Quality and Genetic Evaluation of Some Genotypes of Rice (Oryza Sativa L.) Using Diallel Method
Preamble of the Study
Rice breeding efforts over the past three decades have been concentrated on the development of high-yielding rice varieties to meet the food needs of humanity. Hybrid rice offers the potential to boost rice yield potentials. Virmani and Peng (1999) reported that it has a yield advantage of 15-20% over conventional high-yielding varieties. The choice of outstanding parents with favorable alleles will no doubt offer the opportunity for greater success for higher yields. Improvements in rice quality are crucial in meeting the demands of consumers for healthy, high-quality food (Kennedy et al., 2002). Koutroubas et al. (2004) identified appearance, milling quality, cooking, and processing as well as nutritional quality as the most important rice grain qualities common to all users. The nutritional quality of rice is mainly determined by the protein content of the grain. Tagwireyi and Greiner (1994) reported that 70% of the total protein for human nutrition in African regions comes from cereals. Studies have shown that the protein content of rice is a quantitative trait (Singh et al., 1977). Breeding efforts for increased protein content in rice had been largely unsuccessfully owing to the low heritability of protein content and complexity associated with the inheritance of triploid endosperm tissues, and its protein content has been reported to be negatively correlated with grain yield and some cooking and eating criteria (Juliano, 1990).
Agronomy of Rice
Rice (Oryza sativa L.) is an annual crop and belongs to the tribe Oryzae in the sub-family Poidae of the grass family, Poaceae (Saxena, 1983). It is thought to have been domesticated in India or South East Asia from the wild species O. perennis (Chang, 1987). There are over twenty wild species and two cultivated species of rice. The cultivated species, Oryza sativa L. (Asian rice) and O. glaberrima Steud (African rice) also called the “red rice” can grow in a wide range of water-regimes for a prolonged period of time from fadamas to deep waters and dry land as well as on hilly slopes. It is grown as a monocarpic annual crop although in tropical areas it can survive as a perennial and can produce ratoon crop and survive for up to twenty years (IRRI, 2008).
In Africa, there are basically two rice cultivation ecosystems: the upland system found on well drained soils with crops being rain-fed and the lowland systems called swamp rice production which prefers flooded conditions. Agboola (1979) reported that O. glaberrima is considered to be indigenous to West Africa and has been in cultivation in most parts of Northern Nigeria as “Red Sokoto rice”, since the 16th century. However, the relatively low yield, its red coloration, weak stem, frequent seed dormancy and shattering of the paddy at maturity before harvesting have made the O. glaberrima less acceptable both to farmers and consumers. The white rice was introduced to Nigeria about 1920 (Osifo, 1971) and has become more important than the “red rice” and its production has increased greatly since the 1960s.
Globally, the amount of energy (kcal) per capita supplied from rice has jumped from 411kcal/capita in 1960 to 577 kcal as at 2002, an increase of 40% (Kennedy et al., 2002). A breakdown of this energy in regions shows that trends in dietary energy supplied by rice (kcal/capita/day) increased up to 90% in Sub-Saharan Africa and 28% in Asia and Latin America (FAO STAT, 2001). Nigeria became the third largest producer of rice in West Africa after Sierra Leone and Ivory Coast by 1976 accounting for about 15% of West African rice fields of over 2.1 million hectares and about 16% of the total 2.6 billion tonnes of rice output (Filani, 1980). The draw back to the cultivation of O. sativa has been its increased susceptibility to pests and diseases, which over the years has led to increased application of pesticides and fertilizers to maintain high yield in spite of the associated environmental hazards. The effort of the West African Rice Development Association (WARDA) research scientists in developing the NERICA (New Rice for Africa) lines is commendable. By combining the beneficial qualities of the African and Asian rice species through conventional and modern techniques, they have developed the NERICA lines which have the potential for higher yields, better resistance to diseases and drought and higher protein contents than the O. sativa commonly grown in the region (WARDA, 2000).
MATERIALS AND METHODS
The field experimentation for the research was conducted at the Teaching and Research Farm of the Federal University of Technology, Owerri. It is located on latitude 50271N and longitude 7021E on an elevation of 55.0m above sea level in the humid forest zone of South Eastern Nigeria. The temperature was moderate with high relative humidity and rainfall pattern consistent with that in humid tropical zones. The soil is classified as ultisol. All laboratory analyses were carried out at the Analytic Laboratory of International Institute for Tropical Agriculture (IITA), Ibadan and Quality Laboratory of Africa Rice Center (ARC) Cotonou, Benin Republic.
Sources of Planting Materials
Thirty (30) genotypes of rice were used for the study, and are presented in Table
They were collected from different sources to represent rice genotypes grown and consumed in Nigeria.
Evaluation of 30 Genotypes of Rice in Field Experimentation for Agronomic
Performance to Select Eight Genotypes for Diallel Analysis.
Two genotypes, WAB 365-B1-H₁-HB and FARO 15 did not flower in the course of the experiments for both years and thus were not part of the results reported. The genotypes evaluated varied in the ranges of 3.67(FARO 44) and WAB 181-32 to 21.3(WITA 4) for number of tillers per stand, in 2005 and 5.00(FARO 44) to 19.33(WITA 4) in 2006, percentage fertile spikelets ranged from 68.37 % (WAB 181-32) in 2005 to 94.97% (NERICA 1) and 63.7% (WAB 181-32) to 97% (NERICA 1) in 2006. Number of spikelets per panicle varied from 40.7(NERICA 15) to 153.3(CT 7127-49) in 2005 and 49.7 (NERICA 15) to 166.3(CT 7127-49) in 2006(Tables 4 and 5).
Among the hybrids, WITA 4 x Max (tillers per stand); CT 7127- 49 x EMPASC 105(days to anthesis); WITA 4 x WAB 96-1-1 and IR 57689-73 x WAB 96-1-1(pancle length); Max x NERICA 1 and W WITA 4 x IR 57689-73 (seeds per secondary branch of panicle); WAB 96-1-1 x NERICA 1(spikelets per panicle); Fofifa x NERICA 1 and WITA 4 x IR 57689-73 (percentage fertile spikelets); WITA 4 x Max (seeds per secondary branch of panicle) and IR 57689-73 x Max (1000 seed weight); Fofifa 16 x NERICA 1, EMPASC 105 x NERICA 1 and WITA 4 x Max (fine grain rice )and WITA 4 x NERICA 1, Max x NERICA 1, CT 7127- 49 x NERICA 1, Fofifa 16 x WAB 96-1-1, CT 7127- 49 x Fofifa 16 and EMPASC 105 x Fofifa 16 (higher protein content) can be selected for the traits they expressed best. WITA 4 showed maximum negative GCA effect for plant height at flowering while NERICA 1exhibited the same for days to anthesis and thus are suggested to be important in decreasing such traits. On the other hand, CT 7127- 49 and EMPASC 105 showed highest positive GCA effects for spikelet number, NERICA 1 and CT 7127- 49 for percentage fertile spikelets and seeds per secondary branch of panicle. This indicated the importance of such parental lines for increasing such traits and as such could be selected as elite lines for breeding for increased yield since these traits are yield-related.
In the present study, the lines that exhibited earliness, NERICA 1, Fofifa 16 and WAB 96-1-1 were all of upland adaptation and were not profuse in tillering ability. The parental line CT 7127-49 that produced the longest panicle combined it with tall plants and more spikelets per panicle. Hybrids WITA 4 x Max flowered earlier than the parents with more productive tillers and spikelets with relatively fewer fertile spikelets and heavier seeds indicating diversity of the parents in the loci with dominance in the characters mentioned. Great diversity among the parents utilized for the study was exhibited most in protein content having more than 75% positive SCA effects among its crosses with positive heterosis for the MPH and HPH in the F1 generation. This was followed by grain length/ width ratio, productive tillers per stand, days to anthesis and secondary branch per panicle as inferred by their recording negative SCA effects less than 50% among the crosses for the characters mentioned above. GCA effect conferred maximum protein content on CT 7127- 49 and EMPASC 105 as well as WAB 96-1-1 which also agrees with the results of SCA effects. Out of 14 cross combinations each of the parents were involved in, CT 7127- 49 recorded highest SCA effects involving 12 crosses, followed by EMPASC 105 with 11 and WAB 96-1-1 which had 9. Furthermore, analysis of MP and HP F₁ heterosis indicated that CT 7127- 49 was the only parent that produced higher protein hybrids in all the crosses it was involved in both as pollen and as seed parent. However, it must be noted that GCA, SCA and heterotic values are all estimates.
Preponderance of dominance was noticed for tillers per stand, days to anthesis, grain length/ grain width ratio and percentage protein content. For most of the characters studied, additive, non-additive and epistatic effects were observed. It is equally important to mention that either reciprocal or / and maternal effects were also implicated in the inheritance of tillers per stand, days to anthesis, panicle length, secondary branch per panicle, spikelet number, percentage fertile spikelets seeds per secondary branch of panicle grain length/width ratio and percentage protein content. To exploit such complex genetic makeup, selection of desirable segregates may be postponed to advanced generations so that epistatic gene action may get fixed in the segregates.
The results showed that the mean of BC₁ and BC₂ tended to be located close to those of their respective recurrent parents. For most traits, F1 generation means were higher than the mid-parent values especially for percentage protein content. The F1 and F2 generation means were not significantly different in the majority of cases except for the lowland x upland and upland x lowland hybrids for percentage fertile spikelets and spikelet number per panicle which is thought to be due to the diversity in these traits among the parental lines.
- Abbasi, F.M., M.A. Sagar, M. Akram and M. Ashraf ( 1995). Agronomic and quality traits of some elite rice genotypes. Pakistan J. Sci. Indust. Res., 38:348-350.
- Adair, C. R., Bollich, C.N., Bowman, D. H., Jodon, N. E., Johnston, T.H., Webb, B. D., and Atkins, J. G (1973). Rice breeding and testing methods in the United States. 22-75. In: Rice in the United States: Varieties and Production. Agriculture Handbook 289(revised). U. S. Department of Agriculture, Washington, DC.
- Agbo, C. U. and I. U. Obi (2005). Yield and yield component analysis of twelve upland rice genotypes. Journal of Agriculture, Food, Environment and Extension. 4 (1) 29 -33.
- Agboola, S. A. (1979). Agricultural Atlas of Nigeria. Oxford: New York: Oxford University Press 89 pp.
- Akter, K., K. M. Iftekharuddaula, M. K. Bashar, M. H. Kabir, and M. Z. A. Sarker (2004). Genetic variability, correlation and path analysis in irrigated hybrid rice. J. Subtrop. Agric. Res. Dev., 2: 17-23.