Effects of temperature and leaf age on conidial germination and disease development of powdery mildew on rubber tree

Abstract

Powdery mildew is an important disease of rubber trees worldwide. To assess the effects of temperature and leaf age on conidial germination and disease development, conidia were inoculated onto rubber tree seedlings with leaves at three phenological stages (copper bronze, colour‐changing, and light green) and then incubated at six constant temperatures (10, 15, 20, 25, 30, and 35°C). Leaf age did not affect conidial germination (p = .296) whilst temperature did (p < .0001), although conidia were able to germinate at all tested temperatures. The estimated optimal temperature for conidial germination was 23.2°C. Leaf age, temperature, and their interactions had significant effects on conidial infection and hypha number (p < .0001). At 10 and 35°C, more than 2 and 4 days were needed for infection to complete, respectively, compared to <2, 1, 0.5, and 0.5 days for 15, 20, 25, and 35°C, respectively. Sporulation and mildew symptoms were only observed on those inoculated leaves of all stages at 20 and 25°C, and at the copper bronze stage only at 15°C. The latent period on the copper bronze leaves at 15°C was longer (9 days) than at 20 and 25°C (4 days). The latent period at 20 and 25°C increased from 4 to 7 days as the leaf development stage increased from copper bronze to light green. Therefore, temperature affected germination and postgermination growth of rubber tree powdery mildew, whereas leaf age primarily affected postgermination growth of the pathogen.

Key infection stages defending heat stress in high-temperature-resistant Blumeria graminis f. sp. tritici isolates

“…Temperature is an important abiotic factor having a critical influence, positive, or negative, on infection stages of plant pathogens, such as conidia germination, appressoria formation, germ tube elongation, and haustoria formation in Pst, Puccinia recondita f. sp. tritici, Colletotrichum acutatum, Leveillula taurica, Oidium neolycopersici, O. heveae, Podosphaera xanthii, and Golovinomyces orontii (Guzman-Plazola et al, 2003;Leandro et al, 2003;Mieslerová and Lebeda, 2010;Trecate et al, 2019;Cao et al, 2021). This research showed that conidia germination of two types isolates was not affected at 25°C, which indicates that 25°C was not unfavorable temperature for conidia germination of Bgt.…”

“…Although high temperature has little effect on the quantity of appressoria formation, it significantly increased abnormal morphology of appressoria, such as absence of AGT hooking and multi-lobed appressoria, followed by dramatically decreased haustoria formation frequency. A previous report also found that temperature significantly affected haustoria formation of O. heveae (Cao et al, 2021). In addition, the inhibition rate of haustoria formation in high-temperatureresistant Bgt isolates was lower than the high-temperaturesensitive isolates, suggesting that the haustoria formation of hightemperature-sensitive isolates was more severely inhibited by 25°C than high-temperature-resistant isolates.…”

“…For instance, high temperature affected conidia germination of Pst, P. recondita f. sp. tritici, Beauveria bassiana, and Leveillula taurica (de Vallavieille-Pope et al, 1995;Guzman-Plazola et al, 2003;Devi et al, 2005), appressoria formation in Colletotrichum gloeosporioides (Estrada et al, 2000), germ tube elongation of L. taurica (Guzman-Plazola et al, 2003), and haustoria formation in Oidium heveae, Podosphaera xanthii, and Golovinomyces orontii (Trecate et al, 2019;Cao et al, 2021). In molecular level, heat shock proteins (HSPs) resisted the effects of heat stress by protecting proteins from aggregation and degradation in many fungi (Tiwari et al, 2015).…”

Identification of Climate Influence on Upas Fungus (Corticium sp.) Disease Intensity on Rubber Plants (Hevea brasiliensis Muell.Arg.)

“…Without one of the following three fundamental circumstances, infectious illness cannot develop: (i) an appropriate habitat, with the most crucial environmental parameters being the amount and frequency of rainfall or heavy dews, relative humidity, and air and soil temperatures; (ii) the presence of a virulent pathogen; and (iii) a susceptible host [17].…”

Recognition of Rubber Tree Powdery Mildew Based on UAV Remote Sensing with Different Spatial Resolutions

“…Powdery mildew (PM) is the main infectious disease of rubber trees, caused by Oidium heveae B.A (OH) Steinmann, and it has been widely distributed in all rubbergrowing countries since the disease was first detected in Java, Indonesia, in 1918 [3]. PM can reduce the photosynthesis of rubber tree leaves and slow down the growth rate of rubber trees, and when the infection is severe, it causes secondary leaf drop on rubber trees, Drones 2023, 7, 533 2 of 20 leading to a delayed harvesting period and reduced natural rubber yield by up to 45% [4,5]. Some studies have shown that the rate of natural rubber yield loss is highly correlated with the severity of PM [6].…”