Proc. Internl. Symp. on Technologies to Improve Sugar Productivity in Developing Countries, Guilin, P.R. China, pp 554-560 (2006) EXPRESSION OF SOLUBLE ACID AND NEUTRAL INVERTASE(S) IN RELATION TO CARBON PARTITIONING IN EARLY AND LATE MATURING SUGARCANE CULTIVARS ASHOK K. VERMA, R.P. SRIVASTAVA AND S.B. SINGH* U.P. Council of Sugarcane Research, Shahjahanpur- 242 001, India *E-mail: upcsr@sancharnet.in Summary Aim: This study was conducted to assess thelevel of foliar acid and neutral invertase during different growth stages of sugarcane varieties of varying maturity groups. Methods and Results: The early maturing cultivars consisted more sucrose in their leaves as compared to the late maturing cultivars either individually or at group level resulting more translocation of sugars in their sink. The soluble acid and neutral invertase activities at different physiological growth stages supported the hexose pool present in the cultivars leaves. Significance of Study:Foliar invertase could be a parameter to determine the maturity status of the cultivars in respect of high sugar characteristic which will focus to molecular assisted selection for various molecular breeding programmes. Keywords: Sugarcane cultivars; sucrose; growth stages; invertase(s); reducing sugars INTRODUCTION FOLIAR INVERTASE(S) are important enzymes in translocation and metabolism of photosynthates (Alexander and Sammuals, 1968). Sucrose is synthesized through the UDPG and Fru-6-phosphate mediated reaction in leaves and then translocated to adjoining joints for its storage in the parenchymatous tissues. Virtually all sucrose translocated from leaves enters the metabolic compartment after hydrolysis by invertase(s) (Sacher et al., 1963). Two such invertase(s) i.e. acid and neutral were identified (Hatch and Glasziou, 1963) which are localized in storage parenchyma in bound and soluble forms (Glasziou and Gayler, 1972; Alexander, 1973). Acid invertase is an enzyme that catalyzes the hydrolysis of sucrose to glucose and fructose. This enzyme plays a major role in sugar metabolism in sugarcane. Sucrose is mediated by invertase enzymes in cane tissues. Acid invertase frequently exhibits relationship with cell expansion (Morris and Arthur, 1984, Batta et al., 2002, Sachdeva et al., 2003). On the other hand, neutral invertase functions in controlling the hexose pool size in the mature cells (Gayler and Glasziou, 1972; Willenbrink, 1982). Since invertase(s) participate not only in sucrose utilization, but also in sugar storage, it was felt desirableto study the differential functioning of these enzymes at different growth stages and their association with sugar fractionation in different sugarcane cultivars. It will be useful to develop early maturing high sugared cultivars to get higher sugar recovery in the early part of the crushing season. The present study was conducted with 10 elite sugarcane cultivars for foliar analysis of invertase(s) at different growth stages along with the corresponding sucrose, glucose and fructose contents therein ,to find out the critical limit of activities of enzymes at particular physiological growth stage at cultivar and group level both. This study will give a line to molecular assisted selection for various molecular breeding programmes in developing high sugared cultivars. MATERIAL & METHODS Ten elite sugarcane (Saccharum officinarum L.) cultivars were selected for the study. Five early maturing, high sugared cultivars (CoSe 98231, CoS 96268, CoSe 95436, CoS 95255 and CoS 8436) and five late maturing, low sugar cultivars (CoS 97264, CoS 94257, CoS 91230, CoSe 92423 and CoSe 93232) were included. Planting was done in spring season (2002-2003) consisting two budded setts at 90 cm apart replicated thrice at Sugarcane Research Institute Farm, Shahjahanpur. Crop husbandry practices were followed according to the local recommendations. Plant samples were collected from 240 to 390 days after planting (DAP) at monthly intervals. The maximally photosynthetic active 3 rd leaf of each cultivar was collected separately for enzymatic studies. The leaf samples were collected at 9.00 a.m. to avoid diurnal variation in enzyme activities and sugar level. Extraction and estimation of endogenous free sugars Endogenous free sugars were quantitatively extracted from leaf blade (10 g) separating mid rib; first with boiling 80% ethanol followed by extraction with boiling 70% ethanol. The pooled test extract contained at 40 0 C under diminished pressure to get one aquous syrup. In the test extract, sucrose content was determined after the destruction of free fructose with KOH (Roe, 1934). To 0.5 ml test extract, 0.5 ml 6% KOH was added. The contents of tubes were heated in a boiling water bath for 20 minutes to destroy free fructose. After cooling the tubes