Evaluating Performance of Sixteen Upland Rice Genotypes under Field Conditions for Further Breeding Process

Rice is second most consumed cereal after wheat and it is considered as staple food in Thailand and most of the ASEAN countries. Analyzing yield performance of upland rice genotypes under field conditions is a key step in rice crop breeding program for improved rice production and ensuring food security. The objective of this research was to conduct a yield trial to assess performance of sixteen Thai upland rice genotypes under field conditions for further breeding process. Data from field trial that was conducted in 2016 in field research area of Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Thailand was used in this assessment. Randomized complete block design (RCBD) with three replications was used to layout the experiment in field. Soil was analyzed upto 50 cm soil depth for its fertility and nutrient status to check the fertilizer requirements before planting. Soil moisture contents were recorded using PR2/6 probe. Observed moisture contents indicated that there was 60-70% water available to all genotypes based on filed capacity (FC). Results indicated that genotypes, Hawm Mali Doi, Jao Khao Pichit, Jao Daeng, Sahm Deuan and Ma-led-nai-fai were shorter in plant height while genotypes Ma-led-nai-fai, Goo Meung Lung, Jao Daeng, Dawk Pa-yawm and Hawm Jet Ban had higher number of tillers m. Genotypes Ma-led-nai-fai, Goo Meung Lung, Jao Daeng, Dawk Pa-yawm and Hawm Jet Ban had higher number of panicles m. Genotypes Jao Daeng, Ma-led-nai-fai, Sahm Deuan, Hawm Mali Doi and Jao Khao Pichit were early flowering and maturity considering as early maturity genotypes. Genotypes Goo Meung Lung, Hawm Mali Doi, Jao Khao Pichit, Jao Daeng and Mai Tahk had higher 1000 GW while genotypes Dawk Kham, Dawk Kha, Hawm Jet Ban, Dawk Pa-yawm and Bow Leb Nahag were superior in grain yield response. Performance of genotypes indicated that these genotypes can be used for further breeding process for acquiring desired traits.


Introduction
Rice (Oryza sativa L.) is commonly used cereal as a staple food after wheat for a significant part of human population.Upland rice contributes around 4% in total rice production in the world.Upland rice contributes about 10% of the total rice area in Thailand which is grown in northern and southern parts of country (Nokkoul et al., 2011).The upland rice system prevails in dry lands without irrigation as well as puddling.These environments mostly suffer from various abiotic stresses accompanied with improbable rainfalls.In upland rice areas, environmental conditions are erratic ranging from humid to sub-humid.Soil and topography of these locations are moderately fertile to remarkably infertile and smoothly to sharp sloppy respectively.Rice farming in these rain fed areas is risk-prone.
Global warming increases the drought occurrence (Farooq et al., 2009) which results in global water scarcity.Upland areas mostly suffer from sporadic occasions of abiotic stresses like droughts and floods thus lowering the production efficiency of these areas.In future prediction of climate change, it is estimated that the water shortfall is going to be more severe (Wassmann et al., 2009), and Bates et al. (2008) stated that the concentration and frequency of drought will be increased.Drought occurrence obstructs the rice performance.Rice growth period in rain-fed areas are prone to dry spells occurring anytime which leads to drought of different concentration yet rice is considered highly sensitive when drought occurring at reproductive stages (O'Toole, 1982;Venuprasad et al., 2007) as floral development is badly effected under water stress.Most of the physiological and biochemical processes are slowed down in drought stress conditions.Upland rice without puddling is cultivated in rainy season in southern Thailand.Rainy season lasts from May to October and the upland rice planted in months of May to July is at reproductive stage at the end of rainy season.Due to less rainfall and occurrence of drought in the end of rainy season critically affects the rice yield.Heat is another factor during the growth period which increase the crop damage along with drought.Upland rice is potential source of genetic traits for rice breeding program and its performance is declining every year due to abiotic stresses.Therefore it becomes important to screen the upland rice genotypes having capability to tolerate drought and heat stresses especially at reproductive stages.Number of these abiotic stresses including drought and heat need to combat by screening and developing improved genotypes.Breeding upland rice for drought tolerance and heat to avoid the abiotic stresses is one of the important factor to increase the efficiency of rice production.Selection and development of the drought tolerant upland rice genotypes is important in southern Thailand as the local genotypes has the potential of higher productivity in stress conditions.Keeping in view the problems associated with upland rice production there was a need to assess the performance of upland rice genotypes for different agronomic trains under field conditions to use the suitable genotypes for further breeding process.Therefore, we selected sixteen Thai upland rice genotypes commonly grown in southern of Thailand for evaluating their response for agronomic traits including their growth duration and different yield attributes.

Soil Analysis
Soil analysis involved collection of input data on soil characteristics upto 0-50 cm on soil class, texture, field capacity, electrical conductivity, organic carbon, organic matter, soil texture, pH of soil in water, cation exchange capacity, organic carbon, total nitrogen, phosphorus, potassium, calcium sodium and zinc, which was performed at Central laboratory, Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Thailand.Physical and chemical properties of soil are detailed in Table 1.Goo ferent agronomic parameters including days to flowing and maturity, number of tillers and panicles, 1000 GW and GY have been focused to be accounting for screening genotypes in rice breeding (Yang et al., 2001;Venuprasad et al., 2008& Wang et al., 2010).Results showed that different genotypes could be considered for acquiring required traits in rice crop breeding program.For example early maturity genotypes should be considered for early maturing to escape drought stress which can be benefited in rice breeding for drought.
Early maturity genotypes can be further used for breeding for drought and heat escaping.Authors, suggest for further experimentation for all of these genotypes under diverse range of soil and weather conditions for improved evaluation.
Note.PH = Plant height, NT = Number of tillers, NP = Number of panicles, DF = Days to flowering, DM = Days to maturity, GY = Grain yield, 1000 GW = one thousand grain weight, LSD = Least significant difference.

Table 2 .
Mean square of analysis of variance of agronomic traits of sixteen upland rice genotypes

Table 3 .
Mean of agronomic traits of sixteen upland rice genotypes