Charcoal rot (Macrophomina phaseolina Tassi G. Goid) of maize is a serious problem under light soil and post-flowering water stress conditions (A Compendium of Corn Diseases. 2nd ed., M.C. Shurtleff, ed.). Since the disease is soil-borne in nature and of senescence stage, chemical control measures show little promise and must be replaced by a strong resistance breeding programme. Genetic differences for resistance have been observed in maize for this disease (Payak and Sharma, Crop Improvement 6:75-85, 1979; Ivaschenko and Verenik, Nauchnoteckn. Byul. Vses. Sel.-genet. Inst. No. 2, 65-69, 1982, Plant Breeding Abstr. 53:6258, 1983). A judicious exploitation of such variabilities lies in identifying the source of resistance and its introgression into the breeding programme. In the present study 25 elite, both exotic (obtained from CIMMYT, Mexico) and indigenous germplasms, were evaluated for charcoal rot to detect a source of resistance to this disease.
The materials were evaluated in 2 years (1981 and 1982 monsoon) with 3 common entries in both years. The field used for the evaluation had sandy, loam soil with a past record of charcoal rot, and has been under maize cultivation for several years. The trial was laid using randomized complete-block design with four replications. Each plot consisted of 4 rows of 5m length, and the row-to-row and plant-to-plant distance was maintained at 75 and 22 cm, respectively. The data were recorded on the basis of percent of plants infected. The symptomatology and pure culture isolation of the pathogen confirmed the involvement of Macrophomina phaseolina in the disease. The statistical analysis was carried out using arcsine transformation.
Among the entries evaluated for both years, Across 7726, a CIMMYT population, showed the highest level of resistance (Table 1). The other promising materials were Poza Rica 7926, Across 7926, Tocumen (1) 7931 and Across 7835, four CIMMYT populations, and J684 and EH400175, two Indian populations. However, these were tested for only one year. The populations showing incidence below 5 percent were termed as resistant, and above 5 percent as susceptible.
The yield potential and maturity of the three materials which were evaluated for both years revealed about a 19% yield superiority of Partap, the indigenous composite, over Across 7726 RE, and 36% over Across 7635 RE. However, Across 7635 RE was earlier than Across 7726 and Partap by 3.5 and 4.5 days, respectively (Table 2).
The above findings reveal that of all the entries, keeping in mind the resistance to charcoal rot, Across 7726 RE, Poza Rica 7926 and Partap seem to be of high promise. Partap, the indigenous composite, possesses a distinctly higher yield potential with a reasonable level of resistance. These materials should be further studied and be incorporated into a resistance breeding programme.
Table 1. Reaction of the germplasm to charcoal rot.
Table 2. Agronomic performance of 3 elite populations.
S.K. Dey, V.K. Saxena, B.S. Dhillon and A.S. Khehra
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