cultivars, respectively. The correlation coefficients among the evaluated traits showed that there was a positive and significant correlation between grain yield and number of full grains per panicle, number of fertile stems per plant, plant height and panicle length. In contrast, the correlation between grain yield and unfilled grains per panicle, the number of days to flowering, and the number of days to maturity was negative. As expected, the traits of number of filled grains in panicle and number of filled panicle in the plant as important yield components had a very strong and positive correlation with the grain yield. The yield of rice had the highest correlation with the number of filled grains in panicle (r = 0.85**).
Conclusion:
According to the combined analysis of variance, the results of two years of the experiment showed that only Domsiah cultivar was superior to the control and could be recommended for cultivation in Lordegan and other same areas. This cultivar not only had greater number of filled grains in panicle but also a greater number of fertile tillers. The Kouhrang cultivar, as a control, with a yield production of about 7.5 tons per hectare, ranked as secondcultivar after Demsiah. Generally, in the regions with the possibilty of early-season planting, both Sahel and Domsiah cultivars could be recommended, and for the regions where there are no favorable conditions for early planting, only Domsiah cultivar is recommended.