MARDI Res. l .20(1) 1992: 1-14

Selection for early cassava clones@emilihan klon ubi kayu cepat matang)

S. L. Tan*

Key words: cassava, early harvestability, clonal selection, rate of retums

Abstrak

Potersi wrtuk memilih klon-klon ubi kayu yang cepat matang (dapat dipungut

hasil selepas 6 bulan berbanding dengan 12 bulan) didapati baik. Usaha-usaha ke

arah ini telah menghasilkan klon CM 3906-31 yang dapat megeluarkan hasil

sebanyak 36 tlha pada 6 bulan di ranah gambut dan 43 t/ha pada 6 bulan di tanah

mineral di kawasan-kawasan yang tidak mengalami sesuatu musim kemarau. Jika

kemarau selama24 bulan berlaku semasa musim menanam, hasil ubi pada 6

bulan boleh terjejas. Masa pemungutan klon CM 3906-31 juga boleh

dilambatkan kerana klon ini mengeluarkan hasil ubi yang sama tinggi atau lebih

tinggi daripada hasil Perintis selepas 12 bulan. Sungguhpun mempunyai indeks

pemungutan hasil yang tinggi (iainr cekap menyimpan asimilat untuk hasil

berekonomi), CM 3906-31 mempunyai kandungan kanji yang rendah dalam ubi'

Penanarnan klon-klon cepat matang menunjukkan kelebihan ekonomi

berbanding dengan klon-klon l2-bulan, terutama pada aras hasil yang boleh

diperoleh daripada CM 3906-31. Pada tempoh masa penanarnan 8 rahun, Perintis

dapat ditanam tujuh kali manakala CM 390G31 dapat ditanam 12 kali. Pengiraan

kos dan pulangan menunjukkan bahawa CM 390G31 akan mendatangkan

keuntungan yang melebihi pulangan daripada Perintis sebanyak $1 182-$2 126/

ha setahun pada harga ubi basah $83-$ll6A.

Abstract

The potential for selecting early clones of cassava, harvestable at 6 months

insread of the uaditional 12, is good. Effors in tftis direction have resulted in the

selection of a clone CM 3906-31 capable of yielding 36 y'ha at 6 months on

drained peat and 43 tlha at 6 months on mineral soils in areas which do not

experience a disthct dry season. Where a dry season of 2-4 months occur within

the cropping season, 6-month root yields were severely depressed. CM 390G31

also showed flexibility in harvesting time, being as high yielding or higher

yielding than Perintis at the l2-month harvests. Although having a high harvest

index (efficient in partitioning assimilates towards economic yield)' CM 390G31

tends to have a Iow starch content in the roots.

Planting early clones shows an economic advantage over l2-month clones.

particularly at the levels of yield which may be expected of CM 3906-31. Over

an 8-year cropping period which allows for seven crops of Perintis and 12 of

CM 3906-31, theoretical calculations indicate a profit advantage ranging from

$1 182iha to $2 126fta per year from CM 3906-31 at market prices for fresh

roos varying from $83/t to $ll6/t.

*Dvision of Horriculture, MARDI Headquarten, P.O. Box 1230l,sUn4 Kuala l,umpur, Malaysia

Author's full name: Tan Swee Lian@Malaysian Agricultunl Research and Development lnstitute 1992

Selecriqr for early cassava clones

IntroductionCassava (Manihot esculenta Crantz) haslong been a traditional backyard food cropin Malaysia as well as a commercial starch-producing crop grown on varying scalesranging from a few plans to 500 ha.Although a shortlived perennial by botanicaldescription (Cobley 1963; Purseglove 1974),it is an annual crop by agronomic practice.It is a long-term annual requiring on theaverage 12 months' growth to harvest, andon this very score has not been as popular asshorter term annuals such as maize andgroundnut which promise faster returns.

This last-mentioned scenario is apt tochange with the advent. cf early cassavaclones. Earliness in cassava may be definedas early root bulking leading to early highyields, in this case after 6 months of growth.Earliness has not much to do withphysiological or sexual maturity of the cropsince the economic part of the plant is non-sexual in nature and is in effect a storageorgan, the modified root. So, instead ofwaiting for 12 months to harvest a cassavacrop, it will be possible to expect aneconomic yield after 6 months, reducing theproduction time by half.

Work on the selection of early cassavaclones began in MARDI in 1982 in anattempt, to popularize the cultivation ofcassava as a commercial large-scale crop.Malaysia is in short supply of starchresources, either for industrial use (food,sweetener, textiles, paper, etc.) or forlivestock feed (Tan et al. 1989). Cassava isthe easiest starch-producing crop to grow inthe humid uopics, being adaptable ro a widerange of agro-climatic and edaphicconditions and having relatively few seriouspests and diseases. By contrast, other starch-producing crops are less adaptable: maizehas problems with yield stability, pess anddiseases, sweet. potato is often plagued byweevil attacks, while white potato and wheatare unsuited to the tropical environment.

Materials and methodsSelection for early cassava clones enlailedthe incorporation of an additional harvestinto the selection scheme fcrr new cassavaseedling clones at the stage of advancedyield trials, which follow preliminary yieldtrials, single-row trials and seedlingevaluation CIan 1989b). The use of earlinessas a selection criterion could not beintroduced in the initial stages of selectionas there was insufhcient planting materialsthen. This scheme enables both genotypeswhich produce early high yields (after 6months) as well as those which arerelatively slower in root bulking (high yieldsat 12 months) to be differentiated.

A seed lot introduced from CIAT(Centro Intemacional de AgriculturaTropical) in 1982 went through the aboveselection scheme. By 1987, l2 clones wereshortlisted as having the early characteristic.These were tested in four yield fials from1989 !o 1990, two seasons at the MARDIIntegnted Peat Research Station in Pontian,and one season each at, MARDI researchstations Bukit Tangga and Serdang,respectively. Both Pontian and Serdang arein Agro-ecoiogical Zone 3 ( EZ 3) with nodistinct dry period, while Bukir Tangga is inAEZ I, having a dry period lasring from 3-4months per year (Nieuwolt et al. n.d.t le82l).

A randomized complete block designwas adopted, witi four replications per trial.Although each plot provided for twoharvests, the design was not strictly a split-plot because the harvest areas were fixedand not randomized. At Pontian, C 5 [a 9-month clone hitherto recommended as early(Chan et al. 1983)l and Perintis [a newlyreleased high-yielding clone (Anon. 1988b)lwere used as check clones. At Bukit Tanggaand Serdang, the same two as well as BlackTwig, tlre widely cultivated commercialvariety, were used as checks.

The usual agronomic practicesrecommended for peat and mineral soils(Tan 1989a) were adopted accordingly, andthe planting distance of 0.9 m x 0.9 m was

used. Plot size measured 6.3 m x 11.7 m.This provided for the harvest of 25 cennalplants at 6 and 12 months, leaving out aborder row all round.

At each of the two harvests, data werecollected on fresh root yield, harvest index(ratio of root weight over total plant weight),starch content of the roots [estimated bymq$urements on the specific gpvity (NoorAuni and Tan 1980)l and starch yield(calculated by the relationship of fresh rootyield x starch content).

Combined analyses of the data werealso carried out in two ways: over twoseasons at Pontian and over three locations.As clones were considered fixed effectswhile seasons were random, expectations ofmean squares (EMS) for a combinedanalysis of variance over two seasons atPontian are as in Table l.

The mean squares for clones (M,) aretherefore tested against the mean squares forclone x season (M). The test for seasonsuses a composite of lr4, + ItIr divided by M,+ Mo. For clone x season (M) and replicatewithin season (MJ, ttte error term M5 isused.

S. L. Tan

In the combined analysis over locations(using data from only the fint season trial atPontian together with data from the BukitTangga and Serdang trials), clones andlocations were considered as fixed effectswith the expectations of mean squares giveninTable 2. As Black Twig did not feature inthe Pontian trial, data from this clone wereeliminated from the combined analyses ofvariance.

In this case, testing for clones (M,) usesthe mean squarcs for clone x location (lr{),while for locations the composite Lt * Mtis tested with M, + Ir40. Clone x location(M) and replicate within location (Mq) arebottr tested using the error term Mr.

Results and discussionPerformance at Pontian over two seasonsFor the 6-month harvest data, althoughclones were not significantly different forroot and starch yields (Table 3), ttte LSDtest still detected a significant difference inthe yields of CM 390G31 compared withthe yields of the check clone,s (Table 4). CM3906-31 stands out as a promising earlyclone, giving a mean fresh rmt yield of 36.2

Table l Expected mean squares (EMS) for the different sources of variance in a combined

analvsis of variance over two seasons at Pontian

EMS Mean squaredf

Clones (C) 13

Seasons (S) I

C x S 1 3

Replicate within S 6

Error 78

o ! + 4 o f , + 8 I ( C , - e f n r+ 1 4 o f t , . ; + 4 o L + 5 6 0 3+ 4 o ] "+ 14 of131

oZo3o3o!

M r

M2

M3

M4

M5

Table 2. Expected mean squares (EMS) for the different sources of variance in a combined

analysis of variance over the three locations viz. Pontian (lst season), Bukit Tangga and Serdang

Sotuce Mean squareEMSdf

Clones (C)

Locations (L)

C x L

Replicate within LError

l 32

26

9tt7

ol + 4 ol-1+ 12I, (Cj -e)2n3

al + 14 ofu + 4 ofu + 56 ,- (L,-tr2n

0 3 + 4 o 3 1

03 + 14 oftr)o Z

Mr

M2

M3

M.Ms

Selectiqr for early cassava clones

Table 3. Mean squares for variance components of four traits at 6 montln over two seasons of testing atMARDI Integrated Peat Research Station Pontian

Mean squares

Source df Rootyield

Harvestindex

Starchcontent

Starchyield

Clones (C)Seasons (S)C x SReplicateIS]Enor

146.6741 < a A 1

80.194**7.776

13.65r

0.0545**0.00990.0121* *

0.0261**0.0040

5.97'lI I 1 .196* *

2.6945.229**1.637

8.23225.393**4.287**1.3530.881

I J

Ii 36

78

**Significant at probability level ofp = Q.Ql

Table 4. Effect of clone and season on harvest data at 6 months at MARDI Integrated Peat ResearchStation Pontian

FactorRoot yield(t/ha)

Harvestindex

Starchcontent (7o)

Starchyield (t/ha)

ClonecM337r-22cM 3380-10cM 3388-15cM2527-:lcM2975-2rcM3299-26cM 3906-31cM 3707-31cM 3906-13cM 3898-6cM 3855-37cM 3303-21c 5Perintis

Meanc.v.(qo)HDo.t

SeasonFirstSecond

HDo.t

29.r30.628.623.624.52t.736.226.328.126.727.718 .720.429.4

27.013.73.7

27.826.2

1.4

0.590.610.570.430.460.580.610.500.550.520.570.420.370.63

0.5312.00.06

0.540.520.02

24.223.222.622.822.523.822.022.622.823.1z ) . I

23.02r .920.822.85 .6l . J

23.821.80.5

7.07.26.45.45.56.68 .16.06.56.26.6Z+. J

4.56.0

6.215.20.9

6.65.70.4

t/ha at 6 months (Plate 1) compared wirhonly 20.4 t/ha from C 5 and 29.4 t/hafromPerintis. Starch yield was also superior at8.1 t/ha at 6 months.

It should be mentioned that 0re firstseason's yield of CM 3906-31 was evenmore spectacular at 41.'l tlha at 6 months(data not presented). In the second season,Perintis showed some promise as an early

A

clone with a root yield of 35.7 tlha at 6months.

Harvest index of CM 3906-31 was ashigh as in Perintis and significantly betterthan that of C 5. A high harvest indeximplies efhciency in producing economicyield. Srarch content of this new clone wasnot significantly different from the contentsof the check clones.

Ptate 1 . Yizld and plant type of CM 3ff6-31 at 6

nnntls frorn cultiwtion on drained peat (MARDI

Integratcd Peal Research Station Pontian)

Seasons produced significantdifferences in sarch content and starch yield(Table 4),being higher in the first season.The clone r season interaction hadsignificant effects on root and starch yieldsas well as for harvest index, but not forstarch content (Table 3).

Analysis of variance on data at 12months show clones to be significant forroot yield, starch content and harvest index(Table 5). By 12 months, Perintis hadovertaken CM 390G31 as the highestyielding clone, giving a mean root yield of

S. L Tan

43.3 tltta per year (Table 6). Nevertheless,CM 3906-31 which featured second highesthad a non-significantly different yield of42.5 VhA per year. The starch yields ofPerintis and CM 3906-31 were also non-significantly different at this stage, butharvest index of Perintis was significantlyhigher. Starch content of CM 390G31at12months was similar to that of Perintis butsignificantly lower than that of C 5.

Seasons were significant in producingdifferences in root yield, harvest index,starch content and starch yield, again higherin the first se:$on (Table 6). As at 6 months,except in the case of starch con0ent, theclone x season interaction was significantfor the other three traits.

P erformanc e at B ukit T anggaSix-month root yields at Bukit Tangga werefar below expectations (Table 7), munlybecause the dry se:won set in just 2 monthsafter crop establishment and the 6-monthcrop was harvested soon after the onset ofthe rains. Perintis had the highest yield of15.3 t^a at 6 months while CM 3906-31produced a non-significantly different yieldof 14.1 t/ha at 6 months. Differences in thelow starch yields of the various clones weretoo small to debct statistically.

Nevertheless, harvest indices in CM3906-31 and in Perintis were high,indicating that under less favourableconditions of growth there was still higherefficiency in partitioning assimilates towards

Table 5. Mean squares for variance components of four traits at 12 months ove,t two seasons of testing

at MARDI Integrated Peat Research Station Pontian

Mean squares

df Rootyield

Harvestindex

Starchcontent

Starchyield

Clones (C)Seasons (S)C x SReplicate[S]Error

t79.298*2329.673**

67.777*. 65.487

2738

0.0411**0.0405*'r0.0061'r.0.00570.0030

17.013**115.480*'r'

1.8535.1462.4r0

4.722212,067**

3.523*6.840'f *1.605

131

t36

78*Significant at probability level ofp = Q.g5

**Significant at probability level ofP = 0.01

Selection for early cassava clones

Table 6. Effect of clone and season on h.rvest data at 12 months at MARDI Integrated Peat ResearchStation Pontian

FactorRoot yield(t/ha)

Harvestindex

Starchcontent (7o)

Srarchyield (t/ha)

ClonecM337t-22cM 3380-10cM 3388-15CM2527JcM 2975-2rcM3299-26cM 3906-31cM3707-ircM 3906-13cM 3898-6cM 3855-37cM 3303-21c 5Perintis

Meanc.v.(qo)6Do.*

SeasonFirstSecond

HDo.t

33.235.438.836.734.734.642.830.732.734.430.328.627.643.3

34.615 .15.2

39 .130.02.0

0.620.650.660.550.610.620.660.520.580.610.620.560.440.73

0.60s.r0.05

2r.221.220.723.022.823.6r9.32r.6u.222.122.822.722.619.4

2r.9t . r1 .5

23.020.90.6

7.17.58 .18.58.08.28.46.68.07.77.06.56.28.4

7.616.71.3

0.620.580.02

9.06.20.5

the economic part of the plant than in C 5 orBlack Twig. Strrch conrenr of CM 3906-31(at 17.ZVo) was similar to that of Perintis(l8.0Vo) but lower than those of C 5 (l9.6va)and Black Twig (2l.2vo).

However, at 12 months (Table 8), rootyields had improved considerably [provingyet again that. even areas in AEZ I canproduce high cassava yields if timing ofplanting provides sufficient time for the cropto recover from the effects of the 3 to4-month drought (Tan 1989a)1. Perinris andCM 3906-31 gave the highest fresh rooryiolds (> 43 tlha per year). Equally high-yielding were CM 3898-6 and CM 3299-26. These two clones had starch yieldssecond only to Perintis.

At 12 months, only CM 3906-31retained its high harvest index, whereas inPerintis harvest index was not significantlydifferent from that of C 5. Starch content of

CM 3906-31, however, had becomesignificantly lower than the check clones.

Performance at SerdangFresh root yield was again outstandinglyhigher in CM 3906-31 ar 6 monrhs (43.0 tlha at 6 months) ftan any of the other clones,witlr C 5, Perintis and Black Twig at2l.7,26.5 and 18.2 tlha at 6 monrhs respecrively(Table 7). Hence, CM 3906-31 producesearly high root yields on both drained peatand mineral soils. Starch yield was alsohighest in this clone.

Harvest index in CM 3906-31 wassignificantly higher than any other clone,including Perintis. Unfortunately, starchcontent of this new clone was inferior tothose of the check clones.

At 12 monrhs, the highest yielder wasstill CM 3906-31 ar a fresh roor producr,ionof 59.3 t/ha per yeu (Table 8). Starch yieldson the other hand were not significantly

S. L Tan

Table ?. Mean harvest data on five top cassava clones at 6 months against the checks C 5, Perintis and

Black Twig at MARDI research stations at Bukit Tangga and Serdang

Root yield(t/ha)

Harvestindex

Starchcontent (7o)

Starchyield (t/ha)

Buklt TanggacM2975-21cM 3905-3rcM 3906-13cM 3380-10cM 3898-6c 5PerintisBlack Twig

Mean of 15 clonesC.Y. (7o)HDo.-

SerdangcM 390G31cM3'.to7-ilcM2527-:7cM337r-22cM 3855-37c 5PerintisBlack Twig

Mean of 15 clonesc.Y. (qo)sDo.t

t4.214.112.5r2.09.78.3

15.312.810.643.26.5

43.029.126.925.224.22r.726.518.225.5l 5 . l5.5

0.590.690.590.520.450.520.620.M0.54

13.40.10

0.670.490.450.500.500.380.540.36

0.4910.20.07

19.6r7.219.02r.220.419.618.02r.2r9.94.61.3

20.523.824.324.225.822.r21 .824.523.33.4l . l

2.82.42.42.62.01 .62.72.82.r

M.9lls

8.86.96.56.16.24.8f . /

4.5

5.915.31.3

different for CM 3906-31, Perintis andBlack Twig, mainly because of the inferiorstarch content of the first. Harvest indicessignificantly higher than in C 5 and BlackTwig were recorded by CM 3906-31 andPerintis.

Performance over three locationsClones and clone x location interaction weresignificant for the four traits studied at 6months (Table 9). l,ocations were notsignificant for harvest index. Over the threelocations, CM 3906-31 outyielded C 5 andPerintis as well as the other clones in bothroot and starch yields (Table 10). Root andstarch yields as well as starch content werehigher at Pontian and at Serdang than atBukit Tangga (Table 10).

At 12 months, locations were significantfor the four traits, whereas clones were not

significant for starch yield while clone xlocation was not significant for fresh rootyield (Table 11). Here again, CM 3906-31had a significantly higher mean root yieldcompared with the other 13 clones,including the checks (Table 12). The LSDtest was also able to detect that five clones,these being CM 3898-6, CIl{3299-26,CM252'7-7, Perintis and CM 3906-13, hadstarch yields similar to that of CM 3906-31.Again, Pontian and Serdang showed highermean root and slarch yields than BukitTangga (Table l2).

Variance components and theirimplicatians in breedingGenerally, whether the cassava crop isharvested at 6 or at 12 months, strrch yieldis a character which is significantlyinfluenced by season and location, as well as

Selectiqr for early cassava clones

Table 8. Mean harvest data on five top cassava clones at 12 months against the checks C 5, Perintis andBlack Twig at MARDI research stations ar Bukit Tangga and Serdang

Clone Root yield(t/ha)

Harvestindex

Starchcontent (9o)

Starchyield (tlha)

Bukit TanggacM 3906-31cM 3898-6cM3299-26cM 3707-31cM 3855-37c 5PerintisBlack Twig

Mean of 15 clonesc.v. g,)LSDo.o5

SerdangcM 3906-31cM 2975-21cM 3898-6CME27JcM 3388-15c 5PerintisBlack Twig

Mean of 15 clonesc.v.(Eo)6Do.t

43.342.941.638.136.432.849.426.036.223.712.3

59.346.245.9M.643.432.9A r a

35.5

4 1 . 114.58.5

0.630.590.560.490.590.510.520.390.53

13.50 .10

0.750.590.610.570.700.470.710.48

0.609.50.08

19.023.224.523.525.623.520.9a ^ a

23.04.91 .6

21.627.727.728.026.226.525.029.2

26.93.01 .2

8.29.8

10.28.99.37.7

10.36.38.3

24.02.8

12.912.812.712.5tl.48.7

tu.z10.4

11 .015 .32.4

Table 9. Mean squares for variance components of four traits u 6 months from testhg over tfueelocations (MARDI Integrated Peat Reseach Station Pontian, MARDI research stations ar Bukit Tanggaand Serdang)

Mean squares

Source ot Rootyield

Hawestindex

Starchcontelt

Starchyield

Clones (C)Locations (L)C x LReplicateIL]Error

208.315 * *4674.527**

42.723+18.53723.239

0.0501**0.03870.0074*0.0168**0.0037

11 .6M**262.962**

2.417**3.303,r.*0.878

9.064**322.662**

2.416**1 . 218t.t44

132

269

117*Significant at probability level ofp = 0.05

**Significant at probability level ofp = 0.01

clone x season and clone x locationinteractions. Starch content, however, isaffected by season, Iocation and clone xlocation interaction, but not by clone xseason interaction. In other words. a clone

8

with a high starch content in one season,may be expected to be superior in this traitrelative to the other test clones in anotherseason. This implies that starch content canprohtably be used as a selection criterion

S. L. Tan

Table 10. Effect of clone and location on harvest data at 6 months from testing at three locations

Factor

Root yield(t/ha)

Harvestindex

Starchcontent (7o)

Starchyield (Vha)

ClonecM337t:22cM 3380-10cM 3388-15CM2527JcM 2915-2rcM3299-26cM 3906-31cM 3707-31cM 3906-13cM 3898-6cM 3855-37cM 3303-21C 5Perintis

Meanc.v.(E")LSDoos

LocationPontianBkt. TanggaSerdang

LSDo.o5

20.823.219.219 .620.02r.334.022.723.722.221.2t6.4r6.722.22 r .722.23.9

27.811.226.0

1 .8

0.530.560.530.440.500.550.680.530.550.490.550.470.420.590.53

l 1 .60.05

0.540.540.50

0.02

22.923.322.022.62 t .823.820.522.422.022.323.6a a /

2r.620.622.34.20.8

? ? R

19 .823.2

0.4

4.95.54.44.64.55 . 17.25.25.45 .15.23.75 . 1

4.65.0

2t.60.9

6.62.26.00.4

Table 11. Mean squares for variance components of four raits at 12 months from testing over thlee

locations (MARDI Integrated Peat Research Station Pontian, MARDI research stations at Bukit Tangga

and Serdang)

Mean squares

Source df Rootyield

Harvestindex

Starchcontearl

Starchyield

Clones (C)

l.ocations (L)

C x LReplicateIL]Error

370.571**I 824.589**

85.044141.660*56.422

0.0455**0.1038**0.0104**0.00250.0038

23.776**271.782+*

3.174**2 .81 l *+0.979

10.327128.095**

5.783*I 1.554**3.490

I J

J

269

tt7

*Significant at probability level ofp = 0.05**Significant at probability level ofp = 0.01

when selection is carried out over differentseasons.

At 6 months, neither season nor locationhad significant effects on harvest index, butthe interactions clone x season and clone xlocation affected this trait at both times ofharvest. Fresh root yield, on the other hand,

is influenced strongly by the clone x seasoninteraction as well as by locations at bothtimes of harvest.

Conclusions on CM 3906-31CM 3906-31 is an early yielding clone byvirtue of its high rate of root bulking, which

Selcctiqr for early cassava clones

Table 12' Effect of clone and location on harvest data at 72 months from testing at tfuee locations

FactorRoot yield(t/ha)

Harvestindex

Starchcontent (7o)

Starchyield (q/ha)

ClonecM 3371-22cM 3380-10cM 3388-15cM2527-:lcM 2975-2rcM3299-26cM 3906-31cM3707-ircM 3906-13cM 3898-6cM 3855-37cM 3303-21c 5Perintis

Meanc.v.go)6%rLocatlon

PontianBkt. TanggaSerdang

6Do.t

38.040.642.843.239.843.656.239.042.047.338.638.233.848.5A a a

17.86 .1

48.337.041.5

2.8

0.600.600.680.540.560.590.690.520.580.620.610.540.470.660.59

10.50:05

0.620.540.61

0.02

24.824.r23.424.7'u.325.420.424.424.724.925.925.224.422.224.24 .10.8

23.022.926.8

0.4

9.49.7

10.010.89.9

11 .01 1 .69.5

10.41r.710.09.68.2

10.6r0.218.41 .5

l l . t8.4

1 1 . 0

0.7

carries through n 12 months (especially onmineral soils in AGZ3). This provides theflexibility, for harvesting either early or atthe end of the normal l2-month period, totake advantage of prevailing prices for freshroots. However under environmentalconditions of moisture sEess such as inAEZ l, CM 3906-31 is unable ro expressits full productive potential when harvestedearly. Perintis shows marginally bett€rtolerance to such condilions.

Another shortcoming is a lower scarchcontent relative to C 5 and Black Twig, butstarch yield per hectare at 6 months is stillhigher than these clones in AEZ 3 wherethere is no prolonged moisture stressthroughout the cropping season. This starchyield advantage, however, disappears whenharvest of the crop is delayed until 12months.

Theoretical calculations of net incomefrom early clonesTwo scenarios will be examined relative !oretums to be expected from using an earlyclone over the raditional l2-month croppingsquon: one, with regard to cultivation ondrained peat, and two, on mineral soils.

To date, the highesr yielding clone at 12months in terms of both root and strrchyields is Perintis (Table 6 and Table 8). Acomparison of the yields of Perintis and CM3906-31 is given in Table 13.

Drained peatComparing a single l2-month croppingseasion with Perintis with two Gmonthcropping seasons using CM 3906-31 (TableI4), itmay be seen that two 6-month cropsof the early clone within a year bring inbetter net retums than a single crop of

l0

S. L. Tan

Table 13. Six and l2-month yields of Perintis and CM 3906-31

6-month yields (t/ha) l2-month yields (t/ha)

Root Starch Root Starch

On peatPerintis 29.4 6.0 43.3 8.4cM 3906-31 36.2 8.1 42.8 8.4

72.4* 16.2*

On mineral soilsPerintis 26.5 5.7 41.2 10.2cM 3906-31 43.0 8.8 59.3 r2.9

86.0* 17.6**Computed yields of CM 3906-31 (6-month yields x 2)

Table 14. Costs and returns from a l2-month crop of Perintis vs. two 6-month crops of CM 3906-31 ondrained peat

Perintis12-month season

cM 3906-31Two 6-mon0r seasons

Costs ($/ha)*Land preparationPlantingWeed controlFertilizers

Subtotal

Harvesting @ $17^Perintis 43 tlhaCM 3906-31 36 y'ha

Total costs

Returns ($iha)Cross income at prices

$83^$99/t$1 16^

Net income at prices

$83^$e^$lr6^

1 3 11003129M

| 487

t 5 l

2 2r8

l 3 l + 3 l100 + 100312 + 3129M + 794

1 487 + 1237 = 27'A

612 + 612 =1224

3 948

3 4864 1584 872

| 268| 9402 654

2 9 8 8 + 2 9 8 8 = 5 9 7 63 5 6 4 + 3 5 & = 7 1 2 84 1 7 6 + 4 1 7 6 = 8 3 5 2

2 0283 1804404

*Source: Tan (1987, with revisions to wage rate and input costs)

Perintis in the same time frame. land The difference in profits from CMpreparation in the second season is confined 3906-31 is in the region of $760/ha per yearto only chemical conFol of weeds as tillage over those to be expected from Perintis at ais unnecessary (Tan l99l). Similarly, in tlre root price of $83/L At a root price of $i l6lt,second season fertilizer costs are reduced this difference increases to $l 750/ha perbecause liming is unnecessary, having a year.residual effect lasting 3 to 5 years (Chewr977\.

l l

Selectian for early cassava clones

Mineral soilsDoing the same comparison for mineralsoils, it will be appreciated $rat costs are notreduced in the second season unlike on peat(Table 14).Effectively, costs are doubledwhen two crops are planted in one year.Since the costs of production are lower onmineral soils than on peat, the profits to beexpected at the range of market. prices forfresh roots are higher than those fromcassava cultivation on peat. This is more sowith CM 3906-31 which produces a higher

fresh root yield at 6 months on mineralsoils.

Thus, as in the case of cultivation onpeat, the net retuns from two crops of CM3906-31 from the same piece of land in oneyear are higher than from a single crop ofPerintis. The profit margins range from$l 838/ha to $3 323lha per year at rootprices ranging from $83/t to $ll6lt.

In practice, there may be a time lapse ofl-2 months between the harvest of the firstcrop tro the planting of the second to allow

Perintls (12-month crcp)

Y l t 2 l l 1 2

Y2 t 2

6crop I

6 l 0 l l t 2land prep

l 2

8crop 2

8Y3

Y4

Y5

Y6

Y7

Y8

land preparation

1 2 3

l 0 u t 2crop 3 -

1 0 1 l t 25land prep

5

crop 4 -

7land prep

'7

l 0 l l 1 2

9 l 0 l l t 2land preparation

9 1 0

- crop 5

1 2 4crop 6

4 5crop 7

l l 1 2land preparation

l 0 l l 1 2

CM 39G31 (6-month crop)

Y l 1 2 3 5 6 7land preparatron

4 5 6 ' t 8

PreParatlon

t 0

l 0Y2

l 0

land prepararion r- crop 3

r 2 3 4 5 6 7

+ c r o p

t 2 3

F-- crop 4

t 2 3----------------+ land preparation

1 2 3 4F_ crop 7

I L J

4 5 6 7 8 l 0crop 6

6 ' l 8land preparation

6 7 8 l 0

land prep

1 1 1 2

l l 1 2crop 2 -

l l t 2

crop 5 -

l l 1 2

crop 8 -

l l t 2

Prcpara[on

n t 2crop I I

l l t 2

Y3

Y4

Y5

Y6

Y7

Y8

l 0

land preparation

1 l 1 2

------------i land preparation F-- crop 9

4 5 6 ' 1F-- crop 10

t 2 3land preparation

6 7 8 l 0

l 0

land PreParation 1--- crop 12

Figure l. Crop scheduling for Perintis ad CM 3m6-31 oyer an 8-year cropping period

t 2

land prcparation

S. L. Tan

Table 15. Costs and returns from a l2-month crop of Perintis vs. two 6-month crops of CM3906-31 on mineral soils

Perintisl2-month season

cM 3906-31Two 6-month seasons

Costs ($/ha)*Land preparationPlantingWeed controlFertilizers

Subtotal

Harvesting @ $tZ7tPerintis 4l t/haCM 3906-31 43 tlha

Total costs

Returns ($/ha)Gross income at prices

$83^$99^$ 1 1 6 A

Net income at prices$83^$99^$1 l6lr

250100354428

T l : 2

3 4034 0594 756

5002W708856

2264

7 1388 5149 976

3 4124 7886 250

| 462n%

697

r8n

| 5742 2302 927

*Source: Anon. (1988a)

Table 16. Costs and returns from seven l2-month crops of Perintis vs. 12 6-month crops of CM 390G31 on mineral soils over an 8-year period

Per cropPerintis7 crops

cM 3906-3112 crops

Costs ($/ha)Land preparationPlantingWeed conrolFertilizers

Subtotal

Harvesting @ $l7nPerintis 4l tlhaCM 3906-31 43 t/ha

Total costs

Returns ($/ha)Cross income at prices

$83/t$99^$116^

Net income at prices$83/t$99/r$116/r

| 132

6971 462I 701

I 750700

2 4782 9967 924

4 879

12 803

23 82128 4r333 292

1 1 0 1 815 61020 489

3 0001 2 m4 2485 136

13 584

8 ' t7222356

250100354428

42 82851 08459 856

20 47228't2837 500

Dif ference ($/ha/year)

@ $83/t@ $ee^@ $116^

I 182r & 02 126

l 3

Selecriq for early cassava clones

for land preparation, so tlnt in fact two Gmonthcrops will take about 14 months. Bearingthis in mind, over an S-year period, it willbe possible to get seven l2-month cropsfrom Perintis or l2 6-month crops from CM3906-31 (Figure 1). Using the same basis asTable 15 for calculations but adjusting forseven and 12 cassava crops respectively,CM 3906-31 will still give profits which arehigher than those of Perintis by $l 182, $1640 and $2l?6lha per year at the marketprices of $83, $99 and $116/t respectively,for fresh rcos (Table 16).

AcknowledgementsThe autlror is grateful to her assistantresearch officer, Mr Mohsin Yusof, and herresearch assistants, Mr Zunal Abidin Karimand Ms Inthirani R. at MARDI ResearchStation Serdang, Mr Ab. Majid Bakar andMr Hasli Ali at MARDI Research StationPontian, and Mr Jamaluddin Kasa atMARDI Research Station Bukit Tangga, fortheir active involvement. at each step ofclonal selection and evaluation.

She wishes also to acknowledge that thetrial at Bukit Tangga was funded by aregional sub-project agreement No. 9-89VICA under the auspices of the AsianRegional Cassava Research Program ofCIAT (Cenro Internacional de AgriculturaTropical).

ReferencesAnon. (1988a). Anggaran kos pengeluaran dan

pendapatan untuk tanaman dan ternakan,Techno-Economic and Social StudiesDivision, MARDI, Serdang ( mirneo.)

- (1988b). CM 9E2-7: Hon ubi kayu baru untuktanah Sambut Serdang: MARDI (brochure)

Chan, S. K., Khelikuzaman, M. H., Tan, S. L., Geh,S. L. and Lo, N. P. (7983). Cassava inP enins ul ar blal ay s ia : w it h par t ic ularreference lo production lechniqucs (a specialreport) 97 p. Serdang: MARDI

Chew, W Y. (1977). Assessment of cassava as anindusrial crop on Malaysian pat. MARDIRep. No. 57 12 p. Serdang: MARDI

Cobley, L. S. (1963). Starch storage crops In: Anintrodrrction to tlv botany of tropical cropsChap. VL p.174J. London: Longrnans,Green and Co. Ltd.

Nieuwolt, S., Ghazdli, M.Z. and Gopinathan, 8.,n.d. [1982]. Agro-ecological regions inPeninsular Malaysia 2O p. Serdang: MARDI

Noor Auni, H. and Tan, S. L. (1980). Perbandingandi antara cara-cara menentukan kandungankanji di dalam ubi kayu (Manihot esculentaCranu). Tektol. Pertanian, MARDI 1:304

Purseglove, J. W. (1974). Tropical crops:Dicotyledons p. 172-80. London: Longman

Tan, S. L. (1987). CM 982-7: a new cassava clonerecomnpnded for cultivation on pat. Teknol.P elbagai T anarnan, M AR D I 3 : | -5

- (1989a). Prestasi klon ubi kayu Perintis (CM982-7) di pelbagai lokas\. Teknol. PelbagaiTanatnan, MARDI 5:234

- (1989b). The root of the problems in cassavabreeding Proc. plant and aninal breedingworkshop 7-9 Oct. 1986, Serdang (AhmadTamzalr1 M. and Tan, S. L., ed.) p. l3l-8.Serdang: MARDI

- (1991). Minimal tillage in cassava cultivationon drained pzt MMDI Res. J. 19(1): 1-7

Tan, S. L., Chan, S. K and Yeong, S. W. (1989).Potential uses of cassava and projections onnational requirements. Pape.r presented atworkshop: Cassava production on acommercial scale, 16 Nov. 1989, Serdang,12 p. Organizer: MARDI

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Acccpcdtor publication on21 August I99l