VNTR-based diversity analysis of 2x and 4x full-sib Musa hybrids

Abstract

Summary of inheritance of maternal (AAB genome) and paternal (AA genome) VNTR amplification fragments in the full -sib 2x and 4x progeny populations. ____________________________________________________________________________ Maternal fragments Paternal fragments (Obino l’Ewai) (Calcutta 4) # % # % ____________________________________________________________________________ Diploid progeny Segregation 10 46 15 65 No segregation 8 36 3 13 Absent 4 18 5 22 Tetraploid progeny Segregation a 18 82 20 87 b No segregation 4 18 1 4 Absent 0 0 2 9 _________________________________________________________________________ ___ a segregation of 7 fragments solely due to absence of that fragment in TMPx 548 -9 b segregation of 1 fragment solely due to absence of that fragment in TMPx 548 -9 TMPx 7002-1 are most closely related to the maternal genotype (Obino l’Ewai). In cont rast, all the diploid hybrids form two groups associated at the 60% level of similarity, which are distinct from both parental genotypes (Figure 1). The major exceptions are TMPx 548 -9, which is separated at the 20% level of similarity from all other genotypes, tested and hybrid 5860-1 (4x) that is grouped with the diploid progeny. Hybrid 5860-1 (4x) was found to haveCalcutta 4 were very similar; 0.42 (±0.046) and 0.39775% similarity to TMP2x 1549 -5, both of which have 65% similarity to hybrid 1549-7 (2x) (Figure 1). This anomaly may be a consequence of hybr id 5860-1 (4x) possessing a high proportion of bi-allelic loci in common with these particular diploid full -sibs, as compared to multi -allelic loci of the other tetraploid hybrids. Clearly, this type of molecular marker analysis can not be used for inferring hybrid ploidy. Finally, TMP2x 1448 -1 and hybrid 1586 -2 (2x) appear particularly distinct from the majority of their 2x and 4x full -sib hybrids (Table 2). Both diploid and tetraploid hybrids had comparable mean levels of similarity to Calcutta 4 (32.2% and 34.3 %, respectively). However, tetraploid hybrids had more fragments in common with Obino l’Ewai than their diploid full-sibs (56.1% and 44.6%, respectively). This relationship was expected because the tetraploid hybrids have 75% of their genes donated by the maternal plantain 2n gametes (and the remaining 25% from the diploid banana), while their diploid full-sibs inherit 50% of their genes from each parent. The average phenotype of the tetraploid hybrids was also more closely related to Obino l’Ewai than Calcutta 4 (Table 3). The phenotypic distance between the tetraploid hybrids and Obino l’Ewai was 0.322 (±0.027), while the phenotypic distance between the tetraploid hybrids and Calcutta 4 was 0.470 (±0.021). Conversely, the phenotypic distance indic es for comparisons of diploid hybrids with Obino l’Ewai and (±0.043), respectively. This was expected based on the gametic contributions to diploid and tetraploid hybrids described above. For the relationship between hybrids and Obino l’Ewai, there was a significant association between the genetic similarity (based on VNTR) and the phenotypic resemblance (r = -0.546, P = 0.042). The linear relationship (R