EVALUATION OF INTERACTION EFFECT OF DROUGHT STRESS WITH BORIC ACID, SALICYLIC ACID AND COBALT CHLORIDE ON SOME PHYSIOLOGICAL AND YIELD PARAMETERS IN COMMON BEAN (Phaseolus vulgaris L.) GENOTYPES
Priya* and Usha Rana
Department of Biology & Environmental Sciences, College of Basic Sciences,
CSKHPKV, Palampur – 176062
Corresponding Author* – email@example.com
Received: 04-07-2019 Accepted: 02-01-2020
This study investigated the effect of drought on the growth and yield components of common bean genotypes i.e. KR 60 and KRC 5 when stress was induced at flower initiation stage and also the effect of foliar spray of different concentrations of salicylic acid, boric acid and cobalt chloride. Drought significantly decreased the growth rate and had a negative impact on the yield components in both genotypes but it was confirmed that the yield and growth of KRC 5 genotype was significantly better than KR 60. Evaluation for drought tolerance was done on the basis of inherent stress tolerance characters viz. plant dry weight (g/plant), root length (cm), relative water content (%), chlorophyll fluorescence (fv/fm) and drought susceptibility index (DSI). The results revealed that drought stress at flower initiation stage increased root length of plant and significantly reduced plant dry weight, relative leaf water content, chlorophyll fluorescence (fv/fm) and yield. Foliar application of salicylic acid, boric acid and cobalt chloride effectively ameliorated the negative effects of drought stress in both genotypes and was shown to have the most positive impact on the physiological, yield and growth parameters. However, salicylic acid had a better general effect than boric acid and cobalt chloride. Reduction in drought susceptibility index was also observed under these treatments as compared to stressed non treated plants. SA (150 ppm) and BA (0.1%) was found to be most effective and surpasses other treatments. We believe that the current study could have an important practical application in the field of legume production.
Key words: harvest index, root length, chlorophyll fluorescence, Phaseolus vulgaris, drought tolerance
Common bean (Phaseolus vulgaris L.) belongs to family Fabaceae, is world’s most important food legume. It is cultivated globally on an area of 1.21 million ha with production of 30.24 million tons (Anonymous, 2010). About 60% of common bean production in developing countries occurs under conditions of drought stress (Graham & Ranalli 1997). Moisture stress frequently occurs, either at one or more phenological stage of Common bean under rainfed condition. Therefore, it is imperative to evaluate the performance of Common bean genotypes under moisture deficit condition (Majeed et al., 2010). Various morphological and physiological traits have been reported to be associated with drought resistance in plants growing naturally in arid environment. Identification of these traits is necessary to incorporate such desirable traits in the crop breeding programme (Baruah et al., 1998). Though attempts have been made to study how the plants overcome the impact of stress (on growth and yield reduction) on account of moisture deficit, a lot is yet to be understood as to the physiological and biochemical basis of drought tolerance in Common bean. So, this study has been taken up with the objective to have an insight into the physiological basis and yield of drought tolerance in Common bean, which would help in designing the crop ideotypes for drought prone environments. Drought causes impaired, mitosis, cell elongation and expansion and thus resulting reduction in growth and yield traits (Hussain et al., 2008). Drought stress significantly reduced yield traits in common bean (Beebe et al., 2008).
Plant stress tolerance can be improved with the exogenous use of stress alleviating chemicals. Some of the important plant bioregulators tested act in low concentrations to inhibit, promote or modify the morphological, physiological and biochemical processes of the plants. The response of a plant to environmental stress is also determined by nutritional status. Foliar application of nutrients is also one of the precautionary measures to tolerate drought. These substances can be applied directly to plant leaves, fruit and seed, provoking alterations of vital and structural processes (Olaiya, 2010). Salicylic acid was found to be very effective and increased flower diameter, flower stem length, fresh weight, dry matter percentage and improved secondary metabolism (Ghorbani et al., 2013).Application of salicylic acid through spray inoculation has been shown to have significant increase in plant biomass (Farjam et al., 2014). Several studies support the stimulatory effect of SA on a number of morphological and physiological processes of plants, including growth, photosynthesis and other metabolic processes. This demonstrates a function as a protective agent in plants, modulating the plant response to various biotic and abiotic stresses, such as drought, cold, heat and osmotic stress (Hayat et al., 2010). Exogenous treatment of drought stressed plants with different levels (0.5 and 1.0 mM) of SA not only caused a decline in the adverse effect of drought in yellow Maize (Zeamays L.) plants, but also stimulated physiological traits, productivity and plant resistance to drought stress (Elgamaal & Maswada 2013). Plant height, leaf area and grain yield increased with the interaction between water stress levels and boric acid (Mohammad, 2014). Treatment of boric acid exhibited the highest leaf area and proved as the most effective treatment in increasing the nutrient content (Singh et al., 2004). Boric acid at 0.1% resulted in the greatest plant height, plant spread, average fresh weight of flower, and flower diameter and seed number per peduncle (Kumar & Sharma 2010). The influence of naphthalene acetic acid and cobalt chloride on growth and yield of cotton hybrids was observed and concluded that among the treatments naphthalene acetic acid (20 μg ml-1) and cobalt chloride (10μg ml-1) increased the number of bolls per plant, dry matter partitioning and seed cotton yield (Sarlach & Sharma, 2012).Hence the present investigation was undertaken to evaluate the efficacy of foliar application of BA, SA and Cobalt chloride in alleviating the negative impact of drought stress on common bean genotypes.
MATERIALS AND METHODS
Preliminary studies were conducted in the laboratory conditions for screening of seeds of fifty common bean genotypes procured from MAREC, Sangla, HP. Seeds were surface sterilized with mercuric chloride (0.1%) and were treated with two level of osmotic potential (-0.3 and -0.5 MPa) by polyethylene glycol 6000.Three replications of each genotype for each concentration were germinated in 12cm diameter glass petridish at 25+20C in seed germinator. Observations for germination percentage (%) were recorded when control showed 100 per cent germination (data not given).Two best performing common bean genotypes i.e. KR 60 and KRC 5 were selected for further study and trial was carried out at Department of Biology and Environmental Sciences in the College of Basic Sciences, CSKHPKV, Palampur. The site is located at 32.60 N latitude, 76.30S longitudes and an altitude of 1290 m above mean sea level. Seeds were planted in July, in pots having 30 cm diameter in completely randomized block design (CRD) with four replications. The pots were prepared by mixing soil, vermicompost and sand in the 3: 2:1 ratio along with addition of N, P and K in the ratio of 20:60:0. Nitrogen was applied in two doses, one at time of sowing and other at the time of flowering. The experiment was performed in the net house covered from the top with polysheet and stress was created at flower initiation stage by withholding water until the appearance of slight wilting symptoms and control/unstressed plants were watered regularly, hand weeding was done regularly. Foliar spray was applied after stress imposition and treatments were Stress + BA (0.01 %), Stress + BA (0.1%), Stress + SA(150 ppm), Stress + SA ( 300 ppm ), Stress +CoCl2 (10 ppm) and Stress + CoCl2 (15 ppm ). Various morphophysiological parameters like root length, plant dry weight, relative water content and Chlorophyll fluorescence (fv/fm) were recorded after 30 days of stress imposition and drought susceptibility index and yield parameters were also taken after harvest. Length of the root was measured with the help of scale by uprooting the plant, a fully expanded and mature leaf from top part of the plant was collected and relative water content was calculated by formula given (Merah, 2001). Chlorophyll fluorescence (fv/fm) was measured using a portable PEA (Plant Efficiency Analyzer Flurometer Hansatech Instrument version 1.21).Drought susceptibility index was calculated by formula given (Fischer & Maurer 1978).
RESULTS AND DISCUSSION
Promising Common bean genotypes KR 60 and KRC 5 selected at germination stage were subjected for further investigation under pot culture. Drought stress imposed at flower initiation stage had deleterious impact on various evaluated morphophysiological parameters. This study revealed that drought stress at flower initiation stage in these genotypes significantly increased plant root length and decreased dry weight, RWC and chlorophyll fluorescence (fv/fm) in both genotypes which were selected for pot trial after preliminary screening in lab condition. These results are in conformity with the results obtained (Ghanbari et al., 2013). Roots are the chief organs of water absorption, increase in root length in both genotypes was recorded under water deficit than unstressed plants. Present investigation revealed that application of BA (0.1%) had significant positive influence on root length under stress in both genotypes. Foliar application of boric acid increased root length by the regulation of cell metabolism, growth of meristematic cells and transportation of water and sugar through tissues (Hartung et al., 1994). BA (0.1%) showed (10.32 %) increase in KR 60 genotype and (6.14%) in KRC 5 genotype but all the treatments enhanced root length in treated stressed plants as compared to non treated stressed plants and genotype KR 60 responded better to these treatments (Table 1). Drought stress significantly reduced plant dry weight in both genotypes as compared to unstressed plants but it was significantly enhanced by foliar spray and genotype KRC 5 responded effectively by showing negligible reduction (2.5%) in SA (150 ppm) treatment whereas BA (0.1%) is also effective in causing less reduction in both genotypes (Table 1).Cobalt chloride treatments are ineffective especially in dry weight. This finding corroborated the findings that exogenous application of salicylic acid improves fresh and dry weight percentage (Ghorbani et al., 2013). Salicylic acid increased number of branches per plant, fresh and dry weight as well as leaf area (Khafaga et al., 2009). Leaf relative water content shows the water status of plant tissues pertaining to physiological consequence of cellular water deficit and hence it is used as one of the parameter to estimate the degree and intensity of water stress. This study clearly indicated negative impact of drought stress on leaf relative water content parameter as both genotypes displayed significantly greater reduction. Both genotypes showed variable degree of improvement in relative water content under various treatments over stressed plants. In both genotypes SA (150 ppm) and BA (0.1%) treatments significantly elevated leaf water content and reduction in RWC reduced to half with foliar spray (Table 1). Boric acid treatments showed positive influence on relative water content under drought stressed condition (Upadhyaya et al., 2012). Enhancement in leaf relative water content under treatments is in agreement with the results of (Kadioglu et al., 2011). Exogenous application of SA improves RWC due to osmotic adjustment (Saxena & Misra, 2009). Chlorophyll fluorescence parameter (fv/fm) has been suggested as a quantitative measure of photochemical efficiency of PSII complex and photo yield of oxygen evolution under different environmental stress (Yang, 1999).Reduction in fv/fm was recorded under drought stress. Drought stress significantly reduced chlorophyll fluorescence (fv/fm) in both genotypes. All foliar treatments effectively enhanced chlorophyll fluorescence (fv/fm) in both genotypes. However, SA (150 ppm) and BA (0.1%) showed less than 1% reduction in both genotypes, KR 60 was most effective genotype showing very low reduction in chlorophyll fluorescence i.e. only 0.26 % compared to normal plants whereas other treatments also showed positive influence. Positive influence of SA treatment on (fv/fm) parameter was observed (Shi et al., 2006).Drought tolerant cultivars showed a smaller decrease in photosynthetic efficiency (Almeselmani et al., 2011).Water stress decrease the Chlorophyll fluorescence in Faba bean and reduction was very low in genotypes Gazira-2 (drought tolerant) (Ammar et al., 2014). Maximum drought susceptibility index was showed by unsprayed stressed plants, SA (150 ppm) foliar treatment was most effective with lower drought susceptibility index. Higher drought susceptibility index of unsprayed stressed plants clearly indicated negative impact of drought stress on plant productivity. Lowest DSI was recorded in SA (150 ppm) treatment and other treatments also indicated comparatively lower drought susceptibility index which indicates that foliar application of boric acid, salicylic acid and cobalt chloride increased drought tolerance of plants (Table 1).
Numbers of pods per plant were reduced under water stress in both genotypes (KR 60 and KR C 5). SA (150 ppm) treatments were more effective in increasing the number of pods per plant followed by BA (0.1%) treatment. Number of pods per plant responded positively to the application of salicylic acid (Ghanbari et al., 2013). In KR 60 genotype CoCl2 (15 ppm) showed maximum reduction ( 25 %) and BA (0.01% ) showed minimum reduction ( 5 %) in stressed plants over control in terms of number of seeds/pod. SA (150 ppm) showed no reduction in KRC 5 and is as good as well irrigated plants (control). In 100 seed weight minimum reduction (3.29 %) in KRC5 and (4.21 %) in KR 60 was recorded in SA (150 ppm) treatment followed by BA (0.1%) treatment (Table 2). Foliar spray of boric acid increases the 100 seeds weight in Faba bean (Reda et al., 2014). Exogenous application of SA (150 ppm) resulted in minimum reduction (4.15 %) in KR 60 genotype and (2.66 %) in KRC 5 under stress over control plants in harvest index followed by BA (0.1%) treatment (Table 2). Foliar application of salicylic acid also increased yield of different crops due to reduction in stress induced inhibition of plant growth (Gunes et al., 2007).
Overall study revealed that the presence of these treatments can ameliorate the stress injury and KRC 5 was performing better with respect to KR 60 genotype for foliar treatments but KR 60 has also improved its performance a lot.Based on these parameters it seems that KR 60 is susceptible genotype whereas KRC 5 is tolerant that is why KR 60 is effectively responding to foliar treatments and improved the reduction to 50%, but KRC 5 is coming at par with control in most of the parameters of yield attributes. The study concluded that foliar application of boric acid, salicylic acid and cobalt chloride can counteract the deleterious effects of drought stress on common bean genotypes but boric acid and salicylic acid were found to be more effective treatment in alleviating drought stress.
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