Disease reaction of wild relatives of maize to Erwinia stalk rot and Helminthosporium leaf blight
--R.C. Sharma, M.M. Payak and J.K.S. Sachan

Erwinia stalk rot (ESR) caused by E. chrysanthemi p.v. zeae is a major disease, particularly in the plains and hilly regions of India. The disease occurs when the plants are about 40 days old. As the disease causes soft rot, the affected plants die prematurely. Leaf blight caused by Helminthosporium maydis is the most widely distributed disease of maize not only in India but in all the tropical and subtropical regions of the world. Various collections of Coix, Chionachne, Trilobachne and teosinte were evaluated for these two diseases under conditions of artificial inoculations at I.A.R.I. farms during summer.

Table 1. Reaction of Coix, Trilobachne, Chionachne and teosinte to Erwinia chrysanthemi p.v. zeae and Helminthosporium maydis of maize under artificial disease inoculations.
 
Pedigree Origin ESR (%) H. maydis (1-5*)
Cultivated Coix-7 Nagaland 20.0 1.0
Cultivated Coix-8 Nagaland 80.0 1.0
Cultivated Coix-9 Nagaland 60.0 1.0
Cultivated Coix-11 Nagaland 20.0 1.5
Cultivated Coix-13 Nagaland 40.0 2.0
Cultivated Coix-14 Nagaland 60.0 1.0
Wild Coix-24 Matheran 0.0 1.0
Wild Coix-25 Pune 0.0 1.0
Wild Coix-28 Talegaon 0.0 1.0
Wild Coix-29 Dombivili 0.0 2.0
Wild Coix-30 Purander 0.0 1.0
Wild Coix-33 Almora 0.0 2.0
Trilobachne-1 Dang Forest 0.0 1.0
Trilobachne-2 Matheran 0.0 1.0
Chionachne-1 Western Ghats 0.0 1.0
Chionachne-3 Pune 0.0 1.0
Chionachne-5 Kolhapur 0.0 1.0
Teosinte-1 Guatemala 60.0 1.0
Teosinte-2 Mexico 100.0 1.0
Teosinte-3 Mexico 100.0 2.0
Teosinte-4 Mexico 60.0 2.5
_______________
*1 = no disease; 5 = maximum disease

The data obtained were not only interesting but useful. All the collections of Trilobachne and Chionachne were highly resistant to both the diseases tested. Among Coix collections, cultivated ones showed a high degree of susceptibility to ESR, but wild Coix-25 (2n=10) showed immunity to both the diseases. In the case of teosinte also, susceptibility reaction to ESR was observed (Table 1). The information may serve a useful purpose for transfer of disease resistance traits to cultivated maize. 


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