Surveillance on Corynespora Leaf Fall Disease: Incidence and Severity on Natural Rubber (Hevea brasiliensis) in Certain Hot Spots Areas in Kerala

Abstract

Survey on corynespora leaf fall (CLF) disease was undertaken in the hot spot areas in Thodupuzha and Kothamangalam regions of Idukki and Ernakulam districts respectively in Kerala for 3 years from 2011 to 2013. During this survey two aspects were covered; the number of units infected in a given village which was expressed in per cent disease incidence and the disease severity that was expressed in Per cent Disease Index (PDI). The study revealed that in 2011, Nalpathu Acre of Neyassery village in Thodupuzha region registered maximum disease incidence (85%) and PDI of 47.15. In Kothamangalam region, Varapetty and Kanjiravelli villages registered 100 % disease incidence. In this region, maximum PDI (38.0) was observed in Pinavoorkudy. In 2012, the disease incidence was on rise as reflected by more number of units being infected in Nalpathu Acre (90%) in Thodupuzha region while Kadavoor, Varapetty and Kanjiravelli villages of Kothamangalam region registered 100 % disease incidence. However, there was a sharp decline in disease severity as maximum PDI (13.9) was registered in Nalpathu Acre whereas it was 22.5 in Varapetty village of Kothamangalam. In 2013, the disease incidence remained constant (90%) in Nalpathu Acre. However, the other four villages in Todupuzha region showed increasing trend in disease incidence. The Kothamanagalam region gave almost same trend as that of 2012. The disease severity too gave almost similar trend as that was noticed in 2012. These two regions where the disease was prevalent are surrounded by forest which may be contributing to the disease development. The immature phase of most popular clone RRII 105 was very much prone to the disease while in other clones like PB 260, RRII 414 and RRII 430 the disease was negligible to less. The disease was severe mainly in February/March months and it was declining thereafter. The probable reason for the decline in disease 2012 and 2013 is immediate plant protection measures taken up by the growers.

Guarding the ridge gourd: Characterization and in vitro management of Phytophthora nicotianae causing fruit rot of Luffa acutangula in North Kerala

“…Occurrence of this pathogen in ridge gourd was common during the warm, humid climate with frequent rains. These findings agreed with reports by Chowdappa et al (2016) [1] on ridge gourd and Sharma and Sohi (1975) [20] , Singh (1999) [25] , Gupta and Paul (2001) [6] , Housebeck (2004) [7] , Granke (2012) [4] , Shankar et al (2014) [21] and Panabieres et al (2016) [14] , in other vegetable crops. Our findings validate the positive correlation between warm, humid climatic conditions and the fruit rot disease.…”

“…6). The above findings matched with Mushrif et al (2005) [11] , who tested five bacterial antagonists (two Bacillus spp. and three Pseudomonas spp.)…”

Sensitivity of Hevea brasiliensis clones to isolates representing distinct races of the Corynespora cassiicola pathogen

“…Screening of available sources for resistance is the pre‐requisite to identify the genes responsible for resistance and incorporate them into the desirable clone. Several screening studies using clones from different countries have been reported (Atan et al., 2011; Chee, 1988; Fernando, Jayasinghe, Wijesundera, Silva et al., 2010; Fernando et al., 2019; Manju et al., 2001, 2010; Mushrif et al., 2020; Nghia et al., 2008; Shuib et al., 2015). However, there is much dissimilarity among the reports.…”

“…However, the clone PB 260 was reported to have shown no sign of infection in the bud wood nurseries and plantations in Sri Lanka (Fernando, Jayasinghe, Wijesundera, Silva et al, 2010;Fernando et al, 2019). Recent field observations in Kerala, the southern state of India, also confirmed the lack of infection (Mushrif et al, 2020). In the bud wood nurseries and plantations, the rubber plants are exposed to one or more strains of the pathogen and will be influenced by the climatic conditions.…”

“…Race 1 was discovered to infect the older H. brasiliensis clones, while Race 2 was found to infect the newer clones (Atan & Hamid, 2003). Different clones of H. brasiliensis show a varying degree of susceptibility and resistance towards different isolates (Achuo et al., 2001; Atan et al., 2011; Chee, 1988; Fernando, Jayasinghe, Wijesundera, Silva et al., 2010; Fernando et al., 2019; Manju et al., 2001, 2010; Mushrif et al., 2020; Narayanan & Mydin, 2012; Nghia et al., 2008; Shuib et al., 2015).…”