Per se performance and genetic behavior for quality traits viz, 100-kernel weight, protein per cent, tryptophan and lysine in protein, specific gravity and grain yield were studied in seven selected QPM hybrids in two locations during kharif 2000. Specific gravity, tryptophan and lysine content in protein and protein per cent found as primary quality traits to improve QPM genotypes along with yield. F1 crosses CML-176 x CML 186 and CML-177 x CML-176 were identified as best high yielding QPM hybrids and proposed for their multi-location testing before commercial utilization.
Key words: Tryptophan, lysine, maize, carbohydrates, per se profile.
Maize is the principal source of carbohydrates and protein in the areas where it is used as staple food. However, because of deficiency of lysine and tryptophan and presence of excess leucine, the poor nutritional quality of maize protein was long back recognized (Osborne and Mendel, 1914). With the discovery of mutant allcles opaque-2 (0-2) (Mertz et al, 1964), floury-2 (fl-2) (Nelson et al., 1965) genes presently major use in the QPM programme along with other genes viz., 0-7, 0-6, fl-3, mucronate and defective endosperm have increased opportunities immensely for the improvement of quality protein maize since these mutant genes alter the amino acid profile (lysine, tryptophan and other amino acids) and composition of endosperm protein in corn. This aspect was further strengthened by the development of modified hard endosperm genotypes (Paez et al., 1969) and different breeding procedures to develop different types of QPM germplasm (soft endosperm or opaque-2 based germplasm), genetic modifiers, hard endosperm or their different combinations etc.) and their utilization in the development of high yielding QPM maize hybrids (Vasal 1980 and Vasal et al., 1984 and 1994) comparable With Honnal (non QPM) high yielding com hybrids. Therefore, ill the present investigation, an effort was made to collect information on the per se performance, quality characters and their genetic behavior in few selected QPM hybrids known for their heterotic combinations and compared with released best QPM cultivars.
The materials for the investigation comprised of seven selected genotypes (5 QPM hybrids + 2 checks) raised in two locations with randomized block design replicated four times during kharif season of 2000 both at College of Agriculture, Rajendranagar, Hyderabad(location 1) and at Agricultural Research Station (Maize), Amberpet, Hyderabad (location 2). Each genotype was sown in two rows of 5.0 m length adopting a spacing of 75 cm between rows and 20 cm between plants within a row. The crop was provided with fertilizer dose of 120:60:50 N, P, K in kilograms per hectare and followed all recommended package of practices to raise a successful maize crop. Observations on the whole plot basis for each entry was recorded for grain yield, while five competitive plants were randomly selected from each entry for recording data on 100-kernel weight and specific gravity.
Pericarp and embryo removed from the maize samples with the help of pincer and scalpel. Only endosperm was collected. The samples were coarse grinded by hand grinder and defatted by Soxhelet apparatus adding petroleum either. The moisture content in the sample was determined by the method A.O.A.C. (1990). The flour of these varieties was prepared by cyclone sample mill protein content was determined according to the method A.O.A.C. (1965). Tryptophan was estimated by papain hydrolysis method Hernandez and Bates (1965). Lysine was determined by method Tsai et al., (1972) and Villegas, E. and Martz, E.T. (1971). Specific gravity estimated by Gustafson et al., (1970) . Means were computed for two locations and the mean pooled data were analysed for RBD analysis as described by Panse and Sukhatme (1978). The phenotypic and genotypic coefficient of variation by adopting the formula of Burton and Devane(1953), broadsense heritability using the formula given by Hanson et al., (1956) were computed. Genetic advance was computed based on broadsense heritability values in accordance with the formulae given by Jhonson et al., (1953).
Analysis of variance revealed highly significant differences for all the five quality characters studied, indication inherent variability in the material taken up for the investigation (Table-1). From coefficient of variation, it is clearly observed that, the variation was maximum for 100-seed weight (8.57%), followed by yield per plot (6.14%), tryptophan in protein (5.48%), percent lysine in protein (3.49′)0), specific gravity (4.73%) and the lowest being for protein percent (3.04%). Similar ‘0’ the present investigation significant difference and variation for protein per cent and yield characters were also reported by Satyanarayana (1990) and Chandra Mohan (1999).
Table.1. Mean per se performance and analyzed data on grain yield and quality characters in selected hybrids of QPM-genotypes.
|Quality Parameters||Specific Gravity||Grain yield (kg/plot)||Pedigree|
|Tryptophan (g/16g N)||Lysine (g/16 N)|
|CMJ..,-186 x CML-149||24.00||7.50||0.72||2.81||1.13||2.40|
|lCIvIL-142 x CI-IL-I501 x CML 186||23.00||6.78||0.68||2.26||1.09||2.35|
|CML-176 x CML-186||28.00||6.75||0.75||2.93||1.08||1.08|
|CML-175 x CML-176||23.00||8.05||0.62||2.50||1.10||1.10|
|CML-177 x CML-176||23.95||6.86||0.78||3.00||1.13||1.13|
|Shakti-1 (QPM( Local Check)||21.86||8.09||0.72||2.93||1.08||1.08|
|C.D. at 5%||2.64||0.26||0.044||0.161||0.065||0.174|
The estimates of various genetic variability parameters are presented in Table-2. Hundred seed weight exhibited higher genotypic (4.60) as well as phenotypic (9.03) variances, compared with other traits revealing existence of higher magnitude of variability for this trait, and indicated its possible prime role in the selection programme for improvement of grain yield in maize. This corroborates the statement made by Manmohnan (1984) and Satyanarayana (1990)
Table.2.Genetic studies for quality characters and yield in selected hybrids of QPM
|Character||Variance||Co-efficient variation||Herit ability (%)||Genetic advance||GA as % over mean|
|Tryptophan (g/16 N)||0.0094||0.0079||14.176||13.075||85.06||0.1696||24.84|
|Yield per plot(kg)||0.0725||0.0500||11.020||9.150||68.96||0.3825||15.66|
The higher values of phenotypic and genotypic coefficient of variation were observed for traits ‘viz., specific gravity (14.553, 13.763) , tryptophan percentage in protein (14.176, 13.075) and lysine percentage in protein 910.280,9.680 indicating a good deal of genetic variability in these characters and thus, suggesting, direct selection for these three characters would also b effective. Other traits viz., 100-seed weight (12.247, 8.750), yield per plot (11.20, 9.150) and protein percentage (10.356,9.949) exhibited relatively moderate values of PCV and GCV indicating more influence of environment interaction on the expression of these characters. Such observations were also reported earlier by ManMohan (1984) and Satyanarayana (1990 and 1996)
Estimates of high heritability combined with higher genetic advance as percent over mean for traits, specific gravity (89.43, 26.81), tryptophan (85.06, 24.84) lysine (88.80, 19.24) and protein percent (92.31, 19.69) indicated that these characters are largely governed through the additive effect of genes and improvement in these characters may be achieved through simple phenotypic selections. Similar results were also reported by satyanarayana (1990, 1995) and Chandramohan (1999), for protein and yield contributing characters. Johanson et at 91995) have suggested that, heritability estimates along with genetic advance shall be more helpful in predicting genetic gain under phenotypic selection than heritability estimates alone. The other characters such as, yield per plot (68.96, 15.66) and 100-seed weight(51.04, 12.88) exhibited moderate values of heritability coupled with moderate to low values of genetic advance, indicating that these traits were mainly under the influence of environmental interaction with non-additive and epistatic gene effects(Panse 1957).
Hence, from the present investigation it was evident that, while going for selection in quality protein maize genotypes more emphasis should be given for the characters specific gravity, tryptophan, lysine and protein per cent as they exhibited higher variability, heritability coupled with genetic advance. Further, among the selected crosses viz., CML-176 x CML-186 and CML_177 CML-176 which possessed higher values of tryptophan, lysine, specific gravity, i.e. quality protein,100-seed weight and also good grain yield found significantly superior compared with Shakti-1, the best QPM released variety in the country. Whereas QPM hybrid CML-176 x CML-186 which recorded highest plot grain yield of 2.70kg, in addition with all high quality traits were compared with one of the best normal popular high yielding maize hybrid (PRO-311). Therefore, it is worthwhile to evaluate these two QPM hybrids under multi-season and multi-location testing to confirm their superiority in yield coupled with high quality protein before their release for commercial cultivation as QPM hybrids.
Om Prakash, E.Satyanarayana, P.Shanti, and R.Sai kumar
Directorate of Maize Research, Indian Agricultural Research Institute, New Delhi-110012