Physiogenetical Studies On Some Citrus Species And Varilmes:

Ahmed Ahmed Resk El-said Atawia

The present investigation was carried out during1985, 1986 and 1987 seasons,in order to study theeffect of cross-pollination and some growth regultorson yield and fruit quality of some citrus speciesand varieties ( Washington navel orange, Jaffaorange, Mazizy orange, Clementine tangarine andAgami lime). The pollination and growth regulatorstreatments used in this study were as follows;-1 - Open pollination ( control ) .2 - Bagging only.3 - Emasculation and bagging.4 - Cross pollination with Balady lime pollen.5 - Cross pollination with Marsh grapefruit pollen.6- Cross pollination with Balady mandarin pollen.7 - Cross pollination with Suckarry orange pollen.8 - Dipping emasculated flowers in a solution ofGA3 at 1000 p.p.m.9 Di ’pping emasculated flowers in a solution ofGA3 at 2000 p.p.m.10 - Dipping emasculated flowers in a solution ofN.A.A. at 25 p.p.m.11 - Dipping emasculated flowers in a solution ofN.A.A. at 50 p.p.m.12 - Dipping emasculated flowers in a solution ofGA3 at 1000 p v p v m , + N.A.A. at 25 p.p.m.13 - D1Hlng emasculated flowers in a solution ofGA3 at 1000 p.p.m. + N.A.A. ar 50 p.p.m.24814 - Dipping emasculated flowers in a solution ofGA3 at 2000 p v p v m , + N.A.A. at 25 p.p.m.15 - Dipping emasculated flowers in a solution ofGA3 at 2000 p.p.m. + N.A.A. at 50 p.p.m.The cytology of chromosomal behaviour and pollenformation and the histology of ovules fertilizationand embryo development were also studied among somecitrus species and varieties to correlate thesevariations to fertility of each.The results of these studies could be summarizedas follows ;-1 - In Washington navel orange, it was found that,Cross-pollination with Balady mandarin and Crosspollinationwith Suckarry orange caused significantincrease in fruit set, remaining fruits afterJune DROP, mature fruits, fruit weight, fruitheight, fruit diameter, juice weight and thenumber of well developed seeds per fruit. Onthe other hand, Cross-pollination with differentpollinators caused significant decrease in T.S.S/acid ratio of fruit juice.GA3 at 1000 p.p.m, GA3 at 2000 p.p.m. andthe combinations between GA3 and N.A.A. treatmentshad resulted in a considerable increasein fruit set, remaining fruits after June DROP,fruits remained to maturity ( yield ), fruitweight, fruit height and fruit shape index.However, T.S.S of fruit Juice and T.S.S / acidratio were significantly decreased.The ascorbic acid content in fruit juicewas significantly increased by GA3 at 1000 p.p.m.GA3 at 2000 p.p.m. and GA3 2000 p.p.m. + N.A.A. at50 p.p.m. treatments.2 - In the Jaffa orange , Cross-pollination withBalady mandarin and Cross-pollination withSuckarry orange increased fruit set, yield,fruit weight, fruit diameter, Juice weight andnumber of well developed seeds per fruit. Thetwo treatments resulted in decreasing fruitshape index and did not affect T.S.S, acidity,T.S.S/ acid ratio or asc(,rblc acid content.On the other hand, GA3 at 1000 p.p.m. , GA3 at2000 p.p.m. and GA3 2000 p.p.m. + N.A.A. 50p.p.m. treatments significantly increased fruitset and yield, while N.A.A. at 25 p.p.m. andN.A.A. at 50 p.p.m. caused significantly decreasedin fruit set and yeld. The treatments ofGA3 at 1000 p.p.m., GA3 at 2000 p.p.m. andN.A.A. at 25 p.p.m. treatments caused in significantincreased of fruit weight, fruit height,fruit shape index, peel thickness, Juice weight.T.S.S, total acidity T.S.S/acid ratio.3 - In the Mazizy orange, Cross-pollination withBalady mandarin and Cross-pollination with5uckarry orange caused significant increase infruit set, yield, fruit weight, fruit height,peel thickness , juice weight and well developedseeds per fruit.The treatments of GA3 1000 p.p.m. , GA3 at2000 p.p.m. and GA3 2000 p.p.m. + N.A.A. ar 50p.p.m. increased fruit weight, fruit height,fruit diameter, fruit shape index, peel thicknessand juice weight but decreased T.5.5/acidratio. On the other hand, treatments of N.A.A.at 25 p.p.m. N.A.A. at 50 p.p.m. fruit juiceincreased fruit set and yield but decreasedfruit weight, and fruit juice acidity.4 - In the Clementine tangarine, bagging only treatmentgave low percentages of furit set and maturefruits than Cross-pollination treatments. Thisresult may indicate that the Clementine tangarineis partial self-incombatibility •Cross-pollination with Balady mandarin and crosspollinationwith 5uckarry orange caused significantincrease in fruit set and yield. Allpollinizers used caused significant increase infruit weight and T.5.5. Cross-pollination withMarsh grapefruit and Cross-pollination with Baladymandarin caused in increasing fruit diameter,peelthickness and fruit juice weight.The treatments of CA3 at 1000 p.p.m. andGA3 at 2000 p.p.m. were significantly increasedfruit set, yield, fruit weight, fruit height,peel thickness and total acidity of fruit Juice.On the other hand, GA3 at 2000 p ,p v m , + N.A.Ao at50 p.p.m. and N.A.A. at 25 p.p.m. caused in decreasingfruit set and yeld.5 - In the Agami lime, All Cross-pollination treatmentsresulted in increasing fruit set, yield,fruit weight, fruit diameter and the fruitsresulting from these treatments seem to be moreflattend. Cross-pollination with Balady limeand Cross-pollination with Balady mandarin causedin significant increase in peel thickness, Juiceweight and well developed seeds per fruit.The treatments of GA3 at 1000 p s p v m , , GA32000 p.p.m. and GA3 1000 p.p.mo + N.A.A. at 50p.p.mo caused significant increase in fruit set,yield, fruit weight, fruit diameter, peel thickness,juice weight and total acidity. Only, GA3at 1000 p.p.m. treatment resulted in significantincrease of ascorbic acid content in fruit Juice.I6 Generally, it was found that, the emasculationand bagging treatment did not give any maturefruit in Jaff orange, Mazizy orange, Clementinetangarine and Agami lime. This result indicatethat these species and varieties are need ofpollination and fertilization to produce yield.On the other hand, mature fruits which producedfrom emasculation and bagging treatment in theWashington navel orange is eVidintly due to theability of this variety to set fruits parthenocarpicallywithout pollination and fertilization.7 - The mitotic investigations showed that, thechromosome number in Washington navel orange,Jaffa orange, Mazizy orange, Clementine tangarineand Agami lime was 2n=18. Thus, thesecitrus species and varieties are normal diploids.8;:’ In meiotic cI oid numberstudies, it was found that, the haplofchromosomes in Balady lime, Marshgrapefruit, Balady mandarin, Suckarry orange,Jaffa orange, Mazizy orange, Clementine tangarineand Aga~i lime was 9, while the diploid numberwas 18 chromosomes.9 he chromosome behaviour at meiosis in each ofhese citrus species and varieties showed 9ivalents at late diakinesis and metaphase Istages. There were univalent chromosomesbeside the bivalents in some PMC’s in differentpropartions. More PMC’s with univalents wereobserved in the Agami lime and Marsh grapefruitthan those in the other citrus species andvarieties.10- Clementine tangarine, Balady mandarin andSuckarry orange showed the maximum percentagesof pollen fertility, while Agami lime and Marshgrapefruit showed the minimum percentages ofpollen fertility.11- A positive correlation was found between thepercentages of stainable pollen and the percentagesof pollen germination.12- A negative correlation was found between thepercentages of PMC’s with univalents on onehand and the percentages of stainable pollenand pollen germination onthe other hand,13- A negative correlation was found between thepercentages of PMC’s with univalents and thenumber of well developed seeds per fruit.14- A positve correlation was found between thenumber of well developed seeds per fruit on onehand and the percentage of stainable pollen andthe percentage of pollen germination on the otherhand.15- As a result of these cytological studies, onemeight conclude that, the Balady mandarin,Suckarry orange, Mazizy orange and Clementinetangarine were nearly cytologically stable,Therefore, these species and varieties can besafly used in breeding programs for citrusimprovement.16- Histological studies showed that, the embryo sacwas completely differentiated within 3 days afterpollination. The fecundation occured within 7-13days after pollination of the citrus species andvarieties under this study.17- Within 13-20 days after pollination, the freenuclear endosperm divisions occured and becomemore visible.18- The degeneration of ovules in all citrus speciesand varieties under this investigation was notobserved within the first 3 days after treatmentswith the exception of Clementine tangarine andAgami lime when their flowers were emasculatedand bagged.19- The percentage of deteriorated -ovules increasedfor all treatments within 7 to 30 days and reachedto the maximum at 45 and 60 days after pollinationtreatments.20- Cross-pollination with Balady mandarin pollengave the lowest percentage of deteriorated ovulesand the hgihest dimensions of well developed ones.21- At 60 days after pollination, the adventitiousembryos were appeared.22- At 60-85 days after pollination, the successivedivisions of both sexual and adventitious embryosdeveloped to the main body with globular shapeand the nuclear endosperm developed to formcellular endosperm.23- At 100 days after pollination, the embryos hadreached to the cotyledonary stage and thecellular endosperm began to disapear.24- At 120 days after pollination, the various partsof the complete embryo were formed ( hypocotyle,radicle, cotyledons and plumule ) and the seedcoats were completely differentiated.