Research Article - Journal of Genetics and Molecular Biology (2021) Volume 5, Issue 2

Physiological traits coupled with water deficit tolerance by using multivariate analysis in cotton genotypes.

¹Department of Plant Breeding and Genetic, Central Cotton Research Institute, Multan, Pakistan

²Institute of Molecular Biology and Biotechnology, Bahauddin Zakriya University, Multan, Pakistan

Corresponding Author:

Syed Bilal Hussain Institute of Molecular Biology and Biotechnology, Bahauddin Zakriya University, Multan, Pakistan Tel: 00923366332925 E-mail: drsyedbilal@hotmail.com

Accepted date: April 15, 2019

Citation: Akbar M, Hussain SB. Physiological traits coupled with water deficit tolerance by using multivariate analysis in cotton genotypest. J Genet Mol Biol. 2019;3(2):1-11.

Abstract

The water shortage is a serious hazard for food security in the world. It is the alarming situation for the plant breeders to recognize and build up drought tolerant field crops germplasm. The water deficit tolerance magnitude rely on various soil and plant associated factors such as capacity of soil to accumulate moisture, rainfall distribution, rate of evapo-transpiration and root uniqueness. The present study was done at Central Cotton Research Institute, Multan to screen cotton germplasm against water deficit by irrigating the plants at three moisture levels at seedling stage i.e., 40, 70, and 100% of the pot capacity. The data on root length, fresh root weight, shoot length, fresh shoot weight, dry root weight, dry shoot weight and ratio of root and shoot were collected of 45 days plants after exposing to water deficit. Mean values of seedling parameters revealed differences for water deficit tolerance. Cluster analysis was performed by using Ward's method (1963). Five clusters (I, II, III, IV and V) comprised of various genotypes of cotton were observed at three moisture levels. Cluster I showed the genotypes having almost maximum values of root shoot parameters while cluster V with minimum values at all the moisture levels. These results showed the presence of drought tolerance genotypes in cluster I and susceptible genotypes in cluster V. In Biplot analysis, variables and genotypes are super imposed on the plot as vectors. The genetic variation in genotypes in different cluster showed the existence of water deficit tolerance which could be applied for the evolution of drought tolerant genotypes.

Keywords

Biplot, Cluster analysis, Drought, Moisture stress.

Introduction

Cotton is a miraculous fiber that has a variety of uses, from fashion to home stuff to medical products Cotton, all around the world is known as very most valuable and abundant produced agricultural as well as industrial crop. Drought is a meteorological expression that means lack of precipitation of adequate amount in specific time to exhaust soil water resulting injury to plants [1]. From agricultural point of view, when existing precipitation is approximately depleted in root zone to which extent that wilting may occur. Drought is a multidimensional pressure disturbing plant at many levels of their organization. Many definitions have been given based on moisture content of soil, the potential evapotranspiration, precipitation profile or their combinations [2,3]. Drought is the more damaging factor on growth and productivity of plants as compared to any other biotic and abiotic stress in arid and semi-arid areas [4]. But cotton is one of the most important cash crop of Pakistan covering 7.86 million acres area [5]. Cotton and its other products are the integral component of economy of Pakistan with approximately 60% of total foreign exchange earnings and gross domestic products up to 10% [6]. However, per acre yield is less in Pakistan as other cotton growing countries. Drought has rigorous hazard for yield and quality among many factors [7]. Drought stress minimizes nutrient uptake and distribution within the body of plant, resulting reduction in growth and yield [8]. Different mechanisms have been adopted by plants to overcome water shortage as the developing varieties against drought are more cost-effective and viable to sustain cotton plant growth under water stress conditions [9]. In cotton, species having diploid chromosome number encompass more drought tolerance feature due to their deep rooted nature [10]. Normally, plants exhibit greater drought tolerance having deep-rooted system than shallow rooted. Thus, delay in first irrigation up to forty days in cotton, due to this mechanism roots may go longer look for soil water. Therefore, root associated characteristics might be helpful in screening of cotton genotypes against water stress. Findings have been given that root parameters can be used for drought tolerance adaptation in many crops including cowpea [11] and maize [12]. In addition to this, many wheat physiological parameters might be in second-hand for cotton genotypes screening under drought namely fresh and dry biomass, boll diameter, number of bolls and boll weight [13,14].

Soil moisture availability cope the requirement of plant growth and seed cotton yield in plentiful degree [15-17]. Roots are the main source of gaining of moisture from soil. Therefore, strategy must be changed for drought response in root growth, density and size and proliferation modification [18]. In a study by Burke et al. [19] revealed in his finding the more negative effect of drought on shoot growth as compared to root growth [20], also showed drought affect in young cotton plants. He found the prior drought effect on shoot growth as root growth. Another study by Ball et al. [12] found the effect of drought on root shoot length. He observed that there is less increase root length sensitivity than shoot to water deficit. Performed experiment under drought period after 36 days sowing of with succeeding revival time [21]. There is decrease in different traits under drought than control. Thus, root growth elongation was higher up in drought than control. The study showed the increase in length of tap roots under moisture stress than control, demonstrating that there is no effect of drought on length of tap roots of cotton. The main aim of present work is to study the behaviour of different growth stages of 50 accessions in upland cotton against water deficit situation at seedling stage. The knowledge from these findings might be supportive for plant researchers to sort out genetically potential accessions for developing drought stress tolerant germplasm designed for water stress locale.

Materials and Methods

The response of 30 cotton genotypes of upland cotton to three moisture levels was conducted in glasshouse with day and night temperature of 35°C and 28°C, respectively at Central Cotton Research Institute (latitude 31°25΄N, longitude 73°09΄E and altitude 184.4 m from sea level), Multan (Table 1). Screening in glass house was done at three moisture levels such as 100%, 70% and 40% of the field water capacity at seedling. Seeds of accessions were sown in October, 2013 in polythene bags with measurement of 18 × 10.2 cm size, filled with 800 g silt and 100 g of farmyard manure. Before planting of seeds all polythene bags were saturated to the designed field capacity. Overnight seeds were soaked prior to planting in bags. In each experimental bag three holes with one inch depth were made and three seeds were planted in every hole. Thinning was done after germination in such a way that one bag containing three seedlings were left. A total of four hundred and fifty (450) polythene bags were prepared for three repeats. Each repeat was divided into three sets, 100% (T0) was treated as control and 70% (T1) and 40% (T2) was predicting water stressed conditions at field capacity. The bags were arranged in completely randomized design.

Table 1. Mean values of seedling traits of cotton accessions grown under 100% moisture level of field capacity.

Irrigation and fertilization was done in seedlings till the development of first true leaf grown under three water regimes and after that, daily irrigation was done for seedlings grown under 100% water level (T0) to keep the soil at field capacity. Withholding water supply, water stress condition was developed for seedlings at 70% (T1) and 40% (T2). Soil moisture meter (HH2 Theta Probe Type, Delta-T device, Cambridge, England). At initial wilting stage (observed visually), irrigation was done to stressed plants to relieve the wilting signs but irrigation was not more to reach field capacity level. From the date of emergence, experiment was sustained for forty-five days. After uprooting, plants were cut into roots and shoots for measuring root length, root fresh weight, shoot length and shoot fresh weight. The roots and shoots were dried for 72 h at 65 ± 5°C and the dry weight was recorded. Root: shoot ratios were calculated by dividing root traits on shoot traits. The mean values of all the parameters of each treatment grown under three moisture levels were compared to study the genotypic differences. While, grouping of genotypes on the basis of their mean performance was conducted by using [22] and the biplot graphs were formulated by software SPSS.

Results

Mean values of all the seedling traits i.e., root length, fresh root weight, dry root weight, root: shoot length ratio, fresh root: shoot weight, ratio, dry root: shoot weight ratio, shoot length, fresh shoot weight, dry shoot weight are shown in Tables 1-3.

Root parameters

Root length: Perusal of mean (Tables 1-3) for all the root parameters under controlled (100% moisture) and under two moisture levels 70% and 40% of the pot capacity. It revealed that root lengths of all the accessions measured under control conditions differed from each other, and ranged from 6.77 cm for (MS-64) to 13.97 cm for (DPL-45). Under 70% moisture conditions; root lengths were markedly reduced and ranged from 4.40 cm for GS-444 to 11.70 cm for DPL-45. Under 40% moisture level average range of root length was 2.80 (GS-444) to 9.20 cm for (Tree cotton). These genotypes performed better in all conditions are considered as drought tolerant genotypes while entries showed drastic reduction in root lengths under stressed condition may be rated as susceptible to water stress.

Fresh root weight: Means for fresh root weight under controlled (100% moisture) and at two moisture levels 70% and 40% of the pot capacity are given in Tables 1-3. Fewer than 100% moisture level maximum fresh root weight was shown by Tree cotton followed by F-14, GH-11-9-75 and MPS-11 with average values of 0.536, 0.521, 0.516 and 0.489 g respectively. Similarly minimum fresh root weight was exhibited by VS-212, NIAB- 112 and CIM-84 with mean values of 0.279, 0.289 and 0.294 g respectively in Table 1. Under 70% moisture level, entries Cyto- 62, GS-11-9-75, CIM-86 and SLH-41 exhibiting maximum root weight 0.360, 0.358, 0.350 and 0.350 g respectively while minimum fresh root weight was shown by GS 444 (0.203 g), VS-212 (0.219 g) and NIAB-112 (0.219 g) in Table 2. Fewer than 40% moisture level, Tree cotton, F-14, BP-52 and MPS- 11 revealed maximum value 0.299, 0.293, 0.289 and 0.282 g respectively while COOKER-315 (0.152 g) and GS-444 (0.155 g) showed minimum fresh root in Table 3.

Table 2. Mean values of seedling traits of cotton accessions grown under 70% moisture level of field capacity.

Dry root weight: Based upon dry root weight, data is given in Tables 1-3, 50 accessions again appeared to respond differently to controlled and stressed conditions. At 100% moisture level maximum dry root weight was exhibited by Tree cotton (0.063 g) followed by DPL-45 (0.063 g), Cyto-62 (0.062 g), BH-176 (0.060 g) and F-14 (0.059 g) while minimum by GS- 444, MS-64 and COOKER-315 with 0.047, 0.048 and 0.048 g respectively. Similarly, in DPL-45 reduction was from 0.063 g at 100% to 0.049 g at 70% moisture level followed by Tree cotton, Cyto-62 (0.062 g to 0.049 g) and MPS-11 (0.048-0.059) g. Based on this performance these entries can be marked as most tolerant genotypes. While minimum dry root weight exhibited at 70% moisture level was by MS-64 (0.039) and COOKER-315 (0.039). When 40% moisture was applied Tree cotton was most tolerant genotype with 0% reduction in weight with increase in stress level and dry root weight also remained constant with value of 0.049g at both stresses levels while GS 444 was most susceptible (0.023 g). After applying 100% water and both moisture stress levels i.e., 70% and 40% respectively maximum average performance was exhibited by Tree cotton (0.054 g) followed by Cyto-62 (0.052 g), DPL-45 (0.052 g) and RA-31-21 (0.050 g). These entries reduced their weight about 14% after exposure to stress condition while susceptible entries reduced about 27% average weight after stress treatment and these entries include GS-444, MS-64, Cooker-315 and CIM-608 with average dry root weight of 0.034, 0.039, 0.040 and 0.041 g respectively.