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Sugarcane Breeding lnstltuto (Indian Council of Agricultural Resemh) ~ t o r e - 6 4 l a n;, ~
ugarcane (Saccharurn spp.) is an important crop globally not only for sugar production, but also increasingly as a bioenergy crop due to its phenomenal dry matter production capacity. Drought is one of the most important environmental stress limiting sugarcane production worldwide. Due to the erratic nature of rainfall, sugarcane growers rely heavily on irrigation to meet production goals. However, water for irrigation is a limited and continuous resource and its effective management is critical, not only in reducing wasteful usage, but also in reducing production costs and sustaining productivity. In view of the sugar requirement of 27 million tonnes by the year 2020 and scope for further increase in area under sugarcane cultivation being limited the evolution of drought resistant varieties has become a major research priority. Hence, each year advanced breeders materials are being evaluated in field condition with the objective of identifyingresistant genotypes to drought.
Critical phenological phase for water demand In sugarcane, four distinct growth stages have been characterized, namely: germination, tillering, grand growth and maturity. The tillering phase is known as the formative phase and has been identified as the critical water demand period, mainly because during this phase maximum number of shoots are formed. In most of the sugarcane growing areas, the crop experiences moisture stress during the formative phase, affecting germination and tillering. As a result stalk population and stalk growth are reduced, resulting in 30-50% yield loss. Varieties response to water deficit stress during this growth stage could therefore be useful in identlfyrng drought tolerant genotypes.
Screening methodology fBt drought tolcmce: in field Field experiments were conducted in split plot design with control and moisture stress treatment as main plot and genotypes as sub plot (in replicated .id) to evaluate the elite breeders materials (lVT/AVT genotypes) for drought osed from 60 to 150 days of crop age olding irrigation in treatment plots (Fig.1). The lusion of border rows and a gap of 3 m treatment blocks (to minimize seepage effect). Soil
Rating for drought tolerance The harvest index proposed by Donald was used as one of the criteria to assess the potential yield and stability in different environments. The relative performance of the genotypes in terms of cane yield and sugar yield was assessed by plotting the cane yield under drought treatment against yield under normal condition. Similarly, for sugar yield also relative performance was worked out. The graph was constructed in such a way that the plot area of the graph was divided into four quadrants by dividing the X axis at the point of mean cane yield under normal condition and Y axis at the point of mean cane yield under drought condition. Genotypeswith better cane and sugar yield in normal as well as drought treatment falling in quadrant- I were considered as tolerant types; genotypes falling in quadrant I1 & 111 were considered as moderately tolerant, while genotypes falling in N quadrant were considered as susceptible types.
Sugarcane genotypes tolerant to drought Varieties CoC 671, Co 8208, Co 85007, Co 85004, Co 86032, Co 85019 and Co 87263 are suitable for 'water limited condition. AVT clones screened during 2004 (Co 99004- Damodar) and 2006 (Co 2001-13 (Sulabh) and Co 2001-15 (Mangal) were recently released for peninsular zone (Fig. 2). New promising drought tolerant genotypes also have been identified (Table 1).
Table 1. Drought tolerant aenatvws VSI
Drought tolcmt wlctles