Differential response of some cowpea genotypes to different zinc supply regimes
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Date
2016-03
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
A sand culture experiment and also a separate pot experiments were conducted to study the differential response of cowpea genotypes to different zinc supply regimes. Nine different cowpea genotypes were raised in sand culture with two treatments (with Zn and without Zn) to study the effect of Zn application on root parameters, Zn concentration and uptake in shoot and roots. A soil culture experiment was also conducted using twelve cowpea genotypes receiving three treatments namely, no application of Zn, soil application of 2.5 mg Zn kg-1soil and conjoint use of soil application of 2.5 mg Zn kg-1soil + foliar application of Zn. In sand culture pot experiment, the highest average total root length (944.9 cm), surface area (227.4 cm2), diameter (0.75 mm) and root volume (0.71 cm3) were recorded in V1.The highest average number of root tips was observed in V11 (1676.1). The highest average number of forks (7085.0) and number of crossings (1194.8) was noted in V10. The highest average cation exchange capacity of roots (0.398 meq g-1) and the highest average Zn concentration in shoots (83.8 mg kg-1) was recorded in V5. Zinc application increased the average root length, surface area, root volume and number of forks but decreased the average root cation exchange capacity. The interaction effect of genotypes and Zn levels significantly influenced only root cation exchange capacity. The highest average shoot weight per plant (0.92 g), ratios of Zn concentration and uptake in shoot and roots, Zn uptake in shoot and total Zn uptake were recorded in V6. The highest mean root weight per plant (0.190 g) was recorded in V10. The highest average zinc concentration in shoot and Zn uptake in roots were noted in V5. The highest average Zn concentration in roots was recorded in V3. Zinc application had favourable effect on these parameters except root dry weight. Based on Zinc efficiency index (ZEI) of shoot dry matter the genotype V3, V5, V6, V9 and V10 indicated tolerance to Zn deficiency. In soil culture experiment, genotypic differences were noted in plant height, thousand seed weight, seed and straw yield beside the differences in the concentration of micronutrient cations, P in seed and straw and also phytic acid and protein concentration in seeds. Soil application of 2.5 mg Zn kg-1 soil and conjoint use of soil application of 2.5 mg Zn kg-1 soil + foliar application of Zn increased the average plant height, thousand seed test weight, seed yield, straw yield and Zn concentration in seed and straw significantly over no application of Zn. Soil application of Zn and conjoint use of Zn through soil and foliar application had significant influence on Zn and Mn concentration and uptake of micronutrients cations in seeds and straw of all cowpea genotypes. A significant effect of Zn supply regimes was also noted on P concentration in straw, P uptake in seed and straw, phytic acid and protein concentration in seed. The interaction effect of genotypes and Zn supply regimes influenced the yields, the concentration and uptake of micronutrient cations by cowpea and also the concentration of phytic acid and protein in cowpea seeds. Zinc efficiency indices calculated based on soil application of Zn, genotypes V5, V6, V8 and V9 were tolerant to Zn deficiency and further based on conjoint use of soil + foliar application of Zn, genotypes V3, V8 and V9 appeared to be tolerant. Genotype V2 behaved as the most susceptible genotype under both Zn supply regimes. These tolerant genotypes need to be used for sustainable pulse production and breeding program.