Morphological Characteristics of High Yielding Rice Varieties

Why Rice is Important to us?•World’s most important food crop

• A primary source of food for more than half of the world’s population

•>90% of the world’s rice is grown and consumed in Asia

•Rice accounts for 35 -75% of the calories consumed by more than 3 billion Asians •Planted 154 million hectares annually or on about 11% of the world’s cultivated land.

Need of new improved verities

• Total requirement can not supply by traditional rice varieties

• So scientist try to Increase the Yield Potential of Rice

Strategies for Increasing the Yield Potential of Rice

• Conventional hybridization and selection procedures

• Ideotype breeding• Heterosis breeding • Wide hybridization• Genetic engineering

By those methods the plant morphology is improved

Unhealthy Healthy canopy

Where we can see Changes?• Plant height• Plant leaves• No of tillers per plant• Plant type • Panicle weight and number• Leaf area index• Ratio of leaf area to grains• Harvest Index

Morphological Improvement• Several models for super high-yielding rice

(new plant type)

• main features, big panicles (250 spike lets per panicle) fewer tillers (3-4 productive tillers per plant) short and sturdy culm

Plant Height• Short and sturdy Culm

Semi dwarf cultivars characterized by lodging resistance

Increase nitrogen responsive

• Ideal height Early crop :55-60 cm late crop :60-76 cm

• Generally; 100 cm with culm length of 70 cm

Initial Semi-Dwarf Rice Varieties in the world

Plant Leaves• Tall erect-leaved canopy

• The upper three leaf blades should be long, erect, narrow, V-shaped and thick

• Long and erect A larger leaf area receive Light on both sides Not put each other in the shade Light is used more efficiently

• Erect leaf canopy before appearance of panicles

Plant leaves cont…

• Narrow leaves Relatively small space - higher effective leaf area

index• The V-shape

Makes the leaf blade stiffer and not prone to droopiness

• Thick leaves Have a higher photosynthetic function and are

not easily senescent

• Flag leaf, length of 50 cm (19.7 in) long and located 20 cm (7.9 in) higher than the top of the panicle

• 2nd leaf from the top, length is 55 cm (21.6 in) and is located higher than the top of the panicle

Plant leaves cont..

• Ideal length of the first leaf under the top leaf, Early crop: 40-44 cm Late crop: 42-60 cm

• Ideal width of the first leaf under the top leaf, Early crop: 1.2-1.4 cm Late crop: 1.2-1.3cm

• Ideal length of the second leaf under the top leaf, Early crop: 39-44 cm Late crop: 37-43cm

Plant leaves cont..

• Ideal width of the second leaf under the top leaf, Early crop: 1.1-1.4cm Late crop: About 1.1cm

• Ideal top leaf angle at the active tillering stage Early crop: 22-58° Late crop: 4 12°

• Based on these results, a new concept of "dynamic plant type structure"

Leaf Angles

• Flag Leaf: about 5o

• 2nd leaf : about 10o

• 3rd leaf: about 20o

Leaf Area Index

• The greater leaf area index (LAI) with smaller area per stem

• Important morphological factor contributing to the high yield

Productive Tillers Per Plant

• Ideal tiller number per plant, Early crop: About 15 tillers Late crop : 14-19 tillers

• Less tillers- less tillers for flowering• More tillers- less no of panicle baring tillers• Rice tiller angle more vertical• Fewer tillers (3-4 productive tillers per plant)

Panicle Length• With range values of 13.3 – 29.6 cm

• Maximum panicle length is contributes positively, Grain size, grain shape Higher numbers of tillers/plant

• Longer panicles and greater number of grains/panicle ultimately contribute to higher grain yield

• Panicle height, top of filled panicle is about 60 cm (23.6 in) from the ground

Lower Panicle Position• The tip of the panicle is only 60 to

70 cm above the ground during the ripening stage

• The plant to be highly resistant to lodging - an essential character for breeding super high-yielding rice varieties

Harvest Index• Harvest Index is very high (above 0.5)

• Make the stem thicker and sturdier, which usually results in HI decrease,

that it is difficult to obtain super high yield by increasing HI.

Morphological Model of Super High-Yielding Rice

•Uppermost three leaves:Flag leaf, long, 50 cm, higher than the panicle top 20 cmThe 2nd leaf from the top: 10% longer than the flag leaf, and over the top of the panicleThe 3rd leaf = the middle position of the panicle

•Plant height ; 100 cm, with culm length = 70 cm

•Erect: the leaf angles of the flag, 2nd and 3rd leaves are around 5, 10, 20 degrees, till mature

•Narrow, V-shape and thick: narrow with 2 cm when flattened

Morphological Model cont…

• Plant type: Moderate compact with moderate tillering capacity Drooping panicles after filled Above ground ~ 60 cm Erect-leaved canopy without appearance of the

panicles

• Leaf area index (LAI) and ratio of leaf area to grains: the LAI is ~ 6.5 based on the uppermost three leaves, the ratio of leaf area to grain weight is 100 : 2.2-2.3, meaning that to produce 2.2-2.3 grams of rice, 100 cm2 of the upper three functional leaves are needed

Morphological Model cont…

• Panicle weight and number: Grain weight per panicle = 5 g 2.7 million panicles per hectare

• Harvest index > 0.55

• Leaf area index (LAI) and ratio of leaf area to grains: The LAI is ~ 6.5 based on the uppermost three leaves The ratio of leaf area to grain weight is 100 : 2.2-2.3

(meaning that to produce 2.2-2.3 grams of rice, 100 cm2 of the upper three functional leaves are needed)

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