The role of growth regulators, embryo age and genotypes on immature embryo germination and rapid generation advancement in tomato (Lycopersicon esculentum Mill.)

One of the most important problem of tomato breeders is lengthy seed to seed cycle in a breeding program. In vitro techiques provide a lot of advantages for breeders. The objective of this work was to determine the effect of growth regulators and immature embryo age on embryo germination and rapid generation advancement in different tomato genotypes. For this purpose, four different tomato genotypes were used. Immature embryos were derived from fruits 20, 24, 28, 32 and 36 days after pollination. Fruits were left on the plant to mature as control (conventional breeding cycle). MS, MS + 0.1 mg/l kinetin, MS + 0.1 mg/l IAA and MS + 0.1 mg/l kinetin + 0.1 mg/l IAA were used as growth regulators. Growth regulators and genotypes resulted in nonsignificant effect on germination rate and rapid generation advancement, but embryo age resulted in significant effect. Germination rate from immature embryos ranged between 55.22 and 100%. Twenty eight (28) and thirty two (32) days old embryos gave the best germination rate. Days from pollination to flowering, shortened between 53,36 and 63,96 days in comparison with the conventional breeding cycle. This study showed that using immature embryo technique in tomato breeding offers more generation per year when compared to conventional breeding practice.Key words: Growth regulators, immature embryo culture, embryo age, tomato, kinetin, IAA, shortened breeding cycle

Control of powdery mildew (Leveillula taurica) on tomato by foliar sprays of liquid potassium silicate (K2SiO3)

A foliar application of soluble silicon (liquid potassium silicate) was tested for the control of powdery mildew of tomato for 2 years in the field conditions on susceptible cultivar Alida F1. Powdery mildew in field-grown staked tomato, caused by Leveillula taurica was significantly controlled by a foliar spray of either K2SiO3 or Bayleton + sulfur. Potassium silicate applied on a 12 day schedule was highly protective against natural infection by the mildew fungus in the field conditions. The disease severity indexes (DSI) were 77.5 and 74.7% in control plots in 2006 and 2007, respectively, and were significantly different (P < 0.05) from those in the K2SiO3 plots with 5.8 and 4.6% in 2006 and 2007, respectively. Potassium silicate concentration (1 g/1 L water) used in the present study were not phytotoxic to plant foliage. The inhibitory effectiveness of potassium silicate makes it a useful biocompatible fungicide and possibly ideal foliar fertilizer for disease control in the field.Key words: Powdery mildew, potassium silicate, fungicide, tomato