Production of New Almond-Peach Hybrid Rootstocks Resistance to Root-Knot Nematode

Aims: This research was conducted to hybridize almond (Om El-fahm and M. Dalet) female parent with Okinawa peach rootstock as a male parent to introduce new almond rootstock resistance to root-knot nematode.

Methodology: Okinawa peach rootstock used in crosses with both of Om El-fahm and M. Dalet almond cvs. and the resulting hybrids identified by SSR and STS markers for the presence and/or absence of the expected resistance marker. Inoculation by M. incognita with suspension of 2500 eggs per plants through holes in the soil to evaluate hybrids resistance.

Results: Fruit set percentage was higher with Om El-fahm than M. Dalet while, the opposite was true for fruit drop. No significant differences were observed for seed germination with the used females. Hybrid no.3 resulting from M. Dalet x Okinawa crosses showed the highest significant value of vegetative growth parameters. The STS marker; the OPA11 primer pair with Okinawa x Om El-fahm showed the resistant marker at the expected size (166 bp) for all of the tested hybrids except for hybrids no. 7 and 8. Meanwhile, only one hybrid (no. 8) of Okinawa x M. Dalet failed to amplify the resistant marker. The Okinawa parent was clustered with hybrids no. 1, 2, 3, 4 and 14 for Om El-fahm and hybrids no. 1, 2, 3, 4, 5 and 6 for M. Dalet indicating a common genetic resistance for root-knot nematode.

Conclusion: Hybrid rootstocks slightly varied in their resistance to the root-knot nematode Meloidogyne incognita. However, line no. 6 (Okinawa × Om El-fahm) could be considered as highly resistant (HR).