Excerpt
Table of Contents
1. INTRODUCTION
1.1 Background
1.2 Objectives
2. LITERATURE REVIEW
2.1 Variance analysis
2.2 Correlation
2.3 Path coefficient analysis
3. MATERIALS AND METHODS
3.1 Research site
3.2 Climatic condition and season
3.3 Experimental details/materials/selection of genotype
3.4 Data collection
3.5 Statistical Analysis
4. EXPERIMENTAL RESULTS
4.1 Mean performance of genotypes
4.2 Analysis of variance
4.3 Correlation studies
4.4 Path coefficient analysis
5. DISCUSSION
5.1 Variability
5.2 Association of characters
5.3 Path coefficient analysis
6. SUMMARY AND CONCLUSION
7. REFERENCES
1. INTRODUCTION
1.1 Background
Maize (Zea mays L.) was domesticated around 7000 years ago in Central Mexico. Maize belongs to family Poaceae and tribe Maydae. Maize is grown in different ranges of environment condition. Thus, through introduction and breeding, it has gained adaptation all over the world. The spread of maize cultivation in the world was due to its diversity, high adaptability and versatility. The reasons for its popularity include high yields per unit area, husk protection against birds and rain, fairly easy to weed as well as possession of a good competition rate with weeds because of its rapid vertical growth. In Nepal, maize is the second most important cereal crop in terms of area and production (Kandel et al., 2017; Kandel et al., 2018; Sharma et al., 2018; Thapa et al., 2019). Maize is grown in an area of 891583 ha with a total production of 2231517 metric tons and productivity of 2.503 ton/ha (MoAD, 2015/16). The contribution of maize to national GDP is 3.15% and to agricultural GDP is 9.5% (MoAD, 2013). Out of total maize cultivated area in Terai region, 95.95% area is under improved maize and 4.05% under local maize. In plain, it is grown as Rabi maize and spring maize with irrigation (Paudel et al., 2001). In Nepal, the productivity of maize is very low compared to other developed countries. There are various factors that directly affect the productivity of maize. This yield gap can be narrow down by cultivating improved varieties. High yielding maize varieties for normal planting season should be developed to overcome the food deficiency.
Farmers and breeders want successful new maize hybrids that show high performance for yield and other essential agronomic traits. Their superiority should be reliable over a wide range of environmental conditions. The basic cause of difference between genotypes in their yield stability is the occurrence of genotype-environment interaction (GEI). Genotype – environment interaction may be expected to be high when environmental differences are high as in Ghana. Hence, it is important to assess the importance of interactions in the selection of genotypes across several environments besides calculating the average performance of the genotypes under evaluation (Fehr, 1991; Gauch and Zobel, 1997).
Per capita maize consumption in Nepal was 98g/person/day (Ranum et al., 2014). Therefore, total quantity of maize requirement for food per year is around 2.9 million mt and the production during 2014 was 2.283million mt, hence the deficit was 0.67 million mt. The feed demand is also increasing at the rate of 11% per annum. Maize is grown both (as sweet corn) for human consumption and (as field corn) for other uses such as animal feed and bio-fuels. Worldwide, only around 15% of maize production is used for food consumption with most production going to animal feed.
A number of studies in maize have been conducted to evaluate the performance of winter maize genotype in NMRP along with study the nature of association between yield and its components which identified traits like ear length, ear diameter, grains per row, ears per plot, 1000 grain weight and rows per ear as potential selection criteria in breeding program.
1.2 Objectives
- To elucidate out superior genotypes for varietal development
- To analyze the correlation study of grain yield with other parameters
- To estimate the direct and indirect effects of various parameters on grain yield
2. LITERATURE REVIEW
2.1 Variance analysis
Variability is the occurrence of differences among individuals due to differences in their genetic makeup or the environment in which they are raised was described by (Allard, 1960).
The availability of variances in germplasm collections of any crop is most important towards breeding for better varieties for a given trait which is the prerequisite for its improvement by systematic breeding (Engida et al., 2007).
2.2 Correlation
The grain yield of maize crops is associated with various variables that influence yield either singly or jointly and either directly or indirectly through other related characters. The correlation between the characters may exist due to different reasons such as pleiotropy, genetic linkage and association of loci or presence of block of loci governing variability for different characters on the same chromosomes.
(Patil et al., 1969) stated that there was a positive and significant correlation of grain yield with ear height.
(Subramanian and Mahboob Ali, 1974) reported that only ear diameter was significantly and positively correlated with grain yield although ear length and grain rows per ear showed positive correlations with yield.
(Panchanandhan et al., 1978) reported that grains per ear, ear length and 100 grain weight exhibited positive and highly significant correlation with grain yield.
A close correlation between grain yield, 100 grain weight and number of grains per ear was reported by (Karavaer, 1982).
(Tyagi et al., 1988) stated that, ear weight, ear length, plant height and 100 grain weight were positively correlated with grain yield in maize.
(Annapurna, 1989) found that, there was positive and significant correlation between grain yield, plant height, ear length, ear girth, number of kernels per ear and 100 grain weight whereas days to 75% tasseling and 75% silking had a negative correlation.
(Mahajan et al,. 1995) reported that, the grain yield was only correlated with ear length. Among the yield contributing characters, ear length and diameter, grains per row and grain weight contributed directly or indirectly towards grain yield in maize.
(Krishnan and Natarajan, 1995) concluded that, there was a significant and positive association of grain yield with plant height, ear length, ear weight and number of kernel rows per ear in maize.
(Malwar et al., 1996) did not find any significant correlation among yield attributing components viz., number of grains per row, ear length and kernel weight.
(Netaji, 1998) reported that, there was a significant and positive correlation between grain yield and 50% tasseling, silking and maturity.
(Rather et al., 1999) in a study found that days to 50% silking was positively correlated with ear height and grain yield but plant height had no association with grain yield.
(Umakanth and Sunil, 2000) stated that, there was a significant correlation of grain yield with yield attributing characters except ear diameter and days to 50% silking. Highest correlation of grain yield was found with plant height followed by ear weight and ear length.
(Jha and Ghosh, 2001) concluded by their study that, both green fodder as well as grain yield had positive and significant correlation with plant height.
(Kumar and Satyanarayana, 2001) reported that, there was a positive association of grain yield with plant height, ear height, ear length, ear diameter, number of grain rows per ear and thousand grains weight. Ear length and ear diameter had positive association with thousand grain weight while ear diameter was positively associated with number of grain rows per ear and thousand grains weight.
(Choudhary and Chaudary, 2002) stated that there was no association of days to tassel and ear weight with other traits at phenotypic level. Significant correlation was found between plant height and ear length, grain yield per plant and grain yield per plot in the negative direction. Ear length was positively and significantly correlated with grain yield per plant.
(Mohan et al., 2002) reported that, grain yield was positively and significantly correlated with days to 50% tasseling, silking and maturity, plant height, ear length, ear diameter, grain rows per ear, number of grains per row and 100 grains weight.
(Bao Heping et al., 2004) stated that, the maize yield was mainly influenced by ear length, followed by number of grains per row, ear diameter, number of rows per ear and 100 grain weight.
(Hossain et al., 2004) reported that, there was a positive correlation of grain yield with plant height, ear height, ear length, ear diameter and test weight while days to 50% tasseling and silking had negative correlation with grain yield.
(Tang Hua et al,. 2004) showed that single plant yield was significantly correlated with ear diameter, grains per row, weight of 100 grain, ear length, row number, grains per row and weight of 100 grain which were significantly and negatively correlated with each other. Significant negative correlation was found between ear length and ear diameter.
(Malik et al., 2005) found that, there was a positive correlation of grain yield per plant with plant and ear height, leaf number per plant, leaf length, width and area, ear weight, grain number per row, days to silking and tasseling. There was negative correlation of grain yield with grain moisture.
(Farzana, 2005) stated that, grain yield was positively and significantly correlated with number of grains per ear, 100 grain weight, number of grains per row, ear diameter and ear length over three locations.
(Kumar et al., 2006) observed that, grain yield was positively and significantly correlated with ear length, ear height, grain rows per ear and 100 grain weight both at genotypic and phenotypic levels.
(Sadek et al., 2006) observed that, grain yield had positive and significant correlation with plant height, ear height, ear length, dry weight of ears per plant, number of grains per row, 100 grain weight and ear diameter while days to 50% tasseling and silking and days to maturity were negatively correlated with grain yield.
(Tan HePing et al., 2006) found that,there was high correlation of grain yield with ear diameter followed by 100 grain weight, plant height, ear length and grain production rate.
(Jayakumar et al., 2007) reported that, grain yield had highest positive and significant correlation with ear diameter followed by grain rows, grains per row, grain weight, ear length, shelling % and crude protein and also positively and significantly correlated with plant height. Negative and significant correlation of grain yield was found with days to maturity, silking and tasseling.
(Sofi and Rather, 2007) reported that, there was positive correlation of grain yield with ear diameter, 100 grain weight, ear length, number of grain rows per ear and number of grains per row while days to 50% silking had negative correlation with grain yield.
(Brar et al., 2008) stated that grain yield per plot had significant positive genotypic and phenotypic correlations with plant height, ear height, ear length, ear diameter and number of ears per plot.
(Hemavathy et al., 2008) reported that ear length, grain rows per ear, grains per row and 100 grain weight had positive correlations with grain yield.
According to a study of association analysis in maize made by (Shinde et al., 2009) grain yield had high positive correlations with ear weight, ear length, plant height, total dry matter, 1000 grain weight, leaf area per plant and shelling %.
2.3 Path coefficient analysis
The magnitude of direct and indirect effects of characters on complex dependent characters like yield was measured by path coefficient (Wright, 1921; Dewey and Lu, 1959) and thus make the breeders to find best of component characters during selection.
Among three characters viz., grain number per ear, ear length and 100 grain weight, the latter had maximum direct effect on yield, while ear length and grain number per ear had their influence on yield through 100 grain weight was observed by (Panchanadhan et al., 1978).
(Rupak et al., 1979) exhibited maximum direct effect of plant height on yield followed by 100 grain weight, ear diameter and ear length.
(Subramanian et al., 1981) illustrated that yield was directly affected by grain weight per ear.
(Kang et al., 1983) concluded large and positive direct effect of ear weight on grain yield at both genotypic and phenotypic levels. Positive direct effect of plant height on grain yield was also reported.
(Sharma and Kumar, 1987) reported through a study that there was a direct influence of number of grains per row, plant height, ear diameter and 100 grain weight on grain yield of maize. Among them, the role of grains per row was prominent.
(Swarnalatha Devi, 1990) through her path coefficient studies reported maximum direct effect of 100 grain weight and total number of grains per ear on grain yield.
(Gyanendra Singh et al., 1995) revealed that grains per row, days to maturity and rows per ear had direct effects on yield.
(Chandramohan, 1999) concluded that there was direct effect of number of grains per row, 100 grain weight and ear diameter on grain yield.
(Geetha and Jayaraman, 2000) reported that number of grains per row had maximum direct effect on grain yield of maize.
(Devi et al., 2001) stated that grain yield was directly and positively influenced by plant height, days to 75% silking and maturity, ear length, number of grain rows per ear, number of grains per row and 100 grain weight and also indirectly through several yield components.
(Mohan et al., 2002) reported that there was the highest positive direct effect of grain yield with number of grains per row, 100 grain weight, grain rows per ear and ear length. Maximum negative direct effect on grain yield was showed by ear height followed by plant height and days to 50% tasseling.
(Viola et al., 2003) reported that early silking, plant height, ear length, ear height and lesser ear diameter directly contributed to grain yield.
(Kumar and Singh, 2004) revealed that maximum positive direct effect on grain yield was shown by days to 50% silking and ear length.
(Kumar et al., 2006) observed that maximum direct effect on grain yield was shown by days to 50% tasseling, anthesis-silking interval, ear height and 100 grain weight while days to 50% silking exhibited negative direct effect on grain yield.
The greatest direct effect on yield was shown by 100 grain weight, number of grains per row, number of grain rows per ear, ear length and ear diameter which was observed by (Sofi and Rather, 2007)
(Brar et al., 2008) revealed that ear diameter had highest direct effect on grain yield followed by ear length, number of ears per plot, ear height and days to 50% pollen shedding.
(Saidaiah et al., 2008) reported that maximum positive direct effect of 100 grain weight followed by plant height and number of leaves above ear on grain yield. Plant height, ear height, number of leaves above ear, chlorophyll content at 50% silking, flag leaf area, ear length, ear diameter and 100 grain weight had positive indirect effect on yield.
(Shinde et al., 2009) observed that ear weight followed by plant height and shelling % had the highest positive or indirect effect on grain yield.
3. MATERIALS AND METHODS
3.1 Research site
Research was carried out in the field of National Maize Research Program (NMRP) where field experiment was conducted from Oct. 2016 to Apr. 2017. The location is at 27°40’ N latitude and 84°19’ E longitude with an elevation of 228 meters above sea level (NMRP, Chitwan).
3.2 Climatic condition and season
Climatic condition of research site was humid and sub-tropical with cool winter. The average annual rainfall was 1500 mm (NMRP, Chitwan). The soil is a sandy loam and is slightly acidic to strongly acidic.
3.3 Experimental details/materials/selection of genotype
For this experiment ten maize genotypes were used as treatment with three replications was laid out in Randomized Complete Block Design (RCBD). These genotypes were allocated randomly to the ten plots of each replication. The plot size was 5 m × 2 m with crop geometry 60*25 cm[2]. Each genotype was sown in each plot with four rows each of 5 m length. All genotypes were obtained from NMRP, Chitwan. Following are the genotypes used in the research:
Table 1. List of ten maize genotypes
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