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542 K Adhikari, K.B. Koirala alld M. SubediStalk rot complex: In a fanner's field in Chitwan about 80% grain yield loss was estimated dueto stalk rot complex (Batsa and Neupane, 1982).Development of disease resistant varietiesGermplasm screening against major diseases of maize has been an integral part of maizeresearch and developoment program in Nepal. In the past, most of the screenings were based on fieldtest under natural disease pressure. These days attempts have also been made through artificialinoculation.Downy mildew: The importance of downy mildew disease was well recognized in the past.However, work on development of downy mildew resistant varieties started only from 197 I byintroducing downy mildew resistant germplasm Thai Compo x Suwan-l from Thailand and throughlACP trials (Lal, 1983). Due to its excellent performance both in research stations and farmers field itwas recommended in 1975 by the name Rampur Composite.Similarly, Philippines DMR-2 (College white x Tuxpeno) was also found high yielding andresistant to downy mildew in lACP trials-2 after extensive testing at research stations and farms. Itwas recommended in the same year (1975) by the name of Sarlahi Seto to meet the long felt need ofwhite maize growing areas of Terai and inner Terai (Lal, 1983) and eastern mid and lower hills.Northern leaf blight: Most of the maize genotypes so far tested were observed susceptible tomoderately susceptible to the disease. However, some genotypes such as BA 932126, Pool 9A andArun-l have been found moderately resistant. At present, efforts have been made to improveManakamana-l for resistance to northern leaf blight (Table 9).Table 9.Improvement cycle of Manakamana-1 maize variety for resistant to H. lurcicum,1989-1996.YearMaterialTotal no. of families testedNo. of selected families1989/90WinterManakamana-l variety(1500 plants were selfed)1990/91Manakamana-l families250481991192312841992/9336151993/9481251994/951995/961996/97Selected families were bulkedMaintenance and seed increaseof bulked materials.Comparative study of resistanceversion of Manakamana-l withother varieties for agronomictraits