INDUCTION AND STABILITY OF PHENOTYPIC VARIATION IN SUGARCANE AS AFFECTED BY PROPAGATION PROCEDURE

Sugarcane (Saccharum L. spp. hybrids) propagated in vitro from shoot t ips is generally assumed to be less phenotypically variable than from callus culture. The objectives of this research were to study stalk, m illing, and morphological variant characteristics of plants of 'CP 74- 383' from callus culture, direct regeneration, shoot tip culture, and conventional bud propagation, and to assess the phenotypic stability a fter vegetative propagation. Plants were evaluated in plant-cane and f irst-ratoon crops (Experiment 1). Plants with normal or off-type pheno types selected from Exp. 1 were similarly evaluated in two successive plant-cane crops (Experiment 2). The frequency of variants was high fo r all tissue culture CTC) treatments. The frequency of normal TC plant s was 10 and 22% in plant-cane and first-ratoon crops, respectively, s howing that some variation was transitory. However, phenotypes of norm al or off-type selections were stable with vegetative propagation. The TC plants had low mean plant height, stalk diameter, and stalk weight . Normal TC plants and controls (from bud propagation) were similar fo r stalk number and plant height, but normal selections had thinner, li ghter stalks. Treatments did not differ in milling characteristics in either experiment, indicating that morphology was independent of cane composition. The results demonstrated that shoot tip culture of this c ultivar induced considerable phenotypic variability. Little useful in- vitro induced variability occurred for important phenotypic characteri stics.