Association of morphological and biochemical features of mulberry lines with resistance to bacterial leaf spot

Abstract

Xanthomonas campestris pv. mori causes bacterial leaf spot (BLS) of mulberry (Morus spp.) worldwide. Twenty mulberry lines with contrasting response to BLS showed significant (p < 0.01) variation between resistant and susceptible groups for stomata frequency (SF), trichome density (TD), total soluble sugar (TSS) and polyphenol (PP) content, while non-significant for chlorophyll content. Heritability (broad-sense) estimates obtained from the variance component analysis were high (≥0.72) for these traits. The disease severity index values of the lines were significantly negatively correlated with TD (r = −0.66; p < 0.01), TSS (r = −0.73; p < 0.01) and PP (r = −0.61; p < 0.01), while positively correlated with SF (r = 0.65; p < 0.01). The cluster analysis was based on highly significant four variables and DSI values, and classified the lines into two major clusters. The resistant lines that come under cluster-I had high TD, TSS and PP, while those in susceptible category had high SF in cluster-II. These findings suggest that direct selection for SF, TD, TSS and PP will be effective for development of host resistance against BLS in mulberry.