Triticeae Research Institute, Sichuan Agricultural University, Dujiangyan City 611830, Sichuan, P.R. China


Summary

The genetic diversity among 40 Sichuan elite wheat cultivars, which had once popularized above 66,700 ha per year during recent 50 years, was evaluated by esterase isozyme, gliadins and RAPD markers. These wheat cultivars showed a considerably low level of variability for esterase isozyme, while had greater genetic variability for gliadins and RAPD markers. Only seven different esterase patterns were found, while 32 out of 40 cultivars (80%) had identical esterase patterns. There were 38 different gliadin patterns present in 40 Sichuan wheat cultivars, while 36 out of 40 cultivars (90%) did not have identical gliadin patterns with others. In RAPD analysis, a total of 183 bands were amplified using 55 primers in the 40 cultivars. Ninety-three put of 183 bands (50.8%) were polymorphic, with 1.7 polymorphic bands per primer on an average. The RAPD-based genetic similarity (RAPD-GS) among Sichuan wheat cultivars ranged from 0.804 to 0.991, with an average of 0.887.

Key words: esterase, genetic diversity, gliadins, wheat


Introduction

Choice of parents for developing base populations is crucial in breeding of line cultivars because it largely predetermines the outcome of subsequent selection steps and affects the optimum allocation of resources in breeding programs. Evaluation of genetic diversity levels among adapted, elite germplasm can give breeders much information for selecting less related parents in breeding program. It also can provide predictive estimates of genetic variation among segregation progeny for. pure line cultivar development (Manjarrez-Sandoval et al. 1997) and may estimate the degree of heterosis in progeny of some parental combinations (Cox and Murphy 1990). Genetic diversity in wheat has been evaluated using markers such as quantitative morphological traits (Zeven and Schachl 1989), isozymes (Cox et al. 1988), gliadins (Cox et al. 1985) and DNA. markers (Devos and Gale 1992; He et al. 1992; Vaccino et al. 1993; Chen et al, 1994; Plaschke et al. 1995).

In China, Sichuan is the largest spring wheat (Triticum aestivum L.) planting region. In Sichuan, prior to 1950, landraces were widely cultivated, but its yield was much low (Yen 1999). During 1950s, landraces were replaced by modem cultivars step, by step. From then on, the wheat production of Sichuan was largely increased (Yen 1999). During 1990s, Sichuan wheat changed more vulnerable to biological and environmental stress because the same parental genotypes (i.e. Fan 6 and Mianyang 11) were used for breeding cultivars (Yu 1998). It becomes a very important work to evaluate the genetic diversity among Sichuan wheats (Yu 1998; Yen 1999). To date, the isozyme, gliadin and RFLP variations in Sichuan wheat landraces had been investigated (Yang et al. 1992; Ward 1998; Wei et al. 2000), but no information was available on the genetic variation in Sichuan wheat cultivars. The objective of this paper is to describe the genetic variations for esterase, gliadins and RAPDs present in Sichuan wheat cultivars.