EVALUATION OF SUGARCANE ELITE CLONES THROUGH PHYSIOLOGICAL RESPONSES AND YIELD RELATED TRAITS UNDER EARLY RAINFED DROUGHT STRESS CONDITIONS.

Sugarcane (Saccharum sp.) is one of the most important sugar producing crops, and plays a key role in ethanol production in most tropical and subtropical countries. Selection of sugarcane varieties has traditionally been based on yield and agronomic traits; however, the use of physiological traits in sugarcane selection may increase selection efficiency. The objective of this study was to investigate the effects of physiological responses on yield and yield components in sugarcane under rainfed conditions. Nineteen elite sugarcane clones were evaluated in a randomized complete block design with three replications, from January, 2015 to January, 2016; at the Agronomy Research Station, Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand. The plots consisted of four rows, six meters in length, and spacing of 1.5 m x 0.5 m. Data were recorded for chlorophyll fluorescence, SPAD chlorophyll meter reading (SCMR), relative water content (RWC), stomatal conductance at 90 and 180 days after planting (DAP), stalk height, increased stalk height rate, number of tillers/stool, number of stalks/stool at 90, 180, and 270 days after planting (DAP); stalk diameter, stalk length, number of stalks/stool, single stalk weight, millable cane, cane yield, and total soluble solids at 12 months after planting (MAP). KK3 proved to be a superior clone for agronomic traits; such as cane yield, millable cane, stalk diameter, stalk length, total soluble solids; and was also associated with several physiological traits; such as high photosynthesis efficiency, SCMR, and stomatal conductance. Other comparative clones; such as KK07-037, MPT02-458, CSB07-79, K88-92, KKU99-01, and TBy28- 0941 had similarly high cane yields; whereas CSB07-219, MPT02-458, KKU99-02, KKU99-03, TP06-419, and UT13 had higher total soluble solids. [ABSTRACT FROM AUTHOR]