Abstract
Improving the yield and quality of sorghum ( Sorghum bicolor ) forage for livestock feeding is a major breeding objective, because of sorghum’s inherently high biomass accumulation, high productivity per unit water utilized and its ability to produce a ratoon crop after harvesting of the plant crop. Newly bred sorghum lines, including 36 lines falling in 5 different categories, i.e. 12 experimental dual-purpose lines, 6 germplasm accessions from the ICRISAT collection, 11 commercial varieties and hybrids, 6 forage varieties and 1 bmr mutant line, were evaluated in terms of fodder yield, quality and ratooning ability. The main crop produced more dry biomass (P<0.05) at 80 days after planting (mean 22.87 t DM/ha; range 17.32‒33.82 t DM/ha) than the ratoon crop (mean 8.47 t DM/ha; range 3.2‒17.42 t DM/ha) after a further 80 days of growth. Mean nitrogen concentration in forage did not differ greatly between main and ratoon crops (2.56 vs. 2.40%, respectively) but there was wide variation between lines (2.06‒2.89%). The line N 610 recorded highest N percentage of 2.89%, followed by SSG 59 3 (2.86%) and SX 17 (2.81%). Highest acid detergent fiber % was recorded by ICSV 12008 (42.1%), closely followed by CO 31 and IS 34638 (40.0%). The least acid detergent lignin % was observed in MLSH-296 Gold (3.59%), ICSV 700 (3.75%) and ICSSH 28 (3.83%). Metabolizable energy concentration was highest in N 610, Phule Yashodha and SX 17 (mean 8.34 MJ/kg DM), while in vitro organic matter digestibility ranged from 52.5 to 62.6%. The main crop contained much higher mean concentrations of the cyanogenic glycoside, dhurrin , than the ratoon (639 vs. 233 ppm, respectively) with ranges of 38 to 2,298 ppm and 7 to 767 ppm, respectively. There was no significant correlation between dhurrin concentration and dry biomass yield so breeding and selection for low dhurrin concentrations should not jeopardize yields. Hence, breeding for sorghum can target simultaneously both quality and biomass improvement. Keywords: Cyanogenic glycoside, digestibility, dry biomass production, fodder quality, tillering ability.
Highlights
Sorghum (Sorghum bicolor) is a dual-purpose crop used for both human food and animal feed in many Asian and African countries (Sarfraz et al 2012; Bean et al 2013), with key characteristics being wide adaptability across environments and tolerance to biotic and abiotic stresses (Krishnamurthy et al 2007; Dahlberg et al 2011; Gill et al 2014)
The first sampling from the main crop was performed at 15 cm from ground level from the middle 2 rows excluding borders at 80 days after sowing, and the second sampling 80 days later
Agronomic traits recorded during the experiment were: plant height; tillering ability; ratoon scoring and dry biomass yield
Summary
Sorghum (Sorghum bicolor) is a dual-purpose crop used for both human food and animal feed in many Asian and African countries (Sarfraz et al 2012; Bean et al 2013), with key characteristics being wide adaptability across environments and tolerance to biotic and abiotic stresses (Krishnamurthy et al 2007; Dahlberg et al 2011; Gill et al 2014). The contribution of sorghum as a fodder crop has increased the value of production in recent years, so selection criteria in breeding programs could include biomass production and quality as well as grain yield (Hassan et al 2015). This thinking has been applied in breeding programs with emphasis given to forage quality improvement and selection of nutritious varieties for fodder purposes (Bean and McCollum 2006), as sorghum is the most preferred alternative silage crop after corn (Zea mays) (Kurle et al 1991). Sorghum has good ratooning ability from stubble of the plant crop, which is a desirable trait, as it reduces overall inputs in terms of seed for planting and labor for field preparation (Willey 1990)
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