Genetic Improvement of Maize for Tolerance to Acid Soils in the Tropics

1
Genetic Improvement of Maize for Tolerance to
Acid Soils inthe Tropics

• Alejandro Navas
• ISU Agronomy
• October 29 / 98

2
OUTLINE

• 1. Acid soils in the world
• 2. What are the acid soils?
• 3. The problem
• 4. Some solution approaches
• 4.1 Liming
• 4.2 Genetics of tolerance to soil acidity
• 4.3 Physiology of tolerance

3
OUTLINE

• 4.4 Populations Recurrent Selection
• 4.5 Inbred lines
• 4.6 Molecular markers
• 5. Summary
• 6. Future Research

4
1. Acid soils in the world

• 48 developing countries with 1.7 billion ha
• 43 worlds tropical land area
• 38 of tropical Asia
• Indonesia, Thailand, Malaysia, India, China, and
  the Philippines.
• 27 of tropical Africa
• Ivory Coast, Zaire, Zambia, Tanzania, Uganda and
  Zimbabwe.
• 10 of Central America, Caribbean and Mexico

5
1. Acid soils in the world

• In South America 80 of agricultural area
• Brazil, Colombia, Ecuador, Peru and Venezuela
• Colombia Llanos Orientales
• 17 millions ha.
• Brazil acid savannas 205 million ha of which 112
  are suitable for agricultural

Ref Sanchez, 1977 Torres et al., 1997
6
2. What are the acid soils?

• Aluminum ( Al) and Manganese (Mn) toxicity
• pH lt 5.6
• Deficiency Ca, Mg, P, Mo, and Fe
• Al saturation gt 35
• P lt 16 p.p.m

Ref Granados et al., 1993 Duque-Vargas et al.,
1994.
7
Environmental characteristics for some acid soils

Country Colombia Brazil India Indonesia
Site Carimagua Sete lagoas Meghalaya Sitiung
pH Al P 5.2
60 10 4.9 40
5 4.7 49 1.3 4.0
53 3


mg kg-1
Source Granados et al., 1993 Pandey et al.,
1994.
8
3. The problem

• Between 8-20 million ha are planted
• Maize is more susceptible than rice, wheat,
  sorghum, cotton and soybean.
• Maize produces fewer and smaller roots
• Reduces survival and function of micro-organisms
  in the soil gt organic matter gt availability of
  N, P, S
• A survey of 48 developing countries only five are
  conducting research

Ref TropSoils, 1991 Pandey and Gardner, 1992
Tan, 1993.
9
4. Some solution approaches4.1 Liming

• Lime is a reliable soil amendment
• For poor farmers is not an economic option
• At the sub-soil level is difficult
• Temporal solution
• Incompatible with conservation tillage

Ref Pandey and Gardner, 1992 Pandey et al.,
1994.
10
4.2 Genetics of tolerance to soil acidity

• Acid tolerant varieties are reliable, permanent,
  economical, and environmental clean solutions
• Several authors have reported genetic variation
  for tolerance to acid soils in maize.
• Quantitative inheritance Magnavaca et al., 1987
  Pandey et al., 1994 Borrero et al., 1995
  Salazar et al., 1997.
• Qualitative inheritance Rhue et al., 1978
  Miranda et al., 1984.

11
4.2 Genetics of tolerance to soil acidity

• Additive genetic variance is generally most
  important in yield Magnavaca et al., 1987
  Pandey et al., 1994.
• Dominance genetic variance has been also
  reported Duque-Vargas et al., 1994 Borrero et
  al., 1995.

12
4.2 Genetics of tolerance to soil acidity

• CIMMYT has conducted several field-based studies
  to determine inheritance of yield
• GCA accounting for 89 of the genotypic
  variation and SCA n.s for yield.
• Heritability, estimated using half-sib family
  mean averaged 38 for yield.
• They suggested that recurrent selection would be
  effective.

Ref Duque-Vargas et al., 1994 Pandey et al.,
1994, and Borrero et al., 1995.
13
4.3 Physiology of tolerance

• Aluminum (Al) toxicity is the most severe
  limiting factor Foy, 1988.
• Al resistance is prerequisite for adaptation to
  acid soils. There are some evidences in wheat and
  barley.
• P and water deficiencies are correlated with Al
  toxic effect.
• Root elongation of seedlings, in nutritive
  solutions Al, can be measured Horst et al.,
  1992.

14
4.4 Populations Recurrent Selection

• Several authors have reported good results using
  recurrent selection to improve maize yield on
  acidic soils.
• Magnavaca et al., (1987), in Composto Amplo after
  four cycles half-sib selection, reported
  significant yield improvement
• Granados et al., (1993) in SA3 after 14 cycles
  MER and two FS reported yield improvement of 2
  and 14 per cycle, respectively.

15
4.4 Populations Recurrent Selection

• Ceballos et al., (1995) in five populations and
  two acidic and one no-acidic environments
  reported 4.72 per cycle.
• CIMMYT-NARS has developed six maize populations
  SA3, SA4, SA5, SA6, SA7 and SA8
• Narro et al., (1997) diallel study conclude
• (SA3 SA5 ) x SA4 and (SA7 SA8) x SA6
• ETO x Tuxpeño was used as heterotic pattern

16
4.4 Populations Recurrent Selection

• Granados et al., (1994) compared SA3 and Tuxpeño
  across 20 sites, with a wide range of acidities,
  SA3 range from 96 to 1500 of Tuxpeño. SA3 was
  released in Colombia as
• ICA SIKUANI V-110
• Brazil has released 3 hybrids and some
  varieties
• Indonesia One variety

17
4.5 Inbred lines

• CIMMYT-NARS and CNPMS/ENBRAPA
• are developing maize inbred lines. These
  lines are being used in
• - Hybrids
• - Inheritance and physiological studies
• - Molecular markers.

18
4.6 Molecular markers

• At this level only a few reports are available in
  maize for tolerance to tropical acid soils
• Torres et al., (1997) worked F2 population
  derived from L53 x L1327 (CNMPS/EMBRAPA) with
  bulked segregant analysis (BSA) and RFLP markers.
  They concluded that there is a region on
  Chromosome 8 related to aluminum tolerance

19
4.6 Molecular markers

• Arias et al., (1997) In tolerant and susceptible
  S6 lines from SA3, SA4, SA5, and Tuxpeño Sequia
  C8 populations AFLPs were applied. They did not
  find molecular differences between susceptible
  and tolerant lines.
• They recommended to include new lines, new probes
  and increase endogamy level at the lines.

20
5. Summary

• Acid soils with 1.7 billion ha cover a
  significant part of a least 48 countries.
• Maize is one of the most susceptible crop.
• Lime is one reliable but expensive and temporal
  solution.
• Acid tolerant varieties are one reliable,
  permanent, economical and clean solution.

21
5. Summary

• Both quantitative and qualitative genetic
  variation have been reported.
• Additive genetic variance is more important but
  dominance is present.
• Aluminum (Al) toxicity is the most severe
  limiting factor
• Recurrent selection has been effective to improve
  maize yield on acidic soils.

22
5. Summary

• Maize inbred lines are being development in order
  to use them in Hybrids, inheritance /
  physiological studies, and
• molecular markers.
• There is a region on Chromosome 8 possibly
  related to aluminum tolerance

23
6. Future Research

• In general trials in acid soils have high
  experimental error, which reduces heritability
  and gains from selection.
• Soil acidity involves H , Al, Mn toxicities
  and deficiencies of P, Ca, Mg, and OM.
• More multi-environmental field testing are
  needed.
• Mechanisms for tolerance and efficient screening
  techniques must be research.

24
6. Future Research

• Isogenic and near-isogenic lines must be use in
  molecular studies with RFLP, RAPD and SSR.
• Physiological mechanisms of Al tolerance and P
  uptake and utilization must be studied
• Field data must be supplemented with
  Molecular and Physiological information

25

• Extension- Expansion- Overlap of the networks
  working in the tropical acid soils.
• Hannover University Germany, France, Spain,
  Brazil, Guadeloupe, and Camerun
• CIMMYT- NARS - NGOs Brazil, Colombia, Peru,
  Venezuela, Malawi, Ivory Coast, Indonesia, The
  Philippines, Thailand, Vietnam
• Consortium on Developing Maize Cultivars for
  Sustainable Production System in Acid Soils 5
  years and 4 U million

26
ACKNOWLEDGMENTS
CIMMYT Dr Shivaji Pandey Dr Carlos De Leon Dr
Luis Narro Mr. Juan C Perez
ISU Dr Arnel R. Hallauer Dr Michael Lee
CORPOICA MV. Sony Reza Mr. Jose G. Ospina Mr.
Guillermo Torres
CNPMS/ EMBRAPA Mr. Sidney N. Parentoni
University of Hannover Dr. W. J. Horst
NARS of CIMMYTs network for acid soils