Ajit Kumar Dubedi Anal

Leaf, panicle and fruit blight of litchi (Litchi chinensis) caused by Alternaria alternata in Bihar state, India

Abstract India is one of the leading litchi (Litchi chinensis Sonn.) producing countries in the world. A leaf blight on litchi was observed in April 2012 on nursery plants at Muzaffarpur, Bihar, India. Light to dark brown necrosis starting from leaf tips resulted in complete drying of leaves. Blighting of panicles and fruits were also noticed during April–June, 2014. Panicles dried out as a result of necrosis, while necrosis of pedicels led to complete drying of the rind of developing fruits. Infected tissues collected from different sites in diseased fields were cultured on potato dextrose agar (PDA), and the pathogen was identified as Alternaria alternata (Fr.) Keissler on the basis of morphological and cultural characteristics. The fungus produced greyish-black colonies on PDA with obclavate or obpyriform conidia in chains. Conidia had 1–4 transverse and 0–3 longitudinal septa, and measured 16–40 × 4–13 μm. Morphological identification was confirmed by sequencing the internal transcribed spacer (ITS) region of rDNA using ITS1 and ITS4 primers. Pathogenicity tests indicated that A. alternata infected and caused blights of the leaves, panicles and fruit of litchi. Alternaria alternata has been reported to cause post-harvest decay of litchi fruit, but this is the first report of A. alternata causing blights of leaves, panicles and fruit in the field.

Important Diseases of Litchi and Their Management

Litchi (Litchi chinensis Sonn.) is a juicy fruit belonging to the Sapindaceae family and is one of the most important evergreen fruit trees. Diseases are one of the constraints on the production of litchi fruits. They indirectly reduce yield by debilitating the tree and directly reduce the yield or quality of fruit before and after harvest. Diseases are more important after harvest, although undoubtedly many of the fruits are infected before picking. Some of the pathogens infect leaves, flowers, and fruit, and a few others are associated with tree decline and tree deaths. Some pathogens also affect multiple phenophases of this fruit crop. So far, only diseases caused by fungal pathogens have been reported. This chapter provides information on the major diseases of litchi in terms of their importance, symptoms, and management strategies.