Corynespora Leaf Blight of Cotton in Brazil and Its Management

Abstract

In recent years, Corynespora leaf blight is on the increase in cotton and has become an important disease in the State of Mato Grosso, Brazil. It attacks several plant species including soybean. It is not yet known whether the same strain of this pathogen attacks both the crops. The objectives of the present investigation were to verify the genotypic and phenotypic variation between the isolates attacking cotton and soybean and to verify the sources of resistance in cotton. Differential response of 23 cotton genotypes was studied under glasshouse conditions using mixture of two randomly selected isolates of C. cassiicola of cotton in equal proportion. Genotypic variation among three cotton and two soybean isolates was studied using ERIC/REP-PCR and rDNA molecular techniques. With one exception, all the cotton genotypes tested so far were susceptible to C. cassiicola isolates of both cotton and soybean. Similarly, results of both molecular techniques indicated that the C. cassiicola isolates attacking cotton and soybean belong to the same strain of the pathogen in Brazil. Since Corynespora blight is a newly immerging disease of cotton and soybean in Brazil, integration of crop rotation and the sanitary practices are suggested to manage the disease.

Clonality and geographic structure of host-specialized populations of Corynespora cassiicola causing emerging target spot epidemics in the southeastern United States

“…Isolates of C . cassiicola isolates from cotton and soybean in Brazil share the same group and are genetically similar to the isolates from soybean in the southeastern U.S. Isolates that were genetically identical, based on ERIC/REP-PCR and rDNA molecular techniques, were reported to cause target spot outbreaks on cotton and soybean in Brazil [ 20 ]. Our results support the finding that soybean and cotton epidemics of target spot in Brazil may be caused by the same populations, which are similar to soybean populations in the U.S., but different from cotton populations in the U.S. Additional isolates need to be assessed to determine whether these genotypes are representative of the overall population causing the epidemics in Brazil.…”

“…Corynespora casssiicola (Berk & Curtis) Wei is causing target spot epidemics on cotton ( Gossypium hirsutum ) [ 10 – 15 ], soybean ( Glycine max ) [ 16 – 18 ], and tomato ( Solanum lycopersicum ) [ 19 ] in the southeastern U.S. Moreover, target spot epidemics on both cotton and soybean have become severe in Brazil [ 20 ] where these crops are also widely grown. The phylogenetic diversity and host specialization of C .…”

Prevalence of Fungal Phytopathogens on Transgenic Bt Cotton Plant: Isolation and Characterization

“…c Sporulation was measured after 7 days of incubation at 28 . (Bashan et al, 1991, Galbieri et al, 2014.…”

The fungal pathogen Corynespora cassiicola: A review and insights for target spot management on cotton and Soya bean

“…In 1995, target spot was reported on upland cotton in Brazil but under the name Corynespora leaf spot (Mehta et al., 2005). The first occurrence and re‐emergence of the disease on upland cotton appeared from China (Wei et al., 2014), Brazil (Galbieri et al., 2014) and several states in the United States, including Georgia (Fulmer et al., 2012), Alabama (Campbell et al., 2012; Conner et al., 2013), Louisiana (Price et al., 2015) and Tennessee (Butler et al., 2016). Target spot has been a concern for farmers and researchers due to its increasing occurrence especially on Soya bean (Godoy, 2015) and cotton (Sumabat et al., 2018), owing to monoculture farming, adoption of conservation tillage systems, susceptibility of current cultivars, lack of crop rotation and optimal weather patterns for disease development (Avozani et al., 2014; Koenning et al., 2006).…”

“…Frequently, leaf symptoms can be associated with a dull‐green or yellowish‐green halo with a typical ‘target spot’ in the centre. Leaf veins, petioles and stems exhibit dark brown lesions with different shapes and sizes; lesions on pods are usually circular, depressed and dark in the centre with brown margins (Galbieri et al., 2014; Godoy, 2015; Koenning et al., 2006). Symptoms on Soya bean roots include dark reddish‐brown lesions that will turn dark violet‐brown when the fungus sporulates (Godoy, 2015).…”