No abstract

The application of molecular methods as complementary or alternative methods can help identifying the plants containing the resistance gene at genotypic level. Therefore, DNA markers can be useful tools for selecting resistant genotypes and can save the evaluation time and improve the precisions. Selection takes productive and genetic lines resistant to nematodes have been known in sugar beet genotypes by Polymerase chain reaction (PCR). Sugar beet (Beta vulgaris L.) is the greatest vital crops that standing following to sugar cane as sugar crop in the world, later it produces about 20 % of sucrose production annually in the world. In Egypt, Sugar beet is cultivated in 523188 faddans with an average production of 20.7 tons per faddan. Recently, reclaimed desert irrigated lands at West Nubaryia and El-Bostan regions has shown that sugar beet can be successfully grown under sandy soil area condition and its considered as the extended area for sugar beet production in Egypt. The most serious problem against sugar beet extension in new lands is root-knot nematode, Meloidogyne incognita and Meloidogyne javanica which were reported as major nematode pests of sugar beet in Egypt. Importance of employed resistance nematode sugar beet genotypes (cultivars/hybrids) in infested areas has a great concern.The present study was carried out during the growing season 2015 -2016 at pots experiment in Sabahia Agricultural Research Station, Alexandria, Egypt, for evaluating the reaction of seventeen sugar beet genotypes against the most serious nematode, (Meloidogyne incognita). The seventeen sugar beet genotypes tested in this test were twelve sugar beet commercial varieties, three sugar beet inbred lines and two sugar beet breeding materials. Computed damage index classified the seventeen sugar beet genotypes into five categories according to the varietal assessment. (Four were resistant(R), three were moderately resistant (MR), six were tolerant (T), two were susceptible (S) and two were hyper susceptible (HYS)). The results for conventional PCR indicated that genes of Hs1pro-1and HSPRO2 shows resistance to, (Meloidogyne incognita) beside the known function of these genes as resistant against cyst nematode (Heterodera schachtii). Mi-1.2 gene consider resistance to root knot nematode (Meloidogyne incognita) was found in (Mi-3) inbred line.

Filtrates of several fungi (Arthrobotry oligospora, Dactylella brochopage, Nematochomus concurrence, Fusarium exsporium, Trichoderma harzianum and Varticillium chlamydosporium) and bacteria (Bacills cereus, B. thuringiensis, Psendornonas fluorescens and Serratia odorifera) as biocontrol agents were tested for their nematicidal against the root-knot nematode, M. javanica infecting sugarbeet plants, as well as for their effects on yield and quality parameters. These microbial filtrates were applied as soil drench at the three concentrates (50, 75 and 1000%). Results showed that all fungi and bacteria filtrates significantly reduced the numbers of nematode population and reproduction factor comparing to the check treatment. The reduction percentage of nematode counts and reproduction factor was affected by microbial filtrate type and concentration used. Enhanced reduction followed increased concentration in each microbial filtrate. Moreover, root, leaves and sugar yields, as well as quality characters (i.e. T.S.S., sucrose and purity %) were also significantly increased. Among the fungi filtrates, V. chamydosporiusm filtrate at the highest concentration recorded the maximum effect in reducing number of nematode population and reproduction factor. Also, the highest increase percentages of leaves, root, sugar yields and sucrose, T.S.S and purity% were obtained at the highest concentrations of V. chlamydosporium. In case bacteria filtrates, the highest reduction of nematode population and reproduction factor as well as, the greatest root and sugar yields increases were achieved at the highest concentration of B. cereus and S. odorifera, filtrates. Generally, the plants treated with V. chlamydosporium, B. cereus and S. odorifera filtrates had less nematode population and higher productivity of sugarbeet than those plants treated with the other tested microbial agents. In addition, these filtrates had nearly the same effect of the nematicide, Oxamyl on root-knot nematode, M. javanica. Also, these biocontrol agents are ecological sound, economical viable and partial substitutes for costly and pollution causing chemical nematicides and have been a successful instead of these chemical nematicides management strategy when used alone or in combination with other strategies.

Water shortages have increased growers interest to investigate the effects of deficit irrigation (DI) levels, i.e. 25, 50 and 75% of irrigation water requirement (IWR) compared with the full irrigation level (100 % of IWR) on sugarbeet productivity and on final population size (p f) and reproduction factor (RF) of root-knot nematode, Meloidogyne incognita, as well as on water use efficiency (WUE) at the end of growing season, under greenhouse conditions. Results showed that DI at the levels of 25, 50, and 75% of IWR decreased significantly yield characters (root and gross sugar yields) and sugar percent of sugarbeet, and increased WUE compared to full irrigation level (100%) treatment, without significant difference between 75 and 100% DI levels in root yield. The yield characters were greatly reductions at DI levels of 25 and 50% of IWR. Among the irrigation levels treatments, WUE was lowest in the 100% irrigation level and highest in the 25% irrigation level. Also, the results indicated that the p f and RF were significantly lower at irrigation levels of 25, 50, and 75% than 100% level. The 75% irrigation level caused minor reductions in root yield, gross sugar yield and sugar percent, but significantly reduced nematode infection (p f and RF) compared to 100% irrigation level. Thus, deficit irrigation to level of 75% of IWR can be utilized to the management of root-knot nematode, M. incognita infection without significant reduction in sugarbeet yields.

Four amino and organic acids, L-arginine, L-glutamic (as amino acids), ascorbic and salicylic (as organic acids) solution applied as soil drench in three concentration levels to evaluate for nematicidal effects against root-knot nematode, Meloidogyne javanica infecting sugarbeet. Their effects on sugarbeet yield and its components and quality parameters were determined. All of the tested compounds reduced the number of juvenile larvae in soil, immature stages, mature females in root, final nematode population as well as reproduction factor, comparison to the check treatment. These compounds were mostly variable in their effectiveness in reducing nematode infesting or reproduction factor and enhancing plant yield and quality according to compounds type and concentration level used. Then, the percentage of reduction in nematode parameters or/and the increases in crop parameters increased by increasing the concentration level of each tested compound. The ascorbic acid was more effective in reducing nematode fecundity, final nematode population and reproduction factor followed by salicylic acid, L-arginine acid and L-glutamic acid in a descending order. Also, the ascorbic acid component showed the best results in improving leaves, roots, sugar yields and quality parameters of sugarbeet in comparison with the other tested compounds. In comparing between the effects of both ascorbic acid and nematicide, Oxamyl on nematode development and reproduction factors as well as productivity of sugarbeet, the ascorbic acid recorded reduction in juveniles larvae in soil, final population number and reproduction factor with values of 76.3, 71.6% and 2.1 fold, respectively as well as increases in root yield and sugar yield with values of 65.73 and 126.51%, respectively, however, Oxamyl recorded reduction to 73.6, 77.3% and 1.9 fold in juveniles in soil, final population number and reproduction factor, respectively as well as increases to 68.09 and 124.12% in root and sugar yield, respectively. The problems associated with nematicides application turned the workers view to focus on new strategies or use new safe components or chemicals for nematode management program. On the other hand, it was obvious from the obtain data, the

The objectives of this study were to determine the effect of inoculum level, inoculation date, assessment date and inoculum type, on evaluating M. incognita resistance in sugar beet, and to optimize the resistance screening technique used to categorize root-knot nematode resistant sugar beet cultivars under the greenhouse conditions (25±2.5°C). A series of greenhouse tests were done using seven sugar beet varieties with three levels of resistance to M. incognita. The three resistance levels could be separated based on gall indices as early as two weeks after inoculation (WAI) using 6000 eggs of M. incognita per plant. Results indicated that based on gall index, low inoculum level (500 and 1000 eggs/ plant) could separate four sugar beet varieties from each other only on the fourth assessment date (8 WAI) for inoculum level 500 eggs/ plant and on the third assessment date (6 WAI) for 1000 eggs/ plant inoculum level. Harvest date affected galling in sugar beet roots (P ≤ 0.001); there was a significant interaction of harvest date × variety (P ≤ 0.001), the increase of gall index was greater for variety Elan than for the other tested verities.Based on galled area index, the resistant and susceptible varieties could be separated successfully as early as 2 WAI. At the highest tested inoculation level (12000 eggs/ plant), but it couldn't be separate between the moderately resistant and the susceptible or between resistant and moderately resistant ones at P ≤ 0.001. Based on eggs per gram root, the four sugar beet varieties with three levels of resistance to M. incognita were separated at the inoculation rate of 8000 eggs/ plant by 6 WAI and at 500, 1000, 2000, 4000 and 12000 eggs/plant by 8 WAI. In addition to gall number, gall index, galled area index, eggs per gram root, egg mass number and egg mass index were also used to assess the resistance levels in the sugar beet varieties. Gall index was found to be the most sensitive method of all measures used for assessing resistance. Inoculum type i.e. eight thousand eggs and 2000 J2 did not result in significant differences in galled area index at the two investigated harvest dates. Plant age at time of inoculation affected gall development on the tested sugar beet varieties however; the effects on Av poly, Lados and M 9680 were not as great as on Del 939 and Elan. But, the same tested verities could not be separated into their appropriate resistance categories with inoculation at 0 and 40 day after planting.The importance of such study is the identification of a rapid method for assessing resistance in sugar beet varieties to root-knot nematodes, takes less than 100 days.

Four experiments were carried out in West Nubariya region ; two of them were field trials and the other two were outdoor pots trials throughout seasons of 2009/ 2010 and 2010/ 2011 that to evaluate a collection of M. javanica susceptible sugar beet varietiess for differing levels of yield decline (tolerance), their tolerance to parasitism by this nematode. If nematode tolerant (low yield decline) but susceptible (high nematode reproduction) sugar beet varieties can be identified, they could be grown rather than intolerant varieties to reduce yield loss. The yield potential and percentage yield loss to M. javanica were measured in 15 sugar beet varieties in

Sugar beet productivity is highly constrained by the root-knot nematode (RKN) Meloidogyne incognita. Eight sugar beet genotypes were screened under greenhouse conditions for their susceptibility to M. incognita according to an adapted quantitative scheme for assignment Canto-Saenz’s host suitability (resistance) designations (AQSCS). Besides, the degree of susceptibility or tolerance of the examined genotypes was recorded by the modified host-parasite index (MHPI) scale based on yield performance. In addition, single nucleotide polymorphism (SNP) also determined. Sugar beet genotypes have been classified into four categories for their susceptibility or tolerance according to the AQSCS scale. The first category, the moderately resistant (MR) group implies only one variety named SVH 2015, which did not support nematode reproduction (RF≤1), and had less root damage (GI≈2). Second, the tolerant group (T) involving Lilly and Halawa KWS supported fairly high nematode reproduction (RF>1) with relatively plant damage (GI≤2). Whereas the susceptible (S) category involved four varieties, FARIDA, Lammia KWS, Polat, and Capella, which supported nematode reproduction factor (RF>1) with high plant damage (GI>2). The fourth category refers to the highly susceptible (HYS) varieties such as Natura KWS that showed (RF≤1) and very high plant damage (GI>2). However, the MHPI scale showed that Lammia KWS variety was shifted from the (S) category to the (T) category. Results revealed significant differences among genotypes regarding disease severity, yield production, and quality traits. The SVH 2015 variety exhibited the lowest disease index values concerning population density with 800/250 cm3 soils, RF=2, root damage/gall index (GI=1.8), gall size (GS=2.3), gall area (GA=3.7), damage index (DI=3.4), susceptibility rate (SR=2.4), and MHP index (MHPI=2.5). However, Lammia KWS showed the highest disease index values regarding population density with 8890/250 cm3 soils, RF= 22.2, GI= 4.8, and SR= 14.1. Meanwhile, Natura KWS the highest GS, GA and MHPI with 7.1, 8 and 20.9, respectively. The lowest DI was achieved by Capella (DI= 6) followed by Lammia KWS (DI= 5.9). For yield production, and quality traits, SVH 2015 exhibited the lowest reductions of sugar yields/beet's root with 11.1%. While Natura KWS had the highest reduction with 79.3%, as well as it showed the highest reduction in quality traits; including sucrose, T.S.S, and purity with 65, 27.3, and 51.9%, respectively. The amino acid alignment and prediction of the DNA sequences revealed the presence of five SNPs among all sugar beet verities.