Assessment of som (Persea bombycina) clones for resistance against Phyllosticta persae

Abstract

Som (Persea bombycina) is an economically important tree used as food source by the muga silkworm, Antheraea assamensis. Phyllactinia leaf spot (PLS), caused by Phyllosticta persae, affects all som cultivars during June to September (rainy season) and is responsible for foliage losses up to 26%. Information about the effect of this disease at the farmer level and host resistance is lacking. PLS severity was assessed in six major sericulture areas of Assam, India. Furthermore, eight clones were evaluated for resistance in experimental field trials. Disease incidence and severity index (DSI), area under disease progress curve (AUDPC), apparent infection rate, lesion diameter and frequency all indicated differences among clones. DSI and AUDPC values were 3.6 fold and 4.2 fold higher in the most susceptible accession M-8 compared to M-5. High broad sense heritability (h 2 = 0.80) of DSI suggested an additive nature of resistance. Correlations of DSI (r range: 0.55 to 0.91) with other parameters provided a good empirical evidence of obtained PLS responsiveness. M-5 showed partial resistance on the basis of all measures and appeared as the most diverse accession based on Euclidean distance. These results suggested that clone M-5 may be a potential source of resistance for use in PLS breeding programs.

Evaluation of Gladiolus Genotypes for Resistance to Different Isolates of Fusarium oxysporum f. sp. gladioli

“…gladioli, growth and corm yield parameters. Cluster analysis was used to analyze the effect of different pathotypes of Verticillium dahlia on various olive cultivars (Calderón et al, 2014) and assessment of som (Persea bombycina) for resistance against Phyllactinia leaf spot disease (Chattopadhyay et al, 2014).…”

“…AUDPC takes into account disease severity in a timeline, while disease incidence percentage are calculated based on data collected at a single point of time. Since AUDPC embodies the interaction of host, pathogen and environmental effects during the disease development, assessment of AUDPC would be crucial for evaluation of disease resistance in plants (Chattopadhyay et al, 2014). Pouralibaba et al, (2015) claimed that plants with lower AUDPC shows delayed symptoms and suffer less during the infection and that AUDPC is informative in assessing the level of resistance in plants against various diseases (Meles et al, 2004).…”