Somaclonal variation for disease resistance in wheat and production of dihaploids through wheat x maize hybrids

Abstract

Seven wheat cultivars having some degree of resistance to Bipolaris sorokiniana, Magnaporthe grisea or Xanthomonas campestris pv. undulosa (Xcu) provided somaclonal variation for disease resistance. Callus induction varied from 69.4 to 100% across the cultivars, whereas regeneration frequency of R1 plants (regenerated plants of first generation) varied between 2.7 and 23.1%. Resistance variation in the R2-regenerated second generation plants was observed for B. sorokiniana and M. grisea but not for Xcu. Attempts were made to fix the resistance characteristics of R3-regenerated third generation somaclones through wheat x maize hybrids. Wheat and maize hybridization of seven wheat somaclones yielded 81 embryos. A total of 11,624 somaclone florets were pollinated, of which 8.4% produced haploid embryos across the seven wheat genotypes. Hybrid embryo production varied between 0 and 25%. The somaclones had a constant chromosome number as observed in their original hexaploid wheat genotypes (2n = 6x = 42) whereas the haploid plants had n = 21. Hybrid embryo production and haploid and dihaploid plant production were affected by 2,4-D concentration, but not by the wheat genotype.<br>Sete cultivares de trigo possuindo certo nível de resistência a Bipolaris sorokiniana, Magnaporthe grisea, Xanthomonas campestris pv. undulosa (Xcu), foram usadas para variação somaclonal, a fim de induzir um nível maior de resistência. A freqüência de indução de calos variou entre 69,4 e 100 entre as cultivares, enquanto que, a freqüência de regeneração de plantas R1 variou entre 2,7 e 23,1, dependendo da cultivar. A variação para resistência entre as plantas de R2 foi observada para B. sorokiniana e M. grisea, mas não para Xcu. Procurou-se fixar as características de resistência dos somaclones (R3) através de hibridação com milho. A hibridação entre trigo e milho produziu 81 embriões zigotos. Um total de 11.624 flores de somaclones foram polinizadas, das quais 8,4% produziram embriões haplóides nos sete genótipos de trigo. A freqüência de produção de embriões haplóides variou entre 0 e 25. A freqüência de plantas haplóides totipotentes variou entre 0 e 66,6. A análise citológica de somaclones demonstrou um número cromossômico constante, conforme observado nos seus genótipos originais de trigos hexaplóides (2n = 6x = 42), enquanto que, as plantas haplóides demonstraram apenas metade dos cromossomos (n = 21). A produção de embriões híbridos e plantas haplóides e duplohaplóides foram afetadas pela concentração de 2,4-D, mas não pelo genótipo de trigo

Somaclonal variation in plants: causes and detection methods

“…The occurrence of uncontrolled and random spontaneous variation during the culture process is, therefore, an unexpected and mostly undesired phenomenon (Karp 1994). Contrary to these negative effects however, its usefulness in crop improvement through creation of novel variants are also well documented (Bouharmont 1994;Mehta and Angra 2000;Predieri 2001). Induced somaclonal variation can be used for genetic manipulation of crops with polygenic traits (Brar and Jain 1998;Jain 2001).…”

Mutagenesis in Plant Breeding for Disease and Pest Resistance

“…Seven wheat cultivars having some degree of resistance to Bipolaris sorokiniana, Magnaporthe grisea or Xanthomonas campestris pv. undulosa (Xcu) provide somaclonal variation for disease resistance (Mehta & Angra, 2000). The stability of somaclonal variants must be examined through several generations in order to distinguish from epigenetic changes, which is the reason for lower utility.…”

Somaclonal Variation in Tissue Culture: A Case Study with Olive

“…The literature to date indicates that somaclonal variation can range in scope from specific trait to the whole plant genome. Somaclonal variation provides a valuable source of genetic variation for the improvement of crops through the selection of novel variants, which may show resistance to disease, improved quality, or higher yield [10,11,12,13].…”