DORMANCY BREAKING OF SOUR ALMOND SEEDS AND EVALUATION OF BIOTIC AND ABIOTIC ELICITORS FOR INDUCING SYSTEMIC RESISTANCE AGAINST ROOT-KNOT NEMATODES (MELOIDOGYNE SP.) IN RELEASED SEEDLINGS

Abstract

In a Green –House experiments the effect of gibberellic acid at different concentrations on sour almond (Prunus amygdalus Batsch.) rootstock concerning percentage of radicle protrusion; stratification period; plant height; number of leaves and plant diameter were determined during 2014 and 2015 seasons. Also, the plant growth promoting rhizobacteria Serratia marcescens and the alga Spirulina platensis {as biotic elicitors} compared with, Trafose K (1) and white willow Salix alba extracts {as abiotic elicitors} soil treatments were tested for induction of systemic resistance (SR) in sour almond plants against root knot nematodes. In relation with nematodes population as juveniles in the soil; galls in roots; females; egg masses in roots were counted. Growth parameters plant, such as heights, fresh weight of roots and shoot were recorded. Also, some chemicals components in the plant, such as phenolic; proline ; Salicylic acid and catalase and peroxidase activity were determined. Results indicated that GA3 at 1000 p.p.m. achieved the best effect on percentage of radicle protrusion. Data revealed that using S. marcescens recorded 40%, 58.3% and 75% reduction in numbers of Meloidogyne sp. juveniles in the soil, number of galls and number of females in root respectively in season 2014. While application of S. platensis caused 55.6 %, 62.5% and 33.3% reduction of Meloidogyne sp. respectively in season 2015. Using S. marcescens, S. platensis, Trafose K (1) and Salix extract resulted in 60%, 40%, 80% and 20% reduction in the number of development stages, respectively in season 2014, 75%, 50%, 25% and 25% reduction in numbers of development stages, respectively in season 2015. S. marcescens inoculants and Salix extract improved plant health by increasing vegetative growth parameters similar to control values. The beneficial effects of these treatments extended to increasing not only total phenol and free proline but also the activities of catalase and peroxidase enzymes in comparison with control plants. All tested elicitors showed significant increasing Salicylic acid (SA) levels when being compared with control. It can be recommended that using GA3 at 1000 ppm before stratification is necessary to breaking seed dormancy and enhancing radicle protrusion of sour almond rootstock. Also, using (S. marcescens, S. platensis, as biotic inducers or white willow extracts as natural inducers) as soil treatments increased the induction of systemic acquired resistance (SAR) in the roots of infected with Meloidogyne sp. sour almond rootstock.