Leaf area is an important factor that has effects on sugar beet yield. Estimation of maximum leaf Area Index (L.A.I) and it’s occurrence time for different cultivars are considered as important selection criteria for breeders. There are several methods for estimation of L.A.I. Some of these methods are difficult or time consuming. Therefore they are not practical. Some methods need accurate instrument and as a result are not usable in certain circumstances. There are some mathematical methods that haven’t reliable precision for estimation of single leaf area or a few leaves areas. This investigation demonstrated that, if the number of leaves for estimation of L.A.I exceeds one hundred, the error of estimation will be less than + 1 percent. The area of leaf depends on plant ploidy level. This study has been conducted using a population of mixed: 2n, 3n and 4n ploidy levels. Following equations have been found for each sugar beet leaf group.
Y=6.4736 + 0.84138 L.W L < 16 centimeters
Y=-201.02558 + 12.404 L + 12359 W L > 16 centimeters
In the above equations Y is leaf area in cubic Cm, L is the highest length of leaf in cm and W is the largest width of leaf in Cm.
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