Field assessment of pomegranate germplasm for bacterial blight (Xanthomonas axonopodis pv.punicae) resistance.

Abstract

Bacterial blight (Xanthomonas axonopodis pv punicae) is an important disease of pomegranate affecting yield drastically (60-80% losses) in major pomegranate producing states of the country. At present, no commercial variety resistant to bacterial blight is known, thereby, impeding the impact of prevailing management practices to some extent. With a view to identify suitable resistance source , germplasm maintained at the field gene bank of the NRCP Solapur was screened for comparative bacterial blight reaction. In all 63 germplasm were assessed for bacterial blight development on disease scale of 1 (<10% severity) to 5 (> 75% severity) during 2008-09 and 2009-10. Disease severity was recorded during three different months of the year and germplasm categorized into three groups (Less susceptible, Moderately susceptible and Highly susceptible) on the basis of pooled severity. Although disease assessment was made during two consecutive years , screening performed in 2008-09 appeared more appropriate due to prevalence of conducive meteorological conditions (prolonged rains from June to November 2008) resulting in rapid blight development. Study revealed that out of 63 germplasm screened, 5 germplasm revealed partial resistance (<5.5 disease severity) , 34 were moderately susceptible (>5.5% to <18.0% severity) and 24 germplasm were classified as highly susceptible (> 18.0% disease severity). Five germplasm accessions grouped under partial resistant category included IC-1182, IC-1198, IC-1199, IC-1205 and Nana and were observed significantly less susceptible (partial resistant) than other germplasm categorized as moderately susceptible (Jyothi, P-26, G-137, Ganesh, Kalpitya etc.) and highly susceptible (commercial varieties like Bhagwa, Mridula, Arakta, and accessions Gulesha red etc. ). The 5 germplasm revealing partial resistance expressed as reduced infection of plant by blight bacterium could be an important source of resistance for further conventional / molecular breeding programmes to develop disease resistant varieties, thereby, providing a long term strategy in improving the effectiveness of prevailing Integrated disease Management (IDM) programmes.