MORPHO-GE NETIC VARI ABIL ITY AND CHAR AC TER IZA TION OF NEWLY DE VEL OPED
WIN TER MAIZE IN BRED LINES
S.B. Singh, K.K. Yadav1, P. Bagaria2, R.K. Kasana and Jitender Bhati
Re gional Maize Re search and Seed Pro duc tion Cen tre, (ICAR-IIMR) Vishnupur, Begusarai-851129 (Bihar) 1
ICAR-In dian In sti tute of Maize Re search, New Delhi 2ICAR-In dian In sti tute of Maize Re search, Unit, Ludhiana
E-mail : [email protected]
ABSTRACT
Ninety seven newly developed winter maize inbred lines and thirteen released inbreds were evaluated to estimate the morpho-genetic variability for yield traits. A wide range of variability was observed for kernel type (flint, semi flint, semi dent and dent), grain colour (white, yellow and orange) and kernel size (small medium, bold). Pooled ANOVA revealed the significant mean for all the traits studied. Three inbred in early, ten in medium and seven in late maturity group were recorded high grain yield. High PCV and GCV were recorded obtained for ASI, ear height, kernels per row, plant height, grain yield, ear length. High estimates of heritability were observed for 100 kernel weight, days to 50 per cent anthesis, days to 50 per cent silking, grain yield, days to maturity, grain filling duration and plant height. All these inbred lines were grouped according to maturity, productivity, plant height, kernel colour, and kernel size and kernel type. Ear girth, kernels per row, kernel rows per ear, ear length and 100 kernel weight were positive and high significantly associated with grain yield.
Key words : Ge netic ad vance, heritability, in bred, morpho-ge netic, vari abil ity, win ter maize.
Maize is one of the most important cereal crops of the world and contributes to food security in most of the developing countries. In India, maize is emerging as third most important crop after rice and wheat. Maize is not only worldwide important crop as a food, feed and as a source of divers industrially important products, but is also a model genetic organism with immense genetic diversity (1). The introduction of new hybrid seeds that can survive low winter conditions, off-season disease and pests with high productivity has made maize a profitable alternative ever for small farmers in U.P, Bihar, Andhra Pradesh and Karnataka. In India winter maize could help meet demand requirements consistently throughout the year (2). Winter maize has emerged as an important crop in the non-traditional areas. Under changed climatic conditions, wheat yield decreased whereas the yield of winter maize
increased due to warmer winters and enhanced CO2
compared to baseline further increase in maize cultivation in locations with poor wheat yield could well be considered as an adaptation option (3). The predominant winter maize growing states are Andhra Pradesh, Bihar, Tamil Nadu, Karnataka, Maharashtra and West Bengal. There is potential to increase the production of maize by increasing the production of winter maize in the coming years as winter maize has a higher yield at 4 MT/hectare as against 2.5MT/hectare for kharif maize. In the absence of any major environmental impediments in winter, the desired field operations can be planned and executed at the most desired time (2). Due to low temperature and humidity in winter season, level of infection or infestation by various diseases and insect pests is quite low, resulting in higher yields. Since opportunities are limited for further
expansion of maize area, future increases in maize supply will be achieved through the intensification and commercialization of current maize production systems (4).
Genetic improvement of a crop is pivoted on the strength of genetic diversity within the crop species. Adequate variability provides options from which selection are made for improvement and possible hybridization. Genotypic correlations had been used as an effective tool to determine the relationships among agronomic traits in genetically diverse population for enhanced progress in crop improvement (5). The success of any crop improvement programme not only dependent on the amount of genetic variability in the population but also on the extent to which it is heritable, which sets the limit of progress that can be achieved through selection [6]. Genetic variability for agronomic characters therefore is a key component of breeding programmes for broadening the gene pool of crops (7). Due to higher productivity of winter maize hybrids suitable for winter ecology, they are required to fulfil the rising demand of maize production. The winter maize inbred lines that can be utilised in the development of such hybrids could provide more adaptability due to inbuilt tolerance for biotic and abiotic stress during winter ecology. Therefore, the present investigation was conducted with the objective to assess the genetic variability and characterization for morphological and yield traits among newly developed winter maize inbred lines, further efforts were also made to find the association among these traits and with grain yield in winter maize inbred lines.
Table-1 : Source of germplasm and seed traits of Maize Inbred lines developed for winter season.
S. N. Name of
Inbred line
Source germplasm
Institute of source germplasm
Kernel colour
Kerne l type
Kerne l size
S. N.
Name of Inbred line
Source germplasm
Institute of source germplasm
Kernel colour
Kerne l type
Kerne l size
MATERIALS AND METHODS
Ninety seven new inbred lines of winter maize were developed through pedigree method from the divers source of germplasm. These inbred lines along with thirteen released inbreds were evaluated in randomized block design (RBD) for morpho-physiological and yield traits during winter season of 2014-15 and 2015-16 at Regional Maize Research and Seed Production Centre, (IIMR) Kusmahaut, Begusarai-851129 (Bihar). The detail of inbred lines, source of germplasm, institute and other attributes are presented in Table 1. Each inbred line was sown during first week of November in both the years in a single row of 4 m length spaced at 60 cm with interplant distance of 25 cm. All recommended agronomic practices were followed to raise a good crop. Observations were recorded on thirteen morphological and yield characters. In each entry five plants were randomly selected and utilized to collect observations on plant height, ear height, ear length, ear girth, kernel rows per ear, kernels per row, 100-kernel weight. Observations on days to 50 per cent anthesis, days to 50 per cent silk, anthesis–silking interval (ASI), grain filling duration, days to maturity and grain yield were recorded on plot basis. Grain yield per plot was utilized to obtain the grain yield qtls per hectare. Grain filling duration was considered the period after pollination to 75 per cent dry husk maturity. Pooled mean over year was utilized for analysis of variance (ANOVA) and used to quantify the genetic differences among the genotypes. The data was analysed using windostat software. The mean values were used for genetic analysis to determine phenotypic coefficients of variation (PCV) and genetic coefficient of variation (GCV) according to Singh and Chaudhary (8).
RESULTS AND DISCUSSION
A great variability was exhibited among the inbred lines for morphological characters as well as yield components. The analysis of variance revealed the significant mean square at P=0.0 as well as P= 0.01 for all the traits (Table-2). Large variability was reported for kernel type (flint, semi flint, semi dent and dent), grain colour (white, yellow and orange) and kernel size (small medium, bold). On the basis of phenotypic and morphological characterization all these inbred lines were grouped according to maturity, productivity, plant height, kernel colour, kernel size and kernel type (Table-3). Two inbred lines IMLBG-123-1 and IMLBG-182-1 in early maturity group were recorded high grain yield whereas in medium maturity group ten inbred namely IMLBG-23-2, IMLBG-43-2, IMLBG-46-1, IMLBG-49-2, IMLBG-156-2, IMLBG-183-1, IMLBG-219-2, IMLBG-2032, IMLBG-2083 and IMLBG-2102 recorded high grain yield (>30q/ha). Similarly in late maturity group seven inbreds
IMLBG-164-1, IMLBG-246-2, IMLBG- 457-2, IMLBG-814-2, IMLBG-2103, IMLBG-1298-2 and IMLBG-1298-5 were in high yielding group. Significant genetic variation was exhibited by inbreds for several other yield attributes like ear height, ear girth, ear length, ear height, kernel rows per ear, kernels per row used in this study. Genotypes exhibited a wide range of variation for most of the traits making possible the identification of inbreds with special characters. A wide range of variability was found in different plant characters studied (Table-4). The highest range of variation was exhibited by grain yield (9.83 to 38.64 q/ha.) and lowest by days to maturity (139 to 167 days). High range of variation was observed for plant height (48.67-160.90 cm) and 100 kernel weight (14.73-38.27 gm) indicating importance of these inbreds for maize improvement.
High estimates of phenotypic coefficient of variation (PCV) were obtained for ASI, ear height, kernels per row, plant height, grain yield, ear length. Highest estimates of genotypic coefficient of variation (GCV) were reported for ear height followed by kernels per row, ASI, grain yield, plant height, 100 kernel weight, ear length, grain filling duration and kernel rows per ear. A wide range of variability for grain yield was also reported by (9). Similar results were also reported by (10) in a study of 14 advanced CIMMYT maize landraces and 15 advanced hybrids. The estimates of phenotypic coefficient of variation were greater than the genotypic coefficient of variation, indicating thereby the importance of environmental factors. Heritability ranged from 50.0 to 97.0 per cent. Highest estimates of heritability were observed for 100 kernel weight, followed by days to 50 per cent anthesis, days to 50 per cent silking, grain yield, days to maturity, grain filling duration, plant height. Moderate estimates of heritability were for ear height, kernels per row, ear length, ear girth and ASI. Lowest estimates were
observed by kernel rows per ear. High estimates of heritability was also reported by (5, 11) for days to anthesis, days to silking, ASI, plant height, ear height. Heritability is the percentage of genotypic variance that is attributed to genetic variance. In the present study high heritability (>80 per cent) for the traits indicated that the environmental influence was minimum. Any of these characters can therefore be used for selection. High estimate of genetic advance as per cent of mean was observed for ear height, kernels per row, grain yield, plant height, whereas moderate estimates were observed for 100 kernel weight, ASI, ear length and grain filling duration. The expected genetic advance as percent of mean that was low for days to maturity, days to 50 per cent silking and days to 50 per cent anthesis may be compensated by their high heritability (12). High heritability estimates coupled with high estimates of genetic advance as percent of mean for grain yield, ear height, plant height kernels per row indicated the preponderance of additive gene action for the expression of these traits which is fixable in subsequent generations. This also provides the evidence that larger proportion of phenotypic variance has been attributed to genotypic variance, and reliable selection could be made for these traits on the basis of phenotypic expression. These results find support from the earlier studies (13) that there was greater magnitude of broad sense heritability and high genetic advance in grain yield, plant height, days to anthesis and days to silking. High estimate of heritability and low genetic advance were observed for days to maturity, days to silking and days to anthesis which may be attributed to non-additive gene action governing these traits, therefore, these characters could be improved through the use of hybridization and hybrid vigour. High heritability accompanied with low genetic advance as per cent of mean in days to anthesis and silking had earlier Table-3 : Grouping of winter maize inbred lines on morphological attributes.
Group Attribute No. of Inbred lines Group Attribute No. of Inbred lines
A. Maturity D. Kernel Colour
Early (< 140) day 2 Yellow 34
Medium (140-150) day 51 Orange 66
Late (> 150) day 57 White 10
B. Grain Productivity E. Kernel Size
High (30-40) q/h 30 Bold 39
Medium (20-30) q/h 64 Medium 61
Low (< 20 ) q/h 16 Small 10
C. Plant Height F. Kernel Type
Tall (> 150) cm 3 Flint 45
Medium (100-150) cm 53 Semi Flint 24
Dwarf (< 100) cm 54 Dent 32
been reported by (5, 11). Ear girth exhibited low heritability with low genetic advance indicating non-additive genetic effects governing this trait. Moderate heritability along with high genetic advance was recorded for ear height providing little chance for its further improvement. However, care must be taken while breeding for this complex trait as it is considerably influenced by environmental factors. It seems a limited scope of improvement could be achieved for this trait within this group of genotypes. Days to 50 per cent anthesis, days to 50 per cent silking and days to maturity had high heritability but the genetic coefficient of variations (GCV) was low. This indicates that though, the character is highly heritable, its improvement through early generation selection may not give the desired results. Low genetic coefficient of variation and estimate of heritability obtained for ear girth indicated that character is highly influenced by environment. Therefore, direct selection for ear girth improvement may not be possible, but through indirect selection of other secondary traits may be feasible (11). The greater variability and diversity among the inbreds play an important role in the maize improvement. The heterocyst in hybrid development depends on greater distance whereas variability provides greater choice of germplasm in maize improvement. Therefore these inbred lines may be utilized for the development of better cross combination for winter season.
The estimates of correlation coefficients estimated at genotypic level among different pairs of traits are presented in Table-5. Significant and positive correlations were reported between grain yield and all the traits except days to 50 per cent anthesis, days to 50 per cent silk and days to maturity, where it was negative and significant. Positive and significant correlation between grain filling duration and grain yield was also reported which is important for winter season inbreds that can be utilised for selection of inbreds for higher productivity. Highly significant positive correlation of grain yield with ear length, number of kernel rows per ear, number of kernels per row, 100 kernels weight and plant height was also reported by (14, 15, 16, 17, 18). Moreover, positive and significant correlation towards grain yield was exposed by days to 50 per cent anthesis vis days to 50 per cent silk, days to maturity and plant height; and days to 50 per cent silk through days to maturity. Similarly, plant height, ear height, ear length and ear girth were registered with positive and significant correlation with each other. Ear girth registered positive and highly significant correlation with kernel rows, kernels per row, 100 kernel weight and grain yield. Whereas, positive and significant correlation between grain filling duration and
ear length and ear girth indicated yield enhancement through ear length and ear girth.
CONCLUSION
The study revealed that large morpho-genetic variability was exhibited among the winter inbred lines with respected to yield traits. I was made possible to characterise and classify these inbred lines into groups on the basis of maturity, productivity, plant height, kernel colour, kernel type and kernel size. High estimate of heritability coupled with high estimate of genetic advance as percent of mean was obtained for ear height, kernels per rows, grain yield, plant height for 100 kernel weight, grain yield and plant height indicated that these characters were under the control of additive genetic effects that can be manipulated according to requirements and worthwhile improvement could be achieved through selection. Positive and significant correlation of ear girth, kernels per row, kernel rows per ear, ear length and 100 kernel with grain yield provided the possibility for direct selection of these traits for higher yield. Newly developed high yielding winter maize inbred lines in early (3 inbreds), medium (10 inbreds) and late maturity (7 inbred) provided the opportunity to utilize them in productive hybrid development for winter season after estimation of their combining abilities. Though the inbred lines exhibited large variability but for effectively and extensive utilization of these inbred lines in hybrid development it is desirable to predict their genetic distance by adopting appropriate method. The variation present in inbred lines must be further mined to allelic diversity, and screening them extensively for phenotypes of interest and for new alleles of previously characterized genes [19].
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