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Yam physiology Key word: growth cycle, growth period varietal difference, senescence Increasing the capacity of research technicians in breeding 28 th July 2015 Ryo Matsumoto (visiting scientist from JIRCAS,

Yam Physiology

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Yam physiology

Yam physiology

Key word: growth cycle, growth period varietal difference, senescence Increasing the capacity of research technicians in breeding 28th July 2015Ryo Matsumoto (visiting scientist from JIRCAS, Japan )

Growth cycle of yamDevelopment evaluation protocol for tuber earliness/growth periodEvaluation of tuber earliness characteristicSummaryTodays topic

Growth cycle of YamGeneral

During the growth cycle, there are five distinct phases,

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Changing in dry weight of aerial and tuber part during growth cycle Growth cycle of Yam

The growth cycle of any of the ten cultivated food yam species follows a cycle repeating a rhythm of growth and dormancy every year. Annual cultivars are characterized by the dormancy phase of their tubers, starting at harvest. 4

Growth cycle of YamPhase 1: Tuber germination

The stem is still devoid of expanded leaves, reducing the transpiring surface as much as possible to optimize the reserves for root development.

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Growth cycle of YamPhase 2: Foliage Development

Characterized by a very rapid and massive increase in leaf area and ends the dependence of the yam plant on the tuber sett. The plant reaches self-sufficiency (autotrophy)

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Growth cycle of YamPhase 3: Rapid Tuber bulking

Nutrient are translocated from canopy to tuberThe more rapid is tuber development and the greater its final size.

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Growth cycle of YamPhase 4: Foliage senescence, tuber mature

Foliage senescence and tuber mature:Senescence of foliage start as early as 5-6 months after planting for early maturing genotypes.

Desiccation starts with the fall of the older, basal leaves and drying of the apices.Usually, foliage senescence is synchronized with tuberization and maturity. This senescence is probably initiated by phtotoperiod, but there is a genetic component as well. It is, of course, accelerated by foliar diseases.

The maturation of the tuber corresponds to the end of the photosynthate translocation, which also corresponds with foliage senescence.8

Development evaluation protocol for tuber earlinessPhase 5: Dormancy

Mature, freshly harvested tubers cannot sproutandthey enter a dormancy phase which can last forleads than a month to up to 5 months.

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Five growth phase Growth cycle of Yam

Phase 1Phase 2Phase 3Phase 4Phase 5

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Growth cycle of YamGeneral

During the growth cycle, there are five distinct phases, which can vary according to growing condition, spices and genotype.Phase 1: Tuber germinationPhase 2: Foliage developmentPhase 3: Tuber bulkingPhase 4: Foliage senescence, tuber maturePhase 5: Dormancy

During the growth cycle, there are five distinct phases, which can be vary according to growing condition, spices and genotype.

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Late mature varietyEarly mature varietyVarietal deference in tuber growth pattern of yam (White yam: D. rotundata)Growth cycle of YamDays after plantingTuber maturity rate (%)3 plants x 3 rep. x 6 times x 3 year rep.Aerial part:Dry weightSprouting dateSenescence date

Tuber part:Dry tuber weightEarly mature variety:Tuber growth stop earlier

Dispersion of risk at famer field (dry stress, insect attack at.)Extension of period to provide fresh yam tuber at the materketExpand yam growing area for food security Growth cycle of YamWhy do we need to get different growth period variety for famer and customer ??What is advantage point that farmer has different maturity variety ??

Rice20 cm x 20 cmYam 100 cm x 100 cm

If you have to plan 100 seeds / seed tubers for experiment, how big field do you need ?? Rice: 400 cm2 (4 m2)Yam: 10000 cm2 (100m2)New protocol which is simple and non-distractive for earliness evaluation were requiredQuestions !!!

**Senescence indexSenescence index of aerial part is weekly recorded till surveyed plants each variety had completely been senescence. Senescence level is classified into the five levels and quantified.

Level 1 No senescence leaf aLevel 2 25% senescence bLevel 3 50% senescence cLevel 4 70% senescence dLevel 5 100%senescence e

Senescence index= {(1 No. of level 1 plant)+(2No. of level 2 plant) + (3No. of level 3 plant) + (4No. of level 4 plant) + (5 No. of level 5 plant) / 9}

abcdeDevelopment evaluation protocol for tuber earlinessFocus point: Senescence index

To develop simple and non-distractive protocol for earliness of tuber growth, we focus on the foliage senescence period.

Senescence level was classified using a five stages scale and analyzed the relationship with tuber maturity. Senescence coefficient of aerial part was used to this formula.

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After planting daysSenescence index

Late mature varietyEarly mature varietyDevelopment evaluation protocol for tuber earlinessStart senescence aerial part,Early mature variety160 DAPLate mature variety80 DAPChanging in senescence index during growth period in early and late mature variety

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Days after planting Senescence indexRelationship between tuber growth and senescence of aerial part Tuber growth Senescence indexTuber growth finishPhotosynthesis finishStart senescence of aerial partStart senescence starting time was confirmed to be index parameter for earliness of tuber growth by plant physiologically staudy

Early mature variety:Tuber growth stop earlierSenescence of aerial part also earlierDevelopment evaluation protocol for tuber earlinessLate mature varietyEarly mature varietyNon-distractive evaluation Tuber maturity rate (%)

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Evaluation of tuber earliness characteristicGenetic resources (D. rotundata) Genetic resources (447 lines as core collection)Diversity research set(DRS-EDITS: 100 lines)

Smaller,But retain diversity

Experimental design3 plantsRandomized block design with 2 rep.Characterization Morphological traitsGrowth period

What we are doing by using developed protocol for tuber earliness that evaluation the diversity of earliness characteristic in genetic resources.

In IITA genetic resources center, they has about 500 lines as core collection.However, 500 lines is still big population for earliness evaluation for yam.Therefore, we established Diversity Research set we call DRS.18

No. of accessionsDays from sprouting day to foliage senescence start dayEvaluation of tuber earliness characteristicDays from sprouting day to foliage senescence start day in DRS

No. of accessionsDays from sprouting day to foliage senescence start dayEvaluation of tuber earliness characteristicDays from sprouting day to foliage senescence start day in DRS

New acc. will be selected for parental material to develop new variety !!!!!

Early mature varietyLate mature variety

SummaryPlant Physiology is very important for understanding the plant growth

Whole genome sequence of D. rotundata had already done by IBRC under collaboration research program between JIRCAS, IITA and IBRC. High quality phenotyping will be key factor for further improvement of yam cultivation

To conduct high quality phenotyping, plant physiology knowledge is very important

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FemaleMaleMonoeciousEvaluation of sex / Flowering characteristic