5.1.21
STUDIES ON PRE-HARVEST POD ROT OF GROUNDNUT (ARACHIS HYPOGAEA) CAUSED BY SPECIES OF FUSARIUM

SS ADIVER1 and KH ANAHOSUR1

1AICRP, University of Agricultural Sciences, Dharwad 580 005, Karnataka, India

Background and objectives
The pod rot disease of groundnut caused by Fusarium [1] is a problem in summer cultivated crops in northern parts of Karnataka. Many of the fungi cause diseases of root, pod and fruit which later bring about spoilage of produce [2]. In order to investigate this emerging problem, on which information is scanty, the study was carried out during summer of 1992-94.

Results and conclusions
The survey revealed the widespread prevalence of pod rot in all the summer seasons (1992, 1993 and 1994). The disease was found concentrated in many groundnut-growing localities. The isolations from infected pod shell yielded more frequently and consistently Fusarium spp. Among two dominant Fusarium spp. recovered from infected pods, F. solani was found more abundantly than F. oxysporum. Shell isolations yielded high frequency of pod rot fungi, while kernel isolations were limited. The symptoms of pod rot in the case of F. solani were characterized by black discoloration with irregular rotted patches on the surface, while F. oxysporum infection imparted a purple tinge to the rotting pod accompanied by profuse shredding of the shell and consistent cracking. Levels of inoculum of 15 and 20%, soil moisture range of 5-20%; increase of sand fraction in soil, a temperature of 30C and mature pod stage favoured the development of the disease by F. solani.

The Fusarium isolates obtained from the locations exhibited significant variation in their growth with respect to culture media, carbon and nitrogen sources and pH. They also varied significantly with regard to peroxidase and polyphenol oxidase zymogram patterns. Furthermore, the serological variations were significant among the isolates. Root exudates from seedlings of kidney bean, castor and chilli were inhibitory to the growth of Fusarium. The groundnut genotypes ICG-11285 and R-8972 were less prone to the attack of Fusarium. Addition of farm yard manure (250 g/pot) alone or when integrated with Trichoderma harzianum ( 250 g/pot) before planting were effective in reducing the disease.

References
1. Mercer PC, 1977. Plant Disease Reporter 61, 51.
2. McDonald D,1970. Transactions of the British Mycological Society 54, 453-460.