THE IMPACT OF CLIMATE VARIABILITY ON OCCURRENCE OF SESAME PHYLLODY AND SYMPTOMATOLOGY OF THE DISEASE IN A MEDITERRANEAN ENVIRONMENT

Abstract

Although climate change and variability is considered as an alerting situation and a big challenge to food security, we describe here a positive impact of it regarding disappearance of sesame phyllody in an unusually cool and rainy growing season of 2010 at West Mediterranean region of Turkey where the disease has been devastating last five years and it would occur at any rate in the same field since the start of sesame cultivation in 1995. Phyllody symptomatology and incidence were studied in three groups of plant material; i.e., (1) in a 2year agronomic performance trial, (2) in the breeding nurseries (on the regenerated branches in the stubbles and unselected left-plants), and (3) in the M1 plant progenies (grown as M2 families beyond the commercial growing season for a training purpose). Unexpectedly, in 2010, there was no any single phyllody incidence (0%) in the first and second group material in comparison to the previous years, e.g., 6.0% in 2009). Although the incidence was nil in the third group material of M2 families until onset of capsules (sown very late), phyllody symptoms started to appear as capsules grew and reached at 3% at the physiologic maturity. Also, stubbles of cut plants and unselected-left plants in the field after harvest (especially of F1s with heterosis) grew new late branches like ratoon crop and developed phyllody in them, providing a good match between vectors and plant growth. Much of the impact of climate change and variability on sesame phyllody may be through the vectors of the disease and, thus, subject to the effects of fluctuating climate variables on their biology and population dynamics. To reveal the uniqueness of the year 2010 and its effect on the disappearance of the disease, the climate data clearly indicated a cool and rainy season and possibly a mismatch for the cycle of the vectors and crop growth. Three types of main symptoms which specify the phyllody disease were observed, i.e., `virescence`, `phyllody`, and `ploriferation (witches’ broom) `, but the latter was less-frequent. Also, among several indirect symptoms such as stunted habitus, exudates, vivipary, and yellowing, we described here a new effect of the disease-causing short filament, and thus pin-type flower. Finally, climate change and variability may also offer some positive impact to exploit for the benefit of food security and such cases should be considered in the crop management tactics and strategies as well as in modeling studies aiming to forecast impact of climate variability.