Differential impact of aluminium stress on pigment contents of contrasting rice (Oryza sativa L.) landraces from Sikkim Himalaya

Abstract

Aluminium (Al) toxicity constitutes the major factor restricting plant productivity on acidic soils posing a threat to food security worldwide. Here, we have monitored the impact of Al on pigment (chlorophyll and carotenoid) contents of certain rice (Oryza sativa L.) landraces from Sikkim Himalaya with contrasting Al tolerance namely, Kalo tukmar (KT), Champasari (CP), Krishna bhog (KB) and Dhansey (DH). Seedlings were grown hydroponically with half strength Hoagland solution containing Al (0-1500 µM, pH 4.5) for14-d and chlorophyll (a, b and total) and carotenoid contents were measured. In response to the exposure to Al, pigment levels declined in a concentration dependent manner in all the tested landraces with strong landrace-specific differences. Thus, the extent of Al-induced decline in chlorophyll and carotenoid contents was much lower in KT and CP than that in KB and DH. A decline of 42, 50, 69 and 70% in total chlorophyll content at 1500 µM Al was evident in KT, CP, KB and DH, respectively. The observations are consistent with greater Al tolerance of KT and CP as compared to KB and DH. Chl a : b ratio tended to increase particularly in KB and KT suggesting a higher decline in Chl b content than that in Chl a due to Al treatment. The carotenoid contents were suppressed by 55 and 38% in KB and KT, respectivelydue to 1500 µM Al treatment. Differential response of the tested landraces to Al could be ascribed to more efficient Al resistance mechanisms. The findings have implications for selection of suitable landrace(s) for acidic soil conditions.