The objective of study to estimate genetic variability of some traits in the Egyptian sugarcane breeding program under different harvesting ages (10, 11, 12 and 13 months. Four promising sugarcane verities (C57-14, C203-8, G2003-47 and G99-160) and check cultivar (GT54-9) were evaluated for yield and juice quality traits and genetic parameters were measured in plant cane and first ratoon under Upper Egypt conditions at Kom Ombo Agricultural Research Station, (latitude of 24.28°N and longitude of 32.57°E), Aswan Governorate, Egypt during 2014/2015 and 2015/ 2016 seasons. The experimental design was a split plot with three replications. Harvesting ages were arranged in the main plots, whereas; the sub-plots were devoted to the promising sugarcane varieties. The results indicated that harvest age at 13 months recorded the highest mean values of most studied traits, but harvesting age at 13 months not significantly increased cane and sugar yield compared with harvesting at 12 months. The promising sugarcane variety G2003-47 recorded the highest value of all traits compared with other varieties and the commercial variety GT 54-9 in both seasons. Results showed that high genetic variance (σ 2 g) relative to environmental variance for all traits under study across seasons. Moderate values of genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) were coupled with high heritability for brix, sucrose, richness, sugar recovery and sugar yield. The Highest values of PCV and GCV % across seasons were observed for reducing sugar (54.310% and 47.221%) followed by sugar yield (19.846% and 19.238%), respectively. Heritability estimates across seasons exceeded 80% for all studied traits, except for purity (75.728%) and reducing sugar (75.596%). Finally, this study recommends harvesting age 12 or 13 months because there was no significant increase in cane and sugar yield (ton/fad).

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Sugarcane has been cultivated in Egypt since 641 AD and is a source of raw material to various agro-based industries. The development of new varieties of sugarcane from controlled crosses in Egypt has developed greatly during recent decades with the majority of the present commercial varieties originating from the local breeding program. Egyptian sugarcane breeding program objectives are high cane and sugar yield, early maturing, good ratooning ability, resistance and tolerance to pests as well as diseases. This program depends on artificial flowering at Giza Research Station (latitude of 30.01° N and longitude of 31.20° E) and natural flowering at Sabahia Research Station, Alexandria (latitude of 31° 12 N and longitude of 29.57° E). There are four stations for selection trials, extending from middle to southern Egypt, namely Mallawi (Minia governorate), Shandaweel (Sohag governorate), Mattana Station (Luxor governorate), and Kom Ombo (Aswan governorate), respectively. Current sugar production in Egypt is about 2.458 million tons with 62.2% from sugar beet and 37.8% from sugarcane.

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This study was conducted at El-Mattana Agricultural Research Station, Luxor Governorate, Egypt (latitude of 25.17° N and longitude of 32. 33°E) on three sugar crop cycles 2017/18 (plant cane crop), 2018/19 (the first ratoon) and 2019/20 (the second ratoon) to screen sugarcane genotypes for yield, quality and borer resistance, also estimates the relationship among agronomical and pathological traits based on principal components biplot analysis. Results revealed that significant differences among sugarcane genotypes in susceptibility to the lesser sugarcane borer, Chilo agamemnon infestation measured as bored stalk%, bored joints %, girdled stalks%, mean no. holes/joint, mean no. holes/bored joint and mean no. holes/stalk in the three studied seasons. In plant cane and first ratoon seasons the genotype L 62-96 exhibited the highest bored stalk %. While, in the second ratoon, the genotype G.T.54-9 was recorded the highest bored stalk %. Three genotypes (F. 150, M 57-35 and G. 2008-20) were the most tolerant in plant cane season recording the lowest bored stalk%. While, in the 1 st ratoon season, EH88/5-27 and SP72-5181 genotypes were recording lowest bored stalk%. Meanwhile, in the 2 nd ratoon season, SP 81-3250, F. 150, F 161 and G. 2007-61 genotypes were recording lowest bored stalk% respectively.