Gladiolus is one of the most important bulbous ornamentals for cut flower trade in India. It is also ideal both for garden display, floral arrangements for table and interior decoration as well as making high quality bouquet [1]. The main emphasis in Gladiolus improvement has been on the development of varieties having attractive color and large number of florets mainly for cut flower, viz long spikes, more number of well-spaced large sized florets and good corm multiplication ability. Gladiolus is very rich in varietal wealth and every year there is an addition of new varieties [2]. Multiplication of planting material of Gladiolus is most important because the cut flower trade is lagging behind over the recent years, owing to he unavailability of sufficient quality planting material at large scale [3]. Moreover, new varieties also come from other countries, and the performance of these varieties depends upon climatic conditions of the region under which they are grown. As a result, cultivars which perform well in one region may not perform same in other regions of varying climatic conditions [4]. It is also important to study the performance of existing cultivars for their superior desirable characters [5]. Hence, it becomes very much necessary to study the morphological variation and evaluation of genotypes and also to identify the suitable germplasm for further improvement programme in U.P. region.

Studies on genetic diversity for yield traits is important as the individual plant selection is slowly dependent on variability. More the diversity better are chances of improving the economic characters under consideration in the resulting offspring. Crop improvement in Gladiolus has so far been achieved by exploiting the available sources of the variability. Naturally the genetic variation or diversity for most of the yield attributes is considerably high in Gladiolus. Keeping in view the above facts there is an urgent need to seek improvement in complex quantitative trait such as flower and corm yield of Gladiolus. As a result of free exchange of Gladiolus germplasm and lot of introgression of characters has taken place in many local Gladiolus cultivars resulting in enhancement of variability and new genetic combinations. Mahalanobis D² analysis helps in assessing the diversity among the genotypes and to select the divergent parents for future breeding programmes. Currently, such assessment is mainly based on a small number of phenotypic traits. However, environmental conditions may affect their expression and so assessing only morphological traits may not reflect the genetic diversity available.

The present investigation was carried out with fifty-three varieties of Gladiolus obtained from different parts of India and selected on the basis of phenotypic variability in different quantitative and qualitative characters. The experiment was conducted at Horticultural Research centre (HRC) of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut, Uttar Pradesh, India during winter season 2014-2015. The collected genotypes of Gladiolus were planted in Randomized Block Design with three replications. In each replication corms were sown in a spacing 30 × 20 cm. The corms of different varieties were sown during second fortnight of October, 2014. At the time of final ploughing, well rotten FYM @ 20 tonnes per hectare was incorporated and thoroughly mixed in to field. A dose of NPK @ 180:150:150 kg per hectare was applied in a schedule i.e., full dose of phosphorus, potassium and half dose of nitrogen were given at the time of planting of corms and remaining dose of nitrogen were applied in two spilt doses i.e. 30 and 60 days after planting (DAP). After care and plant protection measures had been done during entire period of crop growth. The observations were recorded on the basis of growth, flowering and yield of spikes and its attributing parameters. The concept of Mahalanobis’s D² statistic is based on the technique of utilising the measurements in respect of aggregate of characters. The D² statistic as a measure of genetic divergence was used for the first time in the field of plant breeding by Nair and Mukherjee in the classification of natural and plantation teak.

For getting high heterosis or for recovering transgressive segregants, parents chosen for hybridization need to be genetically diverse or distant. The cultivars from widely separated localities with good yield have been usually included in the hybridisation programme, presuming the presence of genetic divergence and maximum likelihood of recovering promising segregants. As per expectations, in practice, this has not yielded very satisfactory and consistent results. Eco-geographical diversity has been regarded as a reasonable index of genetic diversity [6,7].

Mahalanobis D² analysis

On the basis of Mahalanobis D² values, all the 53 genotypes were grouped under study into 8 clusters. The distribution patterns of Gladiolus genotypes into 8 clusters are shown in Figure 1 and Table 1. Cluster IV contained maximum number of genotypes (13). The grouping pattern of the genotypes suggested no parallelisms between genetic divergence and geographical distribution of genotypes. These results are in conformity with the findings of observations have been observed by Nimbalkar et al. [8]; Pal et al. [9] and Sheikh and Ahmad [10] in Gladiolus.

Figure 1: Mahalanobis Euclidean² Distance.

Table 1: Clustering pattern of 53 genotypes of Gladiolus on the basis of genetic divergence.

The inter-cluster distance was greater than intra-cluster distance as indicated in Figure 2 and Table 2 revealing considerable amount of genetic diversity among the genotypes studied. The intra-cluster was maximum in cluster VII (D² =372.852) reveals maximum genetic diversity followed by cluster II (D² = 343.392) and cluster V (D² =150.904) and maximum inter-cluster generalized distance (D² =1855.023) was between cluster VII and cluster VIII exhibited maximum divergence followed cluster II and VIII (D² =1568.477).

Figure 2: Euclidean² Distance.

Table 2: Average of intra and inter cluster distance.

It is suggested that selection of genotypes based upon large cluster distance from all the clusters may lead to favorable broad spectrum genetic variability for corm yield improvement. Therefore, it is suggested that selection of genotypes based upon large cluster distance from all the clusters may lead to favorable broad spectrum genetic variability for corm yield improvement. Similar findings are reported earlier by of Sheikh and Khanday [11] and Patra and Mohanty [12]. The grouping pattern of the genotypes suggested no parallelisms between genetic divergence and geographical distribution of genotypes.

Cluster mean

Cluster means for 27 characters are present in Table 3. The existence of diversity among the genotypes was also assessed by the considerable amount of variation in cluster means for different characters. The Cluster VII had highest mean values number of corms per plant and genotypes in cluster VIII had highest mean values of weight of corm, weight of corms per plant indicating that by crossing between these clusters may be helpful in genetic improvement of Gladiolus germplasm. These results are in conformity with the findings of observations have been observed by Ranchana et al. [13].

Table 3: Cluster wise mean values of 27 characters in gladiolus.

D² analysis (Rank method)

The percentage contribution of different characters towards genetic divergence is presented in Table 4. Ranking character wise D² values and adding the ranks for each character for all the entries identified the variables, which contributed towards the divergence. Characters such as days taken to sprouting contributing maximum (19.01%) towards total divergence and this was followed yield of corms per hectare (15.02%), weight of corm (11.39%) and length of spike (7.69%) these can be used for selecting parents from distinctly placed cluster to obtain higher production. The present findings were accordance with the findings of Desh Raj and Misra [14]; Nayak et al. [15]; Dhillon, [16] and Pal et al. [17].

Table 4: Contribution of various characters towards total genetic divergence.

• The grouping pattern of the genotypes suggested no parallelisms between genetic divergence and geographical distribution of genotypes.

• The selection of genotypes based upon large cluster distance from all the clusters may lead to favorable broad spectrum genetic variability for corm yield improvement.

• On the basis of Mahalanobis D² analysis it could be concluded that the Gladiolus germplasm at SVPUAT can be used for future breeding programmes.

• Finally, these studies have given important clues in understanding genotypes relationship, which may further assist in developing and planning breeding strategies.

I am very thankful to Dr. Mukesh Kumar, Assistant Professor, Department of Horticulture, Sardar Vallabhbhai Patel University of Agriculture & Technology, Modipuram, Meerut, for his kind help in analysis of data. I express my sincere regard and heartfelt gratitude to Dr. M. B. Dastagiri, Principal Scientist, Research Systems Management Division, NAARM and Dr. M. Narsi Reddy, Dr. M. Narsi Reddy, Assistant Scientific Officer (Entomology), NIPHM for their precious suggestions untiring help and moral support throughout the study.