AMELIORATION OF IRON DEFICIENCY IN GROUNDNUT (ARACHIS HYPOGAEA L.)

Abstract

Groundnut is an important cash crop of Pothwar region (Attock and Chakwal districts) of Pakistan. This crop faces iron deficiency in the region due to calcareousness of soils. Iron is ranked fourth abundant element comprising 5% of the crust of earth. However due to high pH (7.5-8.5) of soils; iron availability to the plants is limited, as a 44result groundnut yield is significantly decreased. Development of tolerant genotypes under iron limitation is the widely acceptable strategy practiced all over the world. This study was planned to identify locally grown groundnut genotypes tolerant to iron deficiency, and to investigate chemical amendments for mitigation of iron deficiency. To achieve the objectives hydroponics and pot experiments were performed in triplicate in Completely Randomized Design (CRD) under iron sufficient and iron deficient conditions at National Agricultural Research Centre (NARC), Islamabad. Seeds were obtained from BARI (Barani Agricultural Research Institute, Chakwal) and NARC, Islamabad. Amongst all tested genotypes, BARI-2000 performed well in soils as well as in hydroponics under iron limited conditions, whereas BARD-699 was found susceptible to iron deficient conditions with iron deficiency tolerance indexes of 56% and 36% respectively. The data were further supported by iron reducing capacity of both genotypes. Iron reducing capacity of BARI-2000 was the highest 4 days after iron deficiency stress (15.3 μmol per g 2 h fresh weight of plants) as compared to other genotypes, while BARD-699 showed significantly low iron reducing capacity (5.8 μmol per g 2 h fresh weight of plants). For amelioration of iron deficiency in BARI-2000 and BARD-699, various chemicals (Fe-EDTA, FeSO4, citric acid, sequestrene, and surfactant) were used. Several morpho-physiological parameters were recorded under various amendments. BARD-699 was more responsive to foliar applications, while BARI-2000 was found more responsive to Fe-EDTA. Foliar applications were found more effective in reducing iron chlorosis as compared to soil applications of chemical amendments. Molecular markers data showed genotypic similarities amongst genotypes. BARI-2000 was related to 96CG005 and both the genotypes were tolerant to iron deficiency. Four varieties viz., Banki, BARI-2000, BARD-699 and Chakori were used to study the expression levels of eight genes (AhIRT1, AhFRO1, AhNRAMP1, AhYSL1, AhYSL3, AhYSL4, AhYSL6 and AhFER3) involved in uptake and translocation of iron under iron limited conditions through real time PCR analysis. BARI-2000 and Chakori were closely related based on gene expression and pot experiment data. Expression level of AhIRT1 was low in BARI-2000 and Chakori in roots under iron deficient conditions, whereas the same was higher in shoots. The tolerant genotypes can be used in hybridization programs for improving yield and iron deficiency tolerance in groundnut.