Sorghum farmers in the semiarid tropics will have less risk of crop failure and better quality livestock fodder once scientists at the ICRISAT perfect a way to allow the plant to stay green longer by delaying its aging.
Plants that stay green longer seem to provide more nutritious leaf and stem fodder for cattle feed, and are probably better equipped to survive drought at the end of the growing season.
ICRISAT physiologists say the key to delaying aging in sorghum is the stay-green character, which reduces the loss of protein from sorghum leaves and allows a greater accumulation of starch during the later stages of grain filling.
Although most stay-green research has been done on temperate climate sorghum, ICRISAT scientists are studying the physiological expression of the trait and its genetic control in tropical sorghum to develop improved stay-green genotypes for the semiarid tropics.
Green leaf area duration, or GLAD, is the cumulative green leaf area a plant accumulates from flowering to final senescence, or aging. It is shown in three components -- leaf area at flowering, time of onset and rate of aging. ICRISAT scientists note that the progeny from a crossbred has the same level of these leaf area and rate of aging traits as its best parent. From the time of onset of aging, the genetic effects are additive -- somewhere between that of the two parents.
As a result, the inheritance of green leaf area duration showed that individual hybrids had higher GLAD values than their best parent. Breeding for stay-green should therefore be relatively easy because separate components of GLAD can be manipulated in specific crosses, ICRISAT scientists report. They contend cultivation of stay-green varieties, once available, can benefit farmers by