PHENOTYPIC DISSIMILARITIES AMONG INBREDS OF MAIZE (Zea Mays L.)

For development of single cross hybrids in maize, developed inbreds must be evaluated for the determination of highly heterotic inbred combination (HIC). One of the best methodologies for determination of heterotic inbred combination can be multivariate analysis (MVA) or scales of phenotypic distance or dissimilarities or cluster diagram. For it, inbred must be observed for useful trait measurements. Accordingly, an experimental evaluation was conducted including promising 55 inbred lines of winter maize planting on Sep 3, 2015 at National Maize Research Program Rampur, Chitwan Nepal (NMRP/NARC). The distant inbred lines were determined through MVA. Single plot research technique was done where each inbred line was provided with 2 rows of 20 plants each. Data were taken for fifteen traits. By the use of MINITAB software, the data was analysed. Graphics of principle component analysis (PCA) cluster diagram (CD or dendogram) were constructed and phenotypic dissimilarities are examined.The distant inbreds RML-8, RML-88, RML-13, RML-103, RML-89, RML-102, RML-11, RML-17, RML-83,RML-98,RML-85,RML-86,RML-94 and RML-28 could be crossed with RML-75,RML-6,RML-68,RML-36 and RML-32 which could be used as tester inbred for heterotic hybrid combination. Similarly, RML-98, RML-85, RML-86, RML-94 and RML28 could be crossed with RML-24, RML-96 and RML-99. Though distant inbred, RML-104 had less ASI but it wasn’t feasible to use for crossing due to higher anthesis tasseling interval.


Introduction
Maize (Zea mays L.) is one of the most important cereal crops cultivated worldwide, belonging to family graminaceae.Being staple food crops, it is not only important for human consumption but it is also used as feed for animals.It also provides raw materials for manufacture of many industrial products from food processing to manufacturing of ethanol.It has leading position both in case of production and productivity.Maize is ranked in second position after rice in terms of area and production with the productivity of 2.458 t/ha.Similarly, the area under production in Chitwan is 9750 ha, with 29250 mt production and productivity 3000 kg/ha (MoAD 2014).The demand is increasing for food; feed and industrial use (CDD, 2012).Maize has been the main source of food security for the developing country like ours, having 22.2% global hunger index.Globally, 80% of maize consumption is in animal feed.About 80% of egg production and 65% of the broiler production cost goes to the feed (CDD, 2012).In Nepal, The trend of feed demand is increasing at the rate of 11% per annum (CDD, 2012).There is a huge scope of expanding the poultry industry by 3 folds by the next 10 yrs, since the rate of poultry industries expansion is also 8.7% per annum (CDD 2012).Since, the productivity of maize in our country is much more less than that of developed countries we are still importing about 40 to 45 % of maize (CDD, 2012).And in addition to higher price and uncontrollable quality, there is also the problem of unavailability on time of seeds for the farmers.
Thus, for the increased yield and proper availability of maize hybrids, maintenance and improvement of maize genotypes is the foremost requirement.For high production in maize, the precise selection of elite genotypes is very important for any area (Beiragi et al., 2010).Evaluation of important traits of maize lines is the primary factor for the improvement of maize.Information on the genetic distance and relatedness between the breeding materials of available germplasm is important for deciding which method will be applied in breeding programmes.The organisation of germplasm into genetically divergent groups is important for the implementation of the phenomenon of heterosis.This is crucial in the course of developing hybrid varieties with heterosis but it also can be applied in breeding of clones and open-pollinated varieties and synthetics (Chakuya, 2008).At the same time, two important questions arise: 1.How divergent are inbred lines from same and Research Article different heterotic groups and 2. Which criteria and biometric methods allow a dependable grouping of germplasm (Melchinger, 1999).Insufficient hybrid technology on our country had led to the less development of heterotic hybrid with higher yield.Information on morphological evaluation of inbred lines are lacking in Nepal.This study was conducted to examine inbreds for hybrid development and determine phenotypic distance among the fifty five inbreds of maize NMRS/NARC/Nepal evaluating flowering behavior, prolificacy and morphological traits of the inbreds which will be helpful to maize breeders for planning of heterotic inbred combination.

Materials and Methods
The experiment was conducted at the research farm of NMRP Rampur, Chitwan during winter, 2015 to evaluate the morphological traits.The geographical location as located by GPS was 27°40'N latitude, 84°19' E longitude at an altitude of 228 m above sea level.Single plot research technique with 60 cm* 25 cm spacing was done.Each inbred lines were provided with 2 rows of 20 plants each.Planting was done on 3 rd September, 2015.Two seeds per hill were planted.The intercultural operations were carried out as per the package of practice as per National Maize Research Program (NMRP) recommendation.
The sampling for each parameter was done through simple random sampling.Five plants were selected as sample from each inbred line.The parameters included days to 50% tasseling, days to 50%silking, days to 50% anthesis, anthesis-silking interval (ASI), tassel color, silk color, tassel type, tassel size, leaves below and above ear, stem circumference, internode length, husk cover, no of ear per plant and plant height.Days to 50 % tasseling was recorded as number of days from planting to when 50% tassel appears.Days to 50% anthesis was recorded as the number of days from sowing to when 50%of the plants had shed pollen.Similarly, days to50% silking, was recorded when silk had emerged on 50% of the plant.The stem circumference and internode length of the sample was measured for internode just above the upper cobb.Similarly, leaves above the upper ear and below that ear were recorded.The plant height per sample was taken by measuring from the ground level to the base of the tassel after milking stage.Data on husk cover was recorded before harvesting on a scale of 1 to 5, where 1 and 5 represents poor and excellent respectively.
The traits like tassel color, tassel type and tassel size and silk color were assigned with code as per the standard of NMRP, Rampur chitwan for representing different colors (Table 1).These were recorded at the time of 50% tasseling, 50% silking respectively.Among the collected data, tassel color, silk color, tassel type, tassel size, leaves below and above ear, stem circumference, internode length, husk cover, no of ear per plant and plant height were analyzed through the use of MINITAB Ver. 14 statistical software.Principal component analysis and cluster analysis were done to know the phenotypically dissimilar inbreds.The data was divided into 5 clusters in cluster analysis for dendrogram construction.

Results and Discussion
The five different types of line bar (Fig. 1) represents five different clusters.
The assessment of phenotypic traits of different maize genotypes are basically very simple and they are performed by a visual evaluation of individual plants or a group of plants and therefore it is not necessary to engage larger labour power.The massive use of PCs in agricultural studies has been allowed a simple application of the multivariate analysis that provides comprehending a simultaneous interrelation among three or more independent variables (de Galarreta, 2001).In plant breeding, such information can be useful for a comprehensive description of existing heterotic groups, as well as, for clustering inbreds of unknown genetic source and thereby defying a desirable tester.
Then, after the selection of distant inbreds, the inbreds were further checked for self-pollination with narrower anthesis silking interal and for synchronous flowering among distant inbreds.So that they can self-perpetuate.So that they can self-perpetuate.In Table 4 and 5, the distant inbreds were distinguished through underline and bold.

Conclusion
Hence, combined effect of all alleles of 10 traits was observed to determine the longest linear distance.The inbreds with dissimilarity were obtained on five different clusters.The crosses involving parents/inbred lines from most divergent clusters were expected.Thus the distant inbreds with smaller anthesis siking interval and selfperpetuation among inbreds could be used as tester inbreds for heterotic inbred combination.And the hybrid with heterosis could be obtained in smaller number of crossing.

Fig. 2 :
Fig. 2: Loading plot between PCs 1 and 2 showing contribution of various traits towards variability among inbreds

Table 1 :
Traits assigned with codes as per the standard of NMRP,

Table 2 :
Details of principle component analysis through eigen analysis of the correlation matrix HSK CVR-Husk cover; ERS/PLANT-Ears per plant; TSSCOL-Tassel color; SILKCOL-Silk color; TSS TP-Tassel type; TSS SZ-Tassel size; LVS BE-Leaves below ear; LVS AE-Leaves above ear; STM CR-Stem circumference; INT ND-Internode length; PLT HT-Plant height

Table 3 :
Details of principle component analysis through eigen analysis of the correlation matrix Husk cover; ERS/PLANT-Ears per plant; TSSCOL-Tassel color; SILKCOL-Silk color; TSS TP-Tassel type; TSS SZ-Tassel size; LVS BE-Leaves below ear; LVS AE-Leaves above ear; STM CR-Stem circumference; INT ND-Internode length; PLT HT-Plant height