Question:The gemorah says that 3 things that G-d had in mind for this world and if he would not have, it would be logical that he should have. One of the 3 is that grain spoils and Rasshi explains that householders would hoard food and thereby bring food shortages and famine.
Now is is well known that we today store grain for long periods of time. Moreover Joseph stored food for at least 7 years (Rashi says that he added soil to the grain but it is difficult to say that Joseph knew of a secret method that stayed hidden until the time of the Gemorah. We do not find that Joseph was challenged by any of Pharohs advisers as to how he would store the grain).
Moreover the Gemorah seems to descibe 3 things which are intrinsic to the running of this world and that can hardly be the case if thruout much of world history, grain can be stored. Moreover, no calamity occurs today or during Josephs time by grain storage and indeed it is considered to be an innovation that is beneficial.
And finally, the Gemorah itself says that grain can be stored since it says that vegtables are not suitable for Peah because they cannot be storred but of course grain is suitable.
Actually, grain in its raw state does spoil. Today, grain is not stored for long periods, such as for more than a year, except with high-tech methods of vacuum packing, chemical preservation techniques, by being freeze-dried, or through the use of controlled radiation. If I were to pick some wheat and store it in my shack today, it would not last long at all. On an industrial level, grain is not stored for more than a year. (Besides, in the early days of the world there were less people than wheat; it was therefore a blessing for the wheat to rot from year to year. Now, when there are more people than wheat, Hash-m blessed us to allow the wheat to stay from year to year in order to feed more mouths. The problem of finding customers for all that wheat no longer exists.)
As to how Yosef was able to store grain for so long, your assertion that the advisors did not challenge him is actually the reason why he was put in charge -- Pharaoh and his advisors realized that Yosef was blessed by G-d, and was thus able to accomplish that which they themselves were unable to accomplish, and that is why they selected Yosef to be in charge. Also, if it is true that grain can be stored for long periods and Yosef had no great secret, then why didn't anyone else store grain? The answer is that the people did store their grain when they heard that years of famine were approaching, but it spoiled (Rashi Bereishis 41:55), because grain is not something that stores for a long time. (The trick of adding soil is not guaranteed to work, without divine help.)
As for why vegetables are not Chayav in Pe'ah while wheat is, "Machniso l'Kiyum" (56b) means that it stays for a few months. Here, though, the Gemara is saying that wheat does not stay from year to year.
(Alternatively, Tosfos (56b, DH Klal Amru) says that mid'Oraisa, only olives, grapes, and wheat are Chayav in Pe'ah. The Rabanan made other products Chayav based on certain guidelines which determined that those products are a "Davar Chashuv." That does not mean that the Torah, when it obligates olives, grapes, and wheat in Pe'ah, is saying that those items meet all the prerequisites which the Rabanan established for things which are Chayav mid'Rabanan. Therefore, wheat is not necessarily "long-lasting" in storage. Indeed, the Derashah cited by Tosfos from the Toras Kohanim actually leaves out that characteristic when discussing wheat.)
Best wishes,
Yisrael Shaw