What does "しまの入り具合など品質は例年並みだということです。" mean in this sentence?

Question

農家によりますと、ことしはスイカが成長する５月中旬から下旬にかけて寒暖の差が激しかったことから数は少なめですが、しまの入り具合など品質は例年並みだということです。(source)

1)I'm not sure if しま means "island" (because it is written in kana and I don't think this word is generally written in kana but maybe I'm mistaken )

2)I don't find 入り具合 in the dictionary(and jisho.org tells that it can be a suffix but not a prefix so I don't think it is a word that is not supposed to be in the dictionary), I think it means the general conditions (of the cultivation) but it doesn't make sense because apparently 品質 is only used for talking about things that are in the 品物 category.

(I consider "しまの入り具合など" as a relative clause of 品質, maybe it is wrong)

Answer 1

「-----が、しまの入{はい}り具合{ぐあい}など品質{ひんしつ}は例年並{れいねんな}みだということです。」

「しま」 means "stripes" here -- the black stripes seen on the surface of watermelons. In kanji, it is 「縞」. I will not mention how irrelevant "island" would be in the context.

「入り具合」 refers to the way the stripes have formed and appear. You must have heard about how important appearance is in fruit to the Japanese. Poor appearance, low price. Appearance is an important quality in food in Japan.

I consider "しまの入り具合など" as a relative clause of 品質, maybe it is wrong.

No, it is not a relative clause.

「しまの入り具合など品質は例年並み」＝「しまの入り具合など、品質は例年並み」

「しまの入り具合」 is only an example of the overall qualities （品質） of the watermelons this year. It is saying the qualities are as good as those from recent years.