Pre-penetration and latency period of Colletotrichum tamarilloi in resistant and susceptible rubber clones under different environmental conditions

Abstract

The rubber tree (Hevea brasiliensis), is an important natural latex-producing plant which can be limited by several factors, such as the occurrence of diseases, like anthracnose, caused by fungi of the genus Colletotrichum. The clones IAC 502, IAC 507 and RRIM 937 have shown to be promising in the disease control, since in some studies they provide lower percentages of anthracnose. Thus, the objective of this study was to evaluate the pre-penetration and latency period of C. tamarilloi in resistant rubber (IAC 502, IAC 507 and RRIM 937) and susceptible (RRIM 600) clones under the effect of different temperatures and periods of wetting. For germination evaluation and appressorium formation, the studied temperatures were 15, 20, 25, 30, 35 and 40 ± 1ºC and under wetting periods of 4, 6, 12 and 24 hours. The latency period was evaluated at the same temperatures under wetting periods of 24 hours. The percentages of spore germination and appressoria formation were directly proportional to the wetting period, being more expressive under temperatures between 20 to 35 °C, regardless of the clone. After 24 hours of wetting, the clone RRIM 600 showed the highest values of spore germination and appressorium formation. The latency period was shorter in the resistant clones and had an influence on the temperature, since the higher the temperature, the lower the latency period of the fungus in the plant. The results point to a delay in the development of C. tamarilloi in resistant clones, and this can contribute to the delay in the growth rate of disease progression in the field and thus decreasing the amount of disease during a culture phase.