Morphological characterization of garlic (Allium sativum L.) germplasm

Abstract A total of 25 garlic (Allium sativum L.) germplasm were collected from different location of Bangladesh and also from different countries of the world. Each germplasm was planted in each plot of 1m2 at the Allium Field Laboratory, Horticulture Farm, Bangladesh Agricultural University, Mymensingh. This study was conducted during October, 2010 to March, 2011 in the field, using randomized complete block design with three replications. All germplasm were characterized on number of leaves, height of plant, leaf length, fresh weight of leaf, dry weight of leaf, number of cloves per bulb, length and diameter of bulb, fresh weight of bulb, dry weight of bulb, yield per plot and yield per hectare. Analyses of variances showed that garlic germplasm with different origins were significantly different for all characters. Different germplasm resulted better performances but germplasm G49 from Vietnam gave the highest results in respect of number of leaves per plant (10.63), leaf length (43.57 cm), fresh leaf weight (92.47g), dry leaf weight (6.13g), fresh weight of bulb (21.37g), total number of cloves per bulb (42.13), bulb diameter (4.13cm), fresh weight of bulb (21.37g), dry weight of bulb (5.73g) and yield (9.83 t/ha) which could help future researchers in garlic selection program and improvement of yield.


Climate and Soil condition
The experimental area was under a sub-tropical humid climate which is characterized by heavy rainfall, air temperature, sunshine hour, annual average rainfall and relative humidity and have been presented in Appendix I. The soil of the experimental area of Bangladesh Agricultural University Farm was sandy loam and belongs to the Old-Brahmaputra Flood-Plain Alluvial Tract [4]. The soil samples collected at a depth of 0-30 cm from the, experimental area were analyzed in the Humboldt Soil Testing Laboratory, Department of Soil Science, Bangladesh Agricultural University, Mymensingh. Description of the characteristics of soil of the experimental plot have been presented in Appendix II [20][21][22][23][24][25]. The morphological characteristics of the soil of the experimental plot are given below [3].

AEZ: Old Brahmaptura Flood Plain
Soil series: Sonatala series General soil: Non calcareous dark grey Parent material: Old Brahmaptura River-borne deposits.

Land preparation
The experimental land was first opened by tractor one month before planting. Several ploughing and cross ploughing followed by laddering were done until the desired tilth was achieved for planting the cloves. Weeds and stubbles were then removed from the field. Finally, the land was divided into blocks in which small plots (plot size were mentioned in individual experiment) were made as an experimental unit according to the design of the experiment.

Manure and fertilizer
The crop received manures and fertilizers at the rate of cowdung 5 tons, Urea 217 kg, T.S.P. 267 kg, M.P. 333 kg and Zypsum 111 kg per hectare respectively [26][27][28][29]. The entire amount of cowdung and TSP were added to the soil at the time of final land preparation 7 days before planting. Urea and MP were top dressed in three equal installments at 25, 50 and 75 days after planting of cloves or transplanting of seedlings.

Planting materials
Cloves were separated from the bulb, and only the healthy large sized ones were planted. Date of planting: 10 Nov, 2010 Plant spacing: 20 cm x 10 cm

Intercultural operation
Weeding and pulverizing of soil were done regularly whenever necessary to keep the plots free from weeds and to ensure good aeration in soil.

Plant protection
Ridomil MZ 72 WP and Rovral at the rate of 25g and 45g in 10 litre of water was applied at an interval of 15 days from 30 DAP up to one month before harvesting to prevent the purple leaf blotch disease caused by Alternaria porii.

Harvesting
The garlic plants when the tops turn yellowish or light brownish and show signs of drying up indicate the symptom of maturity. The bulbs were lifted, freed from earth and the leaves were tied at the top. The bulbs were cured for 2 to 3 days in t he shade before storing them in an ordinary room. Thoroughly cured garlic bulbs store well in ordinary well-ventilated room/store.

Laboratory works
At the experimental site, a laboratory for weighing and sample drying was used. A good electrical weighing balance and oven were used.

Collection of data
The following data were recorded on the base of physio-morphological growth parameters after planting as well as on yield.

5.1 Number of leaves per plant
The number of leaves per plant was counted from 5 randomly selected plants. The mean number of leaves was calculated by dividing total number of leaves observed from 5 plants by 5.

Height of plant (cm)
Plant height was measured from the base of the leaf sheath to the tip of the longest leaf of 5 randomly selected plants and mean was calculated in cm.

Length of leaf (cm)
Length of leaf was measured from the base to top of the leaf of 5 randomly selected leaves in centimeter and mean was calculated.

Fresh leaf weight (g)
Fresh weight of leaves of 5 randomly selected plants was taken and their average was calculated in gram as fresh weight of leaves of individual plant.

Dry leaf weight (g)
Fresh weight of leaves of 5 randomly selected plants was taken and the average was considered in gram as fresh weight of leaves per plant. The leaves were cut into small pieces, dried in the sun for 3 days and kept in an oven at 80°C for 72 hours, till a constant weight was achieved. Average dry weight of leaves per five plants was estimated.

Number of clove/plant
The cloves were counted from 5 plants and their average was taken as a number of cloves per plant.

Bulb diameter (cm)
Diameter at the widest part of 5 randomly selected bulbs was measured in centimeter and then average diameter of each bulb was calculated.

Fresh weight of bulb (g)
Fresh weight of bulb of 5 randomly selected plants was taken and their average was calculated in gram as fresh weight of bulb of individual plant.

Dry weight of bulb (g)
Fresh weight of bulb of 5 randomly selected plants was taken, and the average was considered in gram as fresh weight of bulb per plant. Bulbs were cut into small pieces, dried in the sun for 3 days and kept in an oven at 80°C for 72 hours, till a constant weight was achieved. Average dry weight of bulb per plant was estimated.

Yield of bulb per plot (kg)
The yield of bulb per plot was taken in kilogram (kg) by harvesting all the bulbs of each plot after removing the roots and pseudo stem.

Yield of bulb per hectare (t)
Per plot yield of bulb was converted into yield per hectare and expressed in ton (t).

Design and layout of the experiment
The experiment was laid out in a Randomized Completely Block Design (RCBD) with three replications. The whole plot was divided into three blocks, each containing 25 unit plots of 1 square meter and one germplasm represented one treatment.

Statistical analysis
Data collected from the experiment were statistically analyzed as per design of the experiment followed in the field using PLABSTAT computer package programmer [30][31][32][33][34]. The means for all treatments were calculated and the analyses of variances for all the characters under consideration were performed by 'F' variance test. The significance of difference between pair of means was performed by Least Significant Difference (LSD) test taking 5% probability level as the minimum unit of significance [5].

Estimation of simple correlation coefficients
Simple correlation coefficients were calculated using PLABSTAT software version 2N by the following formula [6]: Morphological characters of different garlic germplasm: There were significant differences in the number of leaves per plant. The highest number of leaves (10.63) was obtained from germplasm G49. On the other hand, the lowest number of leaves (4.70) was recorded from germplasm G8 followed by G10 (5.03), G35 (5.20) and G32 (5.40). It was observed that germplasm G29 produced the tallest plant (74.60 cm) followed by G2 (66.50cm) and G1 (66.17cm). The shortest plant was found in the germplasm G13 (39.17 cm). Significant differences were also observed in length of leaf. The highest length of leaves (43.57cm) was obtained from germplasm G49 followed by G29 (41.27cm). On the other hand the lowest length of leaves (23.97 cm) was recorded from germplasm G10 followed by G38 (26.63 cm) and G13 (27.60 cm). Remarkable variations were observed on fresh leaf weight. The highest fresh leaf weight (92.47) was obtained from germplasm G49 followed by G38 (85.50), G53 (74.73) and G8 (67.80) gm. On the other hand, the lowest fresh leaf weight (21.17) was recorded from germplasm G32. Germplasm G49 produced the highest amount of dry leaf weight (6.13g). The lowest amount of dry leaf weight was found in germplasm G10 (2.57g) ( Table 1). Level of significance ** ** ** ** ** ** = Significant at 1% level of probability, G1-G53 are the garlic germplasm.

Yield and yield contributing characters of different garlic germplasm
Number of cloves showed per plant significant differences among them. The highest number of cloves (42.13) was recorded from germplasm G49. On the other hand, the lowest number of cloves was observed from G36 (17.57). Highly significant differences were observed in bulb diameter also. Among bulb diameters G49 (4.13 cm) was recorded the highest. On the other hand, G38 (2.73 cm) performed the lowest. It was observed that germplasm G49 produced the highest amount of fresh weight of bulb (21.37 g) and the lowest amount of fresh weight of bulb was found in germplasm G38 (11.83 g) followed by G51 (12.53 g) and G20 (12.70g). Maximum dry weight of bulb was obtained from G49 (5.73 g) which was significantly different from others and followed by G27 (5.10 g). Minimum dry weight of bulb was obtained from G38 (2.87 g) followed by G52 (2.93 g). Highly significant differences were observed in yield of bulb per plot. The germplasm G49 (0.983 kg) produced highest yield per plot whereas the lowest (0.524 kg) was from G13. The yield of garlic per plot was converted into per hectare and was expressed in tons. Yield per hectare of different germplasm showed highly significant variations. Germplasm G49 gave the highest (9.83 t/ha) yield followed by germplasm G53 (8.32 t/ha). The lowest yield (5.24 t/ha) was obtained from germplasm G13 ( Table 2). Level of significance ** ** ** ** ** ** ** = Significant at 1% level of probability, 1 Plot size = 1m2 Different germplasm resulted better performance in respect of height of plant, number of leaves per plant, fresh weight of bulb, total number of cloves per bulb and yield in ton per hectare. Germplasm G49 from Vietnam gave the highest results in almost all the mentioned parameters. This might be due to the fact that germplasm G49 had a good genetic potential which enhanced more cell division and cell elongation resulting the best performance. A study reported that the maximum plant height (60.47 cm), maximum yield per plot (7.57 kg) and the maximum number of leaves per plant (14.60) [7]. Some researchers found in their research the greatest bulb diameter (3.26 and 3.23 cm) [8]. A scientist also reported about the bulb diameter which varied from 66 to 70 cm [9]. These investigations are more or less support with the present findings.

Coefficients of correlation for morphological characters
The estimated simple correlation coefficients were made among different morphological characteristics of garlic germplasm in all possible one way paired combinations. Number of leaves per plant was not significantly and positively correlated with plant height (r = 0.171). Whereas leaf length (r = 0.489*), fresh weight of leaf (r = 0.406*) and dry weight of leaf (r = 0.460*) showed significant positive correlation. Plant height showed significant positive correlation with leaf length (r = 0.480*). On the other hand, fresh weight of leaf (r = -0.112) and dry weight of leaf (r = -0.150) showed non-significant negative correlation. Leaf length was not significantly and positively correlated with fresh weight of leaf (r = 0.084) and dry leaf weight (r = 0.322). Fresh weight of leaf showed highly significant positive correlation with dry weight of leaf (r = 0.689**) which indicated that with the increase of fresh weight of leaf those dry weight of leaf would be increased (Table 3).

Coefficients of correlation for yield and yield contributing characters of different garlic germplasm
Highly significant positive correlation was observed in number of cloves per plant with bulb diameter (r = 0.539**), fresh weight of bulb (r = 0.567**), dry weight of bulb ( r = 0.574**), yield per plot (r = 0.554**) and yield per hector ( r = 0.554**) which indicated that with the increase in number cloves per plant those bulb diameter, fresh weight of bulb, dry weight of bulb, yield per plot and yield per hectare would be increased. Bulb diameter also showed highly significant positive correlation with fresh weight of bulb (r = 0.785**), dry weight of bulb (r = 0.685**), yield per plot (r = 0.679**) and yield per hectare (r = 0.679**). Fresh weight of bulb showed highly significant and positive correlation with dry weight of bulb (r = 0.896**), yield per plot (r = 0.926**) and yield per hectare (r = 0.926**). Highly significant positive correlation was observed in dry weight of bulb with yield per plot (r = 0.875**) and yield per hectare (r = 0.875**) which indicated that with the increase in dry weight of bulb those yield per plot and yield per hectare would be increased. Yield of bulb per plot showed highly significant and positive correlation with yield per hectare (r = 1.000**) that means with increasing in yield per plot with the increasing in yield per hectare (Table 4). Bulb diameter (cm) 0.539** Fresh weight of bulb (g) 0.567** 0.785** Dry weight of bulb (g) 0.574** 0.685** 0.896** Yield (kg/plot) 0.554** 0.679** 0.926** 0.875** Yield (ton/ha) 0.554** 0.679** 0.926** 0.875** 1.000** ** Significant at 1% level of probability