###### Abstract  
High throughput techniques for phenotyping quality traits in root and tuber crops are useful in breeding programs where thousands of genotypes are screened at the early stages. This study assessed the effects of sample preparation on the prediction accuracies of dry matter, protein, and starch content in fresh yam using Near-Infrared Reflectance Spectroscopy (NIRS). Fresh tubers of _Dioscorea rotundata_ (D. _rotundata_) and _Dioscorea alata_ (D. _alata_) were prepared using different sampling techniques--blending, chopping, and grating. Spectra of each sample and reference data were used to develop calibration models using Modified Partial Least Square (MPLS). The performance of the model developed from the blended yarn samples was tested using a new set of yam samples (\(N=50\)) by comparing their wet laboratory results with the predicted values from NIRS. Blended samples had the highest coefficient of prediction (R\({}^{2}\)pre) for dry matter (0.95) and starch (0.83), though very low for protein (0.26), while grated samples had the lowest R\({}^{2}\)pre of 0.87 for dry matter and 0.50 for starch. Results showed that blended samples gave a better prediction compared with other methods. The feasibility of NIRS for the prediction of dry matter and starch content in fresh yam was highlighted. Dioscorea alata; Dioscorea rotundata; quantitative prediction; tuber dry matter; starch 2020 10 6035 10.3390/app10176035 17 July 2020 18 August 2020 31 August 202  
food. Fresh yam tubers also contain approximately 29% vitamin C, according to the USDA National Nutrient Database, and help to boost the immune system [4]. Yam is a key staple crop for smallholders in Africa. It is consumed in various forms depending on the processing approaches--boiling, drying, frying, milling, pounding, roasting, and steaming [5]. Furthermore, yam serves as a valuable source of farm employment and income in Africa, as well as being culturally relevant and involved in society in many life events. In Nigeria and neighbouring West African countries, yam plays an essential role during marriage and fertility ceremonies [6; 7; 8; 9]. Quality components of yam cultivars are essential for their acceptability for cultivation and consumption. Traits such as starch and sugar content, the colour of tuber flesh, and oxidation are routinely measured by breeding programs because they influence the acceptability of new varieties [10; 11]. The visual selection has been used by breeding programs in root and tuber crops to distinguish varieties; however, this approach to quality trait selection is quite challenging [12]. Conventional methods of assessing yam tuber quality traits are time-consuming, cost-intensive, and involve the use of hazardous chemicals. The conventional methods for quality assessment of yam include oven drying the fresh samples for 72 h and then ground dried sample to a fine flour (0.05 mm particle size) before chemical analysis, which will, in turn, take some time. However, analysing the samples freshly using NIRS eliminates the time required for drying and grinding in the conventional method. Therefore, techniques to generate data quickly on tuber quality assessment will be of great significance in yam improvement programs. Near-infrared spectroscopy (NIRS) is among the high throughput techniques for the speedy diagnosis of quality traits of yam tubers. The principle of NIRS is based on the interaction of different chemical groups such as C-H, O-H, and N-H in a sample with electromagnetic radiation at a specific wavelength. Near-Infrared spectra comprise broad bands of overlapping absorptions and combinations of vibrational modes involving chemical bonds within the wavelength range of 780 to 2500 nm [13]. Models of NIRS have been developed for the rapid characterisation of essential quality traits in various _Dioscorea_ spp. [12; 14; 15] and have been successfully applied in many crops, including potato, cassava, and sweet potato [16; 17; 18; 19].