Leaf Chlorophylls and Carotenoids Status and Their Correlation with Storage Root Weight of Some Local and Exotic Sweetpotato Genotypes

Abstract

The investigation was carried out to characterize the chlorophyll components and carotenoids of the leaves of some local and exotic genotypes of sweetpotato viz. Local-1, Local-2, Local-5, Local-8, Exotic-1, Exotic-2, Exotic-4 and BARI SP-4 and their effect on production of total dry matter and storage roots dry weight during November 2016 to March 2017 at farmer’s field of Dashpara village of Sylhet Sadar Upazila, Sylhet, Bangladesh. The experiment was laid out in Randomized Complete Block Design with three replications. Fresh leaves of 5-6th position from the top of vine were collected from the research field into polybag with proper tagging and brought to the laboratory in the morning of 30, 60, 90 and 120 days after planting (DAP). Collected leaves were washed, wiped out of excess water, cut into small pieces, mixed thoroughly, and 250 mg of leaf materials were taken in a mortar. Leaf materials were grinded finely by a pestle with 25 ml of cold 80% acetone for two minutes. Sample tubes were centrifuged for 10 minutes. The homogenate was filtered and made up to 25 ml with cold 80% acetone. The centrifuged samples were incubated in dark for half an hour. The optical density (OD) for each solution was measured at 663, 645 and 440.5 nm against 80% acetone as blank in one cm cell of spectrophotometer. Triplicate estimation was done for each sample. Chemical analyses were performed at Regional Laboratory of Soil Resource Development Institute, Sylhet. Statistical analyses was done using MSTATC software following analysis of variance technique and Duncan’s Multiple Range Test. Results showed that chlorophyll-a gradually increased up to 60 DAP in all genotypes, thereafter continued only in Exotic-4, Exotic-3 and Local-1 up to 90 DAP. The highest amount of chlorophyll-a (10.27±0.45 mg 100 gfw-1) was in Local-1 at 90 DAP. The highest amount of chlorophyll-b was in Exotic-3 (19.13±0.53 mg 100 gfw-1) followed by Local-1 (16.85±0.50 mg 100 gfw-1) at 30 DAP. Carotenoids content in leaves of all genotypes increased gradually up to 90 DAP and thereafter decreased except Exotic-4. The highest carotenoids was in Exotic-3 (10.78 mg 100 gfw-1) followed by Local-1 (10.13 mg 100 gfw-1) at 90 DAP. At 120 DAP, the highest storage roots weight was in Local-8 (232.40±5.97 g plant-1), followed by Local-1 (187.50±5.23 g plant-1). Chlorophylls and carotenoids had no significant effect on total dry matter and storage roots dry weights at 30 DAP. At 120 DAP, all chlorophyll components and carotenoids had positive correlation with total dry matter (TDM) and storage roots dry weights. Genotypes Local-1, Local-8 had the higher chlorophylls while Exotic-3, Local-1 and Local-8 had the higher carotenoids. Genotypes Local-1 and Local-8 showed the highest storage roots dry weight.