Rice (Oryza sativa) belongs to family gramineae. Rice is an annual grass morphologically and one of the most important crops in the world. It is grown extensively in tropical and sub-tropical regions of the world. Rice is one the most important agricultural crops in the world and is ranked the second in the view of annual production after wheat and it constitutes half of world population main meal 1. More than half of the people on the world depend on rice as their basic diet and, generally extensively consumed in the producing countries2. World population is expected to increase by about 2 billion in the next two decades and half of this increase will in Asia where rice is the staple food.
Selection criterion for production may be yield, or one or more of the morphological components of yield. Rice yield might be increased in small grains by selecting for the component of yield and that parental varieties should be selected on the basis of component attributes3. On the other hand, there was report that the components of yield are influenced greatly by the environment and that negative correlations among them are common4. Thus, selection for one of the components may fail to result in yield increase because of negative associations among the components. In contrast, individual yield components may contribute valuable information in breeding for yield 5.
Rice was introduced in Ethiopia during 1970s and has since been cultivated in small pockets of the country6. Even though, rice is not traditional staple food in Ethiopia, it is a high potential emergency and food security crop for the country. Rice production is expanding rapidly and farmers are growing it in many places and over large areas and also have developed many Ethiopian recipe using rice including injera, bread, porridge, couscous and local drink tella and katikalla7.
The government of Ethiopia has named it the ‘millennium crop,’ and has ranked it among the priority commodities of the country, despite rice has just been recently introduced to Ethiopia, recognizing its importance as a food security crop and a source of income and employment opportunities. Since the crop is new there are very few adapted varieties in the country. Hence, varietal adaptability to environmental fluctuations is important for the stabilization of crop production over both the regions and years. An information on genotype x environment interaction leads to successful evaluation of stable genotype, which could be used for general cultivation. Yield is a complex quantitative character and is greatly influenced by environmental fluctuations; hence, the selection for superior genotypes based on yield perseat a single location in a year may not be very effective. Thus, evaluation of genotypes for yield and yield component under varying environmental is important to get adaptable and superior genotype for the research site agro-ecology.
The objective of the study was:
‘ To evaluate yield and yield components of rice genotypes at multi-environment and select one best performing genotype as variety
‘ To show growers and government the adaptation of rice at new area where rice didn’t grow before
MATERIALS AND METHODS
The research was conducted at Shire-Maitsebri Agricultural Research Center on farm and research site. The research area is at Northern Ethiopia specifically Tigray region Maitsebri. Geographically, it is located at longitude 13”35’21” N and 38”8’48” E with an altitude of 1361m, The mean annual temperature of the area ranges from 16to 38”C. The annual rainfall also ranged from 758 to 1100 mm and has a mono-modal pattern. The research was conducted supported by Shire-Maitsebri Agricultural Research Center on the rainy season. Nine rice lines were introduced from Fogera National Rice Research and Training Center. Nine rice introduced lines were evaluated along with Maitsebri-1 as check at Shire-Maitsebri Agricultural Research Center Tigray, Ethiopia in 2014 and 2015 crop year. They were evaluated for their adaptability and performance in the target areas. The trial were carried out in a randomized complete block design with three replications at three location for two years .The plot size was six rows of 5m length and 0.2m between rows(6m2)and the spacing between plotswas0.3m. For all activities, fertilizer was applied based on local recommendation. DAP was applied all at planting while urea was split and applied one third at planting, one third at tillering and the remaining one third at panicle initiation. Planting was done by hand drilling at a seed rate of 70 kg/ha. All recommended agronomic practices were applied. All relevant data were collected and analyzed. Statistical analysis was made using GenStat 16 edition. Descriptive statistics, data screening, combined analysis through years and sites were analysed.
Result and Discussion
The grand mean range of grain yield was 3656 kg/ha (ARRCCU16Bar-4-14-3-2-B-1) to 5222 Kg/ha (ARCCU16Bar-4-14-2-2-B-1) (Table-1). In terms of yield advantage ARCCU16Bar-4-14-2-2-B-1has 42.8% over ARRCCU16Bar-4-14-3-2-B-1.ARCCU16Bar-4-14-2-2-B-1 can be appropriate at area with moderate rainfall. It was reported that highest grain yields (822.7 kg/ha) were recorded from the genotype Ediget followed by Gumara which was 732 kg/ha from their research8. On the other side it was reported maximum yield of 4282 kg ha’1 9. Super hybrid rice variety Liangyoupeijiu produced maximum grain yield of 13.29 t ha-1 in China in 2007 under irrigation condition. This shows researchers must do additional efforts to narrow yield gap between current finding and Chinese super hybrid rice yield10.The grand mean of days to maturity ranges 113 days to 119 days. Genotypes ARRCCU16Bar-4-14-3-2-B-1 and IR82616-B-B-64-3 consistently matured late and earlier respectively across environments and year. Pooled results over three environments and two years indicated that genotypes ARCCU16Bar-4-14-2-2-B-1 and Maitsebri-1 were mostly delayed in maturity (Table-2). Early maturity is important character for genotypes to escape severe water deficit under terminal drought stress condition. Hence, the early maturing genotypes are adaptable for areas with short rainy season. Biomass yield ranges from 12973.07 kg/ha (ARCCU16Bar-4-14-2-2-B-1) to 9168.957 kg/ha (ARRCCU16Bar-9-21-4-1-1-1) (Table-3). Genotype ARCCU16Bar-4-14-2-2-B-1 had better grain yield and biomass yield. It was found under inorganic culture condition, the highest straw yield was found 10.28 t /ha in Bangladesh11. The highest biomass yield was reported 2.7 tones/ha under irrigated condition in Nigeria International Institute of Topical Agriculture (IITA) 12. Since Ethiopia has big number of cattle working on biomass production is important for its amount and palatability. In terms of panicle length Maitsebi-1 and ARCCU16Bar-4-14-2-2-B-1 had better score 22cm and 20 cm respectively (Table-4). The highest panicle length was revealed 20.64cm among the tested eight genotypes in Nigeria13. Additional research finding was found that average panicle length of 19.08cm under rain fed condition14. Thousand seed weight ranges from 28.88 grams to24.35grams (Table-5). Genetic improvement in seed weight can help in total yield production.
Among the top scoring varieties ARCCU16Bar-4-14-2-2-B-1 is relatively early maturing (113-124 days) when compared with the check Maitsebri-1, relatively high yielder under both medium and high rain fall conditions, have good biomass yield, high preference by farmers.IR82616-B-B-64-3 is also relatively early maturing (106-122 days), relatively high yielder under both medium and high rain fall conditions, relatively good straw yield, high preference by farmers. It was reported that days to maturity among rice genotypes ranged from 96.7 to 110.7 tested under irrigation condition in Pakistan15. This indicates testing for early maturing with high yielding genotypes can be fruitful at the research area.
Total yield of ARCCU16Bar-4-14-2-2-B-1 as % of check in trial is 15.5% over the standard check Maitsebri-1(NERICA-13). Similarly, total yield IR82616-B-B-64-3 as % of check in trial is 12.7% over the standard check Maitsebri-1 (NERICA-13). Significant disease occurrence was not observed for both varieties at both locations for three seasons.
Conclusion
Considering the performance yield and yield componentsARCCU16Bar-4-14-2-2-B-1 and IR82616-B-B-64-3 had better score. High yield was found than any other research conducted at the research area. Lines with high yield and biomass can solve farmers’ food security as well as feed for their animal. Both ARCCU16Bar-4-14-2-2-B-1 and IR82616-B-B-64-3can be recommended as improved varieties to low altitude areas of Tigray which have medium and high rain fall distribution as well as similar agro-ecologies in the world. Introducing new crop like rice to new agro-ecology can help to alleviate food security. This research can be bench mark for genetic improvement at research area. This finding lead government use marshy areas which were idle for many years.
The limitation of the research was genotypes not as much for genetic variability and data were few. Testing much more genotypes can be very important much genetic variability so as to get best performing genotypes at the research area.
Future research marker assisted selection can be very important for gene action on yield and yield components for large rice line population in addition to the agro-morphological evaluation.