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                                                                       EXHIBIT 7


                               FIFTH AMENDMENT TO
                         THE DEKALB GENETICS CORPORATION
                           SAVINGS AND INVESTMENT PLAN


                  WHEREAS, DEKALB Genetics Corporation, a Delaware corporation,
with its principal place of business in DeKalb, Illinois (the "Company"), has
heretofore adopted and maintains for the benefit of its employees a profit
sharing plan with a qualified cash or deferred arrangement within the meaning of
section 401(k) of the Internal Revenue Code of 1986, as amended, and the
regulations promulgated thereunder which is designated the "DEKALB Genetics
Corporation Savings and Investment Plan" (the "Plan"); and

                  WHEREAS, the Company desires to amend the Plan in certain
respects;

                  NOW, THEREFORE, pursuant to the power of amendment contained
in Section 12.01 of the Plan, the Plan is hereby amended, effective, unless
otherwise indicated, immediately as of the date of the consummation of the
"Offer" (as that term is defined in the Agreement and Plan of Merger dated as of
May 8, 1998 among Monsanto Company, a Delaware corporation ("Parent"), Corn
Acquisition Corporation, a Delaware corporation and a


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wholly-owned subsidiary of Parent ("Sub"), and the Company), as follows:

                  1.       Section 1.10 of the Plan is hereby amended to read
as follows:

                  1.10 COMPANY means DEKALB Genetics Corporation, a Delaware
         corporation, with its principal place of business in DeKalb, Illinois,
         and any successor thereto whether by merger or otherwise.


                  2.       Section 1.15 of the Plan is hereby amended by
deleting therefrom the phrase "Section 3.02(d)" and substituting in its place
the phrase "Section 3.02(d) or (e)".

                  3.       The first sentence of Section 1.40 of the Plan is
hereby amended by adding at the end thereof the phrase ", and any successor,
whether by merger or otherwise, of any of the foregoing corporations or other
business entities".

                  4.       Section 3.02 of the Plan is hereby amended (i) by
redesignating paragraphs (e) and (f) thereof as paragraphs (f) and (g),
respectively, of such Section, (ii) by deleting from paragraphs (c) and (d)
thereof the phrase ", shares of Company Stock or other property", and (iii) by
adding a new paragraph (e) to such Section which reads as follows:

                  (e)(1) The Employers shall contribute a Discretionary
         Contribution in cash to the Trust Fund for the Plan Year

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         during which occurs the day (the "four-month anniversary") which is
         exactly 120 days immediately following the day (the "Purchase Date") of
         the consummation of the "Offer" (as that term is defined in the
         Agreement and Plan of Merger dated as of May 8, 1998 among Monsanto
         Company, a Delaware corporation ("Parent"), Corn Acquisition
         Corporation, a Delaware corporation and a wholly-owned subsidiary of
         Parent ("Sub"), and the Company). The amount contributed for such Plan
         Year for each eligible Participant shall be 2% of such Participant's
         Compensation for such Plan Year. An "eligible Participant" for purposes
         of this paragraph (e)(1) is a Participant who is employed by an
         Employer both at such Purchase Date and on the four-month anniversary.
         In the case of an eligible Participant whose employment with all
         Related Employers terminates before the end of the Plan Year during
         which occurs the four-month anniversary and who is not a "highly
         compensated employee" as defined in Section 414(q) of the Code for the
         Plan Year during which occurs the four-month anniversary and is not
         such a highly compensated employee for the Plan Year which precedes the
         Plan Year during which occurs the four-month anniversary, for purposes
         of this paragraph (e)(1) his Compensation for the Plan Year during
         which occurs the four-month anniversary shall be his actual
         Compensation for such Plan Year plus the additional base pay and salary
         he would have earned during the remainder of such Plan Year during
         which occurs his termination of employment if such base pay and salary
         would have continued for the remainder of that year at the same rate in
         effect upon his termination of employment. Discretionary Contributions
         pursuant to this subparagraph shall be made to the Trustee no later
         than the time prescribed by law for filing the Company's federal income
         tax return for the applicable Plan Year, including any extensions
         thereof.

                  (2) The Employers shall contribute a Discretionary
         Contribution in cash to the Trust Fund on behalf of each eligible
         terminated Participant for the Plan Year during which occurs such
         terminated Participant's termination of employment after the day (the
         "Purchase Date") of the consummation of the "Offer" (as that term is
         defined in the Agreement and Plan of Merger dated as of May 8, 1998
         among Monsanto Company, a Delaware corporation ("Parent"), Corn
         Acquisition Corporation, a Delaware corporation and a wholly-owned
         subsidiary of Parent ("Sub"), and the Company). The amount contributed
         for such Plan Year for each eligible terminated Participant shall be 2%
         of such Participant's Compensation for such Plan Year. An "eligible
         terminated Participant" for purposes of this paragraph (e)(2) is a

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         Participant who is (i) employed by an Employer at such Purchase Date
         whose employment with his Employer is involuntarily terminated by his
         Employer without cause after the Purchase Date and prior to the day
         (the "four-month anniversary") which is exactly 120 days immediately
         following the Purchase Date and (ii) not a "highly compensated
         employee" as defined in Section 414(q) of the Code for the Plan Year
         during which occurs his termination of employment and is not such a
         highly compensated employee for the Plan Year which precedes the Plan
         Year during which occurs his termination of employment. For purposes of
         the foregoing, "cause" shall be defined as such term is defined in the
         Merger Agreement. For purposes of this paragraph (e)(2), an eligible
         terminated Participant's Compensation for the Plan Year during which
         occurs his termination of employment shall be his actual Compensation
         for such Plan Year plus the additional base pay and salary he would
         have earned during the remainder of such Plan Year if such base pay and
         salary would have continued for the remainder of that year at the same
         rate in effect upon his termination of employment. Discretionary
         Contributions pursuant to this subparagraph shall be made to the
         Trustee no later than the time prescribed by law for filing the
         Company's federal income tax return for the applicable Plan Year,
         including any extensions thereof.



                  5.       Paragraph (f) of Section 3.02 of the Plan is hereby
amended to read as follows:

                  (f) Employer Contributions under the Plan, excluding, however,
         Employer Contributions made pursuant to Section 3.02(e), and Employee
         Salary Reduction Contributions shall be made out of the current or
         accumulated Consolidated Net Earnings of the Company; provided,
         however, that the total of all contributions for any Plan Year shall
         not exceed the amount allowable as a deduction under Section 404 of the
         Code, as amended and in force from time to time.



                  6.       Section 4.01 of the Plan is hereby further amended by
adding at the end thereof a new sentence which reads as follows:

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         Notwithstanding the foregoing, as soon as administratively practicable
         after the "Effective Time" as that term is defined in the Agreement and
         Plan of Merger dated as of May 8, 1998 among Monsanto Company, a
         Delaware corporation ("Parent"), Corn Acquisition Corporation, a
         Delaware corporation and a wholly-owned subsidiary of Parent ("Sub"),
         and the Company, the Company and the Trustee shall take such steps as
         are necessary to eliminate the Class A Company Common Stock Fund, which
         shall after such Effective Time be invested only in cash equivalents,
         and transfer any balance remaining therein to the other investment
         funds pursuant to Participants' instructions.


                  7.       Effective as of the "Effective Time" as that term is
defined in the Merger Agreement, the first sentence of Section 4.02(b) of the
Plan is hereby amended to read as follows:

         Each Participant may change the manner in which his Accounts are
         invested by following the procedures prescribed by the Company, to be
         effective as of the day specified in such procedures.


                  8.       Effective as of the "Effective Time" as that term is
defined in the Merger Agreement, the third sentence of Section 4.02(b) of the
Plan is hereby amended by deleting therefrom the phrase "other than transfers
into any Company Common Stock Fund".

                  9.       The first paragraph of Section 4.03 of the Plan is
hereby amended by adding at the end thereof a new sentence which reads as
follows:

                  Notwithstanding the foregoing, as soon as administratively
                  practicable after the "Effective Time" as that term is defined
                  in the Agreement and Plan of Merger dated as of May 8, 1998
                  among Monsanto Company, a Delaware corporation ("Parent"),
                  Corn Acquisition

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                  Corporation, a Delaware corporation and a wholly-owned
                  subsidiary of Parent ("Sub"), and the Company, the Company and
                  the Trustee shall take such steps as are necessary to
                  eliminate the Class A Company Common Stock Fund, as set forth
                  in Section 4.01.


                  10.      Effective as of the "Effective Time" as that term is
defined in the Merger Agreement, Article IV of the Plan is hereby further
amended by deleting therefrom Sections 4.04, 4.05 and 4.06.

                  11.      Section 6.02 of the Plan is hereby amended to read as
follows:

                  6.02 EMPLOYER CONTRIBUTION ACCOUNTS

                  A Participant shall be one hundred percent (100%) vested in
         his Employer Contribution Account on the first to occur of the
         following:

                           (a)      His attainment of Normal Retirement Age
                  while employed by any Related Employer;

                           (b)      His termination of Employment with all
                  Related Employers due to his Total and Permanent
                  Disability;

                           (c) His termination of Employment with all Related
                  Employers due to his death;

                           (d) His completion of five (5) Years of Service for
                  Vesting;

                           (e) His active employment with any Related Employer
                  on the day (the "four-month anniversary") which is exactly 120
                  days immediately following the day (the "Purchase Date") of
                  the consummation of the "Offer" (as that term is defined in
                  the Agreement and Plan of Merger dated as of May 8, 1998 among
                  Monsanto Company, a Delaware corporation ("Parent"), Corn
                  Acquisition Corporation, a Delaware corporation and a

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                  wholly-owned subsidiary of Parent ("Sub"), and the
                  Company); or

                           (f) His involuntary termination of Employment by all
                  Related Employers without cause after such Purchase Date and
                  prior to such four-month anniversary. For purposes of the
                  foregoing, "cause" shall be defined as such term is defined in
                  such Merger Agreement.


                  12.      Section 6.03(a) of the Plan is hereby amended to read
as follows:

                  (a) A Participant who upon his termination of employment with
         all Related Employers is not one hundred percent (100%) vested in his
         Employer Contribution Account pursuant to Section 6.02 shall be vested
         in the percentage of the value of his Employer Contribution Account set
         forth in the following table:



                  Number of Years of                      Vesting
                  Service for Vesting                    Percentage
                  -------------------                    ----------
                                                      
                      Less than 1                            0%
                          1                                 20%
                          2                                 40%
                          3                                 60%
                          4                                 80%
                       5 or more                           100%


                  13.      Effective as of the "Effective Time" as that term is
defined in the Merger Agreement, Section 7.01 of the Plan is hereby amended by
deleting therefrom paragraph (a)(2).

                  14.      Section 12.01 of the Plan is hereby amended by adding
at the end thereof a new sentence which reads as follows:

                  Further, notwithstanding any provision of this Plan to
                  the contrary, the Plan may not be terminated on or

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                  prior to the day (the "four-month anniversary") which is
                  exactly 120 days immediately following the day (the "Purchase
                  Date") of the consummation of the "Offer" (as that term is
                  defined in the Agreement and Plan of Merger dated as of May 8,
                  1998 among Monsanto Company, a Delaware corporation
                  ("Parent"), Corn Acquisition Corporation, a Delaware
                  corporation and a wholly-owned subsidiary of Parent ("Sub"),
                  and the Company), and the Plan may not be amended to either
                  (i) decrease the amount of, or impose additional conditions
                  regarding a Participant's eligibility for, the Discretionary
                  Contribution to be contributed by the Employers in accordance
                  with Section 3.02(e) or (ii) preclude a Participant from
                  becoming one hundred percent (100%) vested in his Employer
                  Contribution Account as provided under Section 6.02(e) or (f).

                  IN WITNESS WHEREOF, the Company has adopted this instrument by
causing it to be executed by its duly authorized officer on this _________ day
of May, 1998.

                                             DEKALB GENETICS CORPORATION



                                             By: /s/ John H. Witmer, Jr.
                                                --------------------------------
                                             Title: Senior Vice President
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