Eight of forage sorghum genotypes were screened for their resistance against downy mildew disease during 1997 - 1999 growing seasons. In addition, a silage group (26 genotypes) also were evaluated during 1996 – 1999 seasons in the downy mildew disease nursery.
Seven and two selected genotypes from the first and second groups in respect, plus local hybrid-102 as a check, were sown in a field trial for the evaluation of their productivity during 1998 and 1999. A randomized complete block design with four replications was used.
The reaction of selected forage sorghum genotypes (7 genotypes) plus local hybrid-102 against the disease were ranged from highly resistant and resistant during the tested seasons. While, out of 26 silage sorghum genotypes, nine genotypes proved to be highly resistance, one genotype was resistant, the rest of silage genotypes were ranged from susceptible and highly susceptible to the disease, during 1996 and 1997 seasons.
The studied crop parameters were: plant height, stem diameter, fresh and dry leaf/stem ratio, dry matter percentage, crude protein content and fresh and dry forage yield.
The study gave evidence to the presence of significance among the tested genotypes in regard to the concerned parameters. Aon 404 and local hybrid-102 were the tallest plants at most cuts during the two seasons. The previous two genotypes plus MN 1279 exhibited the highest stem thickness in most cases. On the other hand, the genotype G.D. 47819 was distinctive in fresh and dry leaf/stem ratios with few exceptions. Genotypes IS 641, GD 47821 and MN 1279 exhibited the lowest level of dry matter percentage particularly at the first and second cuts during the two seasons.
The highest total fresh yield was recorded with Aon 404 and MN 1279 during 1998 and local hybrid-102 during 1999 growing seasons. Whereas the highest combined total fresh yield was recorded with MN 1279. As regard to total dry forage yield, Aon 404 and local hybrid-102 were superior during 1998 and 1999, respectively. The two genotypes gave best results regarding the combined total dry yield through out the two seasons. They gave also high crude protein content at the three cuts in both seasons. However, GD 47819 genotype had the highest crude protein content at all cuts in the two seasons.
General speaking, the genotype Aon 404 could be recommended as forage yield production as compared to the local hybrid 102. However, MN 1279 can serve as fodder yield production. Moreover, the selected nine genotypes could be utilized in the breeding program as parents for downy mildew resistance.